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Conventional karyotype, nucleolar organizer regions and genome size in five Mediterranean species of Syngnathidae (Pisces, Syngnathiformes)
Journal of Fish Biology
Abstract
Conventional karyotypes, NOR-bearing chromosomes by means of silver impregnation and genome size were investigated in five Mediterranean species in three genera of the Syngnathidae. A karyotype of 48 subtelocentric-acrocentric chromosomes was found in the seahorse Hippocampus hippocampus (FN=48) while a diploid value of 44 occurred in H. guttulatus (2 sm-m+42 a; FN=46) and the pipefish Syngnathus abaster (44 a; FN=44) and S. typhle (44 a; FN=44). The pipefish Nerophis ophidion, possessing a diploid chromosomal set of 58 made up of 50 meta-submetacentric and eight subteloacrocentric elements (FN=108) and a genome size three to four times larger than those known to date, differs cytogenetically from all other Syngnathids studied so far. A single pair of active NOR-bearing chromosomes was found in both species of the genus Hippocampus while in Syngnathus and Nerophis species more than two silver positive chromosomes were found to be involved in nucleolus organization giving rise to NOR-bearing chromosome polymorphism. The possible evolutionary routes of quantitative and qualitative changes in chromosome and DNA are discussed. The resulting phylogenetic scheme is shown to coincide with that constructed from morphological characters.
... Fusions Observed in Syngnathus and Hippocampus. Haploid chromosome number in syngnathid fishes, as assessed by karyotyping and genetic mapping, is reported to be 22 or 24 in seahorse (Hippocampus) species (45,46) and 22 in Gulf pipefish (Syngnathus scovelli) (8). In Gulf pipefish, the reduction in chromosome number from 24, the putative ancestral number in ray-finned fishes (47) to 22, likely resulted from fusion of two pairs of chromosomes orthologous to chromosomes 1 and 24 and to chromosomes 14 and 23 in platyfish (Xiphophorus maculatus) (8). ...
... In Gulf pipefish, the reduction in chromosome number from 24, the putative ancestral number in ray-finned fishes (47) to 22, likely resulted from fusion of two pairs of chromosomes orthologous to chromosomes 1 and 24 and to chromosomes 14 and 23 in platyfish (Xiphophorus maculatus) (8). Though a haploid number of 24 chromosomes in seahorse was reported (with some published confusion about the pertinent species) (45,46), the genome for tiger tail seahorse (Hippocampus comes) (10) provides conserved synteny evidence that both ancestral chromosome fusions were already present in the common ancestor of seahorses and Syngnathus pipefish (SI Appendix, Fig. S5). As stated, our inferred seadragon haploid chromosome number of 23 is based on the size distribution of Hi-C scaffolds, which shows a sharp dropoff in scaffold length after the longest 23 scaffolds (SI Appendix, Fig. S3). ...
Seadragons are a remarkable lineage of teleost fishes in the family Syngnathidae, renowned for having evolved male pregnancy. Comprising three known species, seadragons are widely recognized and admired for their fantastical body forms and coloration, and their specific habitat requirements have made them flagship representatives for marine conservation and natural history interests. Until recently, a gap has been the lack of significant genomic resources for seadragons. We have produced gene-annotated, chromosome-scale genome models for the leafy and weedy seadragon to advance investigations of evolutionary innovation and elaboration of morphological traits in seadragons as well as their pipefish and seahorse relatives. We identified several interesting features specific to seadragon genomes, including divergent noncoding regions near a developmental gene important for integumentary outgrowth, a high genome-wide density of repetitive DNA, and recent expansions of transposable elements and a vesicular trafficking gene family. Surprisingly, comparative analyses leveraging the seadragon genomes and additional syngnathid and outgroup genomes revealed striking, syngnathid-specific losses in the family of fibroblast growth factors (FGFs), which likely involve reorganization of highly conserved gene regulatory networks in ways that have not previously been documented in natural populations. The resources presented here serve as important tools for future evolutionary studies of developmental processes in syngnathids and hold value for conservation of the extravagant seadragons and their relatives.
... For example, a positive association between egg diameter and genome size suggests a linkage to the evolution of parental care (Hardie and Hebert 2004). Other studies in fishes have assessed the relationship between genome size and biological or environmental characteristics such as habitat and physiology (Hinegardner and Rosen 1972;Vitturi et al. 1998;Hebert 2003, 2004;Smith and Gregory 2009), finding, for example, that water temperature is negatively correlated with genome size (Hardie and Hebert 2003). ...
... Although EEA71 was important in highlighting the effect of depth on fish genome size, in light of current best practices in comparative biology the study had several limitations including small sample sizes, lack of statistical analyses, and omission of phylogenetic covariation. Even more recent studies looking at associations between genome size and ecological or life-history traits have also largely failed to account for phylogenetic nonindependence (e.g., Vitturi et al. 1998;Gregory and Hebert 1999;Neafsey and Palumbi 2003;Smith and Gregory 2009;Roddy et al. 2020; but see Brainerd et al. 2001;Gardner et al. 2020). Many tools to access genome size data have been developed in recent years, contributing to the ease of data compilation for hundreds of species (Gregory et al. 2007). ...
A growing body of research suggests that genome size in animals can be affected by ecological factors. Half a century ago, Ebeling et al. (1971; EEA71) proposed that genome size increases with depth in some teleost fish groups and discussed a number of biological mechanisms that may explain this pattern (e.g., passive accumulation, adaptive acclimation). Using phylogenetic comparative approaches, we revisit this hypothesis based on genome size and ecological data from up to 708 marine fish species in combination with a set of large‐scale phylogenies, including a newly inferred tree. We also conduct modelling approaches of trait evolution and implement a variety of regression analyses to assess the relationship between genome size and depth. Our reanalysis of the EEA71 dataset shows a weak association between these variables, but the overall pattern in their data is driven by a single clade. While new analyses based on our ‘all‐species’ dataset resulted in positive correlations, providing some evidence that genome size evolves as a function of depth, only one subclade consistently yielded statistically significant correlations. By contrast, negative correlations are rare and non‐significant. All in all, we find modest evidence for an increase in genome size along the depth axis in marine fishes. We discuss some mechanistic explanations for the observed trends. This article is protected by copyright. All rights reserved
... Developing predominant varieties and improving aquaculture techniques for seahorses are the important strategies to relieve the stress imposed by overfishing. So far, the relevant researches mainly focus on the biology [11], conservation [1], and aquaculture of seahorse species [9,12,13]. One of the key obstacles for selective breeding of seahorses is the lack of knowledge of their transcriptomic or genomic information, and availability of molecular markers. ...
... These unigenes were found to be involved in biological process, cellular components and molecular functions in H. erectus and H. mohnikei, respectively (Fig 3). In both species, unigenes related to cellular process (11,574 unigenes for H. erectus and 11,986 unigenes for H. mohnikei), cell (11,194 unigenes for H. erectus and 11,655 unigenes for H. mohnikei), and binding (10,262 unigenes for H. erectus and 10,645 unigenes for H. mohnikei) were all the most abundant genes in the biological processes, cellular components, and molecular functions, respectively. ...
Seahorse conservation has been performed utilizing various strategies for many decades, and the deeper understanding of genomic information is necessary to more efficiently protect the germplasm resources of seahorse species. However, little genetic information about seahorses currently exists in the public databases. In this study, high-throughput RNA sequencing for two seahorse species, Hippocampus erectus and H. mohnikei, was carried out, and de novo assembly generated 37,506 unigenes for H. erectus and 36,113 unigenes for H. mohnikei. Among them, 17,338 (46.23%) unigenes for H. erectus and 17,900 (49.57%) for H. mohnikei were successfully annotated based on the information available from the public databases. Through comparing the unigenes of two seahorse species, 7,802 candidate orthologous genes were identified and 5,268 genes among them could be annotated. In addition, gene ontology analysis of two species was similarly performed on biological processes, cellular components, and molecular functions. Twenty-four and twenty-one unigenes in H. erectus and H. mohnikei were annotated in the biosynthesis of unsaturated fatty acids pathways, and both seahorses lacked the Δ12 and Δ15 desaturases. Total of 8,992 and 9,116 SSR loci were obtained from H. erectus and H. mohnikei unigenes, respectively. Dozens of SSR were developed and then applied to assess the population genetic diversity, as well as cross-amplified in a related species, H. trimaculatus. The HO and HE values of the tested populations for H. erectus, H. mohnikei, and H. trimaculatus were medium. These resources would facilitate the conservation of the species through a better understanding of the genomics and comparative genome analysis within the Hippocampus genus.
... The black-striped pipefish, Syngnathus abaster (Risso, 1827) is a small pipefish belonging to this family, also found in the open sea, brackish waters, and fresh water [5,6]. The usual habitat of this species is in estuaries and coastal areas [6,7]. It has wide distribution in the Mediterranean, Black and Caspian Seas [7][8][9]. ...
... The usual habitat of this species is in estuaries and coastal areas [6,7]. It has wide distribution in the Mediterranean, Black and Caspian Seas [7][8][9]. ...
The black-striped pipefish, Syngnathus abaster, is a species of the Syngnathidae
family. This study provides data on the morphometric, meristic and genetic structuring of
the Caspian Sea pipefish, Syngnathus abaster. Eight morphometric characteristics based on
total length and five morphometric characteristics based on standard length were analyzed.
A total of 50 specimens were collected in brackish-water biotopes. The average of total
length (LT) and standard length (LS) were 102.37 mm and 98.68 mm, respectively. Also in
this study, DNA barcodes were expanded for Caspian Sea Black-striped pipefish, hence
652 base-pair of the cytochrome oxidase I (COI) gene was sequenced in accordance with
standard DNA barcoding protocols. Since Pipefish (S. abaster) is one of the most
endangered fishes in the Caspian Sea, information about its phylogenetic relationships are
very rare; therefore, DNA barcoding will give a more accurate picture of the future
persistence of Black-striped pipefish populations.
... Large interspecific genome-size differences within both the seahorse and pipefish subfamilies account for the high CV of the syngnathid family. Although a fourfold range has previously been reported among different pipefish species (Vitturi et al. 1998), this is the first report of similar differences among seahorses, which were previously thought to have small genomes (Hinegardner 1968;Vitturi et al. 1998). The high CVs discovered within other diploid actinopterygian families, such as the zeids, callionymids, and atherinids, require further investigation, as each of these families was represented by only two species. ...
... Large interspecific genome-size differences within both the seahorse and pipefish subfamilies account for the high CV of the syngnathid family. Although a fourfold range has previously been reported among different pipefish species (Vitturi et al. 1998), this is the first report of similar differences among seahorses, which were previously thought to have small genomes (Hinegardner 1968;Vitturi et al. 1998). The high CVs discovered within other diploid actinopterygian families, such as the zeids, callionymids, and atherinids, require further investigation, as each of these families was represented by only two species. ...
Fishes possess both the largest and smallest vertebrate genomes, but the evolutionary significance of this variation is unresolved. The present study provides new genome-size estimates for more than 500 species, with a focus on the cartilaginous and ray-finned fishes. These results confirm that genomes are smaller in ray-finned than in cartilaginous fishes, with the exception of polyploids, which account for much genome-size variation in both groups. Genome-size diversity in ray-finned fishes is not related to metabolic rate, but is positively correlated with egg diameter, suggesting linkages to the evolution of parental care. Freshwater and other eurybiotic fishes have larger genomes than their marine and stenobiotic counterparts. Although genome-size diversity among the fishes appears less clearly linked to any single biological correlate than in the birds, mammals, or amphibians, this study highlights several particularly variable taxa that are suitable for further study.
... Owing to the difficulty in obtaining high-quality chromosome preparations, cytogenetic data on syngnathids are scanty, referring in literature only to five Mediterranean species (two seahorses and three pipefishes), and are restricted to only a few aspects, including diploid chromosome number, karyotypic macrostructure, location of active NORs by silver staining, and genome size . With regard to NOR location, staining with silver nitrate and the fluorochrome chromomycin A 3 (CMA 3 ) has been widely applied to metaphase plates of both vertebrates and invertebrates to detect number and position of active NORs and GC-rich NORs, respectively (Sumner 1990, and references therein). ...
... Slides were mounted in an antifade solution containing propidium iodide (5 µg/ml) and viewed under a Leica (Wetzlar, Germany) I3 filter set. Slides were also processed for Ag-NOR banding and chromomycin A 3 (CMA 3 ) staining according to the methods reported by Sumner (1990). Some slides of N. ophidion were sequentially treated with (TTAGGG) n FISH and silver impregnation. ...
... HI-C mapping resulted in 28 larger scaffolds (Figure 1B), indicating the near-chromosome level of the de novo assembly. This result aligns with past karyotype estimations of other pipefish and seahorses, predicting 22 and 22-24 chromosomes,respectively[22][23][24]. The rest of the genome comprises only smaller scaffolds and contigs, which may result from the high amounts of repetitive regions, as detailed in the following section. ...
The snake pipefish, Entelurus aequoreus (Linnaeus, 1758), is a northern Atlantic fish inhabiting open seagrass environments that recently expanded its distribution range. Here, we present a highly contiguous, near chromosome-scale genome of E. aequoreus. The final assembly spans 1.6 Gbp in 7,391 scaffolds, with a scaffold N50 of 62.3 Mbp and L50 of 12. The 28 largest scaffolds (>21 Mbp) span 89.7% of the assembly length. A BUSCO completeness score of 94.1% and a mapping rate above 98% suggest a high assembly completeness. Repetitive elements cover 74.93% of the genome, one of the highest proportions identified in vertebrates. Our demographic modeling identified a peak in population size during the last interglacial period, suggesting the species might benefit from warmer water conditions. Our updated snake pipefish assembly is essential for future analyses of the morphological and molecular changes unique to the Syngnathidae.
... Our new assembly reduces the number of gaps per 100 kilobase pairs (kb) from 6,837.20 Ns per 100 kb to a mere 0.27 Ns per 100 kbp, owing to the increased contiguity.This new S. scovelli genome is on par with the current best genome in the Syngnathus genus, that of S. acus, which is a complete chromosome-scale assembly. The first 22 scaffolds of the S. scovelli genome are of chromosome-scale in line with the genetic map[1] and the karyotype data[27] with a total length of around 380 Mb(Figure 3), comparable to the estimated genome size of 380 Mb (see GigaDB[28];Table 2andFigure 3). In addition, 88.94% of the total assembly length is captured in the 22 chromosome-scale scaffolds.Gigabyte, 2023, DOI: 10.46471/gigabyte.Cladogram of the five Syngnathus species in this study. ...
The Gulf pipefish Syngnathus scovelli has emerged as an important species for studying sexual selection, development, and physiology. Comparative evolutionary genomics research involving fishes from Syngnathidae depends on having a high-quality genome assembly and annotation. However, the first S. scovelli genome assembled using short-read sequences and a smaller RNA-sequence dataset has limited contiguity and a relatively poor annotation. Here, using PacBio long-read high-fidelity sequences and a proximity ligation library, we generate an improved assembly to obtain 22 chromosome-level scaffolds. Compared to the first assembly, the gaps in the improved assembly are smaller, the N75 is larger, and our genome is ~95% BUSCO complete. Using a large body of RNA-Seq reads from different tissue types and NCBI's Eukaryotic Annotation Pipeline, we discovered 28,162 genes, of which 8,061 are non-coding genes. Our new genome assembly and annotation are tagged as a RefSeq genome by NCBI and provide enhanced resources for research work involving S. scovelli.
... This new S. scovelli genome is on par with the current best genome in the Syngnathus genus, that of S. acus, which is a complete chromosome-scale assembly. The first 22 scaffolds of the S. scovelli genome are of chromosome-scale in line with the genetic map [1] and the karyotype data [27] with a total length of around 380Mb (Figure 3), comparable to the estimated genome size of 380 Mb (see supplementary details; Supplementary Table 1 and Figure 1). In addition, 88.94% of the total assembly length is captured in the 22 chromosome-scale scaffolds. ...
The Gulf pipefish Syngnathus scovelli has emerged as an important species in the study of sexual selection, development, and physiology, among other topics. The fish family Syngnathidae, which includes pipefishes, seahorses, and seadragons, has become an increasingly attractive target for comparative research in ecological and evolutionary genomics. These endeavors depend on having a high-quality genome assembly and annotation. However, the first version of the S. scovelli genome assembly was generated by short-read sequencing and annotated using a small set of RNA-sequence data, resulting in limited contiguity and a relatively poor annotation. Here, we present an improved genome assembly and an enhanced annotation, resulting in a new official gene set for S. scovelli. By using PacBio long-read high-fidelity (Hi-Fi) sequences and a proximity ligation (Hi-C) library, we fill small gaps and join the contigs to obtain 22 chromosome-level scaffolds. Compared to the previously published genome, the gaps in our novel genome assembly are smaller, the N75 is much larger (13.3 Mb), and this new genome is around 95% BUSCO complete. The precision of the gene models in the NCBI's eukaryotic annotation pipeline was enhanced by using a large body of RNA-Seq reads from different tissue types, leading to the discovery of 28,162 genes, of which 8,061 were non-coding genes. This new genome assembly and the annotation are tagged as a RefSeq genome by NCBI and thus provide substantially enhanced genomic resources for future research involving S. scovelli.
... Syngnathids have a compact genome not much larger than that of Fugu (Vitturi et al., 1998) so it will be interesting to determine if many of filtration/resorption genes have been lost through compaction, or what large scale changes have been made to their regulation. ...
In this report we describe the embryogenesis of the bay pipefish, Syngnathus leptorhynchus, and the organogenesis of its aglomerular kidney. Early development was analyzed via a series of montages and images documenting embryos collected from the brood pouches of pregnant males. Despite differences in terminal morphology between pipefish and common teleost models such as medaka and zebrafish, the embryogenesis of these highly advanced fishes is very similar to that of other species. One of the unique features of these fishes is their utilization of an aglomerular kidney. Histological analysis revealed a single long, unbranched kidney tubule in late embryos. The development and structure of this organ was further investigated by cloning the sodium potassium ATPase alpha subunit, atp1a, from S. leptorhynchus and developing whole mount fluorescent in situ hybridization protocols for embryos of this species. Fluorescent stereoscopic and confocal visualization techniques were then used to characterize the 3D morphology of aglomerular kidneys in intact embryos. In all embryonic stages characterized, the aglomerular kidney is a single unbranched tube extending from posterior to the head to the cloaca.
... In Salmoniformes, they are among the major mechanisms of karyotype evolution (see Phillips and Ráb, 2001). In Perciformes, numerical variability derived from fusion and fission processes has been reported in numerous families, e.g., Pomacentridae (Ojima and Kashiwagi, 1981;Ojima, 1983;Molina and Galetti, 2002); Gobiidae Amores et al., 1990, Caputo et al., 1997Ene, 2003), and Carangidae (Vitturi et al., 1986), among other groups (i.e., Syngnathiformes; Vitturi et al., 1998). ...
... These results suggest that differential selection on males and females may be having a pervasive effect throughout the genome. Pipefish do not have heteromorphic sex chromosomes (Vitturi et al. 1998), and sex determination is unknown in S. scovelli. Therefore, our males-females comparison could be picking up regions of the genome that are involved in sex determination. ...
A major goal of evolutionary biology is to identify the genome-level targets of natural and sexual selection. With the advent of next-generation sequencing, whole-genome selection components analysis provides a promising avenue in the search for loci affected by selection in nature. Here, we implement a genome-wide selection components analysis in the sex-role-reversed Gulf pipefish, Syngnathus scovelli. Our approach involves a double-digest restriction-site associated DNA sequencing (ddRAD-seq) technique, applied to adult females, non-pregnant males, pregnant males and their offspring. An FST comparison of allele frequencies among these groups reveals 47 genomic regions putatively experiencing sexual selection, as well as 468 regions showing a signature of differential viability selection between males and females. A complementary likelihood ratio test identifies similar patterns in the data as the FST analysis. Sexual selection and viability selection both tend to favor the rare alleles in the population. Ultimately, we conclude that genome-wide selection components analysis can be a useful tool to complement other approaches in the effort to pinpoint genome-level targets of selection in the wild. This article is protected by copyright. All rights reserved.
... Evidence based on ancestral state reconstruction supports an ancestral chromosome number of 24 in the teleosts [26]. Though chromosome number has been shown to vary across the broad group of Syngnathidae, the 22 linkage groups that coalesced in this linkage map in S. scovelli accords well with published karyotypes for two other species in Syngnathus, S. abaster, and S. typhle [27]. Using a genome-wide synteny analysis, we investigated how this change from the ancestral chromosome number likely occurred. ...
Background
Evolutionary origins of derived morphologies ultimately stem from changes in protein structure, gene regulation, and gene content. A well-assembled, annotated reference genome is a central resource for pursuing these molecular phenomena underlying phenotypic evolution. We explored the genome of the Gulf pipefish (Syngnathus scovelli), which belongs to family Syngnathidae (pipefishes, seahorses, and seadragons). These fishes have dramatically derived bodies and a remarkable novelty among vertebrates, the male brood pouch.
Results
We produce a reference genome, condensed into chromosomes, for the Gulf pipefish. Gene losses and other changes have occurred in pipefish hox and dlx clusters and in the tbx and pitx gene families, candidate mechanisms for the evolution of syngnathid traits, including an elongated axis and the loss of ribs, pelvic fins, and teeth. We measure gene expression changes in pregnant versus non-pregnant brood pouch tissue and characterize the genomic organization of duplicated metalloprotease genes (patristacins) recruited into the function of this novel structure. Phylogenetic inference using ultraconserved sequences provides an alternative hypothesis for the relationship between orders Syngnathiformes and Scombriformes. Comparisons of chromosome structure among percomorphs show that chromosome number in a pipefish ancestor became reduced via chromosomal fusions.
Conclusions
The collected findings from this first syngnathid reference genome open a window into the genomic underpinnings of highly derived morphologies, demonstrating that de novo production of high quality and useful reference genomes is within reach of even small research groups.
Electronic supplementary material
The online version of this article (doi:10.1186/s13059-016-1126-6) contains supplementary material, which is available to authorized users.
... The one exception is the ''alligator pipefish", Syngnathoides biaculeatus, which phylogenetically falls with tail-brooding seadragons (Clade ii) despite simple male brood structures on the trunk (Fig. 3). The primary split between these two major lineages was also recovered by Wilson et al. (2003), and is further supported by evidence of a complete genome duplication in early trunk-brooders (Vitturi et al., 1998). We propose a subfamily classification that reflects this wellestablished break: (i) the subfamily Syngnathinae, the tailbrooders, based on the type genus for the family Syngnathus proposed by Linnaeus (1758), encompassing 46 of the 57 valid genera and 244 currently recognized species, and (ii) the subfamily Nerophinae, the trunk-brooders, based on the type species Nerophis ophidion, also described by Linnaeus (1758), including 11 out of the 57 valid genera and 56 species (Supplementary Table 2). ...
The family Syngnathidae is a large and diverse clade of morphologically unique bony fishes, with 57 genera and 300 described species of seahorses, pipefishes, pipehorses, and seadragons. They primarily inhabit shallow coastal waters in temperate and tropical oceans, and are characterized by a fused jaw, male brooding, and extraordinary crypsis. Phylogenetic relationships within the Syngnathidae remain poorly resolved due to lack of generic taxon sampling, few diagnostic morphological characters, and limited molecular data. The phylogenetic placement of the threatened, commercially exploited seahorses remains a topic of intense interest, with conflicting topologies based on morphology and predominantly mitochondrial genetic data. In this study, we integrate eight nuclear and mitochondrial markers and 17 morphological characters to investigate the phylogenetic structure of the family Syngnathidae at the generic level. We include 91 syngnathid species representing 48 of the 57 recognized genera, all major ocean basins, and a broad array of temperate and tropical habitats including rocky and coral reefs, sand and silt, mangroves, seagrass beds, estuaries, and rivers. Maximum likelihood and Bayesian analyses of 5160 bp from eight loci produced high congruence among alternate topologies, defining well-supported and sometimes novel clades. We present a hypothesis that confirms a deep phylogenetic split between lineages with trunk- or tail-brood pouch placement, and provides significant new insights into the morphological evolution and biogeography of this highly derived fish clade. Based on the fundamental division between lineages - the tail brooding “Urophori” and the trunk brooding “Gastrophori” - we propose a revision of Syngnathidae classification into only two subfamilies: the Nerophinae and the Syngnathinae. We find support for distinct principal clades within the trunk-brooders and tail-brooders, the latter of which include seahorses, seadragons, independent lineages of pipehorses, and clades that originated in Southern Australia and the Western Atlantic. We suggest the seahorse genus Hippocampus is of Indo-Pacific origin and its sister clade is an unexpected grouping of several morphologically disparate Indo-Pacific genera, including the Pacific pygmy pipehorses. Taxonomic revision is required for multiple genera, particularly to reflect deep evolutionary splits in nominal lineages from the Atlantic versus the Indo-Pacific.
... In Salmoniformes, they are among the major mechanisms of karyotype evolution (see Phillips and Ráb, 2001). In Perciformes, numerical variability derived from fusion and fission processes has been reported in numerous families, e.g., Pomacentridae (Ojima and Kashiwagi, 1981;Ojima, 1983;Molina and Galetti, 2002); Gobiidae Amores et al., 1990, Caputo et al., 1997Ene, 2003), and Carangidae (Vitturi et al., 1986), among other groups (i.e., Syngnathiformes; Vitturi et al., 1998). ...
... Syngnathids are among the most abundant groups in seagrass-associated fish communities of the benthic habitats (POLLARD, 1984). In terms of a community dominance index, syngnathids were the highest ranked family for both the Atlantic-Mediterranean and Indo-Pacific region in benthic habitats (HOWARD & KOEHN, 1985;VITTURI et al., 1998). The Mediterranean and Western Atlantic species migrate seasonally, moving into shallow, vegetated areas during spring and remaining there until the late fall when migration back to the deeper channel areas occurs (MERCER, 1973;DAWSON, 1982). ...
In this paper we present length–weight relationships of three pipefishes, Syngnathus acus, Syngnathus typhle Nero-phis ophidion, and two seahorse species, Hippocampus hippocampus, Hippocampus guttulatus from İzmir Bay, on the Turkish coasts of the Aegean Sea. Overall, 1010 specimens of five different species of Syngnathidae were weighed and measured. The sam-ple size ranged from 29 for H. hippocampus to 570 for S. acus. The values of the exponent b in the length–weight regressions (W=aL b) varied between 2.42 (N. ophidion) and 3.54 (S. acus). Linear regressions of length–weight relationships were significant for all species. Positive allometry in weight vs. length for S. acus, isometry in S. typhle and H. hippocampus and negative allometry for H. guttulatus and N. ophidion were observed.
... The black-striped pipefish, Syngnathus abaster is a small euryhaline species, commonly associated with vegetated habitats in the Mediterranean, Black and Caspian Seas and the Atlantic Coast up to the Bay of Biscay [15,16]. It has also become established in freshwater biomes like as the River Danube and in the Ukraine [17]. ...
A multitude of anomalies were observed in external bodies and guts of some specimens of S.abaster and were suspected to be related to parasitic infections.A focussed histological study of the fish revealed the presence of microsporidian infections in the epidermis, musculature and the intestine
... Within Percomorpha, the first interspecific valuation of multiple rDNA site systems was performed in Synbranchiformes [Carvalho et al., 2012] and in Syngnathiformes [Vitturi et al., 1998;Libertini et al., 2006]. Among Cyprinodontiformes, multiple rDNA sites have been detected only in Aphanius fasciatus [Vitturi et al., 2005] and Xiphophorus maculatus [Ocalewicz, 2004]. ...
Molecular cytogenetic data on the number and position of 45S ribosomal RNA genes (rDNA; located in nucleolus organizing regions, NORs) detected by FISH in 330 species of 77 families and 22 orders of bony fishes (Teleostei) and, additionally, 11 species of basal ray-finned fishes are compiled and analyzed. The portion of species with single rDNA sites in the sample amounts to 72%. The percentage of species with multiple NORs decreases with increasing numbers of rDNA loci per genome, i.e. scarcely 3% of species carry 4 or more rDNA-bearing chromosome pairs. 43% of all rDNA sites analyzed occur terminally on the short arms of chromosomes or constitute them. In general, terminal rDNA sites account for 87% of all examined cases. Interspecific variation in the location of single rDNA sites among related taxa, polymorphisms of multiple NORs in some groups of teleosts and analytical outcomes on the subject are reviewed. © 2013 S. Karger AG, Basel.
... stainable rRNA-protein complex synthesised only by the active NOR in the preceding interphase (Howell and Black 1980). According toSchmidt (1978: in Vitturi et al., 1998), a single pair of NORbearing chromosomes represents a primitive condition in most vertebrate species. It is difficult to make comparisons within Batrachoidid species since no reports including data on NORs for toadfish are available.Brum et al. (2001)recently attempted to describe NOR patterns on Porichthys porosissimus but they only inferred the occurrence of more than a single NOR-bearing pair based on the presence of one to three nucleoli per nucleus when the silver nitrate technique was applied. ...
For this report, we studied the conventional karyotype and the NOR-bearing chromosomes in the toadfish Halobatrachus didactylus. We found a karyotype of 46 chromosomes made up of 8 metacentric, 12 submetacentric, and 26 acrocentric elements (FN = 66). No heteromorphic sex chromosomes were observed in the species. Metacentric chromosomes were easily classified as homologous pairs according to their morphology and L/S ratio. The rest of the chromosomes could not be accurately classified as homologous pairs because differences in chromosome size and L/S ratio were too slight between adjacent pairs within a size-ranged series. A single pair of NOR-bearing chromosomes was found. Active NORs were terminally located in a submetacentric pair of chromosomes.
... Although much study has been conducted on the aquaculture (Job et al. 2002;Woods 2003aWoods , 2003bLin et al. 2007), biology (Vitturi et al. 1998), conservation (Lourie et al. 1999;Lourie and Vincent 2004), and ecology (Wong and Benzie 2003) of seahorse species, little is known of their biochemical composition. The aim of the present study was to determine the chemical and nutritional characteristics of the six major seahorse species found from the Chinese coast: a first systematic evaluation of seahorses for their medical and nutritional values. ...
The biochemical composition of six seahorse species from the Chinese coast was analyzed in this study. The crude protein content (% dry weight) of Hippocampus kuda, Hippocampus trimaculatus, Hippocampus kelloggi, Hippocampus spinosissimus, Hippocampus histrix, and Hippocampus comes was 70.70 6 2.12%, 77.59 6 1.06%, 78.31 6 1.74%, 71.15 6 1.32%, 68.07 6 1.96%, and 76.59 6 3.25%, respectively. The major amino acids (.5% of the total) in seahorses were arginine, aspartic acid, glutamic acid, alanine, and glycine, and there were significant differences in essential amino acids (EAA) (as % of total protein) among the six species (P , 0.05). The scores of EAA were balanced in the seahorse species, and the essential amino acid indexes of the six species were 41.63, 40.89, 44.84, 39.60, 39.31 and 45.45, respectively. The content of flavor-enhancing amino acids of the six seahorse species was generally high, ranging from 28.16 6 1.12% in H. histrix to 32.90 6 2.17% in H. kelloggi (P , 0.05). The total lipid content was generally low, ranging from 0.96 6 0.08% in H. histrix to 2.02 6 0.24% in H. comes. The most abundant fatty acid was C16:0, ranging from 15.04 6 0.67% in H. trimaculatus to 31.04 6 4.32% in H. spinosissimus. The combination of eicosapentaenoic acid and docosahexaenoic acid as the fraction of the total fatty acids was high (0.14-0.35). The polyunsaturated fatty acid/saturated fatty acid ratio ranged from 0.40 in H. kuda to 1.19 in H. histrix. The trace metal concentrations in the seahorses were generally low. The six seahorse species examined provide a food source for humans with low fat, high protein, good levels of EAA, and high beneficial trace elements. These results are valuable in developing diets for culturing seahorse species.
... Indeed, high degrees of isolation among species inhabiting brackish-water environments may result in a correspondently marked genetic structuring (e.g., Parenti & Tigano 1993; Maltagliati 1999; Ferrito et al. 2003 ) that may raise concerns about the conservation of populations living in fragmented habitats. The black-striped pipefish, Syngnathus abaster Risso, 1827 is a small pipefish belonging to the family Syngnathidae (Teleostea), whose range of distribution includes the Mediterranean, the Black Sea, and the Atlantic coasts northward to southern Biscay (Tortonese 1970; Dawson 1986; Vitturi et al. 1998). It is a very euryhaline species, occurring in either brackish or fresh waters (Cakic et al. 2002), associated with vegetated habitats (Vizzini & Mazzola 2004), at depths between 0.5 and 5 m. S. abaster is characterised by a short life cycle, with one or few reproductive seasons (Franzoi et al. 1993). ...
Syngnathus abaster is a euryhaline pipefish distributed in the Mediterranean, Black Sea, and the north-eastern Atlantic. Although its populations are characterised by high morphological plasticity, neither congruent information about the morphological differentiation of S. abaster populations from the Mediterranean lagoons is available, nor population genetic surveys have been so far performed. In this context, the aims of our study were as follow: i) to describe the variation at nine meristic characters of S. abaster from two western Mediterranean brackish-water areas: the Tunis north lagoon (Tunisia) and the Mauguio lagoon (France); ii) to analyse sequences of four mitochondrial DNA regions in order to evaluate the occurrence of genetic variation between the two areas, if any. The morphological survey revealed a subdivision into two distinct groups: the first included the Tunisian specimens, the second the French ones. Genetic analysis evidenced the occurrence of a sharp genetic structuring with high levels of genetic differentiation between Tunisian and French S. abaster populations. Results suggest that the evolutionary forces driven by the different biogeographical and ecological conditions of the two Mediterranean brackish-water areas have boosted the morphological and genetic divergence of the populations here analysed. The scarce potential of long-distance dispersal of S. abaster may have also enhanced the divergence retrieved.
... A euryhaline species, S. abaster can be found in the open sea, in brackish waters, as well as in fresh water (Luling, 1983;Movčan, 1988). Its typical habitats are estuaries and coasts (Movčan, 1988;Vitturi et al., 1998), although §Author to whom correspondence should be addressed. Tel.: +381 11 764422; fax: +381 11 761433; email: cakic@ibiss.bg.ac.yu early in the 20th century the species was found in the Dnieper River near Kiev, as well as the Dnieper's tributary, the Ros River (Movčan, 1988). ...
Significant differences (ANOVA) in three out of six meristic characters and in 16 out of 18 morphometric characters were found among Syngnathus abaster caught in the River Danube at sites 900 km upwards from the mouth of the Black Sea, the fresh waters of Ukraine, the Black Sea and the Azov Sea. The Danube populations showed significantly greater values for antedorsal (aD) and anteanal (aA) distances, but considerably smaller values for postdorsal (pD) distance and head length (LH) than other populations analysed (Tukey-Kramer's test). The relation of total length (LT) to standard length (Ls) for the Danube populations was Ls= 0–97. Lt, the length-mass relationship was M=4.122. LT3.63 and the mean ± S.D. of Fulton condition factor was 0.34 ± 0.08.
... Le altre hanno tutte un cariotipo costituito da 2n=24 cromosomi a centromero mediano e almeno due paia di elementi NOR. Syngnathidae (Vitturi et al., 1998; Libertini et al., 2006), una famiglia altamente specializzata tra i pesci Teleostei. ...
Cytogenetics may contribute with non conventional characters to the phylogenetic reconstruction and to identify peculiar evolutionary paths. The order Amphipoda (Crustacea) is almost cytogentically unexplored: out of 8000 described species karyological knowledge concerns chromosome number for a hundred of them and the use of the molecular cytogenetics was limited to only two species.
During the PhD course, karyological investigations have been carried out for about forty amphipod species and the following parameters were analyzed: chromosome number, karyotype morphology, distribution and composition of constitutive heterochromatin, location in the chromosomes of specific repeated genomic sequences (ribosomal genes, telomeric sequences ), and nuclear DNA amount. The contribution of present thesis to the cytogenetical knowledge on amphipods is summarized in the following table.
parameter total of known species herein studied species contribution %
Chromosome number 130 27 21
Karyotype formula 47 27 57
Nucler DNA content 41 24 59
18S rDNA 31 30 97
5S rDNA 4 4 100
Telomeric sequence 16 15 94
C-banding 9 8 89
A wide variability in chromosome number characterizes the families Aoridae, Gammaridae and Ischyroceridae, whereas such parameter is relatively constant in the families Talitridae, Niphargidae, Gammaridae and Caprellidae. Within Amphipoda the lowest chromosome numbers were found in Aoridae and Ischyroceridae.
Amphipod karyotypes are generally characterized by a high symmetry due to the preponderant presence of median centromere chromosomes. Due to their relative rarity, the possible presence of sub-telocentric and/or acrocentric chromosomes may be taken into account as a diagnostic tool for related species.
Fluorescent in situ hybridization allowed to locate on the chromosomes the major complex of ribosomal genes. This gene cluster is more frequently located in terminal position, in a single homologous pair, but there are species where NORs involve more homologous pairs.
Different degrees of polymorphism may interest the NORs, both in dimensional and numerical terms. Being the most frequent condition, a single pair of NOR bearing chromosomes is supposed as the ancestral condition for amphidods, as well as it was assumed for vertebrates and mollusks.
The attempts to locate the minor complex of ribosomal genes (5S rDNA) gave positive results only for four species.
The chromosome telomeres of all the analyzed amphipods are characterized by the repeated pentameric sequence TTAGG. This sequence is presumed as the cytogenetical plesiomorphic character for the arthropods and was derived from the hexamer TTAGGG, present in most of invertebrates and in all vertebrates.
The data on the nuclear DNA content pointed out a wide variability of such parameter at family level, and the absence of a direct correlation with chromosome number, also in species for which an increase of chromosome number by polyploidization was supposed.
The increase of Genome Size may be a pre-adaptive character in those species living under extreme conditions like, for instance, those colonizing terrestrial or semi-terrestrial environments or those distributed in the highest latitude geographical areas.
A comparative analysis of the results for some families and/or super-families was carried out. The possible role of polyploidization to justify largely different chromosome numbers was considered. In the families Ischyroceridae and Caprellidae a correlation between number of NOR elements and chromosome number was found, this fact would make reasonable an evolution by polyploidization.
Finally, on a cytogenetical base it was possible to identify a new specie of Jassa, J. cadetta, in the Venice Lagoon. This new species is morphologically close to J. marmorata, and its differentiation was also enhanced by the comparison of species-specific profiles given by RAPD-PCR.
... The same study found evidence for a ZW sex chromosome system in a more distantly related stickleback species, Apeltes quadracus (Chen and Reisman 1970). In contrast, no heteromorphic sex chromosome pairs have been reported in the outgroup family Syngnathidae (Vitturi et al. 1998;Libertini et al. 2006). The existence of different sex chromosome systems within the stickleback family, along with the availability of genetic resources and the complete genome sequence of the female threespine stickleback (Peichel et al. 2001;Kingsley et al. 2004;Kingsley and Peichel 2007) make this fish a compelling vertebrate system in which to study sex chromosome evolution. ...
To identify the processes shaping vertebrate sex chromosomes during the early stages of their evolution, it is necessary to study systems in which genetic sex determination was recently acquired. Previous cytogenetic studies suggested that threespine stickleback fish (Gasterosteus aculeatus) do not have a heteromorphic sex chromosome pair, although recent genetic studies found evidence of an XY genetic sex-determination system. Using fluorescence in situ hybridization (FISH), we report that the threespine stickleback Y chromosome is heteromorphic and has suffered both inversions and deletion. Using the FISH data, we reconstruct the rearrangements that have led to the current physical state of the threespine stickleback Y chromosome. These data demonstrate that the threespine Y is more degenerate than previously thought, suggesting that the process of sex chromosome evolution can occur rapidly following acquisition of a sex-determining region.
... Our phylogeny suggests that the primary split between these two lineages occurred at the same time or shortly before the major morphological radiation of male brooding structures and subsequent radiation of species (Wilson et al. 2001). The early diversification of the ancestral syngnathid into tail and abdominal brooders is consistent with results from a karyotypic study, which highlights a possible total-genome duplication in the abdominal-brooding lineage (Vitturi et al. 1998). Brooding structures within these two lineages independently increased in complexity, culminating in the completely enclosed brood pouches located on the tail of seahorses (Herald 1959; type A5) and the well-defined abdominal pouch of Oostethus brachyrus (type B3), the most complex abdominal pouch type. ...
Modern theory predicts that relative parental investment of the sexes in their young is a key factor responsible for sexual selection. Seahorses and pipefishes (family Syngnathidae) are extraordinary among fishes in their remarkable adaptations for paternal care and frequent occurrences of sex-role reversals (i.e., female-female competition for mates), offering exceptional opportunities to test predictions of sexual selection theory. During mating, the female transfers eggs into or onto specialized egg-brooding structures that are located on either the male's abdomen or its tail, where they are osmoregulated, aerated, and nourished by specially adapted structures. All syngnathid males exhibit this form of parental care but the brooding structures vary, ranging from the simple ventral gluing areas of some pipefishes to the completely enclosed pouches found in seahorses. We present a molecular phylogeny that indicates that the diversification of pouch types is positively correlated with the major evolutionary radiation of the group, suggesting that this extreme development and diversification of paternal care may have been an important evolutionary innovation of the Syngnathidae. Based on recent studies that show that the complexity of brooding structures reflects the degree of paternal investment in several syngnathid species, we predicted sex-role reversals to be more common among species with more complex brooding structures. In contrast to this prediction, however, both parsimony- and likelihood-based reconstructions of the evolution of sex-role reversal in pipefishes and seahorses suggest multiple shifts in sex roles in the group, independent from the degree of brood pouch development. At the same time, our data demonstrate that sex-role reversal is positively associated with polygamous mating patterns, whereas most nonreversed species mate monogamously, suggesting that selection for polygamy or monogamy in pipefishes and seahorses may strongly influence sex roles in the wild.
Unlike birds and mammals, many teleosts have homomorphic sex chromosomes and changes in the chromosome carrying the sex-determining locus, termed “turnovers”, are common. Recent turnovers allow studies of several interesting questions. One question is whether the new sex-determining regions evolve to become completely non-recombining, and if so, how and why. Another is to test the prediction that evolutionary changes that benefit one sex will accumulate in the newly sex-linked region. To study these questions, we analyzed the genome sequences of two seahorse species of the Syngnathidae, a fish group in which many species evolved a unique structure, the male brood pouch. We find that both seahorse species have XY sex chromosome systems, and their sex chromosome pairs are not homologs, implying that at least one turnover event has occurred. The Y-linked regions respectively occupy 63.9% and 95.1% of the entire chromosome of the two species, and do not exhibit extensive sequence divergence with their X-linked homologs. We find evidence for occasional recombination between the extant sex chromosomes that may account for their homomorphic pattern. We argue that these Y-linked regions did not evolve by recombination suppression after the turnover. Instead, it can be explained by the ancestral nature of low crossover rate at the corresponding chromosome location. With such an ancestral crossover landscape, a turnover can instantly create an extensive Y-linked region. Finally, we investigate the adaptive evolution of male pouch related genes after they become Y-linked in the seahorse.
This chapter provides information on Syngnathus hippocampus, whose vernacular names are caballito de mar (ES); cheval marin (FR); seahorse (GB); and cavalluccio marino (IT). All species of seahorses are considered to be endangered and are the subject of protective measures, at the international as well as national levels. These measures are essential, as the resilient capacities of these fish are weak: 1) monogamy in some species; 2) long gestation period, about one month; abnd 3) low fecundity of males per "litter". The chapter also discusses Nerophis maculate, small fish (TL < 30 cm) that are tapered and serpentine‐shaped. Like all the Syngnathidae, species of the genus Nerophis possess only one kidney, an aglomerular right kidney. Syngnathus acus Linnæus are fish whose origin of the dorsal fin is located on the trunk; pectoral, anal and caudal fins are present.
In fishes, as in other vertebrate species, the DNA component of the telomeres consists of the tandemly repeated TTAGGG motif. The length of the telomeric arrays in fishes ranges from 2 to 25 kb and shortens with age in some of the species. To date, chromosomal distribution of the telomeric DNA sequences has been examined in approximately 80 fish species of which about 42% show additional telomeric hybridization signals far from the chromosomal termini. Based on the chromosomal location, such internally located telomeric repeats may be classified into 4 categories: (1) telomeric DNA sequences located at the pericentromeric regions, (2) interstitial telomeric sites observed between centromeres and the bona fide telomeres, (3) telomeric DNA sequences that scatter along the nucleolus organizer regions, and (4) telomeric DNA repeats interspersed with the entire chromosomes. Most of the pericentromeric and interstitial telomeric sequences in fish are possible relicts of chromosome fusion events. The origin of the telomeric sequences co- localizing with the major rDNA sequences or scattered along the whole chromosomes is not clear. Internally located telomeric repeats are considered as ‘hot spots' for recombination and thus may potentially increase the rates of chromosome breaks and rearrangements leading to the various chromosomal polymorphisms in fishes. FISH with telomeric probe applied to metaphase spreads of androgenetic specimens that hatched from eggs exposed to ionizing radiation before insemination enabled the detection of small radiation-induced fragments of maternal chromosomes. Remnants of the irradiated chromosomes were found to be ring chromosomes with the interstitial telomeric signals, telomerless rings, fragments with fused sister chromatids, and linear fragments with telomeres detected at both of their ends. The increasing availability of techniques enabling the study of fish telomeres and telomerase and the easy access to numerous fish species strongly confirm that these animals are promising models in research concerning the role of telomeres and telomerase in vertebrate aging, repair of ionizing radiation-induced DNA double strand breaks, and chromosomal rearrangements.
During the last 10 years, the stickleback has emerged as a promising model system in several biological fields. In particular, it is one of the most investigated fish groups by evolutionary biologists, as a model for understanding the genetic and molecular basis in processes of adaptive radiation, microevolution and development, as well as the genetic basis of sex determination. To provide karyological information about stickleback fish we performed cytogenetic analysis of the threespine stickleback (Gasterosteus aculeatus L.) and the ninespine stickleback (Pungitius pungitius L.). Diploid chromosome number in both species equalled 42; however, the chromosome arm numbers were 62 and 70, respectively. In the threespine stickleback, multichromosomal location of silver (AgNO3) and chromomycin A3 (CMA3) positively stained Nucleolar Organizer Regions (Ag/CMA3-NORs) was observed. The number of silver-stained chromosomes varied among different individuals from two to six. The Ag/CMA3-NORs covered almost entire short arms of one pair of middle-sized submetacentric chromosome pairs in the ninespine stickleback. In one male, the only Ag-NOR was situated telomerically on the long arm of the Y chromosome. The 5S rDNA clusters were observed on short arms of one pair of subtelocentric chromosomes in the threespine stickleback and four pairs of subtelo-acrocentric chromosomes in the ninespine stickleback of both sexes. Chromosome rearrangements responsible for the stickleback karyotype polymorphisms did not leave any internally located telomeric sequences. The results obtained in two stickleback species are therefore of considerable interest and further karyological studies should be carried out on the other populations of the wide species range in order to provide a more general picture of karyoevolutive trends in Gasterosteidae.
Spinal deformities are seen in fishes. Deformities in the family Syngnathidae is rarely reported. Spine curvatures in natural population of pipefish, Syngnathus abaster are reported from the Tunis North Lake. The species is euryhaline and occurs along the Mediterranean coasts. Four hundred specimens of S. abaster were collected from January 2006 to December 2007 from the Tunis North Lake. Two specimens with skeletal abnormalities were described for the first time. X-rays radiographies revealed several vertebral deformities for each deformed specimen, especially at five curvation places of the caudal part. Several factors are believed to be the cause of spinal deformities of S. abaster in the Tunis North Lake, such as environmental disturbances, parasitism infection and nutritional factors.
Recent major developments in molecular biology have revolutionized the study of evolution, providing researchers with powerful new tools to investigate patterns and processes of evolution in nature. Insights gained from molecular population genetics and phylogenetics have played important roles in resolving major debates in evolutionary biology and, in many cases, have categorically changed the way we think about evolution. In this thesis, I present a series of three case studies, using aquatic organisms to demonstrate applications of molecular-based approaches to major questions relating to the role of sympatric speciation, sexual selection, and adaptive radiation in evolution. Detailed ecological study has revealed substantial morphological variation in lacustrine populations of the Midas cichlid, Amphilophus citrinellus, and while this research has led to hypotheses concerning the origins of this variation, the absence of molecular data has hindered rigorous testing of these hypotheses. In the first section of this thesis, I present a suite of novel microsatellite markers and use these neutral markers to investigate present-day population structuring in four Central American lake populations of A. citrinellus. These data suggest that each of the four study lakes was colonized independently and subsequent assortative mating coupled with diversification in coloration has led to divergence between populations of cichlids in at least two of these lakes. Molecular results highlight the diversifying power of sexual selection and provide evidence to support theoretical models of sympatric speciation. In the second section of my thesis, I use molecular phylogenetic techniques to investigate the evolution of male parental care in syngnathid fishes (pipefishes and seahorses). While male parental care is common amongst fishes, this pattern has been carried to its extreme in species of the family Syngnathidae, where males have developed specially-adapted broo Die neue Entwicklungen der Molekularbiologie innerhalb der letzten Zeit haben das Studium der Evolutionsbiologie revolutioniert und Forscher mit leistungsfähigen neuen Hilfsmitteln versehen, um Muster und Prozesse der Evolution in der Natur zu erforschen. Die Einblicke, die durch die molekulare Populationsgenetik und die Phylogenie gewonnen wurden, haben eine wichtige Rolle gespielt, indem sie umstrittene Fragestellungen in der Evolutionsbiologie erhellt haben. In vielen Fällen haben diese Einblicke kategorisch die Weise geändert, wie wir über Evolution denken. In miener Doktorarbeit stelle ich drei Fallstudien vor, in denen ich aquatische Organismen benutze, um die Anwendung molekularer Methoden zur Beantwortung wesentlicher Fragen bezüglich der Rolle von sympatrischer Artbildung, sexueller Selektion und adaptiver Radiation in der Evolution zu demonstrieren. Detailierte ökologische Studien haben erhebliche morphologische Veränderungen des Midas Cichlid, Amphilophus citrinellus, in Süsswassersee-Populationen aufgedeckt. Diese Untersuchungen hat zu verschiedenen Hypothesen hinsichtlich des Ursprungs dieser Variation geführt, doch das Fehlen molekularer Daten hat die rigorose Überprüfung dieser Hypothesen bisher verhindert. Im ersten Kapitel dieser Doktorarbeit stelle ich eine Reihe von neuen Microsatelliten vor und nutze diese neutralen Marker, um die heutige Populationsstruktur von A. citrinellus in vier Zentralamerikanischen Süsswasserseen zu untersuchen. Die erhaltenen Daten legen nahe, daß jeder der vier untersuchten Seen unabhängig voneinander besiedelt wurde. Weiterhin hat assortatives Paarunsverhalten, gekoppelt mit der Diversifikation in der Färbung, zu reproduktiver Isolation zwischen den Cichlid Populationen in mindestens zwei von diesen Seen geführt. Die molekularen Resultate bestätigen die aufspaltende Stärke der sexuellen Selektion und liefern einen Hinweis, um theoretische Modelle der sympatrischen Artbildung zu unterstützen. Im zw
We investigated the population structure, life cycles and gut contents of 2 species of pipefish, Syngnathus taenionotus and S. abaster, in a brackish embayment of the Po River Delta (North Adriatic Sea). These 2 species inhabit the nearshore environment of the bay where the sandy bottom is covered by macroalgae, and were sampled for 1 yr. The main differences in life history traits between S. taenionotus and S. abaster respecitvely can be summarized as follows: life span is about 24 vs 17 mo; reproductive season begins in February vs March, and lasts 5 vs 4 mo; average length of fingerlings at the time they hatch from the male brood pouch is 20.3 (+/- 1.2) vs 13.5 (+/- 1.0) mm; egg incubation period is 2 mo vs 1 mo; average number of ripe eggs per mature ovary is 46 (+/- 9) vs 104 (+/- 40); average number of embryos incubated by male is 84 (+/- 17) vs 109 (+/- 27). Finally, the sex ratio in the reproductive population is more male-biased in S. taenionotus than in S. abaster. The 2 species probably do not compete for food resources, remaining almost completely segregated in 2 different foraging micro-habitats during most of their life span. The new-born spring individuals of both species feed almost exclusively on harpacticoids of the genus Tisbe. As they mature, S. abaster continue to prey on phytal organisms while the larger S. taenionotus become zooplanktivorous.
A 1-step silver-staining technique, requiring only 2 min to perform, is described for the differential staining of nucleolus organizer regions. A protective colloidal developer is used to control the reduction of the silver.
Members of the currently recognized acanthopterygian order Pegasiformes have an unusual feeding mechanism in which enlarged maxillovomerine cartilages are closely associated with the maxillae, premaxillae and dentaries forming a highly protrusible mouth. This is a unique mechanism among living teleosts, but apparently present in the Lower Eocene Ramphosidae, currently placed among the aulostomoid gasterosteiforms. This and other evidence support a gasterosteiform ancestry for the Pegasidae. The Pegasiformes are synonymized with the Gasterosteiformes. The fossil Ramphosidae are resurrected from the synonymy of the Macrorhamphosidae and placed with the Pegasidae in a new superfamily, the Pegasoidea. The Pegasoidea are proposed as the primitive sister-group of the Solenostomidae and Syngnathidae. The Solenostomidae and Syngnathidae are included in a new superfamily, the Syngnathoidea, which together with the Pegasoidea form the primitive sister-group of the Macrorhamphosidae, Centriscidae, Aulostomidae and Fistulariidae.
In the chromosomes of 12 frog species of the suborder Diplasiocoela (Amphibia, Anura), the constitutive heterochromatin and the nucleolus organizer regions (NORs) have been specifically stained. On most of the chromosomes, aside from the centric heterochromatin, telomeric and interstitial C-bands were also found. The various C-bands display a very variable reaction to alkaline pretreatment; this indicates heterogeneity in the constitutive heterochromatin. Sex chromosomes could not be identified in any of the species studied. The number and chromosomal positions of the NORs vary quite strongly between species and between families. In 4 species of the genus Rana, there were, aside from the “standard-NORs” in chromosome pair 10, between 4 and 14 extra, small NORs detectable in the smaller chromosome pairs. As possible causal mechanism of these additional small NORs the reintegration of amplified rDNA during amphibian oogenesis is suggested. Q- or G-bands could only be recognized in mitotic prophase chromosomes. The strong spiralization of metaphase chromosomes prevents the differential demonstration of Q- or G-bands in the euchromatic regions.
For more than a century the physiological role of the Syngnathidae brood pouch has been the subject of scientific interest and debate. Some of the earliest investigators purported that the highly vascular brood pouch was physiologically adapted for the reception of fertilized eggs and for the sustenance of the embryos (i.e., a "pseudo-placenta"). Others posited that the brood pouch served as an osmoregulatory organ for the developing embryos. To determine whether the primary physiological role of the brood pouch is one of nutrition or osmoregulation, Syngnathus scovelli embryos were removed from the brood pouch at different developmental stages (4.0-13.0 mm TL), placed in sterilized, aerated, artificial seawater hyperor iso-osmotic to the blood and pouch fluid, to which no nutritive substances were added. In hyperosmotic media 25.7% of the in vitro embryos completed their normal gestation versus 18.7% in iso-osmotic media. These results appear to indicate that the male Syngnathidae brood pouch serves neither as the primary nutritional source nor as an osmotic buffer for the developing embryos after a length of 4.0 mm TL is achieved.
Diploid modal numbers of chromosomes 2n=48 forHippocampus ramulosus and 2n=44 forH. hippocampus, collected in the Gulf of Palermo in May 1985, are established. No sex-linked heteromorphic pairs are observed in the two species analyzed. The karyotype ofH. hippocampus seems to be a derived condition.
Translocations involving entire chromosomes or whole chromosome arms may not necessarily require deletion of a centromere. Conceivably, in the process of centromeric or telomeric fusion or of fusion of a centromere with a telomere, centromeric inactivation may occur, thus preserving both centromeres--one functional, the other latent--in the resultant translocation chromosome. If such latent centromeres exist and, in addition, are capable of being reactivated, it would explain how additional functional centromeres are acquired in the reverse process of chromosomal fission or fragmentation. A system of nomenclature is proposed for identifying the origin and nature of these chromosomal rearrangements.
Nuclear DNA mass in cells from a reference species can be used to obtain high-resolution estimates of DNA mass from a target species. In our study of DNA mass in cells from 45 selected species, representing each of the major vertebrate classes, we have obtained values of from 1.5 to 110.0 pg of DNA. Because values in or near this range would be expected in the study of nuclear DNA mass in vertebrates and other organisms, the species in this report can provide a useful catalogue of references for comparative studies of DNA.
The five North American species of the stickleback family Gasterosteidae were studied karyologically. They constitute two diploid-count groups; one with 46 includes Λpeltes quadracus and Culaea inconstans, and the other with 42 consists of Gasterosteus aculeatus, G. wheatlandi and Pungitius pungitius. The common occurrence of a distinctly large submetacentric pair in complements of all five species suggests a monophyletic origin of this character. The consistent presence of three additional large chromosome pairs in all members of the 2n = 42 group suggests their close relationship. Culaea probably possesses the closest karyotype to that of the progenitor of the 2n = 42 group. Apeltes is perhaps an offshoot of, and distantly related to, their common ancestor. The phylogenetic scheme constructed from the karyological data agrees with that constructed from grosmorphological and behavioral characters. The possible routes of chromosome evolution among the species and genera are discussed. Although pericentric inversions or reciprocal translocation or both might have achieved specific and generic differences, centric fusions or tandem translocations or both are required to separate the 2n = 46 group from the 2n = 42 group. Both the female Apeltes quadracus and the male Gasterosteus wheatlandi had a heteromorphic pair that was not detectable in the karyotype of the opposite sex. This may indicate a probable occurrence of cytologically expressed heterogamety in these two species.Copyright © 1970 S. Karger AG, Basel
Ordine: Acanthopterygii
- D Ancona
D'Ancona, U. (1932). Ordine: Acanthopterygii. In Fauna e Flora del Golfo di Napoli.
Le specie mediterranee del genere Syngnathus
- Ancona U.
D'Ancona, U. (1934). Le specie mediterranee del genere Syngnathus. Memorie del Regio Comitato Talassografico Italiano 210, pp. 80, II.
Cellular DNA contents of fishes determined by flow cytometry
- Ojima Y.
Ojima, Y. & Yamamoto, K. (1990). Cellular DNA contents of fishes determined by flow cytometry. La Kromosomo II 57, 1871–1888.
Preliminary examination of obtaining chromosome preparation for fish breeding
- Ueda T.
Ueda, T. (1986). Preliminary examination of obtaining chromosome preparation for fish breeding. Bulletin of the Faculty of Education Utsunomiya University 36, 81–85.
Animal Cytogenetics, 4. Chordata I. Protochordata, Cyclostomata and Pisces
- S Ohno
Ohno, S. (1974). Animal Cytogenetics, 4. Chordata I. Protochordata, Cyclostomata and Pisces. Berlin: Borntraeger.
Chromosome banding in Amphibia. II. Constitutive heterochromatin and nucleolus organizer regions in Ranidae, Microhylidae and Racophoridae
- Schmidt M.
Schmidt, M. (1978). Chromosome banding in Amphibia. II. Constitutive heterochromatin and nucleolus organizer regions in Ranidae, Microhylidae and Racophoridae. Chromosoma 68, 131–148.
Karyotypes analysis of Aphanius fasciatus (Pisces, Cyprinodontiformes) Ag-NORs and C-band polymorphism in four populations from Sicily
- R. Vitturi
- E. Catalano
- M. S. Colomba
- L. Montagnino
- L. Pellerito
Karyotypes analysis of Aphanius fasciatus (Pisces, Cyprinodontiformes) Ag‐NORs and C‐band polymorphism in four populations from Sicily
- Vitturi R.