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Scyliorhinus torazame; dorsal view. A, USNM 161525, female, 413 mm TL (Hakodate, Japan); B, CAS 53386, female, 345 mm TL (Chosi, Chiba Prefecture, Japan); C, NSMT 24976, female, 395 mm TL (Shizuoka, Japan, 34º43'N, 139ºE). Scale bar = 20 mm.
Source publication
The catshark genus Scyliorhinus belongs to the family Scyliorhinidae, the most diverse family of sharks, and currently presents 16 valid species according to most modern accounts. The long history of taxonomic rearrangements and inaccurate descriptions of many species have contributed to misidentification of specimens and lack of information on the...
Citations
... The first issue is related to Scyliorhinus duhamelii (Garman, 1913), which is included in the list due to records "recently collected by citizen scientists in northern Croatia". The presence of this species in the Adriatic is based solely on the report of Soares and Carvalho [11], who examined several specimens from the Adriatic Sea and concluded that this species can be distinguished from Scyliorhinus canicula (Linnaeus, 1758) by its color pattern, internasal distance, shape of anterior nasal flaps and clasper components. It has to be noted that none of the published fish checklists, including those published after Soares and Carcalho [11], has ever included this species as the Adriatic one. ...
... The presence of this species in the Adriatic is based solely on the report of Soares and Carvalho [11], who examined several specimens from the Adriatic Sea and concluded that this species can be distinguished from Scyliorhinus canicula (Linnaeus, 1758) by its color pattern, internasal distance, shape of anterior nasal flaps and clasper components. It has to be noted that none of the published fish checklists, including those published after Soares and Carcalho [11], has ever included this species as the Adriatic one. Hence, Serena et al. [12] disagreed with the opinion of Soares and Carvalho [11] and considered this species to be invalid for the Mediterranean Sea and suggested that to clarify this issue more detailed studies, including molecular taxonomy analysis, should be undertaken. ...
... It has to be noted that none of the published fish checklists, including those published after Soares and Carcalho [11], has ever included this species as the Adriatic one. Hence, Serena et al. [12] disagreed with the opinion of Soares and Carvalho [11] and considered this species to be invalid for the Mediterranean Sea and suggested that to clarify this issue more detailed studies, including molecular taxonomy analysis, should be undertaken. That being said, a study [13] that tested the population genetic structure among populations of S. canicula collected across European seas, including the Adriatic, found only S. canicula as the valid species. ...
The authors write that the last checklist for Croatia was carried out in 2009 and that 52 chondrichthyan species were reported in Croatian waters [...]
... In their commentary, Soldo and Lipej [2] stress the difficulties regarding Scyliorhinus duhamelii (Garman, 1913), which we already described in detail in our paper [1]. Scyliorhinus duhamelii was regarded as a junior synonym of Scyliorhinus canicula (Linnaeus, 1758) but was recently resurrected and proposed to be a valid species [25,26]. Despite the ongoing discussion, the fact that it was not included in previous checklists for the Adriatic Sea is no reason to exclude it from any updated checklist. ...
... Soares and Carvalho [26] described the distinct diagnostic morphological characters of Scyliorhinus duhamelii that now make it possible to distinguish the species from the closely related S. canicula in the field [25]. Future studies will require a combination of morphological analyses and genetics to determine whether the genetic regional subclusters observed by Gubili et al. [27] correspond to individuals of S. canicula or rather S. duhamelii. ...
... In their commentary, Soldo and Lipej [2] stress the difficulties regarding Scyliorhinus duhamelii (Garman, 1913), which we already described in detail in our paper [1]. Scyliorhinus duhamelii was regarded as a junior synonym of Scyliorhinus canicula (Linnaeus, 1758) but was recently resurrected and proposed to be a valid species [25,26]. Despite the ongoing discussion, the fact that it was not included in previous checklists for the Adriatic Sea is no reason to exclude it from any updated checklist. ...
... Soares and Carvalho [26] described the distinct diagnostic morphological characters of Scyliorhinus duhamelii that now make it possible to distinguish the species from the closely related S. canicula in the field [25]. Future studies will require a combination of morphological analyses and genetics to determine whether the genetic regional subclusters observed by Gubili et al. [27] correspond to individuals of S. canicula or rather S. duhamelii. ...
... Scyliorhinus duhamelii (Garman, 1913) is not listed in the IUCN Red List, probably due to the taxonomic controversy surrounding this species [12]. The validity of this species was under discussion [82], as it is morphologically very similar to S. canicula and cooccurs in the same area [102,103]. The species is now considered valid by WoRMS and Fishbase [104,105]. ...
... Over the last decades, these two species were regarded as synonyms but are now considered sister taxa [102]. The lectotype of S. duhamelii is from the Adriatic Sea, and all other specimens accordingly described are from the Mediterranean Sea, namely Croatia, Morocco and Algeria (see Soares and Carvalho 2019, Figure 45 [103]). Scyliorhinus duhamelii is differentiated from S. canicula based on: (1) the pattern of its scattered dark spots in varied sizes, which form aggregations (see Figure 1A); (2) the lateral positions of the shallow nasoral grooves and posterior nasal flaps; (3) the size of the lower labial furrow [102,103]; and (4) the dorsal fins are situated more posteriorly than in the other two catshark species [102,103]. ...
... The lectotype of S. duhamelii is from the Adriatic Sea, and all other specimens accordingly described are from the Mediterranean Sea, namely Croatia, Morocco and Algeria (see Soares and Carvalho 2019, Figure 45 [103]). Scyliorhinus duhamelii is differentiated from S. canicula based on: (1) the pattern of its scattered dark spots in varied sizes, which form aggregations (see Figure 1A); (2) the lateral positions of the shallow nasoral grooves and posterior nasal flaps; (3) the size of the lower labial furrow [102,103]; and (4) the dorsal fins are situated more posteriorly than in the other two catshark species [102,103]. Further morphological differences can be found in the intestine valve and the claspers [102,103]. ...
Almost half of all chondrichthyan species in the Mediterranean Sea are threatened with extinction, according to the IUCN Red List. Due to a substantial lack of access to data on chondrichthyan catches in the Mediterranean Sea, especially of threatened species, the implementation of conservation measures is extremely insufficient. This also concerns the Adriatic Sea. Here we present a detailed and up-to-date assessment of the species occurring in Croatian waters, as the last checklist of chondrichthyans in Croatian waters was conducted in 2009. Occurrence records from historical data, literature and citizen science information have been compiled in order to present a comprehensive list of species occurrences. We found 54 chondrichthyan species between 1822 and 2022, consisting of a single chimaera, 23 rays and skates, and 30 shark species. Here, four additional species are listed but are considered doubtful. Five species are reported here for the first time for Croatian waters that were not listed in the survey from 2009. Nearly one-third of the species reported here are critically endangered in the entire Mediterranean Sea, based on the IUCN Red List. Additionally, we revisited the Croatian records of the sandtiger shark Carcharias taurus Rafinesque, 1810 and discussed its potential confusion with the smalltooth sandtiger shark Odontaspis ferox (Risso, 1810). Our results thus provide novel insights into the historical and current distribution patterns of chondrichthyan fishes in the Croatian Sea and provide a basis for further research as well as conservation measures.
... Intraspecific variation between the Atlantic and Mediterranean has also been described for biological features of populations such as adult size, mean length for the egg deposition, first maturity age, and sexual dimorphism (Gubili et al., 2014 and references therein;, suggesting they could represent different subspecies, especially for geographically distant subpopulation as West Africa (Gubili et al., 2014 and references therein). Additional differences such as teeth morphology, and color pattern, were listed to suggest the existence of a second species in the Mediterranean Sea distinct from S. canicula, named Scyliorhinus duhameli (Garman, 1913), distributed in the Adriatic and Mediterranean seas, along the continental shelves of Croatia, Greece, Tunisia, and Algeria (Soares and Carvalho, 2019). ...
The present study, based on microsatellite markers, describes a population genetic analysis of the small-spotted catshark Scyliorhinus canicula (Linnaeus, 1758), representing one of the most abundant and commonly caught cartilaginous fishes in the Mediterranean Sea and adjacent areas. The analyses were performed to unravel the genetic features (variability, connectivity, sex-biased dispersal) of their relative geographic populations, both at the small (around the coast of Sardinia, Western Mediterranean Sea) and at a larger spatial scale (pan-Mediterranean level and between the Atlantic Ocean and the Mediterranean Sea). Individual clustering, multivariate and variance analyses rejected the hypothesis of genetic homogeneity, with significant genetic differences mainly within the Mediterranean between the Western and Eastern basins, as well as between the Mediterranean and the NE Atlantic Ocean. In detail, our results seem to confirm that the Strait of Gibraltar could not represent a complete barrier to the exchange of individuals of small-spotted catshark between the Atlantic Ocean and the Mediterranean Sea. In the latter area, a complex genetic structuring for S. canicula was found. Apart from differences among the Western, Eastern and Adriatic sites, within the Western basin the small-spotted catsharks around Sardinian waters are strongly differentiated from all others (both from the eastern Tyrrhenian Sea and southernmost part of the Algerian basin) and are demographically stable. Several possible mechanisms, both biological and abiotic (e.g., migratory behavior, waterfronts, and oceanographic discontinuities), are discussed here to explain their peculiar characteristics. Overall, the genetic data presented, both at the local and regional level, could represent a baseline information, useful for the temporal monitoring of populations, and to assess the effects of present or future fishing/management/conservation measures.
... The nursehound shark Scyliorhinus stellaris (Linnaeus, 1758) is a medium-to large-sized catshark (Carcharhiniformes: Scyliorhinidae) occurring in the north-eastern Atlantic and Mediterranean Sea, where it lives from the intertidal zone to a depth of about 400 m (Soares & de Carvalho, 2019). It is listed as vulnerable by the International Union for Conservation of Nature Red List of Threatened Species 2021 due to overfishing and subsequent decline of most of its populations (Aldebert, 1997;Ragonese et al., 2013). ...
The metazoan parasite community and the stomach contents of the nursehound shark Scyliorhinus stellaris from the Gulf of Naples (central Mediterranean Sea) were studied. The nursehound shark harboured a poor parasite community composed of a species of gill monogenean (Hexabothrium appendiculatum) and three intestinal cestode taxa (Acanthobothrium coronatum and two unidentified species of the genera Yamaguticestus and Scyphophyllidium), all represented by adult stages. Hosts were mostly parasitized by individuals of A. coronatum, which was the most abundant species and contributed to almost 80% of the total number of parasites found. Conversely, other trophically transmitted parasites (i.e., Yamaguticestus sp. and Scyphophyllidium sp.) showed low prevalence and abundance. The parasite infracommunity was poor, showing low values of species richness, total mean abundance, and diversity indices. Overall, 52 prey items belonging to 13 taxa were identified in the stomach contents. Cephalopods were the most important prey items (represented by nine taxa) and the most diverse and abundant group. In the multivariate space provided by a principal component of mixed data (PCAmix), nursehound sharks distributed along two main axes, related to individual traits (first axis) and stomach contents (including empty ones, second axis). A logistic regression based on the first two axes of the PCAmix showed a significant influence of host individual traits and, to a lesser extent, of stomach contents, regarding the probability of being infected by A. coronatum. Alongside specific traits already associated with parasites transmission, our results highlight the importance of cephalopods in transferring cestode infections through trophic web interactions in the top‐predator nursehound shark.
... In the present study, we conducted long-term daily monitoring of egg case formation for six months using portable ultrasound device in captive cloudy catsharks Scyliorhinus torazame, together with measurement of circulating levels of E2, T and P4 from blood samples taken every three days. The cloudy catshark is a small, benthic, oviparous species distributed along the continental shelves of East Asian countries including Japan (Soares and De Carvalho, 2019). This species is not commercially valuable, and is listed under Least Concern by the International Union for Conservation of Nature (IUCN) (Rigby et al., 2020). ...
The many diverse reproductive strategies of elasmobranchs (sharks, skates and rays) from lecithotrophic oviparity to matrotrophic viviparity have attracted significant research attention. However, the endocrine control of elasmobranch reproduction is less well-documented largely due to their reproductive characteristics, such as a long reproductive cycle, and/or repeated internal fertilization using stored sperm in oviparous species. In the present study, for the first time, we succeeded in non-invasive monitoring of the continuing egg-laying cycle of the cloudy catshark Scyliorhinus torazame using portable ultrasound devices. Furthermore, long-term simultaneous monitoring of the egg-laying cycle and measurement of plasma sex steroids revealed cycling patterns of estradiol-17β (E2), testosterone (T) and progesterone (P4). In particular, a decline in T followed by a reciprocal surge in plasma P4 were consistently observed prior to the appearance of the capsulated eggs, implying that P4 is likely associated with the ovulation and/or egg-case formation. While the cycling pattern of E2 was not as apparent as those of T and P4, threshold levels of E2 (> 5 ng/mL) and T (> 1 ng/mL) appeared to be crucial in the continuation of egg-laying cycle. The possibility to trace the dynamics of plasma sex steroids in a single individual throughout the reproductive cycles makes the catshark a useful model for regulatory and mechanistic studies of elasmobranch reproduction.
... However, there are only a few morphological studies on Scyliorhinus, and information on external characteristics is often missing, especially in premature stages. For adult sharks, Soares and De Carvalho (2019) investigated the 16 Scyliorhinus species of the family Scyliorhinidae [10]. In this study, the external morphological characteristics, neurocranium, claspers, dermal denticles, and tooth morphology for classifying the phylogenetic differences between the species were investigated. ...
... In this study, the external morphological characteristics, neurocranium, claspers, dermal denticles, and tooth morphology for classifying the phylogenetic differences between the species were investigated. They indicated that, in particular, the small-spotted catshark (S. canicula) can be distinguished easily from its congeners due to the unique characteristics in its naso-oral region [10]. ...
... This classification is used as the standard for the age-betting of S. canicula. The present study aims to follow up on the studies by Ballard et al. (1993) [14] and Soares and De Carvalho (2019) [10] to provide further insights into the morphological changes during development to understand the evolutionary changes of the Scyliorhinus in more detail, as ontogenetic changes in the external morphology provide valuable information for evolutionary questions. Additionally, the relationships between growth and morphological changes are relevant because they have an impact on the phenotypic diversity within species [15]. ...
The small-spotted catshark, Scyliorhinus canicula, provides an optimal model organism to include chondrichthyans in studies comparing morphology or physiology through vertebrate evolution. In particular, for investigations with ontogenetic aspects, there are only a limited number of alternative taxa. Therefore, a detailed staging system is a prerequisite to allowing comparison between different studies. This study supplements information on the latest stages of the established system by Ballard and colleagues in 1993 and complements the respective staging system by including the latest pre-hatching stages. During this phase, some significant ontogenetic shifts happen, e.g., reduction of external gill filament length and complete flattening of rostral angle until Size Class 6, change in the ratio of pre- to post-vent length, and establishment of body pigmentation in Size Classes 7 and 8. All these shifts finally transform the embryo into a hatchling prepared for living outside the eggshell. This study provides a framework allowing comparison of investigations on pre-hatchings of the small-spotted catshark.
... The specimens in our sample are strikingly similar to the teeth of various Scyliorhinus species illustrated by Soares and de Carvalho (2019), and we therefore assign the Oligocene specimens to this genus. The teeth of the 11 species of extant Scyliorhinus shown by Soares and de Carvalho (2019) exhibit a wide range of morphologies that reflect both interspecific (among species) and intraspecific (monognathic, dignathic, gynandric heterodonty within species) variation. ...
... With respect to dignathic heterodonty, crown ornamentation is usually more extensive on upper teeth when compared to lowers, and lateral cusplets of upper teeth are generally taller but narrower than those of lower teeth. Development of gynandric heterodonty has not been evaluated for all Scyliorhinus species, but for those species where it has been documented, female teeth are often more coarsely ornamented, the main cusps are lower but broader, and the cusplets are better developed compared to male teeth of the species (Herman et al. 1990, Soares andde Carvalho 2019). ...
Matrix surrounding a dermochelyid carapace and two cetacean skulls recovered from the Givhans Ferry Member of the Ashley Formation (lower Oligocene, Rupelian Stage) in South Carolina, USA yielded a surprisingly diverse assemblage of euselachian and teleost fishes. We identified 21 elasmobranch taxa, including 13 selachians and eight batoids, nearly all of which are known to occur in the overlying upper Oligocene (Chattian) Chandler Bridge Formation. Notable occurrences within the Ashley Formation paleofauna include a new shark, Scyliorhinus weemsi n. sp., and the first South Carolina Oligocene records of Squalus sp., Pristiophorus sp., and Pachyscyllium sp. Numerous teleost taxa were also documented based on isolated teeth, including species of Albulidae, Paralichthyidae, Osteoglossidae, Sparidae, Sciaenidae, Sphyraenidae, Scombridae, Trichiuridae, and possibly Labridae.
... However, the use of subspecies in some taxa is not preferable due to confusion with the population term [57,58], and has been rarely used in the past few decades for marine fishes [59]. For elasmobranchs, this term has only been applied to few taxa, e.g. in catsharks [60][61][62][63], dogfishes [64], smooth-hounded sharks [65], hammerheads [66], eagle rays [67], and skates [68]. Some of those subspecies remain valid such as the smooth-hounded shark (Mustelus canis canis and M. c. insularis) and for several species of skates (from Genus Raja and Leucoraja), while others were considered junior synonyms or have been elevated into distinct species [69]. ...
Background
Delimiting cryptic species in elasmobranchs is a major challenge in modern taxonomy due the lack of available phenotypic features. Employing stand-alone genetics in splitting a cryptic species may prove problematic for further studies and for implementing conservation management. In this study, we examined mitochondrial DNA and genome-wide nuclear single nucleotide polymorphisms (SNPs) in the brown-banded bambooshark, Chiloscyllium punctatum to evaluate potential cryptic species and the species-population boundary in the group.
Results
Both mtDNA and SNP analyses showed potential delimitation within C. punctatum from the Indo-Australian region and consisted of four operational taxonomic units (OTUs), i.e. those from Indo-Malay region, the west coast of Sumatra, Lesser Sunda region, and the Australian region. Each OTU can be interpreted differently depending on available supporting information, either based on biological, ecological or geographical data. We found that SNP data provided more robust results than mtDNA data in determining the boundary between population and cryptic species.
Conclusion
To split a cryptic species complex and erect new species based purely on the results of genetic analyses is not recommended. The designation of new species needs supportive diagnostic morphological characters that allow for species recognition, as an inability to recognise individuals in the field creates difficulties for future research, management for conservation and fisheries purposes. Moreover, we recommend that future studies use a comprehensive sampling regime that encompasses the full range of a species complex. This approach would increase the likelihood of identification of operational taxonomic units rather than resulting in an incorrect designation of new species.
