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Cynolebias elegans sp. n., live holotype, UFRJ 9431, male, 36.1 mm SL. Photograph by W.J.E.M. Costa.
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Two new species of Cynolebias are described from temporary pools of the Verde Grande River drainage, São Francisco basin, in the semiarid Caatinga, a phytogeographical province of northeastern Brazil. Cynolebias elegans sp. n., a member of the C. gilbertoi group, is considered as the smallest species of the genus, reaching about 38 mm of standard l...
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A high concentration of endemic species of seasonal killifishes has been recorded for a small area encompassing the highland plateaus associated with the upper section of the Carnaúba de Dentro River drainage and adjacent drainages of the middle section of the São Francisco River basin, northeastern Brazil. The present study is primarily directed t...
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... pointed in Austrofundulus and Llanolebias, and pointed and frequently with long filaments in Cynolebias) (Costa 2001(Costa , 2014b(Costa , 2017aHrbek et al. 2005, Hrbek and Taphorn 2008 Synapomorphies: The genus group Austrolebias was recovered as monophyletic and supported by eight molecular characters and the following 17 morphological characters (see Supporting Information, Appendix S5): dark grey suborbital bar (character:state 25:1); dark grey dashed bars or spots on flank in females (45:2); deep blue iridescent coloration of the opercular region (28:1); absence of filaments projecting distally on dorsal fin of males (48:0); posterodistal edge of anal fin rounded in males (49:1); absence of scales on the basal portion of the anal fin in males (52:0); 10-13 pectoral fin rays (64:0); anterior nostrils pointing dorsolaterally (72:1); frontal squamation pattern F or other (76:3); absence of scales in suborbital region (77:0); close proximity of the urogenital papillae to the anal fin in males (82:1); bone support of contact organs in the pectoral fins of males absent (89:0); extension of the ventral process of the angulo-articular short, retro-articular projecting slightly below the ventral process of the angulo-articular (123:2); dorsal process of angulo-articular medium sized (127:1); cartilage proportion of basihyal 45-70% (133:1); urohyal shape high (135:1); length of extension of broad dorsal portion of cleithrum, relative to vertical distance between dorsal margin of scapula and ventral margin of coracoid, about twice as high (184:2). Diagnosis: This genus can be distinguished from all other genera of the Austrolebias genus group by presenting iridescent spots on the medial distal portion of the pectoral fin and by the following unique combination of characters: (1) a gap between preopercular and mandibular series of neuromasts; (2) a wide dark grey to black border on most scales on the ventral half portion of the flank, above the anal fin, in mature dominant males (not considering bands); (3) fused iridescent marks on the distal portion of the dorsal fin; (4) black blotch on the most anterior region of the dorsal fin; (5) absence of dark grey to black spots on flanks in males; and (6) dorsal radial of pectoral fin absent (Fig. 3). ...
Killifishes (Cyprinodontiformes) are a group of fish that include a high proportion of small-bodied species living in seasonal aquatic habitats, with narrow geographical distributions and high human impact. They are among the most vulnerable vertebrates in the Neotropical region, with nearly half of the species in threat categories. Herein, we propose a new phylogenetic hypothesis of the Rivulidae genus Austrolebias, based on 10 genes (six nuclear and four mitochondrial) and 191 morphological characters, including 90% of the total valid species of this genus. An updated definition and diagnosis of the existing subgenera of Austrolebias is provided, and these are erected to genera. Also, four new genera are erected to accommodate the taxonomy of the group to the current phylogenetic hypothesis. Additionally, we describe Argolebias guarani sp. nov., from a seasonal pond in the Middle Paraná River basin, which is diagnosed by a unique colour pattern. This addition reinforces this area as a biodiversity hotspot of endemicity and highlights the importance of this region for conservation. Data on the ontogenetic changes in colour pattern, chorion ornamentation of the egg and ecology of this species are also provided.
... These species live in seasonal ponds filled by rain that dry in a part of the year, when the eggs deposited on the substrate survive due to developmental and metabolic diapauses (Murphy and Collier 1997;Berois et al. 2016). In the semiarid Caatinga, composed of four freshwater ecoregions, the genera Cynolebias Steindachner, 1876 and Hypsolebias Costa, 2006 are represented by 20 and 35 valid species, respectively, with highest richness in the São Francisco ecoregion Costa 2017;Costa et al. 2018a, b, c). ...
The Rivulidae fish family, which includes Neotropical seasonal killifishes, is one of the most diverse taxonomic groups in the aquatic systems of Caatinga in Brazil. Cynolebias and Hypsolebias genera, with 20 and 35 endemic species, respectively, concentrate the greatest diversity of rivulid species in the semiarid. Sixty-eight years after the first records of annual killifishes in the Mid-Northeastern Caatinga ecoregion (MNCE), only four valid species have been sampled in this area. Here we combined bibliographic surveys and recent samplings to investigate the distribution of seasonal rivulids in MNCE. Twenty-one records were obtained, nine of which are new localities, expanding the distribution of three species: Hypsolebias martinsi, H. antenori and Cynolebias microphthalmus. Neotropical Biology and Conservation 15(3): 301-315 (2020)
... These studies have identified distinct cryptic species inhabiting the same drainage of the São Francisco River basin, showing that most seasonal killifish species exhibit a very restricted distribution range (Costa et al. 2012(Costa et al. , 2018a. However, while field studies have been conducted to estimate killifish species diversity in the region, drastic anthropic modifications in seasonal killifish habitats of some Caatinga areas have caused extinction of several populations (Costa 2002(Costa , 2017Costa et al. 2012Costa et al. , 2018a). ...
... An uncommonly high concentration of endemic species of seasonal killifishes has been recorded for a small area encompassing the highland plateaus associated with the upper sections of the Carnaúba de Dentro and the Verde Pequeno river drainages, in the middle section of the São Francisco River basin (Costa and Brasil 1993;Costa et al. 1996;Costa and Nielsen 2004;Costa 2006aCosta , 2014Costa , 2017. This area is characterised by a series of plains located at slightly different altitudes, between 500 and 630 m above sea level (asl), separated from each other by an undulating relief and drained by temporary rivers and streams. ...
A high concentration of endemic species of seasonal killifishes has been recorded for a small area encompassing the highland plateaus associated with the upper section of the Carnaúba de Dentro River drainage and adjacent drainages of the middle section of the São Francisco River basin, northeastern Brazil. The present study is primarily directed to the taxonomy of the H.fulminantis species complex in this region, and describes habitat decline and extirpation of natural killifish populations recorded in field studies between 1993 and 2017. Both morphological characters and molecular species delimitation methods using single-locus models (GMYC and bPTP) support recognition of two closely related endemic species, H.fulminantis and H.splendissimus Costa, sp. n. The new species is distinguished from other congeners of the H.fulminantis complex by having a red pectoral fin in males, well-developed filamentous rays on the tips of the dorsal and anal fins in adult males, and the second proximal radial of the dorsal fin between the neural spines of the 8 th and 9 th vertebrae in males. Most recent field inventories indicated possible local extinction of populations of H.fulminantis and H.splendissimus in the studied area, but additional field studies should be made in other parts of the upper Carnaíba de Dentro River basin to evaluate the current conservation status of these species.
... Seasonal killifishes live in temporary pools formed at rainy seasons, where they complete their entire life cycle, surviving as resistant eggs during dry periods (Wourms 1972;Costa 1995). In the Caatinga, pools disappear during a long dry season, frequently between May and October in most of the southern and central part of the Caatinga, which concentrates the great diversity of seasonal killifish species, but a short dry period may also occur between January end and February, with most pools drying again (Costa 2017). ...
... With the discovery of H. picturatus and more frequent field studies between 1999 and 2005, the distribution of the complex was amplified to include records about 420 km N from the type locality of H. magnificus (Costa, 2007). During field studies between 2005 and 2010, a strong decline of natural habitats was progressively recorded, resulting in extinction of several populations of seasonal killifishes (Costa et al. 2012;Costa 2017). During this same period, a third species, H. harmonicus, was recognised and described (Costa 2010). ...
... The first one, sharing a similar colour pattern with H. harmonicus, was collected in 2010 only about 40 km from the type locality of this species. The second one was tentatively identified as H. magnificus (Costa, 2017), but collected about 120 km from its type locality, at the upper Rio Gorotuba floodplains in 2017. However, fish from both populations exhibited a few distinct morphological characters suggesting that they are cryptic species (sense Bickford et al. 2006). ...
A great diversity of animal species adapted to life in the semi-arid Caatinga of northeastern Brazil, including seasonal killifishes, has been reported in the last three decades. More recently, field and molecular data have shown a high occurrence of cryptic species. The killifish group herein analysed, the Hypsolebiasmagnificus species complex, is endemic to the middle and southern portion of the Caatinga, occupying about 120 km along the floodplains of the middle São Francisco River and some adjacent tributaries. Species of this complex are rare and presently considered threatened with extinction, being uniquely found in pools protected by trees and bushes. Single-locus delimitation methods were used to test species limits of populations displaying different colour patterns along the whole distribution of the complex. All analyses consistently supported the three nominal species and two new, herein described: H.gardneri Costa, sp. n. , from the floodplains of the middle São Francisco River and H.hamadryades Costa, sp. n. , from the Gorotuba River floodplains. The phylogenetic analysis highly supports H.hamadryades as sister to a clade comprising H.gardneri and H.harmonicus . Our field observations suggest that H.hamadryades is a miniature species. This study indicates that the H.magnificus complex comprises cryptic species apparently endemic to small areas and extremely vulnerable to environmental changes, deserving high concern.
... For the HAG analysis, we used 14 of the 15 species considered valid, and for the CAC analysis, we used 15 of the 18 species considered valid (species names, their respective collecting locality coordinates and GenBank accession numbers are listed in S1 Table); the only valid species not sampled were Hypsolebias macaubensis ( Costa, 2006) and Cynolebias microphthalmus Costa, 1995, not found during recent field studies, in addition to two recently described but possibly extinct species, C. elegans Costa, 2017 and C. gorutuba Costa, 2017 [26]. In both analyses, outgroup species were closely related members of the tribe Cynolebiini [18] (see S1 Table). ...
The Caatinga is the largest nucleus of seasonally dry tropical forests in South America, but little is known about the evolutionary history and biogeography of endemic organisms. Evolutionary diversification and distribution of terrestrial vertebrates endemic to the Caatinga have been explained by palaeogeographical Neogene episodes, mostly related to changes in the course of the São Francisco River, the largest river in the region. Our objective is to estimate the timing of divergence of two endemic groups of short-lived seasonal killifishes inhabiting all ecoregions of the Caatinga, testing the occurrence of synchronic events of spatial diversification in light of available data on regional palaeogeography. We performed independent time-calibrated phylogenetic molecular analyses for two clades of sympatric and geographically widespread seasonal killifishes endemic to the Caatinga, the Hypsolebias antenori group and the Cynolebias alpha-clade. Our results consistently indicate that species diversification took place synchronically in both groups, as well as it is contemporary to diversification of other organisms adapted to life in the semi-arid Caatinga, including lizards and small mammals. Both groups originated during the Miocene, but species diversification started between the Late Miocene and Early Pliocene, when global cooling probably favoured the expansion of semi-arid areas. Synchronic diversification patterns found are chronologically related to Tertiary palaeogeographical reorganizations associated to continental drift and to Quaternary climatic changes, corroborating the recent proposal that South American biodiversity has been continuously shaped between the Late Paleogene and Pleistocene.
... For vertebral counts, the caudal compound centrum was counted as a single element. Osteological features included in the description are those considered phylogenetically informative by recent studies on Cynolebias (Costa 2001(Costa , 2014(Costa , 2017Costa et al. 2010). Institutional abbreviations follow Sabaj (2016), with addition of UNITAU (Universidade de Taubaté). ...
... The middle Rio São Francisco basin lies within the Caatinga domain, an area with a relatively high rate of biodiversity, with high level of speciation for rivulids, but with a consequently limited distribution of each species. The accelerated pace of environmental degradation, due to the disorderly occupation of the area by human activities, poses a great risk of extinction for rivulid species occurring at the Caatinga domain (Costa 2017). ...
... Cynolebias akroa is not the most abundant species of annual fish at its habitat, being outnumbered by Hypsolebias faouri, with a population ratio of 5: 1 in relation to H. faouri, which may indicate that C. akroa preys on H. faouri, as reported for other syntopic associations among annual rivulids (e.g., Wildekamp 1995). The morphological characteristics of the teeth, typical of piscivorous fishes, common to all Cynolebias species and shared with other annual fishes from both South America and Africa, as Austrolebias elongatus and Nothobranchius ocellatus, which are reported to prey on smaller sympatric congeners (Costa 2006(Costa , 2009(Costa , 2011(Costa , 2017, also points to this possible relation of predator-prey between Cynolebias akroa and Hypsolebias faouri. ...
