Description of two endangered new seasonal killifish species of the genus Cynolebias from the São Francisco River basin, Brazilian Caatinga (Cyprinodontiformes, Aplocheilidae)

Abstract

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 length; it is distinguished from all other species of the group by the long unpaired fins, relative position of anal fin and vertebrae, and morphometric data. Cynolebias gorutuba sp. n. belongs to the Cynolebias zeta-clade, a group of large species supposedly feeding on smaller sympatric seasonal killifishes; it differs from other species of the group by the female colour pattern, relative position of dorsal fin and vertebrae, and cephalic neuromast pattern. Both species herein described were not found in recent collecting trips, after their habitats had been drastically modified, and are also possibly highly endangered if not already extinct. Field data relative to gradual habitat decline in the type locality region of C. elegans indicate that after pools lose the dense vegetation that provides shelter to small species, these species such as C. elegans become exposed to larger sympatric predatory species and are extirpated. These data support the hypothesis that small seasonal killifish species specialised in living within marginal shaded areas of temporary pools are more susceptible to environmental changes than other congeners.

Cryptic species diversity in the Hypsolebias magnificus complex, a clade of endangered seasonal killifishes from the São Francisco River basin, Brazilian Caatinga (Cyprinodontiformes, Aplocheilidae)

“…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 ).…”

Fish fauna of the Pandeiros River, a region of environmental protection for fish species in Minas Gerais state, Brazil

“…Currently, only three species of this genus have been described: Planaltina myersi from the Corumbá River (a tributary of the Paranaíba River), and Planaltina glandipedis and Planaltina britskii from tributaries of the Grande and Tietê rivers, all tributaries of the Upper Paraná River (Menezes et al 2003). Based on a bibliographic review undertaken for this study, and including Planaltina sp., the number of known freshwater fish species in the basin is 233 (Britski et al 1986;Weitzman 1999, 2000;Alves and Pompeu 2001;Lütken 2001;Reis et al 2003;Pompeu and Godinho 2003;Costa 2005Costa , 2006Costa , 2013Costa , 2014Silva et al 2006;Costa and Brasil 2006 Of the sixteen species collected upstream of the three waterfalls, Myleus altipinnis, Characidium aff. zebra, Hoplias intermedius, Pimelodella cf.…”

Synchronic historical patterns of species diversification in seasonal aplocheiloid killifishes of the semi-arid Brazilian Caatinga

“…elegans Costa, 2017 and C . gorutuba Costa, 2017 [ 26 ]. In both analyses, out-group species were closely related members of the tribe Cynolebiini [ 18 ] (see S1 Table ).…”