New species of Scleromystax Günther, 1864 (Siluriformes: Callichthyidae) - extending the meridional distribution of genera endemic to the Atlantic Forest

Marcelo R Britto,Luiz R Malabarba,Clayton K Fukakusa

doi:10.1590/1982-0224-20150158

Abstract

ABSTRACT The genus Scleromystax includes species occurring in several coastal river basins from southern Bahia to southern Santa Catarina States. Examination of Scleromystax specimens sampled from the laguna dos Patos drainage revealed a new taxon, further extending the distribution of the genus to the southern border of the Atlantic forest. The new species differs from its congeners by the second infraorbital ventrally expanded. It is also distinct, except from S. macropterus and S. salmacis , by roughly oblique, elongate, dark brown blotches along body; large specimens displaying cranial fontanel completely occluded, leaving just a shallow fossae; and sexually dimorphic features inconspicuous, i.e. preopercular (cheek) region similar in males and females, and dorsal and pectoral fins of males slightly longer than in females. Herein, we also extend the record of Scleromystax salmacis to the rio Tramandaí drainage.

Highlights

The fish fauna from the coastal river drainages in Brazil shows a high endemism (Vari, 1988; Weitzman et al, 1988; Bizerril, 1994; Buckup, 2011), in species composition, and observable at the level of genera
The discovery of Scleromystax reisi is recent, but the species is relatively rare in fish collections, it has been successfully collected in different occasions in at least one locality (EEA-UFRGS: 1 Apr 2008, UFRGS 16590; 25 Apr 2011, UFRGS 14965; 6 May 2011, UFRGS 14964, UFRGS 14968; 6 Oct 2012, UFRGS 17416; 23 Jan 2013, UFRGS 17414; 20 Sep 2013, UFRGS 19189, UFRGS 19188; 1 Nov 2013, UFRGS 18254; 30 Nov 2013, UFRGS 19191)
That species was described from the rio Mampituba and rio Araranguá, in Santa Catarina State (Britto & Reis, 2005) based on a few lots. These two rivers form, along with the rio Tramandaí drainage, an area of endemism in southern Brazil, sharing a number of endemic fish species (Malabarba & Isaia, 1992; Reis & Schaefer, 1998; Hirschmann et al, 2015), and historically united in a single palaeodrainage in the area exposed with the retreat in sea level during the Last Glacial Maximum (Thomaz et al, 2015)

Summary

Introduction

The fish fauna from the coastal river drainages in Brazil shows a high endemism (Vari, 1988; Weitzman et al, 1988; Bizerril, 1994; Buckup, 2011), in species composition, and observable at the level of genera. Only the genus Deuterodon was known to occur in the southern limit of the Atlantic Forest in the rio Maquiné, rio Tramandaí drainage (Gomes, 1947), but in the last few years the three other genera have had their southern distributional limits extended farther south through the description of recently discovered populations of new species. These records includes the description of a new species of Scleromystax from the rio Mampituba drainage (Britto & Reis, 2005), a new Hollandichthys from the rio Maquiné, rio Tramandaí drainage (Bertaco & Malabarba, 2013), and a new Listrura from the laguna dos Patos drainage (Villa-Verde et al, 2013). We extend the record of Scleromystax salmacis Britto & Reis to the rio Tramandaí drainage and describe a new species of Scleromystax from the laguna dos Patos drainage, further extending the distribution of the genus to the southern border of the Atlantic forest

Methods

Results

Conclusion