Notes on Stygichthys typhlops (Characiformes; Characidae): characterization of their teeth and discussion about their diet

Francisco Alexandre, C Sampaio, Paulo Santos Pompeu, Rodrigo Ferreira
2012 Speleobiology Notes   unpublished
The Brazilian Blind Characid, Stygichthys typhlops Brittan & Böhlke, 1965 is an eyeless, depigmented stygobiont endemic to southeastern Brazil. Its distribution is restricted to phreatic waters in the Rio São Francisco basin 1 in a small area of northern Minas Gerais (Jaíba municipality). Stygichthys typhlops is one of two stygobiotic characids described. It lacks circumorbital bones, which suggests a more advanced stage of specialization to the subterranean environment than the other characin,
more » ... the Mexican Blind Cave Fish, Astyanax mexicanus, which retains a fragment of these bones. Loss or reduction of circumorbital bones is strongly associated with the loss of eyes among cavefish 2. S. typhlops is under extreme risk of extinction due to its highly restricted distribution and the marked lowering of the water table 3 of its habitat due to water diversion for irrigation. Little is known about life history of S. typhlops, particularly its diet. In this study we collected data in the laboratory and in the field about the diet and feeding behavior of S. typhlops, and present a description of their dentition based on scanning electron microphotographs (SEM). Ten S. typhlops specimens (mean = 34.4 mm, S.E. = 0.84 mm, range 18.8-47.9 mm total length) were collected in May 2008 using a handheld dip net from a natural well, which was modified for water diversion. Such wells, locally called "cacimbas", are found in areas where the water table is close to the surface and are used by local residents as a water source. The fish were transported to the laboratory in plastic bowls (volume of 26.6 L) and kept together in one 72 L aquarium at 19-20°C in the dark. Samples of macrophytes found at the sampling locality were collected together with the fish and kept in the same aquarium. They were fed 50 grams of a dry flocculated feed (Alcon Basic) twice daily. After about 5 months, all fish had died, and the specimens were fixed in 10% formalin and placed in the ichthyological collections of the Museu de Zoologia da Universidade de São Paulo (MZUSP 108165) and Coleção Ictiológica da Universidade Federal de Lavras (CI-UFLA 0090).