Reproduction, development, asymmetry and late eye regression in the Brazilian cave catfish Ituglanis passensis (Siluriformes, Trichomycteridae): evidence contributing to the neutral mutation theory

The troglobitic (exclusively subterranean source population) catfish Ituglanis passensis (Siluriformes, Trichomycteridae) is endemic to the Passa Três Cave, São Domingos karst area, Rio Tocantins basin, Central Brazil. This unique population presents variably reduced eyes and melanic pigmentation. We describe reproduction early development in this species based on a spontaneous (non-induced) reproductive-event that occurred laboratory January–February, 2009, while simultaneously comparing with data from cave-habitat previous reproductive event. Egg laying was parceled. Egg-size number were within variations observed epigean congeners. Larvae behavior growth described. A single surviving specimen monitored over two years. Eye-regression started late, one year after birth, followed pattern of stasis phases intercalated slow fluctuating asymmetric rates. Late eye regression, associated asymmetry intra-population variability troglomorphic traits, as shown by several Brazilian fishes, provide support for Neutral Mutation Theory.