P3.149 Friday, Jan. 6 Unique mechanosensory adaptation to extreme environments in cavefish. HASPEL, G*; SCHWARTZ, A; SOARES, D; NINDS; Univ of Maryland College Park; Univ of Maryland College Park firstname.lastname@example.org
Extant cavefishes can be viewed as replicate experiments in adaptation to an extreme environment. Various surface dwelling fishes have independently invaded caves throughout evolutionary time. Thus, the existence of independently derived cave forms provides a unique opportunity to examine parallel evolution and convergence because cavefish species belong to a diverse palette of families. All cavefish ancestors had to outmaneuver and adapt to the harsh constraints imposed by the extreme environment of caves and their perpetual darkness. As a result a suite of specific troglobitic phenotypes have independently emerged. Here we studied the cavefish Astroblepid pholeter which is endemic to a single cave on Ecuador (Jumandy 77°47'33"W 0°52'30"S). Our results show that this fish species is of special interest because it appears to be the first teleost to have no neuromasts. We were not able to detect the presence of neuromasts using neither DASPEI, nor scanning electron micrography, nor serial thin sectioning of the skin. Instead, we found that A. pholeter dorsal skin is covered with novel putative sensory organs that are unique in morphology, respond electorphysiologically to mechanosensory stimuli and influence rheotaxic behavior.