Ontogenetic Change in Phototactic Responses of Surface and Cave Populations of Astyanax fasciatus (Pisces: Characidae)

What is it about?

Differences among three blind cave populations and one surface population of the teleost A. fasciatus in responsiveness to light were studied under natural and experimental conditions. For all populations, scotophilia increases with length and during development; this trend was confirmed by additional experiments in which three small groups of fish were studied in an interval of 8 mo after which they showed increased scotophilia. The level of scotophilia differs among populations: the eyed surface form was the most scotophilic while the captive-bred and the Pachón populations (both totally blind and depigmented) were less scotophilic. The La Cueva Chica population, which is the result of hybridization between surface and cave populations, was intermediate in its level of phototactic responses. The phototactic responses of cave populations probably represent a behavioral relic from the ancestral surface populations rather than a behavioral adaptation to the cave environment. These results do not support the contention that scotophilia of cave populations represents an adaptation to prevent fish leaving the cave.

Featured Image

Photo by Michael Behrens on Unsplash

Photo by Michael Behrens on Unsplash

Why is it important?

Explains how behavioral responses change gradually during development.

Perspectives