Abstract
The subterranean environment is often described as “extreme” and food poor. Laboratory experiments have shown that blind Mexican tetra Astyanax mexicanus (De Filippi, 1853) cavefish are better at finding food in the dark than surface fish. Several morphological and behavioural attributes that could foster this obvious adaptive response to cave environments have been described. Nonetheless, it is currently unknown what young cavefish actually eat in their natural cave environment. Our results from the Pachon cave in Mexico during the dry and rainy season show that fry are efficient predators in their natural cave environment. Their primary food item is aquatic crustaceans. The guts of post-larval, pre-juvenile stage individuals (n=9) contained an average of 17.9 water fleas (Cladocera), copepods, ostracods, and isopods. Thus, the fry in this cave are well-fed. The Pachon cave environment does not appear to be “food poor” for juvenile cavefish. Food regimes change between post-larval and adult stages to become more dependent on partially decomposed material, guano, or detritus from the mud. We discuss the data with regards to our current developmental and genetic understanding of cavefish morphological and behavioural evolution, particularly regarding its enhanced Vibration Attraction Behaviour (VAB).
Highlights
The blind Mexican tetra Astyanax mexicanus (De Filippi, 1853) has become a wellestablished model system in evolutionary developmental biology (EvoDevo)
Our results show that arthropods are the main source of nourishment for 1-2 cm long Astyanax fry in Pachón cave, with 89.8% of their stomach contents being readily identifiable arthropods
It is likely that during this stage, for the Pachón cave population and perhaps other cave populations, arthropods constitute most of their nourishment through active predation
Summary
The blind Mexican tetra Astyanax mexicanus (De Filippi, 1853) has become a wellestablished model system in evolutionary developmental biology (EvoDevo). This species has been the main contributor in the understanding of the genetic and developmental controls of troglomorphic features. There are over 30 known caves harbouring Astyanax cavefish populations in México (Mitchell et al 1977; Espinasa et al 2001). Their conspecific surface-dwelling morph lives in nearby surface streams throughout most of México. The eyed and pigmented surface morph and the eyeless, depigmented cave morph are inter-fertile, making the species well-suited for experimental manipulations (Jeffery 2012; Elipot et al 2014)
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