Response of Three Species of Darters of the Genus Etheostoma to Chemical Alarm Signals From Conspecifics and Congeners
Prior to this study, seven species of darters (Pisces: Percidae) have been identified as having a chemical alarm substance, but it is not known how widespread the chemical alarm substance is within the family Percidae. It has been hypothesized that percid alarm substance is contained in epidermal sacciform cells, and is released only after mechanical damage to the skin. Behavioral bioassays were performed on fantail darters (E. flabellare), rainbow darters (E. caeruleum), and redfin darters (E. whipplei). Redfin darters reacted with a fright response upon exposure to skin extracts from conspecifics and rainbow darters. Rainbow darters responded to skin extracts from redfin darters. Neither rainbow darters nor redfin darters had a significant response to fantail darter skin extract. Fantail darters did not respond to skin extracts from either of the congeneric extract. Fantail darters did not respond to skin extracts from either of the congeneric species or to conspecific skin extract. A histological examination of epidermal tissue demonstrated that sacciform cells were present in all three species. These results suggest that the chemical alarm system is not homologous throughout the family Percidae.
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