Opportunistic exploitation of turtle eggs by Tripanurga importuna (Walker) (Diptera: Sarcophagidae)

Abstract

Tripanurga importuna (Walker, 1849) is a sarcophagid fly whose larvae often occur in nests of freshwater turtles. We investigated this sarcophagid fly to determine whether it is an opportunistic scavenger or a potential predator of eggs, embryos, and hatchlings of the spiny softshell turtle ( Apalone spinifera (Lesueur, 1827)). Fly infestation of spiny softshell turtle nests can occur at any time between oviposition and hatching, but estimates based on larval size and development time, along with observations of adult fly activity, suggest that female sarcophagids deposit larvae over the nest primarily during hatching. Observed temperature variance within the turtle clutch mass and physiological and developmental differences among eggs may result in asynchronous hatching, and chemical cues associated with early hatching may attract adult flies. Egg position within the nest affects embryo hatching success independently of fly infestation while also affecting fly infestation. Tripanurga importuna is a habitat specialist able to find and develop in carrion buried in sand, but it is a food opportunist able to develop on other buried carrion as well as turtle eggs. Tripanurga importuna maggots in turtle nests preferentially scavenge necrotic tissue, including damaged turtle eggs, but will opportunistically prey upon live embryos and hatchlings under some circumstances.