S7-1.6 Sunday, Jan. 6 Synchronization of circadian bioluminescence as a group-foraging strategy in cave glowworms MERRITT, DJ*; MAYNARD, AJ; The University of Queensland, Australia; The University of Queensland, Australia firstname.lastname@example.org
Flies of the genus Arachnocampa are sit-and-lure predators that use bioluminescence to attract flying prey to their silk webs. Some species are most common in rainforest habitat and in others their habitat includes both caves and rainforest. We have studied the circadian regulation of bioluminescence in two species; one found in subtropical rainforest with no known cave populations, the other found in temperate rainforest with large populations in limestone caves. The rainforest species is typical of most nocturnal animals in that individuals are entrained by the light:dark cycle to be active at night: in this case, their propensity to bioluminesce is greatest at night. The dual-habitat species shows the opposite entrainment response; it’s bioluminescence propensity rhythm is entrained by L:D exposure to peak during the day. Nevertheless, in L:D environments, individuals don’t bioluminesce during the day because ambient light inhibits their bioluminescence (negative masking), pushing bioluminescence into the dark period. This unusual and unexpected phenomenon could be related to their association with caves. Entrainment of the bioluminescence rhythm to the photophase causes colonies of larvae in the dark zone to synchronise to each other, creating a daily sinusoidal rhythm of bioluminescence intensity in the many thousands of individuals making up a colony. This synchronisation could provide a group-foraging advantage, allowing the colony to glow most brightly when the prey are most likely to be active.