Learning and memory associated with aggression in Drosophila melanogaster

Abstract

Male Drosophila melanogaster (Canton-S strain) exhibit aggression in competition for resources, to defend territory, and for access to mates. In the study reported here, we asked: (i) how long flies fight; (ii) whether flies adopt distinct winning and losing strategies as hierarchical relationships are established; (iii) whether flies exhibit experience-dependent changes in fighting strategies in later fights; and (iv) whether flies fight differently in second fights against familiar or unfamiliar opponents. The results showed that flies fought for up to 5 h. As hierarchical relationships were established, behavioral strategies changed: winners progressively lunged more and retreated less, whereas losers progressively lunged less and retreated more. Encounters between flies were frequent during the first 10 min of pairing and then dropped significantly. To ask whether flies remembered previous fights, they were re-paired with familiar or unfamiliar opponents after 30 min of separation. In familiar pairings, there were fewer encounters during the first 10 min of fighting than in unfamiliar pairings, and former losers fought differently against familiar winners than unfamiliar winners. Former losers lost or no decision was reached in all second fights in pairings with familiar or unfamiliar winners or with naive flies. Winner͞winner, loser͞loser, and naive͞naive pairings revealed that losers used low-intensity strategies in later fights and were unlikely to form new hierarchical relationships, compared with winners or socially naive flies. These results strongly support the idea that learning and memory accompany the changes in social status that result from fruit fly fights.behavior ͉ dominance ͉ fruit fly ͉ social status ͉ fighting

A single social defeat reduces aggression in a highly aggressive strain of Drosophila

“…The authors declare no conflict of interest. 1 To whom correspondence should be addressed. E-mail: edward_kravitz@hms.harvard.…”

“…Animal care, the standard fighting chamber, and the standard fighting assay have been described (1,14,22). Briefly, flies were grown in temperature-and humidity-controlled incubators (25°C , 50% humidity) on a 12 h light/dark cycle.…”

“…Shortly after experiencing a loss, a male Drosophila never wins a second fight against a familiar winner, unfamiliar winner, or socially naïve opponent. When two losers are paired 30 min after their first fight, hierarchical relationships are rarely formed because the majority of fights do not escalate to midor high intensity (1). Although defeated Drosophila lose subsequent fighting contests, it's unclear whether flies also become less aggressive after losing experience.…”

Social structures depend on innate determinants and chemosensory processing inDrosophila

“…Recent studies also indicate that individuals have the ability to recognize others (6) and regulate their behavior according to group membership (7). The composition of such Drosophila groups forms a social environment that influences gene transcription, pheromone displays, and mating frequency among group members (7)(8)(9).…”

Visual recognition of conspecifics in the American lobster, Homarus americanus

“…Colour variation among wolves, Canis lupus, and African wild dogs, Lycaon pictus, variable, unique patterns in male ruff, Philomachus pugnax (Lank & Dale 2001) and blueheaded wrasse, Thalassoma bifasciatum, defending territories (Warner 1987), and peculiar egg and nestling coloration in common murres, Uria aalge (Gaston et al 1993) and royal terns, Sterna maxima (Buckley & Buckley 1972), respectively, may have evolved to signal identity. Studies on visual individual recognition are limited in invertebrates, although some have helped reveal the importance of vision (Giurfa et al 2001;Herath et al 2001;Horridge 2005;Yurkovic et al 2006). For example, Polistes paper wasps are able to identify individual nestmates by unique facial features (Tibbetts 2002) and the crayfish C. destructor can recognize familiar individuals based on their facial width or on some other features associated with it ( Van der Velden et al 2008).…”