2-D sex images elicit mate copying in fruit flies

Abstract

Although the environment is three-dimensional (3-D), humans are able to extract subtle information from two-dimensional (2-D) images, particularly in the domain of sex. However, whether animals with simpler nervous systems are capable of such information extraction remains to be demonstrated, as this ability would suggest a functional generalisation capacity. Here, we performed mate-copying experiments in Drosophila melanogaster using 2-D artificial stimuli. Mate copying occurs when naïve females observe the mating success of potential mates and use that social information to build their own mating preference. By replacing live demonstrations with (i) photos or (ii) simplified images of copulating pairs, we found that even crudely simplified images of sexual intercourse still elicit mate copying, suggesting that Drosophila is able to extract sex-related information even from a degraded image. This new method constitutes a powerful tool to further investigate mate copying in that species and sexual preferences in general.

A social learning primacy trend in mate-copying: an experiment in Drosophila melanogaster

“…Furthermore, we also found the existence of mate-copying using genetically affected phenotypes [ 24 ], suggesting the generality of this phenomenon. Interestingly, flies are able to detect subtle differences, such as the presence or absence of eyes, wings or legs, as we have discovered through manipulating fly pictures [ 23 ]. This allows us to speculate about the origin of this tendency towards primacy.…”

“…First, a demonstration phase where the observer female can acquire social information from demonstrators, followed by a mate choice test of the observer. We used the same set-up as previous studies ( figure 1 ) [ 23 ]. It was made of two adjacent plastic tubes (0.8 cm × 3 cm each) that were plugged on one side with cotton, and on the other by a microscopy cover slide (1.6 cm × 1.6 cm) that served as a window from which the observer female could watch the demonstration.…”

“…The observer female was placed in the tube adjacent to the side of the demonstration. Demonstrations consisted of one life-sized picture of a female mating with one of the coloured males with a male of the other colour standing by, as previously done by Nöbel et al [23]. Pictures were approximately 0.5 cm from the focal female tube.…”

“…Mate-copying exists in a variety of vertebrates, as well as in the fruit fly (Drosophila melanogaster) (reviewed in [15,16]). In the latter species, evidence comes from a series of experiments involving traits resulting from differential male feeding substrates [17], artificially coloured male phenotypes [17][18][19][20][21][22][23], as well as mutants with a different wing shape [24], suggesting significant levels of behavioural flexibility.…”

“…Here, we experimentally studied the role of the recency and primacy biases in mate-copying in the fruit fly ( D. melanogaster ) by providing them with two opposite pieces of information in sequence. We use a new, more controlled protocol in which demonstrations consist of flat pictures of a female copulating with one of two males with contrasting phenotypes, followed by a mate choice test [ 23 ]. We could thus test whether observer females gave more weight to the first demonstration (primacy bias) or the second one (recency bias).…”