VirginCaenorhabditis remaneifemales are attracted to a coital pheromone released by con-specific copulating males

Abstract

The gonochoristic soil nematode Caenorhabditis remanei strictly requires copulation for species propagation. Males of this species are sexually promiscuous with females of other species; therefore, we asked in this study whether virgin C. remanei females display evidence of mate choice. We digitally recorded and measured the locomotor behaviors of one or more virgin females in the presence of a single male on a 5 mm diameter mating lawn. We observed that initially only the male modifies his locomotor trajectory to another animal on the mating lawn; the virgin females showed no locomotor bias toward the mate-searching male. However, once a male started to copulate, females in the vicinity altered their movement trajectories toward the copulating couple. Newly inseminated females are refractive to the coital signal, but partially regain their attraction to copulating males after 24 h. We found only copulating males with an intact gonad can attract females, and that the coital signal can be broadcasted at least 1.5 mm through the air. Unlike males, which are also attracted to hetero-specific females, virgin C. remanei females will only crawl toward a copulating con-specific male. We suggest that Caenorhabditis females use the coital signal as a pheromone to identify a vigorous male of their own species.

Experimental evolution: Assortative mating and sexual selection, independent of local adaptation, lead to reproductive isolation in the nematodeCaenorhabditis remanei

“…It is interesting to note, however, that previous reports suggest that pheromones are not species specific (Chasnov et al. ), or that female C. remanei are only attracted to copulating males (Markert and García ). We observed that in some crosses—typically within a population—females and males both sought out one another and other times males would completely leave the plate, as if they could not sense the females at all, similar to the response of individuals to plates lacking females (Simon and Sternberg ).…”

Sexual Dimorphism and Sex Differences in Caenorhabditis elegans Neuronal Development and Behavior

“…Gonochorisitic C. remanei males also aerosolize compound(s) only during coitus that attract C. remanei females and may act as species-specific mating pheromones (Markert and Garcia 2013). The gonad is required for the male's ability to sedate its mate and for attracting additional females during copulation (Garcia et al 2007;Markert and Garcia 2013). The nature of the soporific and coital cues is not known.…”

Evolutionary transitions from female to hermaphrodite reproduction remodel olfactory and mating-receptive behaviors

“…The mating behaviors of male nematodes have been characterized in C. elegans and a few other Caenorhabditis species, 3,4,5,6,7,8,9 whereas the more limited analysis of female mating behavior has emerged primarily from studies of the gonochoristic species Caenorhabditis remanei . Virgin females of C. remanei approach conspecific male-female mating pairs 10 via an attractant that has airborne transmission across a ∼1 mm distance 11 . Chemotaxis in a microfluidic arena shows that C. remanei females are attracted to non-mating males as well, likely via nonvolatile pheromones.…”

“…12 When a C. remanei male presses his tail against the female's vulva, a soporific factor requiring the male somatic gonad induces locomotor quiescence and rhythmic vulval muscle contractions in the female as male sperm is transferred. 10 Several behaviors in C. remanei females are decreased after recent mating: mate search (leaving a food lawn in the absence of males), 13 attraction to male odor, 11,12 and maletriggered sedation. 10 In contrast to C. remanei females, young adult C. elegans hermaphrodites do not leave food to seek mates 13 and are not attracted to males.…”