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MicroPubl Biol,
2019]
Nematodes, such as the model organism Caenorhabditis elegans, communicate environmental and developmental information with conspecifics through a class of small-molecule pheromones termed ascarosides (Butcher, 2017; Chute and Srinivasan, 2014; Ludewig and Schroeder, 2013). Nematodes share ascaroside signaling pathways (Choe et al., 2012), but are also capable of eavesdropping on chemical signals of predatory species (Liu et al., 2018). Ascarosides signal vast arrays of information, either individually or as blends, based on concentration, sex, physiological state, and other ascarosides sensed (McGrath and Ruvinsky, 2019; Pungaliya et al., 2009; Srinivasan et al., 2008; Srinivasan et al., 2012). For instance, octopamine-succinylated ascaroside #9 (osas#9) is able to signal starvation conditions in the absence of other ascarosides (Artyukhin et al., 2013).C. elegans (Cel) is an androdioecious species, with the majority of the natural population comprised of self-fertilizing hermaphrodites, and a small proportion (<0.2%) being male (Hodgkin et al., 1979). There are two other similarly androdioecious species in the genus, C. briggsae (Cbr) and C. tropicalis (Ctr). All three species evolved their hermaphroditism separately and uniquely (Ellis and Lin, 2014). Of the male-attracting ascarosides secreted by C. elegans (ascr#2, ascr#3, ascr#4, and ascr#8), ascr#8 is the most potent (Pungaliya et al., 2009). Since ascr#8 is a male attractant in this hermaphroditic species, we asked if other hermaphroditic species retained the ability to attract males using this cue. Males from the gonochoristic (male-female) sister species to C. briggsae and C. tropicalis C. nigoni (Cni) and C. wallacei (Cwa), respectively were also assayed for their ability to respond to ascr#8. The closest relative of C. elegans, the gonochoristic C. inopinata (Cin, formerly C. sp. 34), which has been recently characterized (Kanzaki et al., 2018), was also tested, along with the JaponicaGroup gonochoristic species C. japonica(Cja) and C. afra(Caf).Dwell times were analyzed as previously described using a Spot Retention Assay (Narayan et al., 2016). Dwell times were transformed using a Base 2 Exponentiation (2n, wherein n is equal to the raw dwell time value) to generate only non-zero data in order to calculate fold-changes. The Logbase2 of the fold-changes was then calculated to normalize the data. All data sets were first checked for normality using a DAgostino