Meeting Abstract
The mangrove rivulus fish (Kryptolebias marmoratus) is one of only two self-fertilizing vertebrates. Populations consist of predominantly self-fertilizing hermaphroditic fish, with varying proportions of males (androdioecy). Outcrossing occurs between hermaphrodites and males and rates of outcrossing vary among populations, but is rare in most populations. It is unknown how relatively few males find infrequently laid unfertilized eggs while they are still viable. We hypothesized that males prefer to associate with hermaphrodites that routinely lay a greater proportion of unfertilized eggs. We predicted that males would exhibit a stronger preference for younger hermaphrodites because they are more likely to lay unfertilized eggs; ovarian tissue matures before spermatogenic tissue. To test this hypothesis, two hermaphroditic fish from the same genetic lineage, but at least 150 days different in age, were placed in clear fish brooding boxes on opposite sides of a behavior arena. A male was placed in the middle of the arena, and his movements recorded digitally and scored for thirty minutes. This was repeated with the same trio, but with hermaphrodite positions reversed. The brooding boxes permitted water to freely flow throughout the arena while keeping the hermaphrodites inside the boxes, allowing males access to visual and chemical cues. Contrary to our predictions, preliminary data suggest that the males prefer to associate with older hermaphrodites. This preference was even stronger during the second trial. These results indicate that males actively seek hermaphrodites with higher probabilities of laying unfertilized eggs, which another experiment showed to be older hermaphrodites. Such a preference might explain how males, in a predominantly selfing species, obtain non-trivial reproductive success in wild populations.
