Meeting Abstract
The mangrove rivulus fish (Kryptolebias marmoratus) is one of two self-fertilizing vertebrates; populations consist of hermaphrodites and males. Males result from sex change, and the likelihood to change sex is genotype-dependent. Wild populations vary considerably in rates of outcrossing between hermaphrodites and males, but selfing is the primary mode of reproduction in most populations. In an ongoing attempt to understand when and why outcrossing occurs and why it varies among populations, we questioned whether the ability to successfully self (i.e., self-compatibility) varies among hermaphrodites. We hypothesized that some hermaphrodites would lay more unfertilized eggs and/or have reduced hatching success. We also hypothesized that self-compatibility would vary as a function of age or the lineage’s propensity to change sex to male. We raised 227 individuals from hatching, derived from genetically distinct lineages that vary in their propensities to change sex. Beginning at 67d post-hatch, eggs were collected weekly from each fish, examined to determine if they were fertilized, unfertilized, or dead, and kept until they hatched as a measure of hatch success. Preliminary data suggests that 95% of eggs laid are fertilized while the other 5% are dead and/or unfertilized. The lineages’ propensities to change sex did not predict the proportion of fertilized, unfertilized, or dead eggs. However, older fish laid more dead eggs, which likely were deposited in an unfertilized state. These results suggest that increased rates of outcrossing in some populations might be due to its age structure, with populations having either longer-lived fish or a smaller proportion of younger fish also exhibiting more outcrossing. As a result, male reproductive success might be contingent upon finding older hermaphrodites that deposit unfertilized eggs.
