Hermaphroditic Chalk Bass Cooperate When Mating
While it is estimated that roughly 2% of fish species are hermaphroditic, only a handful of subspecies are simultaneous hermaphrodites, meaning they have both male and female sexual organs at the same time. This is beneficial as it ensures that everyone gets to mate.
These fish can “alternate” their sex up to twenty times a day, and since they do not have the ability to self fertilize, they depend on the cooperation of their mates to propagate the species. Furthermore, acting as both male and female improves their chances of passing on their genes.
Though not entirely monogamous, research published in Behavioral Ecology describes how the chalk bass will engage in a type of mating “rotation” where one female-acting partner will produce 2 egg “parcels” which the male will then fertilize. They will then switch roles and repeat the process. It is theorized that this behavior helps maintain cooperation and decrease instances of infidelity between partners.