Journal of Undergraduate Research


organisms, handedness, livebearing fish


Life Sciences




I address this question in a tropical livebearing fish species that shows a unique form of morphological asymmetry and an unusual form of behavioral laterality. The livebearing fish Xenophallus umbratilis exhibits a mating morphology where the male gonopodium—a structure used to inseminate females—terminates with either a dextral of sinistral corkscrew. That is, males are either ‘left handed’ or ‘right handed’ with respect to their gonopodium. We think that this might be related to a phenomenon in which individuals show a lateral bias in eye use to approach different stimuli, a form of behavioral laterality, that in other vertebrates is linked to cerebral lateralization of the brain. In other words, it is possible that brain lateralization exists in fishes and is related to morphological handedness. But why does such handedness exist in the first place?

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