Meeting Abstract

P2.4  Wednesday, Jan. 5  Examining predation as a cause of sexual dimorphism in two species of Euphilomedes ostracods LAMPE, Rebecca I*; OAKLEY, Todd H; Univ. of California, Santa Barbara; Univ. of California, Santa Barbara lampe@lifesci.ucsb.edu

Sexual dimorphisms usually arise in primary sexual characteristics, such as reproductive organs, and secondary sexual characteristics, such as color differences between males and females in many bird species. But there are instances of sexual dimorphisms that do not fall directly into these categories, including other morphological traits and behaviors. In Euphilomedes ostracods, the males have compound eyes while females do not. In place of the compound eye, the females have an eye rudiment. In addition to this morphological dimorphism, Euphilomedes also exhibit a behavioral dimorphism in the form of sexual segregation. Both males and females spend a majority of their lives in the sand and swim into the water column to mate. Males can likely mate many times, while females possibly only mate once. This causes males to be at a greater risk of predation due to their increased amount of time in the water column. We hypothesized that the compound eyes in males are an adaptation that increase their survival during their longer vulnerable periods during mating, not simply an adaptation to help the males find mates.