Posts tagged: Michael Kopec

Daniel Painter, ’06, Michael Kopec, ’05, Diana Lancaster, ’06

McCurdy, D. G., Painter, D. C., ’06, Kopec, M. T., ’05, Lancaster, D., ’06, Cook, K. A., & Forbes, M. R. (2008). Reproductive Behavior of Intersexes of an Intertidal Amphipod Corophium Volutator. Invertebrate Biology, 127(4), 417-425.

Abstract: Intersexes are common in crustaceans. Typically, these intersexes are sterile or function as females, but prior evidence from laboratory experiments suggests that intersexes of a key species of gammaridean amphipod, Corophium volutator, might function as males. We observed that intersexes of C. volutator behaved as males by crawling (mate-searching) on a mudflat during ebb tides and pairing in burrows with female amphipods. In the laboratory, intersexes and males did not differ in aspects of crawling such as movement rate and measures of burrow investigation. I`ntersexuality was costly in that intersexes crawled less often than males on a mudflat, formed fewer pairs with females than males, and remained in tandem less often with receptive females than males. The use of PCR-based identification methods failed to identify the presence of transovarial, feminizing, microsporidian parasites as a major cause of intersexuality in this species in that infected females did not produce broods that contained more intersexes than broods produced by uninfected females. Because intersexes may be mistaken as females, the percentage of functional males in amphipod populations may be underestimated: an important consideration given male limitation in populations of C. volutator. The occurrence of intersexes has significant implications for studies on the evolution and ecology of sex ratios, and the use of crustaceans as indicators of environmental quality.

Sean Logan and Michael Kopec

McCurdy, D., Forbes, M., Logan, S., Kopec, M., & Mautner, S. (2004).  The functional significance of intersexes in the intertidal amphipod Corophium volutator.  Journal of Crustacean Biology, 24, 261-265.

Abstract: We investigated the functional significance of intersexuality in the amphipod Corophium volutator, a key species in soft-bottom intertidal communities. Intersexes in this species possess morphological and anatomical characters of both males and females. Two broad types of intersexes were identified: those with nonsetose oostegites and two penial papillae (Type I), and those with setose oostegites and one or two penial papillae (Type II). We found little evidence that intersexes function as females, but some females housed experimentally with intersexes became ovigerous, indicating that intersexes can function as males. Females that mated with Type II intersexes produced smaller broods than those that mated with Type I intersexes or males, suggesting that this form of intersexuality may be costly to amphipods (most Type II intersexes possessed only a single testis). Male function of intersexes may be important in populations of C. volutator because males are frequently the limiting sex due to extremely female-biased sex ratios.

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