Category: Dean McCurdy (Faculty Co-author)

Jeff Stephens, ’09

Tingley, R., Herman, T., Pulsifer, M., McCurdy, D., & Stephens, J. (2010). Intra-Specific Niche Partitioning Obscures the Importance of Fine-Scale Habitat Data in Species Distribution Models. Biodiversity and Conservation, 19(9), 2455-2467.

Abstract: Geographic information systems (GIS) allow researchers to make cost-effective, spatially explicit predictions of species’ distributions across broad geographic areas. However, there has been little research on whether using fine-scale habitat data collected in the field could produce more robust models of species’ distributions. Here we used radio-telemetry data collected on a declining species, the North American wood turtle (Glyptemys insculpta), to test whether fine-scale habitat variables were better predictors of occurrence than land-cover and topography variables measured in a GIS. Patterns of male and female occurrence were similar in the spring; however, females used a much wider array of land-cover types and topographic positions in the summer and early fall, making it difficult for GIS-based models to accurately predict female occurrence at this time of year. Males on the other hand consistently selected flat, low-elevation, riparian areas throughout the year, and this consistency in turn led to the development of a strong GIS-based model. These results demonstrate the importance of taking a more sex-specific and temporally dynamic view of the environmental niche.

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 Diana Lancaster

McCurdy, D. G., Forbes, M. R., Logan, S. P., Lancaster, D., & Mautner, S. I. (2005). Foraging and Impacts by Benthic Fish on the Intertidal Amphipod Corophium Volutator. Journal of Crustacean Biology, 25(4), 558-564.

Abstract: We studied feeding site selection and impacts by benthic fish (flounder and skates) on the amphipod Corophium volutator, an ecologically-important species in muddy intertidal communities. We determined that benthic fish foraged mainly in areas that had high densities of amphipods, on a mudflat in Nova Scotia, Canada. This observation was based on recording sediments displaced by benthic fish in areas where samples of amphipods also were taken. From gut-content analysis, we found that benthic fish fed almost entirely on C. volutator, and most consumed smaller amphipods than expected based on samples of amphipods collected from the substrate. Benthic fish also fed on male amphipods more than expected. We determined that daily foraging pressure by benthic fish on amphipods was low (about 0.3% per day) by measuring the new appearance of feeding traces made by fish. Nonetheless, fish are expected to have substantial impacts on demography of C. volutator due to the length of the fish foraging season and because fish appear to contribute to extreme female-biased sex ratios typically seen in this species.

Kristine Degel

Degel, K. and D. G. McCurdy. 2006. Impacts of temperature on emergence of trematode cercariae from the mud snail Ilyanassa obsoleta (Say). MarSci.(3).

Abstract: We assessed prevalence of trematode parasites and impacts of temperature on shedding of parasites infecting mud snails, Ilyanassa obsoleta (Say), collected from Maine. Six species of trematodes were found to infect mud snails: Austrobilharzia variglandis, Zoögonus rubellus, Stephanostomum tenue, Gynaecotyla adunca, Himasthla quissetensis, and Lepocreadium setiferoides. As predicted, snails were more likely to shed cercarial forms of six species of trematodes when experimentally exposed to elevated water temperatures for single 24-hour periods. We argue that even small-scale changes in temperature might have implications for individuals and populations of marine animals that serve as second-intermediate hosts and final hosts of trematodes shed by infected mud snails (e.g., clams, baitworms, birds, fish, humans). We also establish new northern limits for several species of marine trematodes.

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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