Sexing criteria and sex ratio of Corophium volutator (Pallas) in Minas Basin during winter
LE3 .A278 1990
Boates, J. Sherman
Bachelor of Science
This study examined sex ratio in Corophium volutator from Blomidon, Starrs Point, and Evangeline in the Minas Basin, Bay of Fundy, Nova Scotia in winter. This was done in order to gain a better understanding of sex ratio. A new sexing criterion using spines on the first segment of the first antennae of females was tested. This technique makes the sexing of C.volutator < 1mm possible. The primary sex ratio was highly skewed (approximately 1 :4) indicating that sex ratio is biased at a very early age. Variation in sex ratio was found between different cohorts, different exposures, and among different sites. Generally speaking, sex ratios were all biased in favour of females. The ratios found in the juvenile cohorts in areas subject to shorebird predation had more females per male than the adult cohorts or the juvenile cohorts in areas where there was negligible shorebird predation. This variation was examined with respect to shorebird densities, and other extrinsic factors which could possibly be responsible for the different sex ratios were considered. The results of this study do not support previous assumptions concerning shorebird predation of C. volutator. More research is required on the foraging behaviour of the Semipalmated Sandpiper Ca/idris pusilla and other predators. Research should also be done on the primary sex ratios of C. volutator from different sites to determine the cause and evolutionary significance of skewed sex ratios in this organism.
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