Master of Science (M.Sc.)
Virginia Institute of Marine Science
The maintenance of a population within the geographic range is influenced by the physical and environmental conditions under which breeding occurs. It is hypothesized that environmental conditions under which egg capsules are successfully hatched will influence the range of potential habitat of the invasive veined rapa whelk, Rapana venosa, and the native Atlantic oyster drill, Urosalpinx cinerea, in the Chesapeake Bay. This study examines the environmental conditions of temperature, salinity, and the time of deposition of egg capsules within the reproductive period (here quantified as cumulative number of day degrees at egg capsule deposition). The range of R. venosa and U. cinerea habitat in the Chesapeake Bay, in relation to environmental conditions, is important given the potential impact of both species on native shellfish stocks. Egg capsule hatching success and egg capsule incubation time for R. venosa and U. cinerea were examined at temperatures (18oC, 22oC, 26oC, 30oC, and ambient York River water temperature) and salinities (7 ppt, 14 ppt, 21 ppt, 28 ppt, and ambient York River salinity) reflective of the Chesapeake Bay during egg capsule deposition. Salinity is the greatest factor influencing R. venosa and U. cinerea egg capsule hatching success. Increasing salinities increase the percentage of R. venosa and U. cinerea egg capsules to hatch as well as the percentage of U. cinerea embryos alive at hatch. For R. venosa, the percentage of egg capsules to hatch is greatest at 21 ppt. For U. cinerea the percentage of egg capsules to hatch and the percentage of embryos alive at hatch are greatest at salinities of 21 ppt or 28 ppt. R. venosa and U. cinerea egg capsules do not hatch at 7 ppt in the temperature range examined. Temperature within the range examined was not found to be an important factor influencing egg capsule hatching success for either species. However, temperature was an important factor influencing the rate at which the egg capsule hatching process occurs. The percentage of R. venosa egg capsules to hatch increases and the percentage of U. cinerea alive at hatch decreases along the egg capsule deposition time series. For R. venosa, an increase in the percentage of egg capsules to hatch occurs if egg capsules are deposited later in the time series. For U. cinerea the percentage of egg capsules to hatch is not affected by position in the egg capsule deposition time series, but the percentage of embryos alive at hatch decreases along the time series examined. The temperatures and salinities for optimal R. venosa egg capsule hatching range from 18oC to 30oC and from 11 ppt to 28 ppt and vary based on the timing of egg capsule deposition. The temperatures and salinities for optimal U. cinerea egg capsule hatching range from 18oC to 30oC and from 20 ppt to 28 ppt and do not vary based on the timing of egg capsule deposition. Optimal egg capsule hatching for R. venosa and U. cinerea occur at different temperature-salinity combinations throughout the majority of the egg capsule deposition time series.
© The Author
Gera, Stephanie M., "Egg Capsule Hatching Success in Rapana venosa and Urosalpinx cinerea in Relation to Temperature and Salinity" (2009). Dissertations, Theses, and Masters Projects. William & Mary. Paper 1539617885.