Influence of environmental factors and female size on reproductive output in an invasive temperate marine gastropod <Emphasis Type="Italic">Rapana</Emphasis><Emphasis Type="Italic">venosa</Emphasis> (Muricidae) |
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Authors: | Juliana M Harding Roger Mann Catherine W Kilduff |
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Institution: | (1) Department of Fisheries Science, Virginia Institute of Marine Science, P.O. Box 1346, Gloucester Point, VA 23062, USA;(2) Downey Brand Attorneys LLP, 555 Capitol Mall, 10th Floor, Sacramento, CA 95814, USA |
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Abstract: | Life history and reproductive strategies influence population dynamics at the inter- and intra-specific level. Environmental
conditions suitable for gonad development and spawning, the reproductive range, may be a smaller portion of the broader species
distribution. The only known breeding population of veined rapa whelks (Rapana venosa) in North America is in Chesapeake Bay, USA. There is considerable interest in the potential reproductive range of this non-indigenous
species given the rapa whelk’s negative impacts on commercial shellfish species in both its native and introduced ranges.
Weight-specific reproductive output is described for wild caught Chesapeake Bay rapa whelks maintained in flow-through mesocosms
for 2 years. Measured reproductive output within and between egg capsule deposition seasons (years) in relation to water temperature,
salinity, daylength, and female size is used to describe the rapa whelk’s reproductive range. Egg capsule production is influenced
by seasonal and absolute water temperatures as well as seasonal daylength cycles. Egg capsule deposition by Chesapeake Bay
rapa whelks begins at water temperatures of approximately 18°C and continues for 11–15 weeks. Forty to 70% of female whelks
deposited egg capsules in most weeks during this season, producing 150–200 egg capsules female−1 week−1. Water temperatures >28°C caused reduced egg capsule production relative to temperatures of 20–25°C. Egg capsule production
was positively related to seasonal changes in daylength, and two peaks of egg capsule deposition were observed in the 2001
and 2002 deposition seasons. The combination of declining daylength and higher water temperatures in late summer was associated
with the cessation of egg capsule deposition. A lower average weight specific reproductive output in 130–145 mm SL rapa whelks
(average 12 ± 1%) than in 90–106 mm SL rapa whelks (average 22 ± 1% of body weight) may reflect a life history that balances
the physiological costs of maintaining a large body mass with the production of many planktonic larvae from multiple clutches
of egg capsules per breeding season over a 10–15-year lifespan. Estimates of the cumulative day-degree requirements corresponding
to the annual initiation of egg capsule deposition were 238 and 236 for 2001 and 2002, respectively. Reproductive output and
day-degree requirements for Chesapeake Bay rapa whelks were similar to values calculated from previous studies of native muricids
(Eupleura caudata and Urosalpinx cinerea). A latitudinal range of 30–41° (N and S) is predicted as the realized reproductive range for rapa whelk populations on the
basis of the day-degree requirements for native whelks and reproductively active invasive rapa whelk populations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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