Field observations on
growth, gametogenesis, and sex ratio of triploid and diploid Mytilus
edulis
J. Brake, J. Davidson, J. Davis-2004
Aquaculture, 236(1-4): 179-191
Abstract:
Triploid shellfish are sterile and retain product
quality during, and after the spawning period. Field evaluations of diploid
and triploid mussels demonstrated that triploids had a greater growth rate
than diploids. The growth difference was evident in the first growing year
after deployment in a high growth site. This difference was not detectable
in a low growth site until the second year after deployment, suggesting
possible differential growth of triploids versus diploids, related to
environment. Diploid mussels in the low growth site were notably less
sexually mature in the first year; therefore, the differential performance
of triploids between test sites may have been related to spawning. After 11
months in the field, triploids had a mean shell length 1.05% (P=0.48)
larger than diploids in the low growth site versus 8.09% (P<0.001)
larger in the high growth site. Triploids examined after a spawning event
showed no histological evidence of spawning, while 71% of diploids showed
some evidence of spawning. Shell length, relative soft tissue weight, and
condition index were all higher in triploids. This resulted in a maximum
observed increase in dry tissue weight of 62.82% and a mean shell length
increase of 10.95% when triploids were compared to diploids after the local
spawning event. A highly skewed sex ratio in triploid mussels, in favor of
males, confirmed a similar observation in triploid Mytilus
galloprovincialis.
(Department of Health Management, Atlantic Veterinary College, University
of Prince Edward Island, 550 University Avenue, Charlottetown, PEI, Canada
C1A 4P3, e-mail of J. Davidson: davidson@upei.ca)