BIVALVE CONDITIONING

From: Sam Buchanan <buchanansam@hotmail.com>
To: <SHELLFISH@kenyon.edu>
Sent: January 26, 2000

QUESTION:

I have been working on establishing artificial conditioning protocols for a Mytilid mussel with variable success. Some of the experimental results appear to conflict; in some trials using warmer (summer like) temperatures gametogenesis occurs and animals condition suitably. In other trials under similar conditions great gonad growth (size/mass) occurs but little sexual maturation. These results may suggest that sexual development needs to be triggered prior to conditioning; simply supplying adequate food and temperatures typical of the maturation season is therefore not always adequate. I am wondering if the CHANGE in temperature or nutrient environment is the trigger and if animals have suitable reserves and/or developmental status then conditioning will be effective. What evidence is there for means to switch energy allocation from storage to gamete production in mussels?  I would appreciate any comments or advice from people experienced in artificial conditioning of bivalve molluscs (especially of mussels).

Sam Buchanan

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COMMENTS 1:

It is interesting to hear about your results with conditioning of
mussels.
My first thought was: Is there a pattern in what time of the year you get the best results?  Is it possible that you can induce gonad growth only during the period of gonad growth in the nature for your population?  If so, it is possible that your mussels use photoperiod as a calendar for timing of gonad growth to a certain part of the year.  I am dwelling with such thoughts these days in a thesis about reproduction in the great scallop.  It has been reported for scallops in the bay of St. Brieuc in France that gonad growth could not be induced at a point when the natural population had a resting period (Cochard and Devauchelle, 1993).
Influence of photoperiod in timing of seasonal reproduction has been demonstrated for a number of invertebrates,  and Pearse et al. (1986) have an interesting article about different uses of photoperiod for timing of reproduction.
If photoperiod controls timing in your mussels, it could be easy to manipulate them, as for the sea urchin, but it could also be more complicated with longer time to move the natural rhythms, as for the sea urchin.
This far I haven't seen any attempts to move a period of gonad growth to other parts of the year for bivalves, and it would be very interesting to hear if anyone has ideas or results in this context.

References
Cochard, J., Devauchelle, N., 1993. Spawning, fecundity and larval survival and growth in relation to controlled conditioning in native and transplanted populations of Pecten maximus (L) - evidence for the existence of separate stocks. Journal of Experimental Marine Biology and Ecology 169, 41-56.

Pearse, J.S., Eernisse, D.J., Pearse, V.B., Beauchamp, K.A., 1986.
Photoperiodic regulation of gametogenesis in sea stars with evidence of an annular calendar independent of fixed daylength. Amer. Zool. 26, 417-431.

Arne Duinker
Havforskningsinstituttet Institute of Marine Research
Senter for Havbruk Aquaculture division
Po.b. 1870, Nordnes Po. Box 1870, Nordnes
5817 Bergen N-5817 Bergen
NORWAY
Tel.  +47 55 23 63 60 (desk 23 63 50)
Fax. +47 55 23 63 79
E-mail Arne.Duinker@imr.no
http://www.imr.no/
http://www.ifm.uib.no/

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COMMENTS 2:

I have been conditioning and spawning rock scallops (Crassadoma gigantea) throughout the year with various artificial spring/summer photoperiods for about  ten years now.  Appropriate temperature and food levels are necessary, of course.  Saout and colleagues have also done so with P. maximus in the winter at IFREMER. "Spring" conditions trigger much higher energy partitioning to vitellogenesis in these scallop species.

Jon Agosti
qshatch@arctic.net

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