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Brazilian Journal of Oceanography

On-line version ISSN 1982-436X

Braz. j. oceanogr. vol.60 no.2 São Paulo Apr./June 2012


It is possible the daily assessment of the growth of giant oyster larvae?



Unprecedented search shows that oyster larvae, giant Tridacna crocea, are able to acquire environmentally symbiotic zooxanthellae and this seems to benefit the larval survival in cultivation.

The cultivation of oysters, giant Tridacna crocea, has been pursued for a long time by humans, both for food purposes as for fishkeeping. This clam bivalve has size ranging from 10 to 25 cm, striking coloring and beautiful patterns, besides being considered by "gourmets" as delicacy. However, its cultivation has proved to be quite difficult, and one of the critical points of the process are the larval survival rates.

Tridacnas are inhabitants of coral reefs around the world, environments where symbiosis between the various organisms often and intensively occur. The symbiosis between corals and dinoflagellates (zooxanthellae) is particularly well known, being the process responsible for a significant part of the nutrients available to corals. During the day hours the clam spreads out his mantle out of the shell and the algae receive the necessary amount of sunlight for the synthesis of nutrients.

One of the studies presented in volume 60 (2) of the Brazilian Journal of Oceanography investigated the growth of larvae of Tridacna crocea in labortory. The daily growth rates and survival rates of larvae in their first week of life were determined  in cultives with zooxantelae. "The determination of daily survival and growth of the larvae, allows one to have an idea about the viability of eggs fertilized and the quality of zooxanthellae strain offered to the larvae," say the authors. The matrices adult clams were induced to spawn by means of intragonadal injection of serotonin, after which the oocytes were collected, fertilized and maintained in cultivation according to the techniques described in the paper. The authors hypothesized that the growth of larvae can increase non-linearly after the taking of zooxanthellae. Tridacna crocea chosen because it is the smallest among the species of ornamental oyster, which facilitates the handling in laboratory. The larval growth was measured before and after the larvae have benefited from the acquisition of zooxanthellae, which gives greater precision in the evaluation of eventual success or failure of the cultivation.

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Michael Mies
Instituto Oceanográfico da USP, São Paulo, Brazil.

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