||Scallop (Pecten maximus) calcification problems in the Brest Roadsted
||Communication avec actes
||Larvor Helene1, Devauchelle Nicole1, Cuif Jean Pierre2
||1 : IFREMER BREST, DRV-A. Laboratoire PMDC, BP 70, F- 29280 PLOUZANE
2 : Universite de Paris XI, Bat 504. Laboratoire de Paléontologie. F- 91405 ORSAY Cédex
||3e Rencontres Scientifiques Internationales du contrat de baie de la rade de Brest. Brest 14-16 mars 1995
||Calcification abnormalities linked to the appearance of a brown coloration of the internal shell layer are observed in scallops Pecten maximus in the Brest roadsted. It is a widespread phenomenon in shallow waters (about 3 to 10 meters) sometimes associated with an important boring parasitism at the ultimate stage of development. This brown color which can generate a decrease of the consumer appraisal does not affect the commercial value of the shellfish (muscle and gonad quality) when it is not too high. When it covers the all shell with a deap brown color the animal shows many signs of weakening. The color of the internal layer of the valves is due to the presence of a brown pigment, an eumelanin, associated with the insoluble organic matrix of the biocrystals. The appearance of this pigment generates many disturbances of themicrostructure of the scallop internal shell layer. Yet, the biomineralization mecanisms, such as those controling the calcium binding, do not seem to be modified: the mantle structure, the organic and mineral composition of the shell are not very modified in brown shells compared to white shells. The color abnormalities of the internal shell layer can be detected by a spectral analysis of its reflectance before it can be detected with the naked eyes. This method correlated to microstructural observations should be very interesting for a rapid and precise analysis of the appearance of the pigmentation on adult or juvenil scallops. It can be therefore a usefull method for the evaluation of the influence of environmental parameters on calcification and its abnormalities. Such an experimental study is realized in our laboratory at the moment.