Estudios preliminares sobre la crianza de Ostrea chilensis en el laboratorio

Abstract

The purpose of this work has been to find out if Ostrea chilensis from Quetalmahue (41º 51' S. - 72º 55' W.), can live in laboratory conditions at Montemar, and it attempts the possibility of conditioning oysters for spawning during winter time under minimal laboratory facilities, no circulating sea water system with adequate temperature, and only Phaeodactylum as food. Finally, the experiment should yield experience on the rearing of chilean oysters in the laboratory, that will help in the planning of future work.

The delivery of oysters from Quetalmahue to Montemar takes three days as a minimum. During this period the maximum mortalities were 76 and 95% in spring months and a minimum of 12% in winter months (Cuadro 2). Practically, no mortality was detected in the stocking aquarium over 7 months period.

It was impossible to obtain a recovery of the gonads in oysters collected from the natural beds in winter time (April to July), after being in laboratory conditions from 4 to 7 months. The lack of this recovery was due to the poor food. The temperature was only 1 to 2.5º C. higher in the laboratory than in the natural environment. The oysters, could only survived in laboratory conditions, nothing more.

The oysters coming from the natural beds in July and August could not be conditioned to spawn. The reason could be that previously the oysters were in the aquarium over a 2 to 4 months period, which produced the reabsorption of the gonads. As it can be supposed they become useless as spawners, as they did not respond to stimulation (electricity, M and M/2 KCL and NH4CL solutions or suspension of spermatozoa in sea water).

25% of the oysters sent from the natural beds in August, aborted eggs to 12-cell stage after being 1 to 3.5 months in the laboratory. This means that these oysters had their gonads completely recovered in the natural bed. It is interesting to remark, that abortion was complete in all the specimens and no broods was recorded. It was impossible to find out the reasons for this phenomenon, but the suggestion of Walne (1963) that the partial abortion is caused by the large size of O. chilensis eggs, can’t be valid in a total abortion.

Five out of seven oysters had motile spermatozoa in their gonads when they aborted. This means that it is possible to find simultaneously functional spermatozoa and eggs, so, as we witnessed, self-fertilization occurs.