engleski

Response of warty venus Venus verrucosa to two different spawning stimulation techniques

The warty venus is known as a high market value clam species in the Mediterranean. In spite of its commercial value, this species has not been produced aquaculturally. Successful technology for artificial production, from induced spawning to spat production, does not exist. This paper describes and compares two different techniques of spawning stimulation: thermal shock, and the administration of serotonin, the natural neurotransmitter present in the nervous system. Clams were collected from their natural environment in August and September during the natural spawning season in the south-eastern Adriatic. Two groups of 30 individuals were placed in black-bottom plastic tanks with filtered sea water of the same temperature and salinity as in the natural environment. After 24 hours, the first group was transfered in similar tanks with sea water of 30°C. Over one hour, the temperature was lowered to 18°C. This procedure was repeated three times and then clams were returned to the tanks under ambient conditions. The second group was treated with serotonin (5-hydroxy tryptamin) at a concentration of 2mM. 0.3 ml of the solution was injected into the anterior adductor muscle. The release of gametes in both groups started 8-9 hours after the treatment, and lasted for approximately 24 hours. All spawners observed during this period were collected from the common tank and placed in the individual containers. Table 1 shows the number of male and female spawners in both groups. Both treatments gave similar positive results. We counted 17 (57%) spawners in the group treated with temperature shock, and 14 (47%) spawners in the group treated with serotonin. This experiment proves that thermal shock (with the simple and cheap methods), reported to be unsuccessful by several authors, could be successfuly applied in the commercial production of gametes of warty clams.

warty venus; Venus verrucosa; spawning stimulation

nije evidentirano