Effects of Cadmium (CdCl2) on development and hatching of eggs in European squid (Loligo vulgaris Lamarck, 1798) (Cephalopoda: Loliginidae)

Abstract

This is the first study related to the effects of cadmium (Cd) on the development and hatching of eggs of Loligo vulgaris. The eggs were exposed to concentrations varying from 10 to 100,000 microg Cd/l for up to 1 month. During the study period natural sea water salinity (37 PSU), ambient temperature (ranging 16.5-21.5 degrees C) and light conditions of 12-h light: 12-h dark for 744-h were used prior to the hatching. For 96-h, mortality rate of 100% of the eggs was found at cadmium concentration of 100,000 microg Cd/l, and the same mortality rate of the eggs were found at 1,000 and 10,000 microg Cd/l for 744-h and 696-h, respectively. Hatching took place between hours 456 and 576 in the control group and between hours 480 and 576 in 10 and 100 microg Cd/l groups. Total hatching rates were calculated to be 98.2 +/- 1.6% for control group, 99.4 +/- 0.6% for 10 microg Cd/l group and 98.6 +/- 1.2% for 100 microg Cd/l group. Hatching successes were estimated as 69.5 +/- 13.8% for control group, 84.5 +/- 8.2% for 10 microg Cd/l group and 76.9 +/- 5.9% for 100 microg Cd/l group. In the 100,000 microg Cd/l treatment, the egg degeneration began from animal pole of the eggs in 16 h, and 50% and 100% of them died in the initial stage at 72-h and 96-h, respectively. In the 10,000 microg Cd/l group, the eggs which reached at stage 19 (IX) were deformed and 50% and 100% of them died at 312-h and 696-h, respectively. In 1,000 microg Cd/l group, however, the eggs developed abnormally from stage 21 (X-XI) and reached at stage 29 (XIX), and 50% and 100% of them died in 624-h and in 744-h, respectively. There were significant differences in survival rates of the eggs among the concentrations (p < 0.05). The current study demonstrated that Cd adversely affects the development, survival and hatching of L. vulgaris eggs; however, no mortality was observed in 10 microg Cd/l and 100 microg Cd/l groups.