Effects of benzene on growth and survival rates of Spotted Babylon Babylonia areolata (Link 1807)

Abstract

This study determined the effects of benzene concentration on growth and survival rate of spotted babylon (Babylonia areolata Link 1807) during the capsule egg, veliger larva, settled juvenile, juvenile and adult stages. Six benzene concentrations, i.e, 0, 1, 5, 25, 50 and 100 μl/L, were tested. Spotted babylon at different developmental stages were cultured in a closed recirculating system for one week. It was found that egg capsules reared in seawater without benzene had the highest survival rate standing at 90%. However, the embryonic development from cleavage to trochophore took 48 hours, which was slower than usual. This suggested that benzene can delay the embryonic development in egg capsules. To determine the effect
of benzene on verliger larvae, spotted babylon with average shell length of 535.00±20.34 micrometers, raised at the density of 400 spotted babylons per liter and fed with Chaetoceros, was used. It was found that those reared in a treatment without benzene had the highest shell growth and survival rate (p<0.05). In contrast, verliger larvae cultured in seawater at benzene concentrations of 25, 50 and 100 μl/L did not move their vela, resulting in low average shell growth and survival rates. To examine the effect of benzene on initial settled juveniles, spotted babylon with average shell length of 1577.22±12.24 micrometers was raised at the density of 8,000 spotted babylons per m2 and fed with yellow stripe trevally meat. The results showed that those in the treatment without benzene had the highest shell growth and survival rates, while the lowest shell growth and survival rate were noted in the 100 μl/L benzene treatment. For initial juveniles with shell length of 1.57±0.19 centimeters at a density of 400 initial juveniles per liter, it was found that those in treatment without benzene had the highest shell growth and weight gain rates, while the lowest shell growth and weight gain rate was again noted in the 100 μl/L benzene treatment (p<0.05). Nevertheless, the survival rates across different groups were not significantly different. Regarding burrowing behavior of juveniles, the data showed that there was the highest number of juveniles exhibiting such behavior in the 1 μl/L benzene treatment group, while the highest number of juveniles exhibiting attachment behavior was in the 100 μl/L benzene treatment group. In addition, all spotted babylon adults across all treatment groups were found to have 100% survival rate. Furthermore, benzene was found to increase the size of digestive cells in livers. Average cell sizes of digestive cells were 4.14 and 5.09 micrometers in the treatment without benzene and in the 100 μl/L benzene treatment, respectively.