The effects of different algae species and stocking densities on larval development and survival of Black sea urchin (Dianema setosum, Leske 1778)

Abstract

This study investigated the effect of different algae species and stocking densities on larval development and survival of black sea urchin Diadema setosum. The larvae development stages were studied in laboratory by which time the larvae approached to reach competency stage. There is a significant difference (P<0.05) in algae species diets of larvae rearing among the diets after 25 days and compared with the initial (94±0.9%). In the first experiment, the survival of larvae was 40±1% when fed with N. oculata in combination with C. gracillis. The survival was 46±3% when fed with N. oculata and Thalassiosira sp algae diet and 55±1% when fed with Thalassiosira sp algae. The highest survival rate of 60±1% was found for black sea urchins fed with combination of N. oculata algae and C. gracillis algae and Thalassiosira sp algae. In second experiment, the results showed that the stocking density 0.5 larvae/ml was found to improve the survival rate (62±2%) of black sea urchin. The survival rate of 55±1% was found for treatment of 1 larvae/ml and 20±1% (2 larvae/ml). The lowest once (9±1%) was observed for black sea urchin larvae rearing with the stocking density of 4 larvae/ml. At the day 25 the lengths of larvae a lot of changing. While, the total body length of the combination N. oculata and Thalassiosira sp showed (0.24±0.01mm). the best growth the size total body length was 0.24±0.01mm in the combination N. oculata added with Thalassiosira sp algae and the lowest in 3 algae species showed 0.192±0.01mm. in the different of stocking densities, 0.5 larvae/ml was obtained (0.28±0.04mm) the growth highest about sizes of sea urchin larvae and the development lowest in density 4 larvae/ml. The aim of study was to determine of feeding algal species and stocking densities which suitable for the development of black sea urchin larvae to the highest growth archived and improved the survival rate of black sea urchin in settle stage. Research the effect of different algae species and stocking densities on the development and the survival rate of black sea urchin larvae (Diadema setosum) in laboratory condition. The result of this study showed the combination of 3 algae species and culturing in stocking density 0.5 larvae/ml that the best done should be applied for sea urchin larvae rearing.