Crescimento, sobrevivência e desenvolvimento larval do Pepino do mar Holothuria grisea: alimentação com diferentes microalgas

Abstract

This study aimed to evaluate the effect of the supply of microalgae Chaetoceros muelleri and Thalassiosira fluviatilis on growth, survival and larval development time of the sea cucumber Holothuria grisea. Holothuria grisea larvae were obtained from a spawning induced by heat shock and were cultured in incubators conical cylinder with volume of 15 L, kept in a density of 0,5 larvae/ml and constant aeration. The temperature, pH, dissolved oxygen and water salinity were measured daily and total ammonia analysis (NH3 / NH4+) and nitrite (NO2-) were done on days 05, 09 and 14 after fertilization. Four treatments were tested with five replicates each: a diet with 100% Chaetoceros muelleri; a diet with 100% Thalassiosira fluviatilis; a combined diet containing 50% Chaetoceros muelleri and 50% Thalassiosira fluviatilis (mixed diet); and control (unfed). The feed rate ranged from 20.000 the 40.000 cells/ml for different stages of development. The length of the larvae (μm) was observed on days 2, 8 and 14 after fertilization and survival (%) on days 4, 10 and 14 after fertilization. The larval development time was followed for all treatments. There was no significant difference in temperature, pH, dissolved oxygen and salinity, to the different treatments tested. The best treatments in terms of water quality were Chaetoceros muelleri and Control, with the lowest concentrations of total ammonia and nitrite. The highest concentrations of ammonia and nitrite were found in treatments where the microalgae Thalassiosira fluviatilis was present. The survival rate for all treatments decreased over larval development being quite sharp. The best treatment, when considering the larval development time and total length (μm), was Chaetoceros muelleri. Holothuria grisea completed it larval development time in 17 days after fertilization when fed Chaetoceros muelleri, having indirect development with larval stages of auricularia, doliolaria and pentacula until the arrival of the juvenile stage.