Larval development and survival to metamorphosis of sea urchin Tripneutes ventricosus (Lamarck) (Echinodermata: Echinoidea) fed on microalgae at two temperatures

Larval development and survival of Tripneutes ventricosus up to metamorphosis were evaluated. Ten sexually mature specimens were collected from 'Faro de Charagato' to 'Laja Amarilla' (10 degrees 50'07"N, 64 degrees 09'33"O) Cubagua island, Nueva Esparta state, Venezuela. Spontaneous spawning of the organisms was produced during their transport to the laboratory. Pluteus larvae (2 ind mL(-1)) were randomly distributed into 16 plastic recipients (18 L) (32000 larvae/recipient), with 16 L of filtered sea water and continuous aeration. Two groups of eight recipients each were set up; one group was kept at outdoor temperature (29 +/- 1 degrees C) and the other one at laboratory temperature (23 +/- 2 degrees C). For each temperature Chaetoceros gracilis (50000 cells mL(-1)) was added as food to four recipients and a mixture of C. gracilis plus Isochrysis galbana (25000 cells mL(-1) of each species) to the other four recipients. Survival was daily determined, from 4-mL sample taken from each treatment, and the live larvae were quantified. The body length was estimated every other day in five preserved larvae with 5% formaldehyde. Postlarval stage was attained 24 days after spawning in both culture temperatures. Morphological differences were not detected neither body length between treatments, however, survival showed differences (ANOVA, P<0.05) with the best results in larvae fed on C. gracilis and I. galbana mixture (30 +/- 0.30%) at outdoor temperature.