Influence of physico-chemical parameters on the settlement of competent larvae of cultured sea urchin, Paracentrotus lividus

Abstract

Achieving efficient metamorphosis and settlement of larvae is a major bottleneck in the culture of sea urchins; therefore, in order for culture operations to be economically viable, it is urgent to optimize this crucial step under captive conditions. This study aimed to investigate how various parameters, including temperature, salinity, light cycle, and inducer type, affect the settlement of competent P. lividus larvae. Three different salinities (35, 30, 25‰), three temperatures (25, 20, 15 °C), four light conditions (16/8, 12/12, 24/0 and 0/24) and five types of biofilms (three of “natural” origin and the other two from monospecific collection cultures) were tested. The results suggest a relationship between low salinity and decreased survival and settlement rates. Conversely, the photoperiod appears not to have significant influence over survival and settlement rates. It appears that specific temperatures did not affect rates of survival and settlement, rather it was the deviation from initial culture temperature that is responsible for these rates. Finally, the multispecific inoculum of benthic diatoms showed a higher survival and settlement rate and lower mortality rate compared to monospecific inoculum.