Egg production, egg hatching success and population increase of the tropical paracalanid copepod, Bestiolina similis (Calanoida: Paracalanidae) fed different microalgal diets

Abstract

A series of experiments was conducted to evaluate the suitability of ten microalgal diets, including 4 monoalgal, 5 binary and 1 tri-algal diet, for the culture of the tropical paracalanid copepod Bestiolina similis. The four monoalgal diets were the Tahitian strain of Isochrysis sp. (T-Iso), Pavlova 50 (Pav), Tetraselmis chuii (Tet) and the diatom Chaetoceros muelleri (Chaet), the 5 binary diets were Tet + T-Iso, Tet + Pav, T-Iso + Pav, Chaet + Tet and Chaet + Pav while the tri-algal diet was T-Iso + Tet + Pav. After feeding B. similis with 10 algal diets for 3 days, 24 h egg production rate (EPR, eggs female − 1 day − 1 ) was obtained for each diet treatment by averaging the egg output of 6 individual females (replaced daily) for 4 consecutive days. The tri-algal diet T-Iso + Tet + Pav produced the highest EPR (44.1 eggs female − 1 day − 1 ), which was significantly higher than any other diets tested ( p < 0.05). Highest 48 h and 96 h egg hatching rates (EHR) were also found from the eggs produced by B. similis fed with T-Iso + Tet + Pav (48 and 96 h EHR = 91.0% and 96.3% respectively) and significant differences in 48 h EHR were detected for 5 out of the 9 other diets tested, while for 96 h EHR, only for 2 diets. Population increase was determined over a 12 day culture period for 10 initial B. similis adults (7 females and 3 males) and the result showed that the tri-algal diet T-Iso + Tet + Pav produced significantly higher population number by the end of 12 days than any of the mono-algal or binary diets tested ( p < 0.05). When all developmental stages were included (including eggs), the tri-algal diet produced a population increase from 10 to 887 over the 12 days. The binary diet Tet + T-Iso was the second most productive diet, providing a total population increase from 10 to 541, which was significantly higher than the rest of the diets, except that of Pav + T-Iso (479), T-Iso (334) and Chaet + Pav (285) ( p > 0.05). Based on the current results, it is suggested that among the diets tested, the tri-algal diet of T-Iso + Tet + Pav was the best for the culture of B. similis.