Technical improvements of a rearing system for the culture of decapod crustacean larvae, with emphasis on marine ornamental species

The present study compares the efficiency of cylindrico-spherical (CST) and cylindrico-conical tanks (CCT) to culture the larvae of decapod crustaceans, with emphasis to marine ornamental species, and describes a new filter system to flush uneaten preys. The ornamental shrimps Lysmata debelius, Lysmata seticaudata and Stenopus hispidus, the ornamental crab Stenorhynchus seticornis and the ornamental hermit crab Clibanarius erythropus were used as case studies. The two types of tanks displayed different water circulation patterns, with the inflowing water in CST being pushed towards the spherical bottom and vertical tank walls, in a gentle upwelling motion, while in CCT the inflowing water was abruptly pushed towards the surface at the center of the tank. In comparison to the "traditional" system, the average time required to replace the mesh screens to flush uneaten preys was inferior when employing the new filter system (30 and 5 s per tank, respectively). The average survival to metamorphosis ( standard error) recorded for L seticaudata was higher in CST (97.25 +/- 0.50%) than in CCT (94.25 +/- 0.96%), with a higher percentage of L debelius larvae in CST also being able to metamorphose (33.75 +/- 4.77%), when compared to those in CCT (6.50 +/- 3.79%). S. hispidus larvae displayed higher survival to the fifth zoeal stage when raised in CST (93.25 +/- 2.99%) than when cultured in CCT (66.50 +/- 4.20%). A higher number of C. erythropus were able to successfully occupy gastropod shells and metamorphose in CST (80.25 +/- 5.12%) than in CCT (4.25 +/- 2.22%). S. seticornis cultured in CST displayed higher survival to metamorphosis than those cultured in CCT (76.25 +/- 3.40% and 16.00 +/- 2.58%, respectively). A higher percentage of L seticaudata and L. debelius larvae at the last zoeal stage displayed intact fifth pereiopods in CST (96.02 +/- 3.40% and 88.15 +/- 8.70%, respectively), when compared to those raised in CCT (83.95 +/- 3.86% and 36.54 +/- 3.10%. respectively). The percentage of S. hispidus larvae displaying an undamaged rostrum and dorsal abdominal spine was higher in CST than in CCT (95.71 +/- 4.19% and 61.84 +/- 2.50%, respectively). Along with the new filter system, CST appear as a feasible option for the larviculture of decapods, namely marine ornamental species (shrimps, crabs and hermit crabs), allowing a better use of inert diets and minimizing the risks of larval mortality due to tangling damage, cannibalism and the action of opportunistic pathogens over damaged larvae. (C) 2008 Elsevier B.V. All rights reserved.