Development, Growth, and Survival in the Juvenile Caribbean King Crab Mithrax Spinosissimus (Lamarck) Reared in the Laboratory

Two comparative growth studies were performed on spawns from the Caribbean king crab Mithrax spinosissimus (Lamarck). These studies lasted for 181 and 142 days, respectively. Crabs that exhibited long intermolt periods and a low increase in carapace length at molt during early development, because of a low water temperature and/or early lack of food, later caught up in both respects, compared to individuals raised under more favorable conditions during early development. The growth rate (carapace length) at molt (crab stages 3-12) varied between approximately 22 and 40%, and the corresponding mean weight (live wet weight) increase varied between approximately 90 and 135% (stages 7-12). Pronounced allometric growth was recorded concerning the two parameters of carapace length and width. The carapace of young crabs was considerably longer than wide, while the L/W ratio for adults was close to 1. The abdominal length and width measurements indicated that it should be possible, by visual observations, to distinguish between the sexes at a carapace length of approximately 12-15 mm, i.e., in this study, at crab stage 10 or 11, or at an age of approximately 120-140 days. In early stages prolonged intermolt periods led to a proportionally lower increase in carapace length at molt. A positive relationship was recorded between a low increase in carapace length at molt and a high mortality rate. The length of the intermolt period had, however, no significant effect on the mortality rate.