Effects of eyestalk ablation at different times of the year on molting and reproduction of the estuarine grapsid crab Chasmagnathus granulata (Decapoda, Brachyura)

STELLA, V,S,; LÓPEZ GRECO, L.S.; RODRÍGUEZ, E.M.

JOURNAL OF CRUSTACEAN BIOLOGY

CRUSTACEAN SOC

Año: 2000 vol. 20 p. 239 - 244

0278-0372

The effect of unilateral and bilateral eyestalk ablation on molting and reproduction of the estuarine crab Chasmagnathus granulata was studied, during the pre-reproductive (PRE), reproductive (R) and post-reproductive (POST) periods under constant laboratory conditions. The effect of the laboratory conditions themselves was also evaluated by comparing the control intact crabs maintained in the laboratory with an intact outdoor group. Bilateral ablation was a stronger inducer of molting that was unilateral ablation. The former treatment induced in both sexes the highest percentages of molting (65-100%) in shorter times, as well as a higher size increment at molting, regardless of the period when it was performed. During POST unilateral-ablated and intact crabs from both sexes also molted, females in a higher percentage than males. No spawning was recorded in females that had undergone bilateral ablation. Unilateral-ablated and intact females first spawned and then molted during R. Unilateral ablated females also had during R up to two spawnings before molting, while the laboratory control crabs had only one. The laboratory control and unilateral ablated females  spawned during PRE, while none of the outdoor control did during that period.  We conclude that: (1) Bilateral ablation is a very strong inducer of molting for both sexes, in any season of the year, (2) Unilateral ablation increases the female reproductive output during the reproductive period, and (3) The laboratory conditions used in this study are capable of inducing spawning during the pre-reproductive period.