Meeting Abstract

15.1  Monday, Jan. 4  Differential response to eyestalk removal and multiple autotomy in the fiddler crab, Uca pugilator . HOPKINS, P.M*; DURICA, D.S.; DAS, S.; KHAMBADAKONE, D.; Univ. of Oklahoma, Norman phopkins@ou.edu

Eyestalk ablation (ESA) and multiple limb removal (multiple autotomy, MA) are techniques used to propel crustaceans into a precocious molt. These two techniques are not, however, equivalent. ESA removes the source of many neurosceretory products and their primary release site whereas MA leaves those sites intact. This study compares the effects of these two operations on the ability of animals to regenerate, on circulating levels of multiple hormones, and on the length of the molt cycle. We have shown that during the period leading up to molt, ESA animals produced more total ecdysteroids than MA animals (Hopkins, 1992) supporting an inhibitory role for eyestalk factors. Moreover, ESA crabs had higher levels of ponasterone A (PA) during the entire period whereas MA crabs had higher levels of 20-hydroxyecdysone (20E) suggesting that eyestalk factors may exert some influence over which ecdysteroid product is produced by the Y-Organs at any given time during the molt cycle. Since ESA removes the source of the molt-inhibiting hormone that putatively inhibits the Y-Organ production of ecdysteroids, one would expect that molting would occur fairly quickly after ablation. This is not the case. Crabs collected during the winter and subjected to ESA (or MA) do not molt for at least forty days after ablation or autotomy. The levels of circulating ecdysteroids cycle during the period leading to molt. Of the animals subjected to ESA or MA fully 50% of them do not go through a complete molt. The circulating ecdysteroids in these animals differs substantially from the animals going through the molt. These non-growing crabs have viable limb buds that emerge from the coxa much later than the molting cohorts. There is also a seasonal effect. Crabs removed from the field during the summer can have a shorter molt cycle in response to ESA and MA than do animals collected during the winter.