Zool 250
Best Annotated Bibliography 1999 (#1)
Submitted by Jordon Pon


Tomaschko, K.H. 1994. Ecdysteroids from Pycnogonum litorale (Arthropoda, Pantopoda) act as chemical defense against Carcinus maenas (Crustacea, Decapoda). Journal of Chemical Ecology 20: 1445-1455.

Pycnogonum litorale contain the highest concentrations of ecdysteroids ever found in any animal. They exhibit the presence of ecdysteroids in all stages of development. Since ecdysteroids are molting hormones in Pycnogonids, it does not justify its presence during the non-molting phases. Could there be any other functions? That is, can ecdysteroids be used as a defensive property for Pycnogonum litorale?

Pycnogonum species have no physical defensive capability and, other then their planktonic first larvae stage, have limited locomotion. There are eight different kinds of ecdysteroids. The most important in this study are 20-hydroxyecdysone (20E) and 20-hydroxyecdysone 22-acetate (20E22A).

Tomaschko fed crabs (Carcinus maenas) both pellet forms and living Pycnogonum litorale after 24 hours of starvation, and observed their reaction. He found that crabs first mouthed the pellets containing ecdysteroids (20E and 20E22A) then rejected them. For the living Pycnogonum litorale, there was increased ventilation observed and the crab moved away not touching them.

Tomaschko indeed found that the ecdysteroids 20-hydroxyecdysone and 20-hydroxyecdysone 22-acetate acted as a chemical deterrent in the food acceptance of Carcinus maenas. This study thus illustrated the other possible uses for the uncommonly high levels of ecdysteroids present in all stages of Pycnogonum litorale, and showed that ecdysteroids have defensive capabilities, therefore giving an explanation of its presence during all developmental stages.

(238 words)


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(posted January 18, 2000)