Studies on the analysis of ecdysteroids and on the seasonal variation of the moulting hormones of the barnacle, Balanus balanoides

Abstract

The separation properties of a number of ecdysteroids were examined. The ecdysteroids themselves were separated by thin layer and reverse phase thin layer chromatography. Trimethylsilyl ethers of the ecdysteroids were prepared by reaction with trimethylsilyl- imidazole under varying conditions of time and temperature. The analysis of the trimethylsilyl ethers was examined under thin layer chromatography and gas chromatography with an electron capture detector. Using the data from the chromatographic analysis of the ecdysteroid derivatives, Makisterone A was selected as the most suitable internal standard to use in the extraction scheme.
An analytical scheme adequate to detect the very low levels of ecdysteroids in an average population of barnacles was devised.
The method permitted the use of relatively small samples (500 g. or less) of barnacle Balanus balanoides L. The method incorporated the use of solvent partitions, sephadex gel column chromatography, thin layer chromatography and gas chromatography. Using this scheme it was found that the levels of the predominant ecdysteroid, 20—hydroxy— ecdysone, vary seasonally with peaks occurring in the spring and late autumn. This variation corresponded tc the variation in moulting frequency, and is fully discussed in connection with the sea temperature, availability of food and the breeding cycle of this species of barnacle.
In field experiments at Portsmouth, live barnacles were injected either with sea water, pure ecdysone, pure hydroxyecdysone and a crude ecdysteroid fraction isolated from barnacles. Ecdysteroids did produce an increase in moulting frequency, but the effect was not easy to analyse.