Vitamin A and carotenoids in certain invertebrates: II. Studies of seasonal variations in some marine crustacea

Summary Results are given for measurements of fat, vitamin A and carotenoids in groups of Meganyctiphanes norvegica, Thysanoessa raschii, Crangon allmani, C. vulgaris, Nephrops norvegicus and eyes of Homarus vulgaris, collected at regular intervals for a year or longer. In both species of euphausiids vitamin A was consistently present mainly in the ester form and concentrated chiefly in the eyes. More than half the total astaxanthin was in the eyes. No other carotenoids were detected. Astaxanthin and vitamin A were accumulated by the euphausiids more rapidly during the spring and autumn-feeding periods associated with diatom outbursts than at other seasons. There was a delay in Thysanoessa raschii, but not in Meganyctiphanes norvegica, between resumption of more rapid growth during spring and autumn and increase in concentration of vitamin A and astaxanthin. The difference was possibly due to differences in diet of the two species in relation to the seasonal biological composition of the plankton. In the euphausiids, concentrations of vitamin A and astaxanthin were much higher in larvae and in adults over 30 mm long of M. norvegica, and in larvae and adults over 15 mm of Thysanoessa raschii, than in mature adults of Meganyctiphanes norvegica of 20–30 mm and Thysanoessa raschii of 13–15 mm, respectively. An inverse relationship between fat and vitamin A concentration was noted in both species throughout the year. In Crangon spp. and Nephrops norvegicus there was no evidence of any seasonal variation of either vitamin A or carotenoids. Differences in the carotenoid metabolism of the two species of Crangon are discussed.