BIOCHEMICAL-COMPOSITION OF AURELIA-AURITA IN RELATION TO AGE AND SEXUAL MATURITY

Dry weight (DW), ash free dry weight (AFDW), and proximate biochemical composition were examined for a full range of sizes of whole medusae of the scyphomedusa Aurelia aurita. Dry weight ranged from 3.07 to 3.9 1% of wet weight (WW), and was fairly uniform throughout the size grou ps. Ash free dry weight ranged from 25.6 to 46.0% of DW, with values s ignificantly greater in ephyrae and medusae < 20 mm. The sum of carboh ydrate, protein and lipid fractions, termed ''total organics'', is oft en taken to be synonymous with AFDW, but values were consistently lowe r than AFDW, ranging from 5.56 to 22.76% of DW. Even after AFDW had al so been calculated assuming water of hydration to be 11.7%, there were still differences between the two values. Whole Aurelia aurita medusa e displayed the typical characteristics of gelatinous predators, with low carbohydrate (0.10-1.12% of DW), intermediate lipid (3.50-11.50% o f DW), and high protein (2.07-28.56% of DW) content. The biochemical c omposition of isolated umbrellar and gonadal tissues of medusae > 50 m m were examined, and in every size group, ''total organics'' were grea ter in gonadal than umbrellar tissue. The greater organic content of g onadal tissue was the result of an increase in all three biochemical f ractions, with carbohydrates and proteins displaying the greatest diff erences. Mean values ranged from 0.33 to 0.85% carbohydrate, 2.34-8.31 % protein, and 0.87-2.91% lipid in umbrellar tissue, compared with 1.0 8-2.10%, 4.38-22.98%, and 2.59-6.08%, respectively, in gonadal tissue. The biochemical content of ripe oral arms, i.e. those containing divi ding eggs and planula larvae, was similar to that of the maturing gona ds. Protein content was greatest in gonads of medusae 60-110 mm, befor e decreasing significantly with increasing bell diameter. Rapid growth and maturation in the 60-110 mm size group was coincident with the sp ring peak of mesozooplankton abundance in Southampton Water, while the decline in protein content may be explained by loss in condition of ' 'spent'' medusae.