ANDERSON, M. J.; WILLIAMS, E. E.*; Salisbury University; Salisbury University: The fatty acid composition of gill phospholipids from the blue crab (Callinectes sapidus) changes during the molt cycle

The body and appendages of crustaceans are covered by an exoskeleton called the cuticle and its underlying hypodermis. In most species the cuticle is made rigid by calcification. The lamellae of the gills are also covered by cuticle and hypodermis, but here calcification does not occur. Previously, we found that in the blue crab the fatty acid composition of phospholipids isolated from hypodermal cells of calcified cuticle changed dramatically during the early post-molt period. In this study we examined the phospholipid fatty acid composition of gills during the same period. At predetermined intervals after ecdysis anterior and posterior gill filaments were excised. Total lipids were extracted and the fatty acid compositions of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were determined by gas chromatography. In both anterior and posterior gill filaments the PE pool was highly enriched with polyunsaturated fatty acids, especially eicosapentaenoic acid (20:5) and docosahexaenoic acid (22:6) which together made up 50% of the total fatty acids of the PE pool. The fatty acid profile of PE did not change during the first 72 hours post-ecdysis in either set of filaments. In contrast, at the time of ecdysis the PC pool was characterized by high levels of saturates, which made up 40-50% of the total fatty acids in that pool. By 24 hours post-ecdysis the proportion of saturates had dropped 20% and had been replaced by 20:5 in the anterior gill and 20:5 and 22:6 in the posterior gill. The functional consequences of these changes in gill phospholipid fatty acids are unclear and are currently under investigation. They are likely related to the large changes in whole animal water flux that occur just before and after ecdysis.