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Diets of fan shells (Pinna nobilis) of different sizes : fatty acid profiling of digestive gland and adductor muscle

Pinna nobilis is a large bivalve, endemic to the Mediterranean Sea that was shown in a previous study to ingest significantly different proportions of different food items according to its shell height. Fatty acid profiling of total lipids was used to examine these differences in diet in relation to shell size. Small (shell height 23.0±3.3 cm), medium (SH 41.5±5.5 cm) and large (SH 62.7±4.8 cm) P. nobilis were collected from Mali Ston Bay, Adriatic Sea, in March 2010 and fatty acid analysis performed on digestive gland and adductor muscle tissues. Based on the analysis of the digestive gland, small P. nobilis were associated with a detrital food chain, characterized by saturated and branched-chain fatty acids, while the diets of medium and large individuals had a greater proportion of polyunsaturated fatty acids. This likely reflects the fact that smaller individuals feed within the benthic boundary layer where the detritus concentrations are high. Fatty acid incorporation into the adductor muscle, likely representative of food taken up over a longer time period, was reversed, i.e. larger individuals had lower levels of polyunsaturated fatty acids. This most probably reflects energy expenditure, which typically increases with increasing organism size.

Pinna nobilis; Pinnidae; endangered bivalve; diet; fatty acids; Adriatic Sea

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