| Summary: | VII International Symposium on Marine Sciences (ISMS 2020), 1-3 July 2020 (Barcelona).-- 1 page Doris kerguelenensisis an Antarctic heterobranch molluscf eeding on several demosponges and hexactinellid sponges. To assess the contribution of several sponge species to its diet at Deception Island we used stable isotopes of C and N, as well as fatty acids. We examined the demosponges Axinella crinita, Dendrilla antarctica, Hemigellius pilosus, Kirkpatrickia variolosa, Mycale acerata, Sphaerotylus antarcticus, and Haliclona sp. We also analyzed the macroalgae Desmarestia anceps and Himantothallus grandifolius, and phytoplankton. D. anceps was the most 13C depleted one and phytoplankton the most enriched. The δ13C values of sponges and D. kerguelenensis laid in between. The δ15N values of A. crinita, D. antarctica, M. acerata and Haliclona sp.suggested a trophic position between 2-3, and for H. pilosus and S. antarcticus between 3-4. Kirkpatrickia variolosa was in between the two groups. The δ15N values of D. kerguelenensis revealed a trophic position from 3-4. All sponges and D. kerguelenensis had high levels of 15:0 and EPA and low levels of arachidonic acid, largely differing from macroalgae. Fatty acid profiles of A. crinita, D. antarctica, K. variolosa, M. acerata, S. antarcticus, and Haliclona sp. were similar to phytoplankton, but D. kerguelenensis and H. pilosuswere enriched in 17:0, 20:1n9 and 20:2. D. kerguelenensis, A. crinita, D. antarctica, K. variolosa, Haliclona sp. and S. antarcticus shared a long chain fatty acid absent in phytoplankton and macroalgae.The overall evidence suggests that A. crinita, D. antarctica, K.v ariolosa and Haliclona sp. are the most likely prey of D. kerguelenensis at Deception Island Peer reviewed
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