Age-dependent expression of stress and antimicrobial genes in the hemocytes and siphon tissue of the Antarctic bivalve, Laternula elliptica, exposed to injury and starvation
Increasing temperatures and glacier-melting at the Western Antarctic Peninsula (WAP) are causing rapid changes in shallow coastal and shelf systems. Climate change related rising water temperatures, enhanced ice scouring as well as coastal sediment run-off in combination with changing feeding conditions and microbial community composition will affect all elements of the nearshore benthic ecosystem, a major component of which is the Antarctic soft shell clam Laternula elliptica. 454 RNA sequencing was carried out on tissues and hemocytes of L. elliptica, resulting in 42.525 contigs of which 48% were assigned putative functions. Changes in the expression of putative stress response genes were then investigated in hemocytes and siphon tissue of young and old animals subjected to starvation- and injury-experiments in order to investigate their response to sedimentation (food dilution, starvation) and iceberg scouring (injury). Analysis of antioxidant defense (Le-SOD, Le-catalase), wound repair (Le-TIMP, Le-chitinase), stress and immune response genes (Le-HSP70, Le-actin, Le-theromacin) revealed that most transcript were more clearly affected by injury rather than starvation. The up-regulation of these genes was particularly high in the hemocytes of young, fed individuals after acute injury. Only minor changes in expression were detected in young starved and old animals. The stress response of L. elliptica thus depends on the nature of the environmental cue and on age. This has consequences for future population predictions as the environmental changes at the WAP will differentially impact L. elliptica age classes and is bound to alter population structure.