Meeting Abstract

49.5  Jan. 6  Genome-Enabled Insight into Biogeographic Patterns of Marine Larval Thermotolerance FIELMAN, K.T.*; HOFMANN, G.E.; Auburn Univ.; UC, Santa Barbara fielman@lifesci.ucsb.edu

The role of larval thermotolerance in setting marine species� biogeographic distribution and abundance patterns is unclear and little is known of the underlying genomic-scale molecular physiology. We compared heat shock survivorship among plutei raised at 6C from cold-adapted white (S. pallidus) and green (S. droebachiensis) urchins with their more eurythermal red (S. franciscanus) and purple (S. purpuratus) congeners raised at 15C. White/green larvae had 100% mortality at 23C versus 26C for red/purples, consistent with the rank order of adult habitat and larval rearing temperatures. However, white/green larvae tolerated a greater relative increase (16C) versus the red/purples (10C). Notably, this difference contrasts with the current average habitat temperatures and biogeographic distribution patterns of each species, suggesting that simple predictions of response to change from existing biogeographical information may not be possible without further physiological information. Comparative molecular insight into the species� distinct responses was obtained by transcriptional profiling. Expression patterns were evaluated in purple and green urchins at 0, 5, and 10C above the larval rearing temperatures using macroarrays of >100,000 larval sequences. Species-specific differences were especially evident within the core processes of ribosomal assembly and protein synthesis. Strong up regulation of these genes was observed for purples, whereas a weaker induction or strong down regulation was typical for greens. Similarly, strong down regulation of 18S and 28S ribosomal RNAs in purples contrasted with moderate up regulation in greens. Thus, differences in the transcriptional response to thermal stress may ultimately underlie the distinct thermotolerance and distribution patterns among congeners.