Size and site specific transcriptomic responses of blue mussel (Mytilus edulis) to acute hypoxia.

The Prince Edward Island (PEI) mussel aquaculture industry is being challenged by climate change induced environmental stressors including hypoxic/anoxic episodes, that can impact mussel health and survival. Physiological responses of mussels to hypoxia/anoxia have been studied; however, less is known about how transcriptomic response leads to physiology. The present study examined the transcriptomic response of acute (4 h) hypoxia in blue mussels (Mytilus edulis) from two sites and size classes in PEI, Canada. Overall, major changes in whole-mussel transcriptomics associated with metabolism, cellular organelles/processes and environmental sensing were observed in the first hours of hypoxia exposure. Differences in differentially expressed transcripts were observed between each site and size, indicating that responses to acute hypoxia exposure are highly complex. A size related pattern was observed, with seed size mussels having differential expression of transcripts associated with development, muscle function, and byssal attachment compared to the adults. Adult mussels had higher HSP 90 expression, while HSPs were predominately under-expressed in seed mussels. Seed mussels had significant under-expression of several classes of byssal thread attachment transcripts, indicating a decline in the production of byssal thread or detachment, both which have negative consequences for mussel aquaculture.

Geographic range extensions of stalked, flabelliform sponges (Porifera) from eastern Canada with a new combination of a species of Plicatellopsis in the North Atlantic.

Three new species records, Axinella arctica (Vosmaer, 1885), Semisuberites cribrosa (Miklucho-Maclay, 1870), and Cladocroce spatula (Lundbeck, 1902), and one new combination, Plicatellopsis bowerbanki (Vosmaer, 1885) comb. nov. from eastern Canada are described. The four species have similar growth forms which are either fan or cup-shaped with obvious stalks. This is the first description of a member of the genus Plicatellopsis in the North Atlantic, and the second record of the genus in the northern hemisphere. The four species described here have a history of misidentification in eastern Canada and this work aims to guide future identifications in the region.