MEPS 574:65-74 (2017)  -  DOI: https://doi.org/10.3354/meps12179

ABSTRACT: The drivers determining species’ northern distribution limits remain elusive and, combined with inadequate knowledge of past and current distribution ranges, this prevents accurate determination of potential changes in the Arctic. The northernmost population of the bivalve Mytilus trossulus is found in north Greenland, an area characterized by low temperature, prolonged winters and a short productive period. This population, therefore, provides a unique opportunity to study whether a temperate bivalve species can sustain a population near its pole-ward distribution limit through reproduction. We assessed gametogenesis and biochemical composition in intertidal M. trossulus specimens during the ice-free period (July-September). Results showed that the qualitative traits of gametogenesis and oocyte production in this population were comparable to M. trossulus found in temperate regions. In addition, we found that M. trossulus larvae settle annually in the lowest intertidal zone, indicating successful fertilization of eggs and larval survival. Our combined results suggest that gonadal development or larval survival do not limit the northern distribution of this species, even in a region characterized by limited food supply and sub-zero water temperatures for 9 mo of the year. Instead, for this marine invertebrate with a larval life-stage, oceanographic conditions and dispersal barriers, rather than physiological constraints, could be more important in determining the northern range limit.

KEY WORDS: Arctic benthos · Biochemical composition · Blue mussels · Glycogen · Gametogenesis · Spawning · Temperature · Oogenesis