Very slow development in two Antarctic bivalve molluscs, the infaunal clam Laternula elliptica and the scallop Adamussium colbecki

first_imgEmbryos of the large infaunal clam Laternula elliptica and the scallop Adamussium colbecki, from Antarctica, were cultured over an 18-month period. Their development rates were extremely slow, taking 240 and 177 h, respectively, to reach the trochophore stage. This is x4 to x18 slower than related clams and scallops from temperate latitudes. The relationship between temperature and development rate for bivalve molluscs shows the expected slowing with reduced temperature (Q(10) in the range 2-4) for temperate and tropical species. However, the slowing at polar latitudes is much stronger than at warmer waters, and all of the limited data for Antarctic species are well above the Arrhenius plot for the overall bivalve data, and the Q(10) value for Antarctic to cool temperate species is 11.8, well outside the expected range for biological systems. Either the relationships describing the effects of temperature on the kinetics of biological systems do not apply to Antarctic bivalve molluscs, or some other factor that cannot be compensated for becomes important at low temperature. In the laboratory, L. elliptica embryos stayed viable in very sticky egg capsules for up to 18 months without hatching. However, even the disturbance of removing eggs using a pipette ruptured some egg capsules allowing embryo release. Gametogenesis in Antarctic marine invertebrates is almost universally slowed compared to temperate species, with nearly all cases documented requiring more than 1 year to complete oogenesis. The only exception so far appears to be A. colbecki, which has a 1-year gametogenic cycle. The data here indicate that it has been unable to adapt embryonic development in a similar way, and we are not aware of any exceptions to the markedly slowed development at low temperature rule.last_img read more

Escaping the oligotrophic gyre? The year-round movements, foraging behaviour and habitat preferences of Murphy’s petrels

first_imgThe South Pacific Gyre is the world’s largest expanse of oligotrophic ocean and supports communities of endemic gadfly petrels Pterodroma spp., yet little is known about their foraging ecology in this nutrient-poor environment. We tracked Murphy’s petrels Pterodroma ultima with geolocators from Henderson Island, Pitcairn Islands, for 2 consecutive years (2011 to 2013). During pre-laying exodus, petrels travelled south and southwest of the colony, with males travelling further than females to more productive waters. During incubation, birds foraged at the southern and eastern edges of the Gyre, with some travelling over 4800 km from the colony, the greatest recorded foraging range of any breeding seabird. During non-breeding, the petrels migrated to the Subarctic Gyre in the North Pacific to forage in cool, mesotrophic waters. Habitat models revealed that these birds do not have clear preferences for oceanographic (such as fronts or eddies) or topographic (seamounts) features, generally favouring deep and unproductive waters. Analyses of activity patterns indicated Murphy’s petrels are amongst the most active of all seabirds, particularly during incubation when they spent ca. 95% of their time at sea in flight. The birds did not appear to forage during darkness, but flight activity peaked at dawn, particularly during non-breeding, suggesting they feed on mesopelagic prey that are diel vertical migrants. At-sea protection for such a wide-ranging species would require management at huge spatial scales, and hence in the short term, the principal focus for conservation should be on eliminating the immediate threat from invasive mammals at breeding sites.last_img read more