Most Antarctic bivalves are small and protect their young by holding fertilized eggs or larvae in their mantle cavities for varying periods. Nourishment for these early growth stages is provided by yolk reserves rather than by planktotrophy. The anomalously large Antarctic scallop, Adamussium colbecki, has unprotected planktotrophic larvae that are spawned during the austral spring. Successful recruitment of these larvae, in populations which are most abundant in oligotrophic habitats, may be associated with episodic pulses of organic material. Reasons why planktotrophy persists in A. colbecki are suggested by a comparison with another large Antarctic bivalve, Laternula elliptica. The latter has protected lecithotrophic larvae that are released at the beginning of the austral winter. This comparison suggests that unprotected larval development persists in A. colbecki because of unusual anatomical and ecological adaptations among the adults of the Adamussium lineage that have been evolving in the Southern Ocean since the early Oligocene.

Body size, geographical distribution and biomass make Laternula elliptica one of the most important bivalve species of the Antarctic. A complete study on the population dynamics (reproduction cycle, growth, mortality and productivity) of this species from King George Island gave growth parameters for the von-Bertalanffy-growth-function of: L∞ = 112.2 mm, K = 0.160 yr 1, t0 = 0.000 yr. Total mortality was estimated as Z = 0.392 yr−1. Somatic production and mean biomass of two distinct sub-populations were 8.7 and 67.3 g AFDW m−2 yr−1 at Beach & Glacier and 20.0 and 88.6 g AFDW m−2 yr−1 at Punta Elefante. The following P / B values were calculated; Beach & Glacier = 0.129, Punta Elefante = 0.226. It is suggested that these differences are linked to mortality caused by icebergs which is expected to be higher at the shallower Punta Elefante site.

Variations of metal concentrations with body size were investigated in kidney, digestive gland and gill of the Antarctic clam, Laternula elliptica, collected from a near-shore habitat at King George Island. Positive relationships for metal concentrations with body size were common among the three organs for most of the metals, while an inverse relationship was found only in the digestive gland for Cu, Zn and Mn. In the gill, concentrations of eight out of the ten metals increased linearly with body size, whilst in the kidney concentrations of Cd, Zn, Pb, Co and Ni were best fitted by quadratic regression curves, viz. increasing continuously until reaching a peak at around an 80 mm shell length. This may reflect specific regulatory activities for the extremely high accumulation of these metals in the kidney, particularly Cd (28–354 μg g−1 tissue dry weight). The overall prevalence of positive relationships indicate net accumulation of these metals throughout life, which may be at least in part associated with the slow growth and long life span of this cold-water bivalve species. The study demonstrates distinct body size-metal concentration relationships in the three organs of L. elliptica, and suggests they may be useful as biomonitors for assessing changes in metal concentrations in Antarctic waters.