Laternula elliptica is a species of saltwater clam, a marine bivalve mollusc in the family Laternulidae, the lantern shells. It is the largest bivalve found under the surface of the seabed in the Southern Ocean.
The shell of Laternula elliptica is thin, brittle, and slightly inflated and grows to a length of 10 centimetres (3.9 in). The left valve is slightly larger and more convex than the right. The general shape is an elongated oval with the posterior end somewhat truncated and narrower than the anterior end. The umbone is shallow and slightly nearer the posterior end and there is a characteristic short transverse crack in it. The internal ligament is supported by a diagonal ridge of shell and there are no teeth near the hinge. The exterior of the shell is white, slightly granular and sculptured with fine concentric lines. The interior of the shell is somewhat nacreous, with two adductor muscle scars and a pallial line that is slightly concave at the anterior end and has a broad pallial sinus at the posterior end. There is a gape at both ends of the shell and a pair of long siphons emerge from the posterior end being fused for their full length. The mantle margins are also fused apart from a small gap at the anterior end and the foot is small.
Laternula elliptica is found in the Southern Ocean, round Antarctica and the tip of Patagonia. It has been found in waters as shallow as the intertidal zone and as deep as the continental slope (~700 metres (2,300 ft)), but it is most common in shallow waters. It is found living in soft substrates such as muddy sand and gravel in which it burrows deeply. It is sometimes found in densities of upward of 100 individuals per square metre.
Like other members of the family Laternulidae, Laternula elliptica is a filter feeder. It lies beneath the substrate with its siphons extended to the surface. Water is drawn in through the inhalant siphon by a pumping action of the gills. As it passes over the gill flaps, gaseous exchange takes place and phytoplankton and detritus are captured by cilia and moved in a flow of mucous to the mouth. The water then emerges through the exhalant siphon.
Laternula elliptica is a hermaphrodite. Fertilisation is external and epidemic spawning events sometimes occur. These greatly increase the concentration of gametes in the water and raises the rate of successful fertilisation of eggs. The embryos are lecithotrophic and the larvae remain inside the egg capsules and feed on the yolks of the eggs for some months before hatching direct into juveniles and settling on the seabed.
The concentric sculptured lines on the shell have been shown by radioactive carbon and oxygen dating to occur annually and have been used to tell the age of the animal. It has been found to live for up to twenty years.
