Scientific

Empty shells wash up on the Astarte castanea shoreline

Class: Bivalvia

Order: Veneroida

Family: Astartidae

Genus: Astarte

To the north it occurs in the Gulf of St. Lawrence including the Distribution St. Lawrence estuary, New Brunswick, Prince Edward Island This species of Astarte can and Nova Scotia. It continues south down along the Gulf of be found along the Atlantic Maine to New Jersey. It occupies the Bay of Fundy and is found coast of North America. locally. It also occurs in areas of the United Kingdom.

Habitat It is benthic, living on the ocean floor in areas that are soft and This is a coastal, shallow muddy, or sandy. It lives in areas of the Atlantic where the waters bivalve, occurring at climate is temperate. It is infralittoral. This means living in the depths of 0 to50 metres. region of shallow water closest to the shore.

Food They filter the surrounding water for planktonic and minute As with the majority of detrital food items. They are both deposit feeders and surface bivalves Astarte are filter grazers. Food particles may be suspended in the water or feeders. deposited on the ocean floor.

Reproduction The timing and duration of gametogenesis, which is the The majority of bivalves are formation of gametes, or reproductive cells such as ova and also dioecious, meaning the sperm, varies with each species of Astarte. Surrounding sexes are separate. There is conditions influences the timing of spawning. The boreal forms no copulation between spawn over a relatively short period in spring and summer. In bivalves. Males and females Arctic waters it takes place over longer periods. Astarte castanea release sperm and eggs into is a temperate species and spawning begins in spring and the water for fertilization. summer.

Development Typically a bivalve starts life as a trochophore (early stage larva), Fertilization is in response before becoming a veliger. The free-swimming veliger larva lives to environmental a planktotrophic, pelagic life for several weeks. They float conditions. After it takes around in the currents until they metamorphose into juveniles. place the eggs develop into They begin to look like tiny clams. These juveniles spend their larvae. The length of time first year in a growth season, drifting to and fro, growing and this takes varies being developing before settling down into their eventual chosen dependant also on location in the mud along the shallow coastal waters. They may surrounding conditions create temporary burrows before a final one is selected. such as water temperature.

Characteristics The genus Astarte is characterized by a pointed umbo. The The Chestnut Astarte has a umbo forms while the animal is a juvenile, periostracum (skin like and radial growth subsequently proceeds covering) which is a light around that area. brown to chestnut brown The umbo is situated above the hinge line colour. The triangular Like all molluscs Astarte have annual growth shaped shell has fine, lines. They grow to between 2.5 and 3.2 cm. concentric ridges that The foot is bright scarlet red or orange radiate from its centre. coloured, due to the haemoglobin found These ridges or grooves are in its blood. This is actually an uncommon alternatively strong and trait in molluscs and can therefore be used to weak and show through the distinguish between species. skin covering. The sexes are similar in appearance.

Adaptations The shell is quite heavy and The development of this very distinct skin thick with a strong hinge covering (periostracum) is complex. An and a flexible ligament. The electron microscopic study of the outer and interlocking teeth help to middle folds of the mantle edge of Astarte strengthen closure. castanea reveals the fine-structural details of The periostracum (skin the cells which are involved in the formation covering) is also quite of the shell’s skin covering. As the strong and durable. periostracum matures, the two membranous They have adaptive layers remain remarkably constant in width, colouration. Shells thrown whereas the two inner layers, dark up from deeper waters are homogeneous and fibrous translucent, darker coloured than those increase in thickness. The fibrous translucent found in sandy areas. layer is the third layer of the fully mature periostracum. Status/Threats Storms, dredging and water They have many natural predators at all pollution threaten regional stages of development - crabs, waterfowl, populations. fish, jellyfish etc

Sightings in Nova Scotia These occur in Nova Scotian waters. They can be found on the Burntcoat Head shoreline.