''Poromya granulata'', or the granular poromya, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of marine

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Poromyidae Poromyidae is a family of saltwater clams, marine bivalve molluscs in the order Anomalodesmata. The genus ''Dilemma'', described in 2008, is remarkable for being a predator of copepods, which is very unusual for a sessile mollusc. Genera and sp ...

. It is unusual among bivalves in being carnivorous. It is found in more northerly parts of the Atlantic Ocean.

Description

''Poromya granulata'' is a dull-white coloured shell with dome-shaped valves and grows to about long. The

valves A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fitting ...

are thin and fragile, subequivalve and subequilateral. They are roughly oval in shape with a rounded anterior margin and a subtruncated, sloping posterior margin. The umbones are prominent. The surfaces of the valves have faint concentric sculpture lines and are covered in rows of fine granulations. The margins are smooth and the ligament is mostly internal. The right valve has a single cardinal tooth and the left valve has a ridge-like lateral tooth and a socket for the cardinal from the right valve. The inside of the valves is nacreous and the pallial line has a broad, shallow sinus.''Poromya granulata'' (Nyst & Westendorp, 1839)
Marine bivalve shells of the British Isles. Retrieved 2012-01-13.

Distribution and habitat

''Poromya granulata'' has a

subarctic The subarctic zone is a region in the Northern Hemisphere immediately south of the true Arctic, north of humid continental regions and covering much of Alaska, Canada, Iceland, the north of Scandinavia, Siberia, and the Cairngorms. Generally, ...

and boreal distribution on either side of the North Atlantic Ocean. Around the

British Isles The British Isles are a group of islands in the North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner and Outer Hebrides, the Northern Isles, ...

it is commoner in the north. Off the North American coast its range extends as far south as the

West Indies The West Indies is a subregion of North America, surrounded by the North Atlantic Ocean and the Caribbean Sea that includes 13 independent island countries and 18 dependencies and other territories in three major archipelagos: the Greater A ...

. It is usually found partially buried in the sandy

seabed The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

at ocean depths ranging from to , on the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

and

marginal zone The marginal zone is the region at the interface between the non-lymphoid red pulp and the lymphoid white-pulp of the spleen. (Some sources consider it to be the part of red pulp which borders on the white pulp, while other sources consider it to ...

Biology

Unlike the majority of bivalve molluscs, ''Poromya granulata'' is a

carnivore A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...

.The Bivalve, ''Poromya granulata''
Archerd Shell Collection. Retrieved 2012-01-13. It mostly feeds on small

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

s but is also a

scavenger Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding b ...

. The inhalent

siphon A siphon (from grc, σίφων, síphōn, "pipe, tube", also spelled nonetymologically syphon) is any of a wide variety of devices that involve the flow of liquids through tubes. In a narrower sense, the word refers particularly to a tube in a ...

is enlarged and modified into a cowl-shaped organ that can catch

prey Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...

. Water is drawn in through this siphon and pumped out of the small, exhalent siphon. The large siphon can be retracted rapidly when it has trapped an item of food. In doing so it turns itself inside out and conveys the food to the mouth. This is an opening in the mantle and leads to a gizzard, where the food is ground up before passing into the gut, which is adapted to receive large items of food. The fringe of tentacles round the siphons have sensory cilia which are believed to alert the animal to the presence of moving prey in the vicinity. The blood contains red

amoebocytes An amebocyte or amoebocyte () is a mobile cell (moving like an amoeba) in the body of invertebrates including cnidaria, echinoderms, molluscs, tunicates, sponges and some chelicerates. They move by pseudopodia. Similarly to some of the white bloo ...

containing

haemoglobin Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyte ...

References

{{Taxonbar, from=Q3012552 Poromyidae Bivalves described in 1839