''Chlamys rubida''
[Also known as the Pacific pink scallop, pink scallop, scooter scallop (for its tendency to "scoot" along the sea floor, and the singing scallop (for the noise it sometimes makes while swimming] 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
bivalve mollusc in the
family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
Pectinidae
Scallop () is a common name that encompasses various species of marine bivalve mollusks in the taxonomic family Pectinidae, the scallops. However, the common name "scallop" is also sometimes applied to species in other closely related families ...
found on the west coast of North America from the
Gulf of Alaska
The Gulf of Alaska (Tlingit: ''Yéil T'ooch’'') is an arm of the Pacific Ocean defined by the curve of the southern coast of Alaska, stretching from the Alaska Peninsula and Kodiak Island in the west to the Alexander Archipelago in the east ...
to
San Diego
San Diego ( , ; ) is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the eighth most populous city in the United State ...
,
California
California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...
.
Description
The pink scallop has two convex valves joined together by a hinge joint and grows to a diameter of about . Each valve has an umbo or knoblike protuberance from which 20 to 30 shallow ridges radiate to the margin at the other side of the shell. The left valve is usually uppermost as it lies on the seabed and is some shade of red intermixed with white streaks. The annual growth rings can be seen and there is concentric sculpturing parallel to the margin, often in a different shade of pink. The lower valve is either a paler shade of pink or dull white. There is a large auricle or flap on one side of the umbo. When the animal is feeding, it holds the valves apart and the mantle becomes visible, fringed with short tentacles and with a ring of tiny eyes near the margin of each valve.
The pink scallop can be distinguished from its close relative the spiny scallop (''
Chlamys hastata
''Chlamys hastata'', the spear scallop, spiny scallop or swimming scallop, is a species of bivalve mollusc in the family Pectinidae found on the west coast of North America from the Gulf of Alaska to San Diego, California. A limited number of th ...
'') by the valves being rather more rounded and by the lack of spines on the ribs which gives it a smooth texture. The glossy white interior of the shell does not have the purplish markings that are sometimes present in the spiny scallop.
Distribution
The pink scallop is found on the Pacific Coast of North America at depths down to about . Its range extends from Alaska to San Diego, California but it is more common in the northern half of this range. It is also found in Kamchatka, the Sea of Okhotsk and Japan. It is found on rocks or on sandy or muddy sea beds.
[
]
Ecology
The pink scallop usually has a symbiotic relationship
Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...
with an encrusting sponge, usually the orange ''Myxilla incrustans
''Myxilla incrustans'' is a species of demosponge. It is an encrusting species and is usually yellow.
Description
''M. incrustans'' is an encrusting sponge occurring in patches up to across and high. It is usually some shade of yellow but can ...
'', which grows on its left valve. The sponge provides camouflage
Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...
for the scallop, and may deter predators from attacking it. The sponge also makes it harder for a starfish to pull open the scallop with its tube feet
Tube feet (technically podia) are small active tubular projections on the oral face of an echinoderm, whether the arms of a starfish, or the undersides of sea urchins, sand dollars and sea cucumbers; they are more discreet though present on br ...
, because it makes manipulating the shell more difficult. The sponge benefits from not being submerged by sediment in turbid conditions. In the laboratory, a study showed that when the sediment in seawater tanks was frequently stirred up, sponges on empty scallop shells all died, whereas those on living shells flourished.chemoreceptor
A chemoreceptor, also known as chemosensor, is a specialized sensory receptor which transduces a chemical substance (endogenous or induced) to generate a biological signal. This signal may be in the form of an action potential, if the chemorecept ...
s at the tips of its tentacles. It then takes evasive action, repeatedly clapping its valves together and swimming away, margin first. If a starfish succeeds in touching a sponge growing on the shell, it often turns away, apparently repelled by this distasteful coating.[
]
Notes
References
{{Taxonbar, from=Q3016144
rubida
Bivalves described in 1845
Fauna of Alaska