Chlamys hastata

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Chlamys hastata
Temporal range: Pliocene-recent [1]
Chlamys hastata.jpg
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Pectinida
Family: Pectinidae
Genus: Chlamys
Species:
C. hastata
Binomial name
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 these scallops are harvested by divers or by narrow trawls off the west coast of Canada.

Contents

The spiny scallop lives on the seabed in the sublittoral zone between low tide mark and a depth of 150 metres (490 ft), on soft sediment or on rock, particularly in areas with a strong current. It is a filter feeder, sieving microscopic algae from water that passes through its gills. It is preyed on by starfish, octopuses and sea otters. It can detect predators by smell and by sight and can swim away from them by opening and closing its valves. Other organisms often grow on the exterior of its shell and it often forms a symbiotic relationship with an encrusting sponge which grows on the upper valve and helps protect it from predators.

Etymology

The scientific name is derived from chlamys, the Latin word for a Greek cloak or short cape made of wool and worn by a soldier, and hastata meaning "spear-like" from the Latin hasta, a spear or javelin. [3]

Description

The shell of the spiny scallop is slightly shaped like a fan and is able to grow to a height of about 9 centimetres (3.5 in) though a more normal adult size is 6 centimetres (2.4 in). The shell is composed of two valves, each of which is convex and has a small number of broad ribs covered with blunt spines. These radiate from the umbone, the rounded protuberance near the hinge, and between them are fine etched striations. The background colour is white with radial bands of pale purple and the right valve, which is usually underneath, is paler than the left. The annual growth rings are visible, often as concentric bands of a different hue. Beside the hinge are two irregular shell flaps or auricles with the anterior one normally being much larger than the other. This provides an attachment for the single strong adductor muscle that closes the shell. On either side of the long hinge there are some little ridges and grooves known as teeth. Their function is to prevent the valves moving sideways with regard to each other. Some bivalve shells have large "cardinal" teeth on the hinge immediately below the umbone, but the spiny scallop does not. Instead it has 5 or 6 lateral teeth lying on either side of the hinge. [4] Lining the inside of the valves is the mantle, a membrane that covers the gut and other internal organs. It can be seen round the margins of the valves as a thick layer like a sandwich filling. It is fringed with numerous short tentacles and there is a row of tiny simple eyes close to each of the valves. The animal usually lies on its right valve and its exposed, left valve often has a colonial sponge growing on it. [5] [6]

The spiny scallop can be distinguished from its close relative the Pacific pink scallop ( Chlamys rubida ) by the valves being less rounded and by the small curved spines on the ribs which give it a rough texture whereas the Pacific pink feels smooth. The glossy white interior of the spiny scallop's shell often has a purplish blotch near the umbone, not present in the Pacific pink. [6]

Distribution and habitat

The spiny scallop occurs naturally on the west coast of North America. Its range extends from the Gulf of Alaska to San Diego in southern California. It is found on the seabed in areas of sand, gravel or crushed shell and among boulders to a depth of about 150 metres (490 ft). [4] [6] It is also known from seagrass meadows and rocky shores [2] and favours locations with high currents. [7]

Biology

The spiny scallop anchors itself to the substrate with a few byssus threads. [8] It is unclear what the purpose of these is but they may serve to help orient the scallop with regard to the current for optimal feeding. Another possibility is that they may angle the scallop ready for a quick getaway. They are easily broken when the scallop starts to swim. [9] It is a filter feeder. It exposes its mantle by separating its valves and passes water through its gills by ciliary action. A large scallop can process about 4 litres of water an hour per gram of its weight. [6] Phytoplankton are sieved from the water by the gills and moved to the mouth in ciliated grooves. Here they are sorted by a pair of labial palps (mouth appendages), before being ingested. Rejected particles are formed into mucous-wrapped blobs. These are ejected from the mantle cavity at intervals along with the faeces by a rapid clapping of the valves. [10] When the gonads are ripening, a raised level of microalgae in the diet has been found to increase gonadal development. At this time, glycogen storage in the main adductor muscle is depleted as energy is transferred from there to the gonads. [7]

When the spiny scallop's valves are parted for feeding and respiration, many tentacles protrude from each edge of the mantle. The longer ones have sensitive chemoreceptor cells at their tip which can taste the water and allow the mollusc to react appropriately to, for example, the "smell" of a starfish, by taking evasive action. [11] The shorter ones, forming a ring all the way round the edge of the mantle, have simple eyes at their tips. Each eye contains a lens, two retinas and a concave spherical mirror. The eyes cannot see objects but can detect the difference between light and darkness, enabling the valves to be snapped shut if some large, threatening object looms nearby. They also seem to be able to detect the size and speed of particles moving past the bivalve in the current, enabling it to open its valves wide to feed when conditions are suitable. [12]

Spiny scallops are dioecious, individuals being either male or female. They become mature at about 2 years old and usually live for about 4 years. Breeding takes place in the summer. Gametes are released into the water column and fertilisation is external. Veliger larvae begin to develop from the eggs in about 2 days and drift with the plankton for 40 days, growing to a maximum valve length of 240μ (0.01 inch). The larvae have a tuft of broad, compound cilia near the mouth. The velum, the locomotory and feeding organ, has bands of cilia running down it. The simple eyes and rudimentary gills start developing on about the 25th day. The foot becomes visible on the 15th day and the propodium (the projecting front end of the foot) develops on about the 28th. By the 34th day, the larva is crawling about using its foot and its cilia. [4] Metamorphosis takes place on about the 40th day. Over the course of 48 hours, the internal organs undergo a 90° rotation, the valves, hinge and ligament appear and the gills lengthen. A swimming veliger larva has become a benthic juvenile scallop. [4]

Ecology

Animals that feed on the spiny scallop include starfish, particularly the ochre star ( Pisaster ochraceus ) and the sunflower star ( Pycnopodia helianthoides ), octopuses and sea otters. [9] The scallop can swim and does so to escape from predators, repeatedly opening and shutting its valves in a clapping action. Each time the valves close, water is expelled through a gap in the mantle on the dorsal side of the hinge and the animal moves margin first, a form of jet propulsion. [5] It has chemoreceptors on the mantle margins which detect the approach of a starfish and enable it to take evasive action. [5] It also responds in this way to predators that feed on sponges, such as nudibranchs of the genus Archidoris spp.. [6]

The spiny scallop usually has a symbiotic relationship with an encrusting sponge which grows on its left valve. This is most often the orange Myxilla incrustans but is sometimes the purple or brown Mycale adhaerens . The sponge provides camouflage for the scallop and may deter predators from attacking it as sponges often produce a repulsive odour and tend to be distasteful. It also makes it more difficult for a starfish to get the strong grip with its tube feet that it needs to force the two valves of the scallop apart. [13] The sponge benefits from the fact that living on the scallop prevents it from being buried in sediment. In the wild it has been found that the scallops and their encrusting sponges both grow to a larger size in areas of high turbidity. A laboratory study showed that, in conditions where the sediment was frequently stirred up, sponges on empty scallop shells all died while those on living shells flourished. [14] However, another study showed that growth rates in scallops heavily encrusted by sponges were significantly lower than in unencumbered ones. [5]

Fossil scallop with barnacles Chlamys sp.1+ Balanus - Fosil.JPG
Fossil scallop with barnacles

Other organisms also grow on the scallop's shell. The boring sponge Cliona celata is a parasitic species which makes holes up to 1.5 millimetres (0.059 in) diameter in the valve. Other common epibionts living on the surface of the valve include tube worms, barnacles and bryozoans. In a survey undertaken off San Juan Islands, Washington, 144 scallops, C. hastata and C. rubida were dredged up, mostly from a depth of 90 metres (300 ft). The right valve was much more heavily colonised than the left with 76% clad with epibionts as against 17% of the left valves. The encrusting sponges (mostly Mycale adhaerens) were common as were the barnacle ( Balanus rostratus ) and the tube worms Neosabellaria cementarium , Serpula vermicularis and Spirorbis sp. Also encountered were other bivalves, bryozoans, brachiopods and tunicates. Many of the tubes made by the worms were unoccupied and other organisms overgrew living and dead calcareous tubes. On the lower, left valve, cyclostome and cheilostome bryozoans predominated. [15] Starfish seem equally able to force open the valves of a scallop with barnacles on it as one with none. [13]

Barnacles are normally sessile animals unable to evade predators. When they are attached to a scallop they benefit from the defence response of the mollusc to threats which enables it to avoid predation. The scallop is disadvantaged because the presence of barnacles may reduce its ability to swim. [13] It has been found that encrusting sponges emit chemicals that discourage barnacle larvae from settling nearby. The larvae preferentially settle on shells that are not encrusted with sponges. This is another way in which encrusting sponges are of advantage to the scallops which are less impeded in their ability to swim by sponges than they are by barnacles. [13]

Fishery

Some harvesting of scallops under exploratory fishing licences is done off the west coast of Canada, though a previous commercial scallop fishery has been discontinued. Methods used are diving and small trawls with a maximum width of 2 metres (6 ft 7 in). Minimum size limits are set for the height of the shells, 80 millimetres (3.1 in) for the spiny scallop and 71 millimetres (2.8 in) for the pink scallop. [16] A framework research document was published by Fisheries and Oceans Canada in 2000 which made recommendations on the development of the dive and trawl fisheries. [17]

Related Research Articles

Bivalvia Class of molluscs

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. Bivalves as a group have no head and they lack some usual molluscan organs like the radula and the odontophore. They include the clams, oysters, cockles, mussels, scallops, and numerous other families that live in saltwater, as well as a number of families that live in freshwater. The majority are filter feeders. The gills have evolved into ctenidia, specialised organs for feeding and breathing. Most bivalves bury themselves in sediment where they are relatively safe from predation. Others lie on the sea floor or attach themselves to rocks or other hard surfaces. Some bivalves, such as the scallops and file shells, can swim. The shipworms bore into wood, clay, or stone and live inside these substances.

Scallop Common name for several shellfish, many edible

Scallop is a common name that is primarily applied to any one of numerous species of saltwater clams or 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 within the superfamily Pectinoidea, which also includes the thorny oysters.

Queen scallop Species of bivalve

The queen scallop is a medium-sized species of scallop, an edible marine bivalve mollusk in the family Pectinidae, the scallops. It is found in the northeast Atlantic and is important in fisheries.

<i>Atrina rigida</i> Species of bivalve

Atrina rigida, commonly called the rigid pen shell, is a species of bivalve mollusc in the family Pinnidae.

Bivalve shell

A bivalve shell is part of the body, the exoskeleton or shell, of a bivalve mollusk. In life, the shell of this class of mollusks is composed of two hinged parts or valves. Bivalves are very common in essentially all aquatic locales, including saltwater, brackish water, and freshwater. The shells of bivalves commonly wash up on beaches and along the edges of lakes, rivers, and streams. Bivalves by definition possess two shells or valves, a "right valve" and a "left valve", that are joined by a ligament. The two valves usually articulate with one another using structures known as "teeth" which are situated along the hinge line. In many bivalve shells, the two valves are symmetrical along the hinge line—when truly symmetrical, such an animal is said to be equivalved; if the valves vary from each other in size or shape, inequivalved. If symmetrical front-to-back, the valves are said to be equilateral, and are otherwise considered inequilateral.

<i>Chlamys</i> (bivalve) Genus of bivalves

Chlamys is a genus of small scallops, marine bivalve molluscs in the family Pectinidae. The name is taken from the Ancient Greek, χλαμΰς or Chlamys, a cloak worn by soldiers.

<i>Pecten maximus</i> Species of mollusc, also called St James shell

Pecten maximus, common names the great scallop, king scallop, St James shell or escallop, is a northeast Atlantic species of scallop, an edible saltwater clam, a marine bivalve mollusc in the family Pectinidae. This is the type species of the genus. This species may be conspecific with Pecten jacobaeus, the pilgrim's scallop, which has a much more restricted distribution.

<i>Euvola ziczac</i> Species of bivalve

Euvola ziczac, or the zigzag scallop, is a species of bivalve mollusc in the family Pectinidae. It can be found along the Atlantic coast of North America, ranging from North Carolina to the West Indies and Bermuda.

<i>Myxilla incrustans</i> Species of sponge

Myxilla incrustans is a species of demosponge. It is an encrusting species and is usually yellow.

<i>Arca noae</i> Species of bivalve

Arca noae or the Noah's Ark shell is a species of bivalve mollusc in the family Arcidae. It is found in the Mediterranean Sea from low tide mark to a depth of 60 metres (200 ft).

Antarctic scallop Genus of bivalves

The Antarctic scallop is a species of bivalve molluscs in the large family of scallops, the Pectinidae. It was thought to be the only species in the genus Adamussium until an extinct Pliocene species was described in 2016. Its exact relationship to other members of the Pectinidae is unclear. It is found in the ice-cold seas surrounding Antarctica, sometimes at great depths.

<i>Crassadoma</i> Genus of bivalves

Crassadoma is a genus of rock scallops, marine bivalve molluscs in the family Pectinidae. It is monotypic, the only species being Crassadoma gigantea, the rock scallop, giant rock scallop or purple-hinge rock scallop. Although the small juveniles are free-swimming, they soon become sessile, and are cemented to the substrate. These scallops occur in the eastern Pacific Ocean.

<i>Venerupis corrugata</i> Species of bivalve

Venerupis corrugata, the pullet carpet shell, is a species of bivalve mollusc in the family Veneridae. It is found buried in the sediment on the sea bed in shallow parts of the eastern Atlantic Ocean. It is harvested for human consumption in Spain and other parts of Western Europe.

Neosabellaria cementarium is a species of marine tube worm in the family Sabellariidae, perhaps better known by its previous name, Sabellaria cementarium. It is found in the North Pacific Ocean.

<i>Chlamys rubida</i> Species of bivalve

Chlamys rubida 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.

Hinge teeth

Hinge teeth are part of the anatomical structure of the inner surface of a bivalve shell, i.e. the shell of a bivalve mollusk. Bivalves by definition have two valves, which are joined together by a strong and flexible ligament situated on the hinge line at the dorsal edge of the shell. In life, the shell needs to be able to open slightly to allow the foot and siphons to protrude, and then close again, without the valves moving out of alignment with one another. To make this possible, in most cases the two valves are articulated using an arrangement of structures known as hinge teeth. Like the ligament, the hinge teeth are also situated along the hinge line of the shell, in most cases.

Adductor muscles (bivalve)

The adductor muscles are the main muscular system in bivalve mollusks. In many parts of the world, when people eat scallops, the adductor muscles are the only part of the soft parts of the animal which are eaten. Adductor muscles leave noticeable scars or marks on the interior of the shell's valves. Those marks are often used by scientists who are in the process of identifying empty shells to determine their correct taxonomic placement.

<i>Chlamys australis</i> Species of bivalve

Chlamys australis, common name the "austral scallop", is a species of scallop, a marine bivalve mollusc in the family Pectinidae, the scallops.

<i>Chlamys swifti</i> Species of bivalve

Chlamys swifti, common name Swift's scallop, is a species of bivalve mollusc in the family Pectinidae.

Mycale adhaerens, the purple scallop sponge, is a species of marine demosponge in the family Mycalidae. Mycale is a large genus and this species is placed in the subgenus Aegogropila making its full name, Mycale (Aegogropila) adhaerens. It grows symbiotically on the valves of scallop shells and is native to the west coast of North America.

References

  1. ↑ "Chlamys (Chlamys) hastata Sowerby 1842". PBDB.
  2. 1 2 Dijkstra, Henk (2010). "Chlamys hastata (G. B. Sowerby II, 1842)". WoRMS. World Register of Marine Species . Retrieved 2012-05-22.
  3. ↑ Cassell's New Latin Dictionary. London: Cassell & Co. 1962. pp. 102, 272. ISBN   0-304-92909-3.
  4. 1 2 3 4 Hodgson, Christine A.; Burke, Robert D. (1988). "Development and Larval Morphology of the Spiny Scallop, Chlamys hastata". The Biological Bulletin. 180 (3): 303–318. doi:10.2307/1541956. JSTOR   1541956.
  5. 1 2 3 4 "Chlamys hastata". Race Rocks Taxonomy. Lester B. Pearson College. Archived from the original on 2012-06-09. Retrieved 2012-05-22.
  6. 1 2 3 4 5 Cowles, Dave (2005). "Chlamys (Chlamys) hastata (Sowerby, 1843)". Walla Walla University. Archived from the original on 2012-10-26. Retrieved 2012-05-23.
  7. 1 2 McNeill, Daniel (2010-08-28). "Conditioning the spiny scallop (Chlamys hastate) using microalgae" (PDF). Fisheries and Aquaculture Department at Vancouver Island University. Retrieved 2012-05-24.
  8. ↑ Jeanne Serb (2006). "Pecten Resource". Iowa State University. Retrieved 2012-05-29.
  9. 1 2 Carefoot, Tom. "Scallop: Predators & defenses". A snail's odyssey. Archived from the original on 2012-07-05. Retrieved 2012-05-24.
  10. ↑ Carefoot, Tom. "Scallop: Feeding and growth". A snail's odyssey. Archived from the original on 2012-01-20. Retrieved 2012-05-24.
  11. ↑ "Tentacles detect predators: queen scallop". Ask Nature. The Biomimicry Institute. 2009. Retrieved 2012-05-26.
  12. ↑ Speiser, Daniel I.; Johnsen, Sönke (2008). "Scallops visually respond to the size and speed of virtual particles" (PDF). Journal of Experimental Biology. 211 (13): 2066–2070. doi: 10.1242/jeb.017038 . PMID   18552295. S2CID   17098499.
  13. 1 2 3 4 Farren, Heather M.; Donovan, Deborah A. (2007). "Effects of sponge and barnacle encrustation on survival of the scallop Chlamys hastata". Hydrobiologia. 592 (1): 225–234. CiteSeerX   10.1.1.508.9090 . doi:10.1007/s10750-007-0743-1. S2CID   8430327.
  14. ↑ Burns, Duncan O.; Bingham, Brian L. (2002). "Epibiotic sponges on the scallops Chlamys hastata and Chlamys rubida: increased survival in a high sediment environment". Journal of the Marine Biological Association of the UK. 87 (6): 961–966. doi:10.1017/S0025315402006458. S2CID   44000105.
  15. ↑ Lescinsky, Halard L. (1993). "Taphonomy and Paleoecology of Epibionts on the Scallops Chlamys hastata (Sowerby 1843) and Chlamys rubida (Hinds 1845)". PALAIOS. 8 (3): 267–277. Bibcode:1993Palai...8..267L. doi:10.2307/3515149. JSTOR   3515149.
  16. ↑ "Scallop Fishery - Pacific Region". Fisheries and Oceans Canada. 2011-09-12. Retrieved 2012-05-27.
  17. ↑ Lauzier, R. B.; Campagna, S.; Hinder, R. (2000-12-03). "Framework for Pink (Chlamys rubida) and Spiny (C. hastata) Scallop Fisheries in Waters off the West Coast of Canada" (PDF). Canadian Stock Assessment Secretariat. Retrieved 2012-05-27.

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