Chlamys hastata
Chlamys hastata | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Mollusca |
Class: | Bivalvia |
Order: | Pectinida |
Family: | Pectinidae |
Genus: | Chlamys |
Species: | C. hastata
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Binomial name | |
Chlamys hastata (G. B. Sowerby II, 1842) [2]
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Chlamys hastata, the spear scallop, spiny scallop or swimming scallop, is a
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
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 (
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]
Other organisms also grow on the scallop's shell. The boring sponge
Barnacles are normally
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]
References
- ^ "Chlamys (Chlamys) hastata Sowerby 1842". PBDB.
- ^ a b Dijkstra, Henk (2010). "Chlamys hastata (G. B. Sowerby II, 1842)". WoRMS. World Register of Marine Species. Retrieved 2012-05-22.
- ISBN 0-304-92909-3.
- ^ JSTOR 1541956.
- ^ a b c d "Chlamys hastata". Race Rocks Taxonomy. Lester B. Pearson College. Archived from the original on 2012-06-09. Retrieved 2012-05-22.
- ^ a b c d e Cowles, Dave (2005). "Chlamys (Chlamys) hastata (Sowerby, 1843)". Walla Walla University. Archived from the original on 2012-10-26. Retrieved 2012-05-23.
- ^ a b 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.
- ^ Jeanne Serb (2006). "Pecten Resource". Iowa State University. Retrieved 2012-05-29.
- ^ a b Carefoot, Tom. "Scallop: Predators & defenses". A snail's odyssey. Archived from the original on 2012-07-05. Retrieved 2012-05-24.
- ^ Carefoot, Tom. "Scallop: Feeding and growth". A snail's odyssey. Archived from the original on 2012-01-20. Retrieved 2012-05-24.
- ^ "Tentacles detect predators: queen scallop". Ask Nature. The Biomimicry Institute. 2009. Retrieved 2012-05-26.
- S2CID 17098499.
- ^ S2CID 8430327.
- S2CID 44000105.
- JSTOR 3515149.
- ^ "Scallop Fishery - Pacific Region". Fisheries and Oceans Canada. 2011-09-12. Retrieved 2012-05-27.
- ^ 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.