Abarenicola pacifica | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Annelida |
Clade: | Pleistoannelida |
Clade: | Sedentaria |
Clade: | Maldanomorpha |
Family: | Arenicolidae |
Genus: | Abarenicola |
Species: | A. pacifica |
Binomial name | |
Abarenicola pacifica Healy & Wells, 1959 [1] | |
Abarenicola pacifica or the Pacific lugworm is a large species of polychaete worm found on the west coast of North America and also in Japan. The worms live out of sight in burrows under the sand and produce casts which are visible on the surface.
Polychaetes, or marine bristle worms, have elongated bodies divided into many segments. Each segment may bear setae (bristles) and parapodia (paddle-like appendages). Some species live freely, either swimming, crawling or burrowing, and these are known as "errant". Others live permanently in tubes, either calcareous or parchment-like, and these are known as "sedentary".
Abarenicola pacifica is a large worm growing up to fifteen centimetres in length with an elongated, segmented body which is tapered at both ends. The head has no appendages, palps or eyes but has a prostomium and evertable oesophagus. The body is divided into three regions which are sometimes differently coloured. The segments are wider than they are long and most have setae borne on parapodia. There are between four and seven pairs of oesophageal caeca, the anterior one being larger than the others. There are some capillary setae and the segments in the middle region bear up to thirteen trunk-like sets of gills which are red due to the hemoglobin circulating in the blood. The neuropodia of these segments are short and widely separated ventrally. There are no setae on the segments of the posterior region. [2] [3]
A. pacifica is found in the intertidal and subtidal zones round the coasts of North America between Alaska and northern California and in Japanese waters. [2] It is found living under the surface of sand flats and muddy shores, and in estuaries where it can tolerate salinities of as low as 23% of normal seawater for short periods, although 50% is a more sustainable level. [4]
Like other lugworms, A. pacifica lives under the sand in a J-shaped burrow with its head at the bottom and its tail near the surface. It is a deposit feeder and the head is constantly swallowing muddy sand. This creates a shallow depression on the surface. The cleaner sand, with nutrients removed, is expelled through the posterior end of the worm and ends up as a neat pile of coiled sand on the surface. Bacteria and microfauna may colonise the worm's gut and enrich the faecal casts. Some beaches may have fifty to a hundred lugworms per square metre and the sand is consequently being perpetually recycled by the worms. The lugworm maintains a constant stream of water through the burrow by the alternate contraction and dilatation of its body segments. Gas exchange is facilitated by the bushy tufts of gills which project from its middle region and which continually turn and flex. These adaptations to life under the sediment provide protection for the worm from desiccation and predation while providing a plentiful supply of food and oxygen. [5] At low tide, when the sediment in which the lugworm is living is no longer covered by water, aerial respiration takes place. [6]
When feeding, A. pacifica everts its oesophagus (which then resembles a mushroom) and engulfs a "mouthful" of sand before restoring the oesophagus to its rightful position. [2] Organic detritus and organisms such as nematodes, diatoms, bacteria and microphytes [7] are ingested with the sand and digested in the gut. Periodically, the worm reverses up its burrow and defecates near the surface, creating a mound of coiled cast. [2]
Individuals of A. pacifica are either male or female. Reproduction occurs once a year in the spring at a time when the worm has a high level of stored fats. [8] The embryos are brooded in the burrow. The larvae do not feed and only spend a short time drifting in the water, or possibly none at all. [9] When they have developed to five or six segments, they leave their mother's burrow and start living independently in the top few millimetres of substrate. They grow rapidly and become mature in one to two years. [10]
Pinnixa schmitti , the Schmitt pea crab, is a commensal of A. pacifica and is often found cohabiting in its burrow. The crab may benefit from the protective environment but it is unclear whether the worm gains from the arrangement. [11]
A. pacifica may be useful in the recovery of beaches from the effects of oil pollution. The worm helps transport sediment from lower depths to the surface where aerobic microbes can break down the pollutant hydrocarbons. [12] It is considered to be useful as an indicator species for monitoring ecological conditions after an oil spillage, being the second most useful organism after the Baltic clam ( Macoma balthica ). This is because of the abundance of the lugworm and its widespread distribution near oil facilities. [13]
The burrowing activities of A. pacifica may also cause the release of methylmercury and other heavy metals from underlying sediments into the water above. The breeding success of clams such as Macoma and Mya spp. is reduced when A. pacifica is present. Disturbance to the sediment has also been associated with a decline in the abundance of the polychaete Pygospio elegans and the crustacean Cumella vulgaris , both of which happen to be predators on juvenile lugworms. [9] The rock sandpiper (Calidris ptilocnemis), the shrimp (Crangon spp.) and the isopod, Saduria entomon prey on both adults and young. [13]
Polychaeta is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. More than 10,000 species are described in this class. Common representatives include the lugworm and the sandworm or clam worm Alitta.
Haplodrili, or Archiannelida, is an order of primitive polychaete worms. Zoologist Ray Lankester gave it the name haplodrili, while zoologist Berthold Hatschek later named it Archiannelida. Once considered to be a class under Annelida, and even a separate phylum, Haplodrili is now widely accepted to be an order under Polychaeta. Species in this order are known for completely lacking external segments.
Alitta virens is an annelid worm that burrows in wet sand and mud. They construct burrows of different shapes They range from being very complex to very simple. Long term burrows are held together by mucus. Their burrows are not connected to each other; they are generally solitary creatures. The spacing between the burrows depends on how readily they can propagate water signals.
Pomatoceros triqueter is a species of tube-building annelid worm in the class Polychaeta. It is common on the north eastern coasts of the Atlantic Ocean and in the Mediterranean Sea.
Spirorbis borealis is a sedentary marine polychaete worm in the Serpulidae family. It is commonly called the sinistral spiral tubeworm and is the type species of the genus Spirorbis.
Sabellastarte spectabilis is a species of benthic marine polychaete worm in the Sabellidae family. It is commonly known as the feather duster worm, feather duster or fan worm. It is native to tropical waters of the Indo-Pacific but has spread to other parts of the world. It is popular in aquariums because of its distinctive appearance and its ability to remove organic particles and improve water quality.
Phyllodocida is an order of polychaete worms in the subclass Aciculata. These worms are mostly marine, though some are found in brackish water. Most are active benthic creatures, moving over the surface or burrowing in sediments, or living in cracks and crevices in bedrock. A few construct tubes in which they live and some are pelagic, swimming through the water column. There are estimated to be more than 4,600 accepted species in the order.
Amphitrite ornata or ornate worm, is a species of marine polychaete worm in the family Terebellidae.
Cirratulus cirratus is a species of marine polychaete worm in the family Cirratulidae. It occurs in the littoral and sub-littoral zones of the Atlantic Ocean.
Lanice conchilega, commonly known as the sand mason worm, is a species of burrowing marine polychaete worm. It builds a characteristic tube which projects from the seabed, consisting of cemented sand grains and shell fragments with a fringe at the top.
Arenicolidae is a family of marine polychaete worms. They are commonly known as lugworms and the little coils of sand they produce are commonly seen on the beach. Arenicolids are found worldwide, mostly living in burrows in sandy substrates. Most are detritivores but some graze on algae.
Lagis koreni, commonly known as the trumpet worm, is a species of marine polychaete worm found in European waters. It lives within a narrow conical tube made of grains of sand and shell fragments.
Oweniidae is a family of marine polychaete worms in the suborder Sabellida. The worms live in tubes made of sand and are selective filter feeders, detritivores and grazers.
Hediste diversicolor, commonly known as a ragworm, is a polychaete worm in the family Nereididae. It lives in a burrow in the sand or mud of beaches and estuaries in intertidal zones in the north Atlantic. This species is used in research, but its classification is in dispute; in the literature, it is often classified as Nereis diversicolor. Its specific name "diversicolor" refers to the fact that its colour changes from brown to green as the breeding season approaches.
Eunice norvegica is an aquatic polychaete worm found in deep water on the seabed of the northern Atlantic Ocean as well as in the Pacific and Indian Oceans. It is a tubeworm and is often associated with deep water corals.
Phyllodoce maculata is a species of Polychaete worm in the family Phyllodocidae. It is native to the northeastern Atlantic Ocean where it inhabits shallow water areas of sand, mud and stones.
Scolelepis squamata is a species of polychaete worm in the family Spionidae. It occurs on the lower shore of coasts on either side of the Atlantic Ocean.
Poecilochaetus serpens is a species of marine polychaete worm in the family Poecilochaetidae. It is a benthic worm that burrows into soft sediment.
Sternaspidae, commonly known as mud owls, are a family of marine polychaete worms with short swollen bodies. They have a global distribution and live buried in soft sediment at depths varying from the intertidal zone to 4,400 m (14,400 ft).
Diopatra claparedii is a species of tube-building polychaete worm of the family Onuphidae. It is found dispersed along intertidal and subtidal benthic environments of South Asian waters, especially along the coasts of Malaysia, Singapore, Thailand, and the Philippines. This species is exploited by humans for fishing bait, indication of marine pollution, and as gold and silver nanoparticle biosynthesis agents.