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Eunicidae is a family of marine (bristle worms), inhabiting diverse Benthic zone habitats across Oceania, Europe, South America, North America, Asia and Africa.
One of the most conspicuous of the eunicids is the giant, dark-purple, Iridescence "bobbit worm" ( Eunice aphroditois), a bristle worm found at low tide under boulders on southern Australian shores. Its robust, muscular body can be as long as . Cultural tradition surrounds the palolo worm ( Palola viridis) reproductive cycles in the South Pacific Islands. Eunicidae are economically valuable as Fishing bait in both recreational and commercial fishing. Commercial bait-farming of Eunicidae can have adverse ecological impacts, as it may deplete worm and associated fauna population numbers, damaging local intertidal environments, and introduce alien species to local aquatic ecosystems.
Heteromarphysa Verrill, 1900 & Lysibranchia Cantone, 1983 are nomina dubia, dubious genera that are unlikely to be valid.
Fossilized jaws of Eunicidae are known from as far back as Ordovician sediments. The trace fossil ichnotaxon Lepidenteron likely corresponds to the fossilized burrow of a eunicid. These burrows are often lined with the fossilized remains of the prey of their occupant, which include a diversity of fish taxa; as these elongated burrows are often fully lined with fish bones, it can cause these burrows to be easily mistaken for the complete skeleton of an eel-like fish.
The first body segment of Eunicidae is either whole or consists of two lobes. Some species of Eunicidae have extensions of the body wall that loop into the vascular system. These usually consist of either comb-like or single filaments. The of live specimens are typically identifiable by their bright red colour.
A pair of slender and cylindrical sensory appendages are typically situated near the head of Eunicidae. The lips of Eunicidae can be either reduced or well-developed. In species of Eunice, worms have five appendages on two elongated segmented appendages and three antennae near their heads. This feature is not part of the anatomy of all genera in the Eunicidae family. Eunicidae jaws are typically well developed and partly visible on the underside of the worm or on its surface at the front of the mouth in a complex structure.
During the breeding season, female polychaetes produce a pheromone that induces a mutual release of male sperm and female eggs. This ensures reproductive synchrony, though some species ensure this by forming reproductive swarms in a phenomenon known as epitoky. During this process, there is no actual male to female contact, as the are ejected into open water, being released through an Excretion gland (Nephridium) or by the worm's body-wall rupturing, which Semelparous. Post-fertilisation, most eggs become ; although some remain inside the worm tubes or burrow in external jelly masses attached to the tubes. Epitokes may draw an increased number of Pelagic zone predators, As seen in the Florida Keys where swarming Eunice fucata attract large gatherings of Atlantic tarpon, being highly publicised in local fishing communities. These mass swarming events, or 'risings', are a spectacle that is the foundation of local tradition in Samoa, Fiji, Tonga, Papua New Guinea, Vanuatu, Kiribati and Indonesia.
Research indicates that mudworm survival and growth may be affected by changes in salinity rates.
Anatomy
Members of the Eunicidae family are distinguished from other families in Eunicida by having a rear segment with 1-3 antennae and no ringed bases on their antennae.
Head and jaws
The eunicid anatomy typically consists of a pair of appendages near the mouth () and complex sets of muscular structures on the head () in an eversible pharynx.
Ecology
Distribution and habitat
Eunicidae are distributed in diverse Benthic zone habitats across Oceania, Europe, South America, North America, Asia and Africa. Eunicids play an ecological role in benthic communities, exhibiting a preference for subtidal hard substrates in shallow temperate waters, Tropics and . Most species of Eunicidae inhabit cracks and crevices in assorted rubble, rock, and sand environments. In limestone or , Eunicids create parchment-like tubes within coral or remain in crevices of calcareous algae.
Diet
Eunicid diets vary across genera. For example, Eunice aphroditois crawl on the seafloor where they scavenge in a Carnivore feeding pattern on marine worms, small , Mollusca, algae and detritus. Other species, for example Euniphysa tubifex and large Eunice, hunt the surrounds of their coral habitats and feed on the decaying flesh of dead sea-life. Burrowing species of Eunicidae ( Lysidice and Palola) are primarily . These species feed on matured corals and contained organisms or on types of algae. The diet of Marphysa species of Eunicidae is variable, some worms are , some are , and others .
Life cycle
Most of the class Polychaeta are sexually reproductive and lack external reproductive organs.
As introduced species
Importing Eunicidae species is an established alternative to exploiting local populations for bait. This process may lead to accidental species introductions or Invasive species. Alien species can threaten the foundation of local ecosystems by altering , habitat structures and . Alien species can also introduce and Parasitism. Six species of Eunice, one species of Euniphysa, three species of Lysidice and one species of Marphysa sp. were identified as alien in local aquatic ecosystems across the Mediterranean, Red Sea, the USA Pacific and North Sea. Live bait worms are often emptied into the water body by anglers at the end of a fishing session, this is another practice that can introduce alien species to aquatic ecosystems.
Relation to humans
Marphysa sanguinea, or known locally in Italy as "Murrido", "Murone", "Bacone", and "Verme sanguigno" (literally "blood worm") is the most valuable bait of all Polychaete species collected in Italy. This species is also cultivated in United States and South Korea and is typically commercially harvested once at its optimal length of . Marphysa sanguinea can reach up to long and is collected by excavating in deep sediment. For example, in the Venetian Lagoon, fisherman dig below the sediment layers colonised by the Nereididae and sieve organic material through coarse screens. This process is also common in Italian coastal areas with intertidal and shallow littoral muddy bottoms. Eunice aphroditois, another sizeable (up to in length) species of Eunicidae, is harvested by scuba divers along the Apulia. This species is collected at soft bottom ocean floors at a depth of using specialised harvesting instruments that fit into U-shaped parchment tubes where the worm lives. This species of Eunicidae is suitable bait for fish of the Sparidae family and is used in commercial hook and line practice. Species within the Eunicidae family are also caught by recreational and commercial fisherman in estuaries along the West coast of Portugal and in Arcachon Bay in France. Marphysa are propagated and harvested in Australian estuary communities located along the coast of New South Wales and Queensland. Collecting of Marphysa moribidii as bait occurs along the West coast of Peninsular Malaysia, Marphysa elityeni are caught in subsistence fisheries in Africa and Eunice sebastiani have been reported as being harvested for bait in Brazil. Eunicids are also used as supplementary feed for aquaculture.
/ref> For example, mudworms are a part of the Penaeus monodon diet in some Thailand Hatchery. The practice of harvesting polychaetes (including species in the Eunicidae family) as bait may have negative ecological impacts on intertidal habitats and on worm population numbers. In 2019, Cabral et al. found that Marphysa sanguinea are placed at risk by overfishing and unlicensed harvesting in Portugal. The ecological impacts of bait harvesting activity can also affect associated fauna populations as well as sediment quality and bioavailability of heavy metals.
In culture
In the Indo-Pacific, during 1-2 nights each year, the epitokes of the Palola viridis species are automatised. The sizeable epitokes (up to in length) swim autonomously upwards and rupture, releasing across the surface of the ocean. The epitokes are composed of hundreds of segments, with females emerald in colour and males transitioning from orange to brown during maturation. On 'rising' night it is tradition for some local communities to attract epitokes with artificial light sources or using other traditional methods. In Samoa for example, locals wear necklaces made of mosoʻoi flowers and use the fragrant floral scent to attract palolo worms. The epitokes are scooped from the shallows into nets and containers to be consumed raw, or cooked, baked, dried or frozen for later consumption.
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