| Worm pearlfish | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Ophidiiformes |
| Family: | Carapidae |
| Genus: | Encheliophis |
| Species: | E. vermicularis [2] |
| Binomial name | |
| Encheliophis vermicularis [2] J. P. Müller, 1842 | |
| Synonyms [3] | |
The worm pearlfish (Encheliophis vermicularis) is an eel-like fish in the family Carapidae.
The worm pearlfish is typically 15 cm long and is characterized by its long, slender body and lack of scales. [4] [5]
Worm pearlfish lack the pectoral or pelvic fins that are common characters of the family Carapidae. [5] The upper half of its body is blackish-pinkish in color and its underside is silver. Its tail is black and tapered.
Compared to other members of the family Carapidae, the worm pearlfish has a relatively weak jaw. The maxillaries and premaxillaries in worm pearlfishes are joined by short connective fibers in the small mouth opening. Both the maxillaries and premaxillaries are connected to the fish's skin, which creates a small mouth opening. [6] Worm pearlfishes’ mouths are smaller and weaker than mouths of pearlfishes in other genera because they feed on soft, unresisting food in a confined space, as opposed to swift-moving, unconstrained prey. [7] Their upper jaw is lined with an outside row of strong, curved teeth, and an inner row of conical teeth. [6] Worm pearlfishes’ lower jaws contain one row of 20 conical teeth or more. [7] Teeth are arranged in a cardiform (comb-like) design – Parmentier suggests they are used in a saw-like fashion to cut into internal tissues of their hosts. [7]
E. vermicularis lives in a marine, reef-based environment in a tropical climate. [3] They are an epibenthic species – they live near to the bottom of the seafloor. They seek out shallow-water sea cucumbers around in inshore waters and coral reefs which range in depth from 0-30 meters. [5] [8]
They can be found in the Indo-Pacific, the Gulf of Aden, around the Philippines and Society Islands, and north to the Ryukyus to the eastern Pacific. [3]
The worm pearlfish is a parasite of holothurians, each host is normally home to a pair of these fishes. Species recorded as hosting the worm pearlfish include Holothuria leucospilota , H. scabra , H. lubrica and Thelenota ananas . [3] The worm pearlfish is an uncommon species. [9]
While other members of the family Carpidae can be commensal, the genus Encheliophis is obligately parasitic. Worm pearlfish, specifically, prefer the coelomic cavity of the genus Holothuria (sea cucumbers). In particular, worm pearlfish have been found to prefer the sea cucumber species H. leucospilota, though they have been found in the sea cucumber species Holothuria atra as well. [10] [4]
Worm pearlfish feed exclusively on the internal tissue of the host, entering through the anal region of the sea cucumber without causing the sea cucumber to release its Cuvierian tubules – a defense mechanism which entangles possible predators. [4] The pearlfish appears to be chemotaxic (responsive to chemical gradients in water) and is attracted to chemicals the coelomic fluid and Cuvierian tubules, which leads it to the sea cucumber's anus. [10] Because the other species worm pearlfish prey on, H. atra, lack Cuvierian tubules, worm pearlfish are most likely not only attracted by the Cuvierian tubules. [4] The anus of the sea cucumber contracts upon tactile stimulation by the worm pearlfish, but once it needs to respire and relax the anus again, pearlfish is able to penetrate the anus headfirst. [5] Once inside, the worm pearlfish eats the sea cucumber's internal tissues – mostly the gonads.
Not much is known about the sexual behavior of worm pearlfish. Sexually mature male-female pairs of worm pearlfish been found cohabiting in sea cucumbers, so worm pearlfish are thought to mate and spawn inside their hosts. [11] Larvae may then be expelled by the normal expiration of the sea cucumber. Like all members of the family Carapidae, worm pearlfish are hatched as holoplanktonic – i.e. temporarily planktonic – larvae from planktonic elliptical eggs, but it is unclear if spawning is seasonal or sporadic. [11]
Sea cucumbers are echinoderms from the class Holothuroidea. They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. The number of holothurian species worldwide is about 1,717, with the greatest number being in the Asia-Pacific region. Many of these are gathered for human consumption and some species are cultivated in aquaculture systems. The harvested product is variously referred to as trepang, namako, bêche-de-mer, or balate. Sea cucumbers serve a useful role in the marine ecosystem as they help recycle nutrients, breaking down detritus and other organic matter, after which bacteria can continue the decomposition process.
Ophidiiformes is an order of ray-finned fish that includes the cusk-eels, pearlfishes, viviparous brotulas, and others. Members of this order have small heads and long slender bodies. They have either smooth scales or no scales, a long dorsal fin and an anal fin that typically runs into the caudal fin. They mostly come from the tropics and subtropics, and live in both freshwater and marine habitats, including abyssal depths. They have adopted a range of feeding methods and lifestyles, including parasitism. The majority are egg-laying, but some are viviparous.
Pearlfish are marine fish in the ray-finned fish family Carapidae. Pearlfishes inhabit the tropical waters of the Atlantic, Indian, and Pacific Oceans at depths to 2,000 m (6,600 ft), along oceanic shelves and slopes. They are slender, elongated fish with no scales, translucent bodies, and dorsal fin rays which are shorter than their anal fin rays. Adults of most species live symbiotically inside various invertebrate hosts, and some live parasitically inside sea cucumbers. The larvae are free living.
Evisceration is a method of autotomy involving the ejection of internal organs used by animals as a defensive strategy. Sea cucumbers (Holothuroidea) eject parts of the gut in order to scare and defend against potential predators such as crabs and fish. The organs are regenerated in a few days by cells in the interior of the sea cucumber.
Holothuria atra, commonly known as the black sea cucumber or lollyfish, is a species of marine invertebrate in the family Holothuriidae. It was placed in the subgenus Halodeima by Pearson in 1914, making its full scientific name Holothuria (Halodeima) atra. It is the type species of the subgenus.
Encheliophis is a genus of pearlfishes, with six currently recognized species:
Holothuria forskali, the black sea cucumber or cotton-spinner, is a species of sea cucumber in the family Holothuriidae. It is found at shallow depths in the eastern Atlantic Ocean and the Mediterranean Sea. It was placed in the subgenus Panningothuria by Rowe in 1969 and is the typetaxon of the subgenus.
Holothuria scabra, or sandfish, is a species of sea cucumber in the family Holothuriidae. It was placed in the subgenus Metriatyla by Rowe in 1969 and is the type species of the subgenus. Sandfish are harvested and processed into "beche-de-mer" and eaten in China and other Pacific coastal communities.
Bohadschia argus, the leopard sea cucumber, leopardfish, or tigerfish, is a species of marine invertebrate in the family Holothuriidae.
The star pearlfish, Carapus mourlani, is a species of slender, ray-finned fish in the family Carapidae. It normally lives inside a starfish or a sea cucumber.
Echiodon is a genus of pearlfishes, with these currently recognized species:
Onuxodon is an Indo-Pacific genus of pearlfishes from the family Carapidae. The generic name is derived from the Greek onyx meaning "claw" and odon meaning "tooth", referring to the sharp fang like teeth of Onuxodon parvibrachium. Species in this genus are distributed from South Africa to Hawaii. They live commensally with molluscs. The three currently recognized species are:
Holothuria leucospilota, commonly known as the black sea cucumber or black tarzan, is a species of marine invertebrate in the family Holothuriidae. It is placed in the subgenus Mertensiothuria making its full scientific name Holothuria (Mertensiothuria) leucospilota. It is the type species of the subgenus and is found on the seabed in shallow water in the Indo-Pacific.
Cuvierian tubules are clusters of fine tubes located at the base of the respiratory tree in some sea cucumbers in the genera Bohadschia, Holothuria and Pearsonothuria, all of which are included in the family Holothuriidae. The tubules can be discharged through the anus when the sea cucumber is stressed. They lengthen when they come into contact with seawater and become adhesive when they encounter objects so that they function as a defence against potential predators. They are named after the French zoologist Georges Cuvier, who first described them.
The pinhead pearlfish, Encheliophis boraborensis, is a species of slender, ray-finned fish in the family Carapidae found in the tropical Indo-Pacific Ocean; it normally lives inside the body cavity of a sea cucumber such as the pineapple sea cucumber or the leopard sea cucumber.
The silver pearlfish, Encheliophis homei, is a species of eel-like fish in the family Carapidae. This pearlfish lives inside the coelom of sea cucumbers such as Bohadschia argus, Thelenota ananas , and Stichopus chloronotus. It is native to tropical and subtropical parts of the Indo-Pacific Ocean.
Holothuria fuscocinerea, the ashy pink sea cucumber, is a species of sea cucumber in the family Holothuriidae. It is placed in the subgenus Stauropora, making its full name Holothuria (Stauropora) fuscocinerea. It is native to shallow water in the tropical and sub-tropical Indo-Pacific.
Holothuria pervicax is a species of sea cucumber in the genus Holothuria. It is commonly called the stubborn sea cucumber due to its inability to be kept alive in captivity. It is commonly found buried beneath rocks on reefs in warm waters.
Encheliophis chardewalli is a species of fish described by Parmentier in 2004. Encheliophis chardewalli is part of the genus Encheliophis and the Carapidae family.
Carapus acus is a species of bony fish in the family Carapidae, the pearlfishes, and is native to the Mediterranean Sea and the Atlantic Ocean. It lives as a commensal in association with a sea cucumber, spending the day inside its host and emerging at night to feed.
