| Carapus acus | |
|---|---|
 | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Ophidiiformes |
| Family: | Carapidae |
| Genus: | Carapus |
| Species: | C. acus |
| Binomial name | |
| Carapus acus | |
| Synonyms [2] | |
| |
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.
Carapus acus is a laterally-compressed, elongated fish growing to a length of about 20 cm (8 in). The head measures about one eighth of the total length and there are 84 to 92 vertebrae, which gives the fish great flexibility. The continuous dorsal fin and the anal fin run the whole length of the body. There is no caudal fin and the tail ends with a point. The gut loops back and the anus is located just behind the head, in front of the pectoral fins. This fish is translucent, with a number of silvery or reddish-gold iridescent spots on the operculum and the thoracic region. The peritoneum lining the body cavity is an opaque silvery colour. [3] [4]
Carapus acus is native to the Mediterranean Sea and eastern Atlantic Ocean; [1] it is common in the western half and around the coasts of Spain, France, Italy, Sardinia and the Balearic Islands. It is less common in the Adriatic and Aegean Seas. [4]
Carapus acus usually lives inside the respiratory tree or the body cavity of sea cucumbers. Neither the species nor the size of the host seem important in host choice, and the fish makes use of whatever sea cucumber it happens to encounter; the most common hosts are Parastichopus regalis and Holothuria tubulosa , while others include, H. poli , H. arguinensis , H. sanctori and H. mammata . [5] The fish swims close to the seabed searching for a suitable host. When it finds one, it positions its head beside the sea cucumber's anus, from which a current of water is being expelled. Either it then bends its flexible tail around, inserts it in the sea cucumber's anus and works its way backwards inside, with the tail entering first, or less commonly, it thrusts its head into the orifice and enters with a sharp flick of its tail, turning round when inside the host. In either case, it positions itself with its head close to or protruding from the sea cucumber's anus. Because the fish's anus is located just behind its head, it is able to defecate into the open water without fouling its host. [4]
Pearlfishes are able to produce sounds by means of certain muscles connected to the swim bladder, with each species producing a sound unique to its species. The function of these sounds is unclear, various hypotheses have been proposed including finding a mate, indicating the size of the fish while it is concealed in its host, and establishing a territory. [4] Sometimes more than one fish can occupy the same host, and mating inside the host is possible. Breeding takes place between July and September. A cluster of eggs is produced which rises to the water surface. The eggs hatch into fish fry after three days. When these larvae have grown to a length of about 80 mm (3 in) they undergo metamorphosis into juveniles, becoming elongated and laterally flattened. At this time they move to the seabed to find a suitable host. [4] Juvenile fish may nibble the reproductive organs or the gills of their host; this causes little damage because sea cucumbers have great regenerative powers. Older fish are nocturnal, emerging from their host and feeding on small crustaceans, worms, and fish fry, before returning to their hosts. [4]
A barracuda, or cuda for short, is a large, predatory, ray-finned fish known for its fearsome appearance and ferocious behaviour. The barracuda is a saltwater fish of the genus Sphyraena, the only genus in the family Sphyraenidae, which was named by Constantine Samuel Rafinesque in 1815. It is found in tropical and subtropical oceans worldwide ranging from the eastern border of the Atlantic Ocean to the Red Sea, on its western border the Caribbean Sea, and in tropical areas of the Pacific Ocean. Barracudas reside near the top of the water and near coral reefs and sea grasses. Barracudas are targeted by sport-fishing enthusiasts.
The Moronidae are a family of perciform fishes, commonly called the temperate basses, consisting of at least six freshwater, brackish water, and marine species.
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.
The garfish, also known as the garpike or sea needle, is a pelagic, oceanodromous needlefish found in brackish and marine waters of the Atlantic Ocean and the Mediterranean, Caribbean, Black, and Baltic Seas.
The Indo-Pacific sailfish is a sailfish native to the Indian and Pacific Oceans and is naturalized in the Atlantic where it has entered the Mediterranean Sea via the Suez Canal as a Lessepsian migrant. It is dark blue on top, brown-blue laterally, silvery white underbelly; upper jaw elongated in the form of a spear; first dorsal fin greatly enlarged in the form of a sail, with many black cones, its front squared off, highest at its midpoint; pelvic fins very narrow, reaching almost to the anus; body covered with embedded scales, blunt at end; lateral line curved above pectoral fin, then straight to base of tail. They have a large and sharp bill, which they use for hunting. They feed on tuna and mackerel, some of the fastest fish in the Ocean. Most authorities only recognise a single species of sailfish, I. platypterus.
The serpent eel or sand snake-eel is an eel found in the eastern Atlantic Ocean, western Mediterranean Sea, western Indian Ocean, western Pacific Ocean and the north-east and west coast of North Island in New Zealand. It is an elongated, slender fish with a length of up to 250 centimetres. It spends the day with its body immersed in the sediment, emerging into the open water at night.
The grey triggerfish or gray triggerfish, is a ray-finned fish in the triggerfish family. The species is native to shallow parts of the western Atlantic from Nova Scotia to Argentina and also the eastern Atlantic, the Mediterranean Sea and off Angola on the west coast of Africa.
Hypoplectrus gemma, the blue hamlet, is a species of marine ray-finned fish, a sea bass from the subfamily Serraninae which is part of the family Serranidae, which also includes the groupers and anthias. It is found in the western Atlantic Ocean and occasionally makes its way into the aquarium trade.
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.
The worm pearlfish is an eel-like fish in the family Carapidae.
The Mediterranean scaldfish, also known as the scaldfish, is a species of benthic left eyed flatfish belonging to the family Bothidae. It is found in the eastern Atlantic of Europe and Africa as well as the Mediterranean, and is of minor interest to fisheries.
Holothuria tubulosa, the cotton-spinner or tubular sea cucumber, is a species of sea cucumber in the family Holothuriidae. It is the type species of the genus Holothuria and is placed in the subgenus Holothuria, making its full name Holothuria (Holothuria) tubulosa.
Bohadschia argus, the leopard sea cucumber, is a species of marine invertebrate in the family Holothuriidae. It is the type species of the genus Bohadschia; Jaeger, 1833.
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.
Carapus is a genus of pearlfishes, with these currently recognized species:
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.
Spicara smaris, one of the picarels, is a species of ray-finned fish native to the eastern Atlantic Ocean, the Mediterranean Sea and the Black Sea. It grows to a maximum length of about 20 cm (8 in); females are usually smaller than males.
The common eagle ray is a species of fish in the family Myliobatidae. It inhabits the eastern Atlantic Ocean, the Mediterranean Sea and the south-western Indian Ocean.
Parastichopus regalis, also known as the royal sea cucumber, is a species of sea cucumber in the family Stichopodidae.
