Pygmy ribbontail catshark
Encyclopedia
The pygmy ribbontail catshark (Eridacnis radcliffei) is a species
of finback catshark, family
Proscylliidae
, distributed patchily in the western Indo-Pacific
from Tanzania
to the Philippines
. It occurs around the edges of continental and insular shelves
at a depth of 71–766 m (232.9–2,513.1 ft), typically on or near mud bottoms. One of the smallest living shark species, the pygmy ribbontail catshark grows to a maximum known length of 24 cm (9.4 in). It has a slender body with a low, ribbon-like tail fin, and is dark brown in color with blackish dorsal fin markings and tail bands. This shark feeds mainly on bony fishes, followed by crustacean
s and then squid
. It is aplacental viviparous with females bearing litters of 1–2 relatively large pups. It is of minimal significance to fisheries, being caught as bycatch
in some areas.
Steamer
Albatross
. Hugh McCormick Smith
, Deputy Fish Commissioner and director of the expedition, published a description of this shark in a 1913 issue of the Proceedings of the United States National Museum, naming it for the expedition's General Assistant and Naturalist Lewis Radcliffe
, and creating for it the new genus
Eridacnis. The type specimen is a 23 cm (9.1 in) long adult female caught off Jolo Island
in the Sulu Archipelago
, Philippines
.
, the Gulf of Aden
, the Gulf of Mannar
, the Bay of Bengal
, the Andaman Islands
, Vietnam
, and the Philippines
. This bottom-dwelling shark occurs at depths of 71–766 m (232.9–2,513.1 ft) on outer continental and insular shelves
or upper slopes, commonly over mud.
s. Each nostril is preceded by a short, triangular flap of skin. The mouth is wide and V-shaped, without furrows at the corners and containing numerous rows of small, multi-pointed teeth that become more comb-like towards the sides. There are papilla
e on the roof of the mouth and the edges of the gill
arches. The two dorsal fin
s are of comparable size, the first positioned slightly closer to the pectoral than the pelvic fins and the second over the anal fin. The caudal fin is low and long, comprising a quarter of the total length or more, and lacks a lower lobe. The coloration is a plain dark brown, with black markings on the dorsal fins and darker bands on the caudal fin. The maximum recorded lengths are 23 cm (9.1 in) for a male and 24 cm (9.4 in) for a female. One male shark 18.6 cm (7.3 in) long weighed 14 g (0.493835469471567 oz), and a pregnant female 24.2 cm (9.5 in) long weighed 37 g (1.3 oz).
and the Philippines. One study in Indian waters found that 55% of this shark's diet was composed of bony fishes (mainly lanternfish
es but also bristlemouths and small eel
s), 28% of crustacean
s (mainly shrimp
but also stomatopods and crab
larvae
), 14% of squid
, and the remainder of other items including a bivalve.
Reproduction is aplacental viviparous, with the developing young being sustained by a yolk sac
until they are ready to be born. Female pygmy ribbontail catsharks are capable of becoming pregnant at 16.6 cm (6.5 in) long, though only females over 18 cm (7.1 in) long have been found with fully developed fetus
es, suggesting that they grow substantially during the gestation period
. One or two pups are born at a time; the newborns are extremely large relative to their mothers, measuring around 11 cm (4.3 in) in length. Males reach sexual maturity
at a length of 18–19 cm (7.1–7.5 in) and females at perhaps 15–16 cm (5.9–6.3 in). This is comparable to the sizes at maturity of the spined pygmy shark
(Squaliolus laticaudus) and the dwarf lanternshark
(Etmopterus perryi), ranking the pygmy ribbontail catshark among the world's smallest sharks. Due to the difficulties involved in assessing reproductive maturity in sharks, whether one of these species is truly smaller than the others cannot yet be definitively determined.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of finback catshark, family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Proscylliidae
Proscylliidae
The finback catsharks are a small family, Proscylliidae, of ground sharks.-Genera and species:* Ctenacis Compagno, 1973** Ctenacis fehlmanni * Eridacnis H. M. Smith, 1913...
, distributed patchily in the western Indo-Pacific
Indo-Pacific
The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...
from Tanzania
Tanzania
The United Republic of Tanzania is a country in East Africa bordered by Kenya and Uganda to the north, Rwanda, Burundi, and the Democratic Republic of the Congo to the west, and Zambia, Malawi, and Mozambique to the south. The country's eastern borders lie on the Indian Ocean.Tanzania is a state...
to the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
. It occurs around the edges of continental and insular shelves
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
at a depth of 71–766 m (232.9–2,513.1 ft), typically on or near mud bottoms. One of the smallest living shark species, the pygmy ribbontail catshark grows to a maximum known length of 24 cm (9.4 in). It has a slender body with a low, ribbon-like tail fin, and is dark brown in color with blackish dorsal fin markings and tail bands. This shark feeds mainly on bony fishes, followed by crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s and then squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
. It is aplacental viviparous with females bearing litters of 1–2 relatively large pups. It is of minimal significance to fisheries, being caught as bycatch
Bycatch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...
in some areas.
Taxonomy
The first known specimens of the pygmy ribbontail catshark were collected during the 1907–1910 Philippine Expedition of the U.S. Fish CommissionUnited States Fish Commission
The United States Commission of Fish and Fisheries was established on February 9, 1871 , as an independent commission with a mandate to investigate the causes for the decrease of commercial fish and aquatic animals in U.S...
Steamer
Steamboat
A steamboat or steamship, sometimes called a steamer, is a ship in which the primary method of propulsion is steam power, typically driving propellers or paddlewheels...
Albatross
USS Albatross (1882)
The second USS Albatross, often seen as USFC Albatross in scientific literature citations, was an iron-hulled, twin-screw steamer in the United States Navy and reputedly the first vessel ever built especially for marine research....
. Hugh McCormick Smith
Hugh McCormick Smith
Hugh McCormick Smith was an American ichthyologist and administrator in the Bureau of Fisheries.-Biography:...
, Deputy Fish Commissioner and director of the expedition, published a description of this shark in a 1913 issue of the Proceedings of the United States National Museum, naming it for the expedition's General Assistant and Naturalist Lewis Radcliffe
Lewis Radcliffe
Lewis Radcliffe was a naturalist, malacologist, and ichthyologist. He was Deputy Commissioner of the United States Bureau of Fisheries until 1932 and was the assistant naturalist under Hugh McCormick Smith for the 1907-1910 Philippines Expedition. During his life, he described numerous new species...
, and creating for it the new genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Eridacnis. The type specimen is a 23 cm (9.1 in) long adult female caught off Jolo Island
Jolo Island
Jolo is a volcanic island in the southwest Philippines. It is located in the Sulu Archipelago, between Borneo and Mindanao, and has a population of approximately 300,000 people....
in the Sulu Archipelago
Sulu Archipelago
The Sulu Archipelago is a chain of islands in the southwestern Philippines. This archipelago is considered to be part of the Moroland by the local rebel independence movement. This island group forms the northern limit of the Celebes Sea....
, Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
.
Distribution and habitat
By far the most widely (if sporadically) distributed member of its genus, the pygmy ribbontail catshark has been reported from TanzaniaTanzania
The United Republic of Tanzania is a country in East Africa bordered by Kenya and Uganda to the north, Rwanda, Burundi, and the Democratic Republic of the Congo to the west, and Zambia, Malawi, and Mozambique to the south. The country's eastern borders lie on the Indian Ocean.Tanzania is a state...
, the Gulf of Aden
Gulf of Aden
The Gulf of Aden is located in the Arabian Sea between Yemen, on the south coast of the Arabian Peninsula, and Somalia in the Horn of Africa. In the northwest, it connects with the Red Sea through the Bab-el-Mandeb strait, which is about 20 miles wide....
, the Gulf of Mannar
Gulf of Mannar
The Gulf of Mannar is a large shallow bay forming part of the Laccadive Sea in the Indian Ocean. It lies between the southeastern tip of India and the west coast of Sri Lanka. A chain of low islands and reefs known as Adam's Bridge, also called Ramsethu, which includes Mannar Island, separates the...
, the Bay of Bengal
Bay of Bengal
The Bay of Bengal , the largest bay in the world, forms the northeastern part of the Indian Ocean. It resembles a triangle in shape, and is bordered mostly by the Eastern Coast of India, southern coast of Bangladesh and Sri Lanka to the west and Burma and the Andaman and Nicobar Islands to the...
, the Andaman Islands
Andaman Islands
The Andaman Islands are a group of Indian Ocean archipelagic islands in the Bay of Bengal between India to the west, and Burma , to the north and east...
, Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...
, and the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...
. This bottom-dwelling shark occurs at depths of 71–766 m (232.9–2,513.1 ft) on outer continental and insular shelves
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
or upper slopes, commonly over mud.
Description
The pygmy ribbontail catshark has a thin body with a short, rounded snout and elongated, oval eyes bearing rudimentary nictitating membraneNictitating membrane
The nictitating membrane is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it while maintaining visibility. Some reptiles, birds, and sharks have a full nictitating membrane; in many mammals, there is a small...
s. Each nostril is preceded by a short, triangular flap of skin. The mouth is wide and V-shaped, without furrows at the corners and containing numerous rows of small, multi-pointed teeth that become more comb-like towards the sides. There are papilla
Papilla (fish mouth structure)
The papilla, in certain kinds of fish, particularly rays, sharks, and catfish, are small lumps of dermal tissue found in the mouth, where they are "distributed uniformly on the tongue, palate, and pharynx"...
e on the roof of the mouth and the edges of the gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
arches. The two dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
s are of comparable size, the first positioned slightly closer to the pectoral than the pelvic fins and the second over the anal fin. The caudal fin is low and long, comprising a quarter of the total length or more, and lacks a lower lobe. The coloration is a plain dark brown, with black markings on the dorsal fins and darker bands on the caudal fin. The maximum recorded lengths are 23 cm (9.1 in) for a male and 24 cm (9.4 in) for a female. One male shark 18.6 cm (7.3 in) long weighed 14 g (0.493835469471567 oz), and a pregnant female 24.2 cm (9.5 in) long weighed 37 g (1.3 oz).
Biology and ecology
The pygmy ribbontail catshark is reportedly very abundant in some places, such as off southern IndiaIndia
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
and the Philippines. One study in Indian waters found that 55% of this shark's diet was composed of bony fishes (mainly lanternfish
Lanternfish
Cooper Lanternfishes are small mesopelagic fish of the large family Myctophidae. One of two families in the order Myctophiformes, the Myctophidae are represented by 246 species in 33 genera, and are found in oceans worldwide. They are aptly named after their conspicuous use of bioluminescence...
es but also bristlemouths and small eel
Eel
Eels are an order of fish, which consists of four suborders, 20 families, 111 genera and approximately 800 species. Most eels are predators...
s), 28% of crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s (mainly shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
but also stomatopods and crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
larvae
Larvae
In Roman mythology, lemures were shades or spirits of the restless or malignant dead, and are probably cognate with an extended sense of larvae as disturbing or frightening...
), 14% of squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
, and the remainder of other items including a bivalve.
Reproduction is aplacental viviparous, with the developing young being sustained by a yolk sac
Yolk sac
The yolk sac is a membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals...
until they are ready to be born. Female pygmy ribbontail catsharks are capable of becoming pregnant at 16.6 cm (6.5 in) long, though only females over 18 cm (7.1 in) long have been found with fully developed fetus
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
es, suggesting that they grow substantially during the gestation period
Gestation period
For mammals the gestation period is the time in which a fetus develops, beginning with fertilization and ending at birth. The duration of this period varies between species.-Duration:...
. One or two pups are born at a time; the newborns are extremely large relative to their mothers, measuring around 11 cm (4.3 in) in length. Males reach sexual maturity
Sexual maturity
Sexual maturity is the age or stage when an organism can reproduce. It is sometimes considered synonymous with adulthood, though the two are distinct...
at a length of 18–19 cm (7.1–7.5 in) and females at perhaps 15–16 cm (5.9–6.3 in). This is comparable to the sizes at maturity of the spined pygmy shark
Spined pygmy shark
The spined pygmy shark is a species of dogfish shark in the family Dalatiidae found widely in all oceans. With a maximum known length of , it is one of the smallest living sharks. This shark has a slender, cigar-shaped body with a sizable conical snout, a long but low second dorsal fin, and an...
(Squaliolus laticaudus) and the dwarf lanternshark
Dwarf lanternshark
The dwarf lanternshark is a little-known species of dogfish shark in the family Etmopteridae and possibly the smallest shark in the world, reaching a maximum known length of . It is known to be present only on the upper continental slopes off Colombia and Venezuela, at a depth of...
(Etmopterus perryi), ranking the pygmy ribbontail catshark among the world's smallest sharks. Due to the difficulties involved in assessing reproductive maturity in sharks, whether one of these species is truly smaller than the others cannot yet be definitively determined.