''Bovictus diacanthus'', the Tristan klipfish, is a species of marine

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...

, a temperate icefish or thornfish, belonging to the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Bovichtidae Bovichtidae, the temperate icefishes or thornfishes, is a family of marine ray-finned fishes, classified in the suborder Notothenioidei of the order Perciformes. They are native to coastal waters off Australia, New Zealand, and South America. ...

. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to two isolated, small island groups in the South Atlantic.

Taxonomy

''Bovichtus diacanthus'' was first formally described in 1819 as ''Callionymus diacanthus''by the Scottish

botanist Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek wo ...

and officer in the

British Army The British Army is the principal land warfare force of the United Kingdom, a part of the British Armed Forces along with the Royal Navy and the Royal Air Force. , the British Army comprises 79,380 regular full-time personnel, 4,090 Gurk ...

Dugald Carmichael Dugald Carmichael (born 1772 in Stronacraoibh, Lismore Island, died 1827 in Appin) was a Scottish botanist and officer in the 72nd Highlanders. He is known as the "Father of Marine Botany". The plant genus ''Carmichaelia'' is named after him. He ...

with the type locality given as

Tristan da Cunha Tristan da Cunha (), colloquially Tristan, is a remote group of volcanic islands in the South Atlantic Ocean. It is the most remote inhabited archipelago in the world, lying approximately from Cape Town in South Africa, from Saint Helena ...

in the South Atlantic, When

Achille Valenciennes Achille Valenciennes (9 August 1794 – 13 April 1865) was a French zoologist. Valenciennes was born in Paris, and studied under Georges Cuvier. His study of parasitic worms in humans made an important contribution to the study of parasitology. ...

described the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

Bovichtus ''Bovichtus'' is a genus of fish in the family Bovichtidae found in the Atlantic, Indian and Pacific Ocean. Taxonomy ''Bovichtus'' was formally described as a genus in 1832 by the French zoologist Achille Valenciennes with ''Callionymus diacanth ...

'' in 1832 the only species he classified within the new genus was Carmichael's ''C. diacanthus'' which is therefore the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

of ''Bovichtus''. The specific name ''diacanthus'' means "two spines", a reference to the two robust, needle-shaped and sharp spines on the operculum which are erected when the gill membrane is expanded.

Description

''Bovichtus diacanthus'' is species in the genus ''Bovichtus'' and these fishes are characterised by having a terminal, protractile mouth with teeth on the

palatine A palatine or palatinus (in Latin; plural ''palatini''; cf. derivative spellings below) is a high-level official attached to imperial or royal courts in Europe since Roman times.

. There are two robust backwards pointing spines on the operculum. They have a single

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

and the anterior dorsal fin is spiny and starts above the operculum. The soft rays in the posterior dorsal fin and the

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

are simple, the rear most anal fin rays are thickened and longer than the front rays. They are normally mottled in colour and their gill membranes direct the exiting water upwards, an adaptation for a sedentary benthic lifestyle. In the pectoral fins the lowest rays are unbranched with a thick cuticle, extend a little beyond the membrane and have upturned tips, the rearmost anal fin rays are also structured like this. This species attains a maximum

total length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish ...

of .

Distribution and habitat

''Bovichtus diacanthus'' is restricted to the waters around

and

Gough Island upright=1.3, Map of Gough island Gough Island ( ), also known historically as Gonçalo Álvares, is a rugged volcanic island in the South Atlantic Ocean. It is a dependency of Tristan da Cunha and part of the British overseas territory of Sain ...

in the South Atlantic Ocean. It is found in

rockpool A tide pool or rock pool is a shallow pool of seawater that forms on the rocky intertidal shore. Many of these pools exist as separate bodies of water only at low tide. Many tide pool habitats are home to especially adaptable animals that ...

s which vary in depth from and in coastal waters down to depths of .

Biology

''Bovichtus diacanthus'' has a pelagic stage of larvae which gather in large shoals. Once they have attain a total length of these settle and adopt a benthic lifestyle. The diet of Bovichtus thornfishes is made up of invertebrates, mainly crustaceans and worms. This species is a batch spawner, the spawning season running from July and August. Females reach sexual maturity no later than 5 years old while for males the maximum age of sexual maturity is four years.

References

{{Taxonbar, from=Q2337525 diacanthus Fish described in 1919 Endemic fauna of Tristan da Cunha