Atrophacanthus
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''Atrophacanthus'' is a
monospecific genus In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...
of marine
ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...
belonging to the
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Triacanthodidae, the spikefishes. The only species in the genus is ''Atrophacanthus japonicus'', the upward-mouth spikefish, which is found in the
Indo-West Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the s ...
region.


Taxonomy

''Atrophacanthus'' was first proposed as a monospecific genus in 1950 by the British
ichthyologist Ichthyology is the branch of zoology devoted to the study of fish, including bony fish (Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 35,800 species of fish had been described as of March 2 ...
Alec Fraser-Brunner Alec Frederick Fraser-Brunner (6 April 1906 – 17 Sept 1986) was a British ichthyologist. His career included work with the Colonial Office, the Food and Agriculture Organization, and as the curator of the Van Kleef Aquarium in Singapore and the ...
when he described ''Atrophacanthus danae'', its
type species In International_Code_of_Zoological_Nomenclature, 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 spe ...
by
monotypy In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...
. Fraser-Brenner's ''A. danae'' had its type locality given as the Sulawesi Sea. ''A. danae'' was subsequently shown to be a
synonym A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...
of ''Tydemania japonica'' which had been described in 1941 by the Japanese
ichthyologist Ichthyology is the branch of zoology devoted to the study of fish, including bony fish (Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 35,800 species of fish had been described as of March 2 ...
Toshiji Kamohara Toshiji is a masculine Japanese name, Japanese given name. Written forms Toshiji can be written using different combinations of kanji characters. Some examples: *敏次, "agile, next" *敏二, "agile, two" *敏治, "agile, to manage/cure" *敏 ...
with its type locality given as
Shikoku is the smallest of the List of islands of Japan#Main islands, four main islands of Japan. It is long and between at its widest. It has a population of 3.8 million, the least populated of Japan's four main islands. It is south of Honshu ...
in the
Kōchi Prefecture is a prefecture of Japan located on the island of Shikoku. Kōchi Prefecture has a population of 669,516 (1 April 2023) and has a geographic area of 7,103 km2 (2,742 sq mi). Kōchi Prefecture borders Ehime Prefecture to the northwest and Tok ...
, Japan. This taxon is classified within the
subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...
Triacanthodinae Triacanthodinae is a subfamily of marine ray-finned fishes belonging to the family Triacanthodidae, the spikefishes. This subfamily comprises nine genera and a total of nineteen species and all, except one species, are found in the tropical an ...
of the spikefish family Triacanthodidae, within the suborder
Triacanthoidei Triacanthoidei is a suborder of ray-finned fishes belonging to the order Tetraodontiformes, which includes the pufferfishes, triggerfishes and related taxa. These benthic fishes are mainly found in the Indian Ocean with some of the spikefishes fou ...
of the
order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...
Tetraodontiformes Tetraodontiformes (), also known as the Plectognathi, is an order of ray-finned fishes which includes the pufferfishes and related taxa. This order has been classified as a suborder of the order Perciformes, although recent studies have found ...
in the 5th edition of ''
Fishes of the World ''Fishes of the World'' is a standard reference for the systematics of fishes. It was first written in 1976 by the American ichthyologist Joseph S. Nelson (1937–2011). Now in its fifth edition (2016), the work is a comprehensive overview of t ...
''. Within the subfamily Triacanthodinae this taxon is the
sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...
of '' Macrorhamphosodes''.


Etymology

''Atrophacanthus'' combines ''atrophia'', meaning "rudimentary", and ''acanthus'', which means "thorn" or "spine", an allusion to the poorly developed rearmost 3 spines in the
dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...
. The
specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...
''Japonicus'' refers to the type locality of ''Tydemania japonica''.


Description

''Atrophacanthus'' has the first three spines in the dorsalfin are well developed and clearly exposed, the fourth spine is clearly shorter than the first three but is still visible above the skin but the fifth and sixth spines very poorly developed and either just protrude on the surface of the skin or so not protrude at all. The first spine is rather short, not extending far beyond the fourth spine when folded down. There are 13 or 14 soft rays in the dorsal fin and between 11 and 13 in the
anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...
. The short conical teeth are arranged in a single row on each jaw with between 19 and 23 teeth in upper jaw and 22–27 in the lower jaw. the dorsal profile of the head is neither convex or concave. The mouth is at the end of the short snout. The gill opening is relatively long, typically reaching down to around one-half to four-fifths of the base of the
pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...
. This species has a maximum published
standard length Fish measurement is the measuring of individual fish and various parts of fish anatomy, their anatomies, for data used in many areas of ichthyology, including Taxonomy (biology), taxonomy and fishery biology. Overall length Standard length (SL) is ...
of .


Distribution and habitat

''Atrophacanthus'' is found in the Indo-West Pacific region where it has been recorded from Japan, the Philippines, Sulawesi Sea, off Tanzania, and probably from South Africa, with records as far east as the
Mariana Islands The Mariana Islands ( ; ), also simply the Marianas, are a crescent-shaped archipelago comprising the summits of fifteen longitudinally oriented, mostly dormant volcanic mountains in the northwestern Pacific Ocean, between the 12th and 21st pa ...
. This is a
bathypelagic zone The bathypelagic zone or bathyal zone (from Greek βαθύς (bathýs), deep) is the part of the open ocean that extends from a depth of below the ocean surface. It lies between the mesopelagic above and the abyssopelagic below. The bathypela ...
and
benthic fish Demersal fish, also known as groundfish, live and feed on or near the bottom of seas or lakes (the demersal zone).Walrond Carl . "Coastal fish - Fish of the open sea floor"Te Ara - the Encyclopedia of New Zealand. Updated 2 March 2009 They oc ...
found at depths between .


Biology

''Atrophacanthus'' is carnivorous and the stomach contents of two juveniles collected near
Guam Guam ( ; ) is an island that is an Territories of the United States, organized, unincorporated territory of the United States in the Micronesia subregion of the western Pacific Ocean. Guam's capital is Hagåtña, Guam, Hagåtña, and the most ...
consisted of formanifera and thecosome pteropods. Only large juveniles have been collected in deeper waters while the few adult specimens have been collected from shallower depths continental shelf and slope, suggesting a long period of pelagic larval development before the larger adults settle.


References

{{Taxonbar, from1=Q1951687, from2=Q195877 Triacanthodinae Taxa named by Alec Fraser-Brunner Monotypic ray-finned fish genera