''Butis butis'', the crazy fish, duckbill sleeper, or upside-down sleeper, is a species of sleeper goby that are native to

brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...

and

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

coastal habitats of the

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...

and the western

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

from the

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

n coast to the islands of

Fiji Fiji ( , ,; fj, Viti, ; Fiji Hindi: फ़िजी, ''Fijī''), officially the Republic of Fiji, is an island country in Melanesia, part of Oceania in the South Pacific Ocean. It lies about north-northeast of New Zealand. Fiji consists ...

. They prefer well-vegetated waters and can frequently be found in

mangrove swamp Mangrove forests, also called mangrove swamps, mangrove thickets or mangals, are productive wetlands that occur in coastal intertidal zones. Mangrove forests grow mainly at tropical and subtropical latitudes because mangroves cannot withstand fre ...

s. They are small, drably-colored fish, reaching a maximum length of only . They are

predatory Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

and are known for their behavior of swimming vertically – or even upside down – while hunting.

Description

Crazy fish range in length from in length. The head is subcylindrical and flattened dorsoventrally, and slightly concave in the area between the tip of the snout to just behind the eyes. The mouth is very large, with a lower jaw extending past the upper jaw. Both contain multiple rows of tiny, bristle-like, sharp teeth. A pair of nostrils is present on each side of the snout (four in all) midway between the tip of the snout and the eyes. The front pair of nostrils is far smaller in size than the posterior pair. The relatively small eyes (about a sixth of the length of the head in diameter) are situated near the top of the head, but are oriented sidewise. They are gold and black in coloration. The body is strongly compressed laterally. The

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

s are situated approximately in the middle of the body. The first dorsal fin (with five to six rays) is arched and originates from the highest point of the back of the fish. It has thinner rays than the second dorsal fin (with seven to eight rays). The short triangular

ventral fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

s (each with five rays) are located considerably farther forward than all the other fins. 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 ...

(with seven to nine rays) is located approximately directly below the second dorsal fin, and are roughly the same size and shape as the latter. The pair of

pectoral 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 ...

s (each with eighteen to twenty rays) are large and rounded. They extend past the

anus The anus (Latin, 'ring' or 'circle') is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, the residual semi-solid waste that remains after food digestion, which, d ...

, sometimes reaching the anal fins. The broad and rounded

caudal 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 ...

has about twenty closely compacted rays. The body is covered in

scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number w ...

except the mouth, chin, and the tip of the snout. Small accessory scales of varying sizes are also present at the base of the larger scales on the head and body, numbering at one to six for each larger scale. The scales on the head, nape, and the sides of the body are

ctenoid A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as ...

, while the scales on the belly are

cycloid In geometry, a cycloid is the curve traced by a point on a circle as it rolls along a straight line without slipping. A cycloid is a specific form of trochoid and is an example of a roulette, a curve generated by a curve rolling on another curve ...

. Crazy fish are drably colored, with the body predominantly mottled dusky gray to olive green. Five or six irregular dark transverse bands are present, obscured somewhat in the front, but distinct in the rear half of the body. A black streak may extend from the snout, across the eye, and towards the

gill cover The operculum is a series of bones found in bony fish and chimaeras that serves as a facial support structure and a protective covering for the gills; it is also used for respiration and feeding. Anatomy The opercular series contains four bon ...

s. Dark spots radiate from around the eyes into the gill covers and snout. Each scale along the body has a pale spot that aligns with others, creating noticeable longitudinal rows. One or two red or pinkish spots are also present at the base of the pectoral fins. The fins can be colorless or possess rows of alternating black and light bars. In some individuals, the fins may exhibit broad, bright-red margins. The pectoral fins are invariably colorless.

Taxonomy and nomenclature

Crazy fish are classified under the genus ''

Butis ''Butis'' is a genus of fishes in the family Butidae found in fresh, brackish, and marine waters from the Indian Ocean coast of Africa through Southeast Asia to the Pacific islands and Australia. Species The recognized species in this genus are: ...

'' in 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 ...

Butidae Butidae is a family of sleeper gobies in the order Gobiiformes. The family was formerly classified as a subfamily of the Eleotridae but the 5th Edition of Fishes of the World classifies it as a family in its own right. Molecular phylogenetic anal ...

, which was formerly considered a

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 subfamily botanical names with "-oideae", and zoologi ...

, Butinae, of the family

Eleotridae Eleotridae is a family of fish commonly known as sleeper gobies, with about 34 genera and 180 species. Most species are found in the tropical Indo-Pacific region, but there are also species in subtropical and temperate regions, warmer parts of th ...

(sleeper gobies). They belong to the order

Gobiiformes The Gobiiformes are an order of fish that includes the gobies and their relatives. The order, which was previously considered a suborder of Perciformes, is made up of about 2,211 species that are divided between seven families. Phylogenetic rel ...

, which to some authorities is a

suborder Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...

of the order

Perciformes Perciformes (), also called the Percomorpha or Acanthopteri, is an order or superorder of ray-finned fish. If considered a single order, they are the most numerous order of vertebrates, containing about 41% of all bony fish. Perciformes means ...

called Gobioidei. The crazy fish was first described by the Scottish naturalist

Francis Buchanan-Hamilton Francis Buchanan (15 February 1762 – 15 June 1829), later known as Francis Hamilton but often referred to as Francis Buchanan-Hamilton, was a Scottish physician who made significant contributions as a geographer, zoologist, and botanist whil ...

in 1822 from a specimen recovered from the

Ganges River The Ganges ( ) (in India: Ganga ( ); in Bangladesh: Padma ( )). "The Ganges Basin, known in India as the Ganga and in Bangladesh as the Padma, is an international river to which India, Bangladesh, Nepal and China are the riparian states." is ...

near

Calcutta Kolkata (, or , ; also known as Calcutta , List of renamed places in India#West Bengal, the official name until 2001) is the Capital city, capital of the Indian States and union territories of India, state of West Bengal, on the eastern ba ...

, India. He originally classified it under the genus '' Cheilodipterus''. It was transferred to the genus ''

Eleotris ''Eleotris'' is a genus of fish in the family Eleotridae with a circumglobal distribution in tropical and subtropical regions. Species There are currently 27 recognized species in this genus: * '' Eleotris acanthopoma'' Bleeker, 1853 (Spiny sl ...

'' by the

Danish Danish may refer to: * Something of, from, or related to the country of Denmark People * A national or citizen of Denmark, also called a "Dane," see Demographics of Denmark * Culture of Denmark * Danish people or Danes, people with a Danish a ...

naturalist

Theodore Edward Cantor Theodore Edward (Theodor Edvard) Cantor (1809–1860) was a Danish physician, zoologist and botanist. Born to a Danish Jewish family, his mother was a sister of Nathaniel Wallich. Cantor worked for the British East India Company, and made natur ...

in 1850. In 1856, the

Dutch Dutch commonly refers to: * Something of, from, or related to the Netherlands * Dutch people () * Dutch language () Dutch may also refer to: Places * Dutch, West Virginia, a community in the United States * Pennsylvania Dutch Country People E ...

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, 33,400 species of fish had been described as of Octobe ...

Pieter Bleeker Pieter Bleeker (10 July 1819 – 24 January 1878) was a Dutch medical doctor, ichthyologist, and herpetologist. He was famous for the ''Atlas Ichthyologique des Indes Orientales Néêrlandaises'', his monumental work on the fishes of East Asia ...

moved it to its own genus, ''Butis''. Hamilton did not explain the origin of the specific name. Hamilton is believed to have derived the name from the Indian word ''butis'', decorative circular designs on

sari A sari (sometimes also saree or shari)The name of the garment in various regional languages include: * as, শাৰী, xārī, translit-std=ISO * bn, শাড়ি, śāṛi, translit-std=ISO * gu, સાડી, sāḍī, translit-std= ...

fabric, probably referring to the coloration of crazy fish. Other common names of crazy fish include upside-down sleeper, crimson-tipped gudgeon, duckbill sleeper, crocodile fish, flat-headed gudgeon, pointed-head gudgeon, and bony-snouted gudgeon in English; ''eendbek-slaper'' in

Afrikaans Afrikaans (, ) is a West Germanic language that evolved in the Dutch Cape Colony from the Dutch vernacular of Holland proper (i.e., the Hollandic dialect) used by Dutch, French, and German settlers and their enslaved people. Afrikaans gra ...

; ''kuli'' (কুলি) in

Bengali Bengali or Bengalee, or Bengalese may refer to: *something of, from, or related to Bengal, a large region in South Asia * Bengalis, an ethnic and linguistic group of the region * Bengali language, the language they speak ** Bengali alphabet, the w ...

; ''kuonotorkkuja'' in Finnish; ''butis à épaulette noire'' in French; ''Spitzkopfgrundel'' in German; ''pasel'' in Ibanag; ''nyereh'', ''ploso'', ''puntang'', ''belosoh'', ''belontok'', ''ubi'', and ''ubi muncung itik'' in

Indonesian Indonesian is anything of, from, or related to Indonesia, an archipelagic country in Southeast Asia. It may refer to: * Indonesians, citizens of Indonesia ** Native Indonesians, diverse groups of local inhabitants of the archipelago ** Indonesian ...

and

Malaysian Malaysian may refer to: * Something from or related to Malaysia, a country in Southeast Asia * Malaysian Malay, a dialect of Malay language spoken mainly in Malaysia * Malaysian people, people who are identified with the country of Malaysia regard ...

; ''bloso-watu'' in Javanese; ''jǐ táng lǐ'' (嵴塘鳢) in

Mandarin Mandarin or The Mandarin may refer to: Language * Mandarin Chinese, branch of Chinese originally spoken in northern parts of the country ** Standard Chinese or Modern Standard Mandarin, the official language of China ** Taiwanese Mandarin, Stand ...

; ''vaneya'' in

Sinhalese Sinhala may refer to: * Something of or related to the Sinhalese people of Sri Lanka * Sinhalese people * Sinhala language, one of the three official languages used in Sri Lanka * Sinhala script, a writing system for the Sinhala language ** Sinha ...

; ''bukletkhaeng'' (บู่เกล็ดแข็ง) in

Thai Thai or THAI may refer to: * Of or from Thailand, a country in Southeast Asia ** Thai people, the dominant ethnic group of Thailand ** Thai language, a Tai-Kadai language spoken mainly in and around Thailand *** Thai script *** Thai (Unicode block ...

; and ''cá bống cấu'', ''cá bống đầu dẹp'', and ''cá bong trân'' in

Vietnamese Vietnamese may refer to: * Something of, from, or related to Vietnam, a country in Southeast Asia ** A citizen of Vietnam. See Demographics of Vietnam. * Vietnamese people, or Kinh people, a Southeast Asian ethnic group native to Vietnam ** Overse ...

Distribution and habitat

Crazy fish inhabit

and

habitats near the coast, but they can sometimes be found upriver. They are

demersal The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer of ...

fish, usually found near the muddy bottoms of lagoons,

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...

, and

mangrove forest Mangrove forests, also called mangrove swamps, mangrove thickets or mangals, are productive wetlands that occur in coastal intertidal zones. Mangrove forests grow mainly at tropical and subtropical latitudes because mangroves cannot withstand fr ...

s with abundant vegetation. Crazy fish has a wide distribution range: west from East Africa to as far east as Fiji, north from the

South China Sea The South China Sea is a marginal sea of the Western Pacific Ocean. It is bounded in the north by the shores of South China (hence the name), in the west by the Indochinese Peninsula, in the east by the islands of Taiwan and northwestern Phil ...

and south to Australia and

New Caledonia ) , anthem = "" , image_map = New Caledonia on the globe (small islands magnified) (Polynesia centered).svg , map_alt = Location of New Caledonia , map_caption = Location of New Caledonia , mapsize = 290px , subdivision_type = Sovereign st ...

, including islands in the

Indian Indian or Indians may refer to: Peoples South Asia * Indian people, people of Indian nationality, or people who have an Indian ancestor ** Non-resident Indian, a citizen of India who has temporarily emigrated to another country * South Asia ...

and Pacific Oceans. Countries where it is found include Australia (

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

, Northern Territory,

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

, and Western Australia);

Brunei Darussalam Brunei ( , ), formally Brunei Darussalam ( ms, Negara Brunei Darussalam, Jawi: , ), is a country located on the north coast of the island of Borneo in Southeast Asia. Apart from its South China Sea coast, it is completely surrounded by the ...

; Cambodia, China (

Guangdong Guangdong (, ), alternatively romanized as Canton or Kwangtung, is a coastal province in South China on the north shore of the South China Sea. The capital of the province is Guangzhou. With a population of 126.01 million (as of 2020) ...

, Guangxi,

Hainan Hainan (, ; ) is the smallest and southernmost province of the People's Republic of China (PRC), consisting of various islands in the South China Sea. , the largest and most populous island in China,The island of Taiwan, which is slightly l ...

, Hong Kong, and

Macau Macau or Macao (; ; ; ), officially the Macao Special Administrative Region of the People's Republic of China (MSAR), is a city and special administrative region of China in the western Pearl River Delta by the South China Sea. With a pop ...

); Fiji; India (including the

Andaman and Nicobar Islands The Andaman and Nicobar Islands is a union territory of India consisting of 572 islands, of which 37 are inhabited, at the junction of the Bay of Bengal and the Andaman Sea. The territory is about north of Aceh in Indonesia and separated f ...

); Indonesia; Japan; Kenya; Madagascar; Malaysia; Mauritius (including

Rodrigues Island Rodrigues (french: Île Rodrigues, link=yes ; Creole: ) is a autonomous outer island of the Republic of Mauritius in the Indian Ocean, about east of Mauritius. It is part of the Mascarene Islands, which include Mauritius and Réunion. Rodr ...

); Mozambique;

Myanmar Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John C. Wells, Joh ...

; Papua New Guinea; the Philippines; Seychelles; Singapore; Somalia; Sri Lanka; Taiwan; Tanzania; Thailand; and Vietnam.

Ecology and behavior

Crazy fish are

, preying on

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

s, small fishes, and worms. They are territorial and are most active at twilight and at night. They are known for their behavior of aligning their bodies against the nearest surface, appearing horizontal, vertical, and even upside down. They use this positioning to ambush prey. They also have the ability to change colors to a limited extent to blend in with their environments. During the

monsoon A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscil ...

seasons, the reddish margins of the fins can turn paler (to either orange or white), accompanied by the appearance of numerous reddish spots on the lower half of the body. The upper half of the caudal fin also turns white.

Importance

Crazy fish are caught and sold for the

aquarium An aquarium (plural: ''aquariums'' or ''aquaria'') is a vivarium of any size having at least one transparent side in which aquatic plants or animals are kept and displayed. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aq ...

trade. They are also edible and are sometimes fished for human consumption. They are reasonably abundant and are classified as

Least Concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. T ...

by the

IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

References

External links

Video of crazy fish hunting upside down
at YouTube {{Taxonbar, from=Q2297666

butis ''Butis'' is a genus of fishes in the family Butidae found in fresh, brackish, and marine waters from the Indian Ocean coast of Africa through Southeast Asia to the Pacific islands and Australia. Species The recognized species in this genus are: ...

Taxa named by Francis Buchanan-Hamilton Taxonomy articles created by Polbot