''Amphiprion leucokranos'' (White bonnet anemonefish) is a naturally occurring

hybrid Hybrid may refer to: Science * Hybrid (biology), an offspring resulting from cross-breeding ** Hybrid grape, grape varieties produced by cross-breeding two ''Vitis'' species ** Hybridity, the property of a hybrid plant which is a union of two diff ...

anemonefish Clownfish or anemonefish are fishes from the subfamily Amphiprioninae in the family Pomacentridae. Thirty species of clownfish are recognized: one in the genus ''Premnas'', while the remaining are in the genus ''Amphiprion''. In the wild, the ...

found in the western central

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 contine ...

. Like all anemonefishes it forms a symbiotic mutualism with sea anemones and is unaffected by the stinging tentacles of the host anemone. It is a sequential hermaphrodite with a strict

dominance hierarchy In biology, a dominance hierarchy (formerly and colloquially called a pecking order) is a type of social hierarchy that arises when members of animal social groups interact, creating a ranking system. A dominant higher-ranking individual is so ...

, features which are critical to the direction of gene flow.

Description

The body of ''A. leucokranosis'' is orange or light brown and with a white head bar and a white mark on the top of its head, giving rise to its common name of white bonnet anemonefish. The head band may be continuous or not. They have 9 dorsal spines, 2 anal spines, 18-19 dorsal soft rays and 13-14 anal soft rays. They reach a maximum length of .

Hybridisation

There has been a long-standing theory that ''A. leucokranosis'' was a naturally occurring hybrid between ''A. chrysopterus'' and ''A. sandaracinos'', with the fish being experimentally created in captivity. Its hybrid status was confirmed in 2015 with consistent

ecological Ecology () is the study of the relationships between living organisms, including humans, and their biophysical environment, physical environment. Ecology considers organisms at the individual, population, community (ecology), community, ecosy ...

, morphological and genetic evidence. In any group of anemonefish, there is a strict sized based dominance hierarchy: the female is largest, the breeding male is second largest, and the male non-breeders get progressively smaller as the hierarchy descends. They exhibit

protandry Sequential hermaphroditism (called dichogamy in botany) is a type of hermaphroditism that occurs in many fish, gastropods, and plants. Sequential hermaphroditism occurs when the individual changes its sex at some point in its life. In particular, ...

, meaning the breeding male will change to female if the sole breeding female dies, with the largest non-breeder becomes the breeding male. This strict sized based dominance hierarchy makes the relative size of the parent species critical in shaping the outcome of hybridization In this regard ''A. chrysopterus'' is one of the largest anemonefish, growing to 17 cm in length. while ''A. sandaracinos'' is significantly smaller growing up to 11 cm as a female and just 3 to 6.5 cm as a male. There is strong evidence, consistent with their relative size, of the larger ''A. chrysopterus'' always being the mother and unidirectional

introgression Introgression, also known as introgressive hybridization, in genetics is the transfer of genetic material from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with one of its parent species. Intro ...

of ''A. chrysopterus'' mitochondrial DNA into ''A. sandaracinos'' via hybrid backcrosses. Parent species Image:Amphiprion chrysopterus, Vava'eu.jpg, ''A. chrysopterus'' Image:Amphiprion sandaracinos.jpg, ''A. sandaracinos''

Color variations

Being a hybrid ''A. leucokranosis'' shows a variety of colors and patterns, with the intermediate morphology of the typical

F1 hybrid An F1 hybrid (also known as filial 1 hybrid) is the first filial generation of offspring of distinctly different parental types. F1 hybrids are used in genetics, and in selective breeding, where the term F1 crossbreed may be used. The term is somet ...

and backcrosses tending more towards the features of ''A. sandaracinos''. It does not show any melanism when hosted by ''S. mertensii'' unlike some species of anemonefish, such as ''A. clarkii''

Similar species

The white mark on top of the head is distinctive. The parent ''A. sandaracinos'' has a similar body color, however it has a white stripe on the dorsal ridge from the superior lip to the

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 s ...

and lacks the white bar on the side of the head.

Distribution and habitat

Other constraints upon hybridization are overlap in distribution, depth and host anemone. ''A. leucokranos'' is found in the Western Central Pacific, on the north coast of

New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; id, Papua, or , historically ) is the world's second-largest island with an area of . Located in Oceania in the southwestern Pacific Ocean, the island is separated from Australia by the wide Torr ...

, including

Manus Island Manus Island is part of Manus Province in northern Papua New Guinea and is the largest of the Admiralty Islands. It is the fifth-largest island in Papua New Guinea, with an area of , measuring around . Manus Island is covered in rugged jungles ...

, D'Entrecasteaux Islands and

New Britain New Britain ( tpi, Niu Briten) is the largest island in the Bismarck Archipelago, part of the Islands Region of Papua New Guinea. It is separated from New Guinea by a northwest corner of the Solomon Sea (or with an island hop of Umboi the D ...

and the

Solomon Islands Solomon Islands is an island country consisting of six major islands and over 900 smaller islands in Oceania, to the east of Papua New Guinea and north-west of Vanuatu. It has a land area of , and a population of approx. 700,000. Its ca ...

, being the area where the distribution of ''A. chrysopterus'' and ''A. sandaracinos'' overlap. There is a substantial overlap in depth with all 3 fish found in the range of 1–10 m.

Host anemones

''A. leucokranos'' is hosted by the following species of anemone: *''

Heteractis crispa The sebae anemone (''Heteractis crispa''), also known as leathery sea anemone, long tentacle anemone, or purple tip anemone, is a species of sea anemone belonging to the family Stichodactylidae and native to the Indo-Pacific area. It was first ...

'' Sebae anemone *'' Heteractis magnifica'' magnificent sea anemone *''

Stichodactyla mertensii ''Stichodactyla mertensii'', commonly known as Mertens' carpet sea anemone, is a species of sea anemones in the family Stichodactylidae. It is regarded as the largest sea anemone with a diameter of over , the next largest being '' Heteractis mag ...

'' Mertens' carpet sea anemone At Kimbe Bay ''A. leucokranos'' and its parents were primarily found in the host ''

'' otherwise ''

''.

References

External links

{{Taxonbar, from=Q1852879 Pomacentridae leucokranos Fish described in 1973