''Poromitra crassiceps'', commonly called the crested bigscale (also called large-headed midnight fish, crested melamphid, or one-horned melamphaid) is a species of

deep sea fish Deep-sea fish are fish that live in the darkness below the sunlit surface waters, that is below the epipelagic or photic zone of the sea. The lanternfish is, by far, the most common deep-sea fish. Other deep sea fishes include the flashlight ...

in the

ridgehead Ridgeheads, also known as bigscales, are a family (Melamphaidae, from the Greek ''melanos'' lackand ''amphi'' y both sides of small, deep-sea stephanoberyciform fish. The family contains approximately 37 species in five genera; their distribut ...

family. While the fish with the common name crested bigscale in Alaskan waters had formerly been identified as ''P. crassiceps'', it is now believed that Alaskan crested bigscales are actually ''

Poromitra curilensis ''Poromitra'' is a genus of ridgeheads. The 22 known species of Poromitra have been divided into five species groups according to variation in preopercle anatomy. A Poromitra curilensis specimen from the Shirshov Institute of Oceanology, obtaine ...

'', and that ''P. crassiceps'' is restricted to the Atlantic Ocean. As a result of this mis-identification, ''P. crassiceps'' is occasionally identified as the largest

- while specimens of ''P. curilensis'' as large as 18 cm SL have been found, the maximum length of ''P. crassiceps'' is 14.8 cm SL. Although almost no light penetrates to the deep sea from the surface, the crested bigscale has evolved features that make it practically invisible. Like other deep sea fish, it needs to avoid being seen by predators, some of which hunt for prey by creating their own light by means of

bioluminescence Bioluminescence is the production and emission of light by living organisms. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some b ...

. The crested bigscale achieves invisibility by having a skin that absorbs light with great efficiency. The pigment

melanin Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino ...

is crammed into granules which are grouped into melanophores which cover virtually the whole of the

dermis The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided i ...

. This absorbs almost all of the incoming light, and any remaining light that scatters sideways is absorbed by neighbouring granules. The melanophores also cover the big scales, but these detach easily, and any predator that gets close enough, may end up with a mouthful of scales. Altogether, the absorption of light is 99.5% efficient, a fact that makes photographing this fish in its natural habitat very difficult.

References

External links

Crested Bigscale
at th
Digital Fish Library
- With some images of crested bigscales.

- Much more information with references.
Résultats des campagnes scientifiques - Prince Albert I of Monaco
(''french'') {{Authority control Melamphaidae Deep sea fish Fish described in 1878 Taxa named by Albert Günther