''Macrognathus pentophthalmos'', the Sri Lanka five-eyed spiny eel, is a small species of spiny eel that is endemic to freshwater habitats in

Sri Lanka Sri Lanka (, ; si, ශ්‍රී ලංකා, Śrī Laṅkā, translit-std=ISO (); ta, இலங்கை, Ilaṅkai, translit-std=ISO ()), formerly known as Ceylon and officially the Democratic Socialist Republic of Sri Lanka, is an ...

. Described as a common species as recently as 1980, for unknown reasons its population rapidly declined in the following years and there are no recent confirmed records. In 2012, it was listed as " Critically Endangered, possibly

Extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

" in the Sri Lankan National Red List, which was matched by

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 ...

in 2019. It is up to in

standard 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 m ...

. Compared to ''

Mastacembelus armatus The zig-zag eel (''Mastacembelus armatus''), also known as the tire-track eel, tire-track spiny eel or marbled spiny eel, is a species of ray-finned, spiny eels belonging to the genus '' Mastacembelus'' (Scopoli, 1777) of the family Mastacembe ...

'', the only other spiny eel in Sri Lanka, ''M. pentophthalmos'' has a striped/plain (not mottled) pattern, and clearly separated dorsal,

caudal Caudal may refer to: Anatomy * Caudal (anatomical term) (from Latin ''cauda''; tail), used to describe how close something is to the trailing end of an organism * Caudal artery, the portion of the dorsal aorta of a vertebrate that passes into the ...

and

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 ...

s. The English name of ''M. pentophthalmos'' refers to the series of dark spots on its dorsal fin. Described as a new species in 1854, it was then considered a

synonym A synonym is a word, morpheme, or phrase that means exactly 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 all ...

of the widespread '' M. aral''. In 2008 it was shown that this was mistaken and ''M. pentophthalmos'' was reinstated as a valid species (the true ''M. aral'' is not found in Sri Lanka).

References

{{Taxonbar, from=Q6444802 pentophthalmos Freshwater fish of Sri Lanka Fish described in 1854