''Rhinogobius flumineus'', commonly known as the lizard goby or kawa-yoshinobori, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of goby

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

where it is found in the mid- to upper reaches of fast-flowing

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...

s. This species can reach a length of TL.

Taxonomy and evolution

This fish was first described in 1960 by the Japanese ichthyologist Nobuhiko Mizuno who gave it the name ''Tukugobius flumineus''. It was later transferred to the genus '' Rhinogobius'', becoming ''Rhinogobius flumineus''. The name comes from the Greek, "rhinos", meaning nose, and the Latin, "gobius", meaning gudgeon; the specific name comes from the Latin "flumen" meaning river. This fish is commonly known as the "lizard goby" or in Japanese as "kawa-yoshinobori". ''Rhinogobius flumineus'' seems to have evolved from ''

Rhinogobius brunneus ''Rhinogobius brunneus'', the Amur goby, is a species of fish in the in the family Oxudercidae. It is found in the Asian river basins of the seas of the Pacific coasts of Japan, Hokkaido, Ryukyu, Taiwan, the rivers of Korea, continental China, t ...

'' to which it is morphologically very similar. There is a trend for fish in the genus ''Rhinogobius'' to move from marine to freshwater habitats as they evolve, and ''R. brunneus'' is

amphidromous Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousan ...

(migratory) while ''R. flumineus'' inhabits land-locked river basins.

Distribution and habitat

''R. flumineus'' is endemic to Japan where it is found in riffles and swiftly-flowing mountain streams and small rivers. Its range extends from

Shizuoka Prefecture is a prefecture of Japan located in the Chūbu region of Honshu. Shizuoka Prefecture has a population of 3,637,998 and has a geographic area of . Shizuoka Prefecture borders Kanagawa Prefecture to the east, Yamanashi Prefecture to the northea ...

and

Toyama Prefecture is a prefecture of Japan located in the Chūbu region of Honshu. Toyama Prefecture has a population of 1,044,588 (1 June 2019) and has a geographic area of 4,247.61 km2 (1,640.01 sq mi). Toyama Prefecture borders Ishikawa Prefecture to the ...

Honshu , historically called , is the largest and most populous island of Japan. It is located south of Hokkaidō across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyūshū across the Kanmon Straits. The island separ ...

to the westward tip of the island, and the islands of Shikoku and

Kyushu is the third-largest island of Japan's five main islands and the most southerly of the four largest islands ( i.e. excluding Okinawa). In the past, it has been known as , and . The historical regional name referred to Kyushu and its surroun ...

. It is a

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

species. Where it coexists with the slightly larger '' Rhinogobius nagoyae'', the latter tends to occupy the riffles that are its favoured habitat, and ''R. flumineus'' finds alternative locations.

Ecology

''R. flumineus'' holds itself in a stationary position on a rock in fast-flowing water by means of a "sucker" formed from its two ventral fins. The mouth is slightly asymmetric; dextral fish tend to curve their bodies to the right as they rest while sinistral fish tend to adopt a left-curving posture. The fish are omnivorous, picking edible items of food off the river bed with the side of the mouth, but dextral and sinistral fish have no preference for which side of the mouth they use for this purpose. The breeding season is from June to August. The eggs are deposited in a nest and guarded by the male, and the newly-hatched juvenile fish live on the riverbed.

References

{{Taxonbar, from=Q2706751 flumineus Freshwater fish of Japan Endemic fauna of Japan Fish described in 1960