''Sicyopterus lagocephalus'', the red-tailed goby or blue stream goby, is a species of

goby The Gobioidei are a suborder of percomorph fish. Many of these fishes are called gobies. It is by far the largest and most diverse order within the order Gobiiformes, and one of the most diverse groups of ray-finned fish in general. The subord ...

native to islands of the

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...

from the

Comoros The Comoros, officially the Union of the Comoros, is an archipelagic country made up of three islands in Southeastern Africa, located at the northern end of the Mozambique Channel in the Indian Ocean. Its capital and largest city is Moroni, ...

to the

Mascarene Islands The Mascarene Islands (, ) or Mascarenes or Mascarenhas Archipelago is a group of islands in the Indian Ocean east of Madagascar consisting of islands belonging to the Republic of Mauritius as well as the French department of Réunion. Their na ...

to the

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

where it reaches

French Polynesia French Polynesia ( ; ; ) is an overseas collectivity of France and its sole #Governance, overseas country. It comprises 121 geographically dispersed islands and atolls stretching over more than in the Pacific Ocean, South Pacific Ocean. The t ...

and can be found as far north as

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

. It is an

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 thousa ...

species: adults can be found in swift-flowing streams with rocky beds but the eggs hatch at sea and the larval stage remains in marine waters, migrating to freshwaters when they reach the postlarval stage. This species can reach a

total length Fish measurement is the measuring of individual fish and various parts of their anatomies, for data used in many areas of ichthyology, including taxonomy and fishery biology. Overall length Standard length (SL) is the length of a fish measured f ...

of . In some places it is an important species for local consumption with the post-larvae being caught as they mass in estuaries.

Description

Male ''Sicyopterus lagocephalus'' can grow to a total length of about while females can reach . The dorsal fin is divided in two and has 6 to 7 spines and 9 to 10 soft rays. The anal fin has a single spine and 10 soft rays. The pectoral fin has about 19 soft rays. During the rainy season, males become very colourful; the sides are metallic bluish-green, the tail is orange-red and there are about seven dark, saddle-shaped markings on the back. Females are grey or brown with dark saddle markings, a pale belly and a black and white band at the base of the tail.

Distribution and habitat

This species has a wide distribution in the tropical Pacific. Its range extends from Sri Lanka and the Mascarene Islands to Japan, Taiwan, the Philippines, Papua New Guinea, Australia, the Marshall Islands and French Polynesia. Adults live in fast-flowing streams with rocky beds while the larvae live in the ocean.

Ecology

The female ''S. lagocephalus'' lays its eggs in fresh water. After hatching, the larvae repeatedly rise towards the surface of the stream and then sink down again; this helps them to get carried along by the current. They consume their

yolk sac The yolk sac is a membranous wikt:sac, sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle by the Terminologia Embryologica (TE), though ''yolk sac' ...

s and will die if they do not reach the sea within about seven days. On arrival in the marine environment they are between long, and start to feed on

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

. They are translucent at this stage and remain at sea for somewhere between 133 and 256 days before getting the urge to migrate back into fresh water. The post-larval stage starts as they enter estuaries. They have already developed suction discs, but now they undergo

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and different ...

, their mouths move from the tip of the snout to the underneath of the head, they begin to develop pigment, the pectoral fins transform, the tail loses its fork, they grow teeth on the

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammals h ...

e bone, changes occur in the cranium and changes in

osmoregulation Osmoregulation is the active regulation of the osmotic pressure of an organism's body fluids, detected by osmoreceptors, to maintain the homeostasis of the organism's water content; that is, it maintains the fluid balance and the concentration ...

take place. As the rake-like teeth push through, they start to feed on

diatom A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...

s and

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

that they scrape off the

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (aquatic environment), the earthy material that exi ...

. After two days in the estuary, the juvenile fish move upstream, overcoming small waterfalls with the aid of their suction discs, and after about three or four weeks of

migration Migration, migratory, or migrate may refer to: Human migration * Human migration, physical movement by humans from one region to another ** International migration, when peoples cross state boundaries and stay in the host state for some minimum le ...

start to take up

territories A territory is an area of land, sea, or space, belonging or connected to a particular country, person, or animal. In international politics, a territory is usually a geographic area which has not been granted the powers of self-government, ...

in the fast-flowing streams where they will breed.

References

{{Taxonbar, from=Q644014 Sicyopterus Freshwater fish of Sri Lanka Taxa named by Peter Simon Pallas Fish described in 1770 Taxonomy articles created by Polbot