Parioglossus galzini is a species of dartfish

Dartfish

Dartfishes are a family, Ptereleotridae, of goby-like fishes in the order Perciformes. They are saltwater fish.The dartfishes were formerly classified as the subfamily Ptereleotrinae of the wormfishes, Microdesmidae, but this classification made Microdesmidae polyphyletic, hence the elevation to a...

. Presently it is only known from the island of Rapa Iti

Rapa Iti

Rapa or Rapa Iti as it is sometimes called in more recent years , is the largest and only inhabited island of the Bass Islands in French Polynesia. An older name for the island is Oparo Its area is 40 km2 with a population of almost 500 and a max elevation of 650 m...

, French Polynesia

French Polynesia

French Polynesia is an overseas country of the French Republic . It is made up of several groups of Polynesian islands, the most famous island being Tahiti in the Society Islands group, which is also the most populous island and the seat of the capital of the territory...

.

This tiny fish (standard length

Fish measurement

Fish measurement refers to the measuring of the length of individual fish and of various parts of their anatomy. These data are used in many areas of ichthyology, including taxonomy and fisheries biology.-Overall length:...

 up to 25 mm) is found in shallow inshore waters. It can be distinguished from its congeners in several ways, most notably by the complete absence of a dark lateral stripe and the presence of a membrane linking the two dorsal fin

Dorsal fin

A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

s in both sexes.