Sleeper goby

Eleotridae
Mogurnda mogurnda
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Perciformes
Family:	Eleotridae Bonaparte, 1835

Eleotridae is a family of fish commonly known as sleeper gobies found predominantly in the tropical Indo-Pacific, with about 32 genera and 180 species. While many eleotrids pass through a planktonic stage in the sea and some spend their entire lives in the sea; as adults, the majority live in freshwater streams and brackish waters. A few species (Caecieleotris, Milyeringa, Typhleotris, and some Bostrychus) are troglobitic. They are especially important as predators in the freshwater stream ecosystems on oceanic islands such as New Zealand and Hawaii that otherwise lack the predatory fish families typical of nearby continents, such as catfish. Anatomically, they are similar to the gobies (Gobiidae), though unlike the majority of gobies, they do not have a pelvic sucker.

Like the true gobies, they are generally small fish that live on the substrate, often amongst vegetation, in burrows, or in crevices within rocks and coral reefs. Although goby-like in many ways, sleeper gobies lack the pelvic fin sucker and that, together with other morphological differences, is used to distinguish the two families. The Gobiidae and Eleotridae likely share a common ancestor and they are both placed in the suborder Gobioidei, along with a few other small families containing goby-like fishes.

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Wikipedia