Eleotridae
The Eleotridae, commonly known as sleepers, goby-eels, or sleeper gobies, are a family of perciform fish found in both freshwater and saltwater environments, mostly in tropical and subtropical regions. They are characterized by their elongated, eel-like bodies and the lack of scales on most of their body. These fish are generally small, ranging from 2 to 60 cm in length, and are known for their burrowing habits, often found hiding in crevices, under rocks, or in burrows they excavate themselves. They play an important role in their ecosystems, feeding on a variety of invertebrates and small fish, and serving as prey for larger fish.
Characteristics
Eleotridae exhibit a variety of characteristics that distinguish them from other fish families. Their most notable feature is their elongated, eel-like bodies, with a compressed head and a tapering tail. Most sleepers lack scales, except for a few small scales near their heads or dorsal fins. They possess a single dorsal fin, which may be continuous or divided into two sections, and a well-developed anal fin. Their mouths are generally wide, with small teeth that are adapted for feeding on invertebrates and small fish.
Most species have a distinctive feature called a "preopercular spine," a small, sharp bone located on the lower edge of the operculum (the bony flap covering the gills). This spine, which is absent in some species, helps them defend themselves against predators.
Habitat
Eleotridae are found in a variety of habitats, including freshwater rivers, streams, lakes, and brackish estuaries, as well as coastal marine environments. They are typically found in areas with soft substrates, such as sand, mud, or gravel, where they can burrow and hide from predators. Some species are known to live in coral reefs, rocky shores, or mangrove swamps.
Behavior
Sleepers are generally solitary fish, although some species may form small groups. They are active at night, spending their days hiding in burrows or crevices. During the night, they emerge to feed on a variety of invertebrates, including worms, crustaceans, mollusks, and insect larvae. Some species may also consume small fish.
Eleotridae are known for their elaborate courtship displays, which may involve changing colors, producing sounds, or constructing nests. The males of some species are territorial and will defend their nests from other males.
Distribution
Eleotridae have a wide distribution, with species found in tropical and subtropical regions worldwide. They are most abundant in the Indo-Pacific region, but also occur in the Atlantic Ocean, the Mediterranean Sea, and the Caribbean Sea. The family includes over 200 species, divided into approximately 30 genera.
Notable Genera and Species
Some of the most well-known genera of Eleotridae include:
- Eleotris: This genus contains the largest number of species, with about 80 known species.
- Dormitator: The "burrowing sleepers" of this genus are notable for their large size and their tendency to create burrows in soft substrates.
- Cryptocentrus: This genus includes the "sand gobies," which are characterized by their long, slender bodies and their ability to bury themselves in sand.
- Guavina: The "crested sleepers" of this genus are known for the distinctive crests on their heads.
References
Wikipedia: Eleotridae
FishBase: Eleotridae
NCBI Taxonomy: Eleotridae