Exastilithoxus is a small genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of catfish

Catfish

Catfishes are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the heaviest and longest, the Mekong giant catfish from Southeast Asia and the second longest, the wels catfish of Eurasia, to detritivores...

 (order

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Siluriformes) of the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Loricariidae

Loricariidae

Loricariidae is the largest family of catfish , with almost 700 species and new species being described each year. Loricariids originate from fresh water habitats of Costa Rica, Panama, and tropical and subtropical South America. These fish are noted for the bony plates covering their bodies and...

. It includes two species, E. fimbriatus and E. hoedemani.

Distribution and habitat

Exastilithoxus are South America

South America

South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

n catfish. E. fimbriatus is distributed in the Caroní

Caroní River

The Caroni River is the second most important river of Venezuela, the second in flow, and one of the longest, 952 km from the Tepui Kuquenan, where she originates with the same name Kuquenan, up to its confluence with the River Orinoco to which basin she belongs...

 and Matacuni River basins in the Orinoco drainage. E. hoedemani is distributed in the Maurauiá River in the upper Rio Negro drainage.

Appearance and anatomy

Exastilithoxus species are small, cylindrical loricariids. E. fimbriatus reaches a length of about 6 centimetres (2.4 in) SL

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:...

. E. hoedemani reaches a length of about 5 cm (2  in) SL.

These species exhibit a round lower lip with fleshy barbels

Barbel (anatomy)

A barbel on a fish is a slender, whiskerlike tactile organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, sturgeon, the zebrafish and some species of shark...

. Color pattern is generally mottled and dark brown with paler areas under and just posterior to the dorsal fin. The abdomen is white, fins are mottled, and the ventral surface of the caudal peduncle is colored as the sides, but slightly lighter. Like other loricariids, the body is armored, however the abdomen is naked.

Ecology

Exastilithoxus species are unique among loricariids in that they subsist entirely on insect

Insect

Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

 larva

Larva

A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

e.