Ammoglanis is a 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...

es (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...

 Trichomycteridae

Trichomycteridae

Trichomycteridae is a family of catfishes commonly known as the pencil or parasitic catfishes. This family includes the infamous candiru fish, feared by some people for its alleged habit of entering into the urethra of humans....

. It includes three species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

, A. amapaensis, A. diaphanus and A. pulex.

Taxonomy

The phylogenetic

Phylogenetics

In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...

 position of A. pulex is problematic. It seems to be closely related to A. diaphanus due to some derived

Derived

In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...

 characters of the internal anatomy, but a conclusive assessment of its relationships has not been prevented by its paedomorphic features and scarcity of study material. This generic placement seems to be well supported.

The relationships of the genus Ammoglanis are unknown; it is thought that this genus along with undescribed forms are the sister group

Cladistics

Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...

 to a large intrafamilial clade

Clade

A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 composed of several genera and subfamilies. In the interim, this genus is included within Sarcoglanidinae

Sarcoglanidinae

Sarcoglanidinae is a subfamily of catfishes of the family Trichomycteridae. It includes six genera, Ammoglanis, Malacoglanis, Microcambeva, Sarcoglanis, Stauroglanis, and Stenolicmus.-Taxonomy:...

.

Distribution

A. amapaensis originates from three different drainages of the Amazon River

Amazon River

The Amazon of South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined...

, the Jari

Jari River

The Jari River, is a northern tributary of the Amazon river on the border between the states of Pará and Amapá in northeastern Brazil. It is in the most downstream regions of the Amazon Basin and borders the Guiana Highlands and the Guianas and French Guiana to the northwest.-Tributaries:*...

, Amapari

Amapari River

-References:*...

, and Araguari River

Araguari River

-Brazil:* Araguari River * Araguari River also called Rio das Velhas...

. A. diaphanus originates from a stream tributary to the Javaés River of the Araguaia River

Araguaia River

The Araguaia River or, in Portuguese, Rio Araguaia is one of the major rivers of Brazil, and the principal tributary of the Tocantins. It has a total length of approximately 2,627 km. Araguaia means "river of macaws" in the Tupi language....

 basin in Tocantins

Tocantins (state)

Tocantins is one of the states of Brazil. . The state was formed in 1988 out of the northern part of Goiás, and construction began on the capital, Palmas, in 1989, in contrast to most of the other cities in the state which date back to the Portuguese colonial period...

, Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

. A. pulex originates from the Paria Grande River, the Pamoni River, and Caño Garrapata of Venezuela

Venezuela

Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...

.

Description

Ammoglanis species grow to about 1.5–1.9 centimetres (.59–.75 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:...

. A. pulex is among the smallest known vertebrates. A. pulex can be distinguished from A. diaphanus by a number of characteristics, including the presence of a faint pattern of eight bands formed by internal chromatophore

Chromatophore

Chromatophores are pigment-containing and light-reflecting cells found in amphibians, fish, reptiles, crustaceans, and cephalopods. They are largely responsible for generating skin and eye colour in cold-blooded animals and are generated in the neural crest during embryonic development...

s and the lack of teeth.

Ecology

A. diaphanus inhabits shallow, narrow, clear water, moderately swift-flowing stream and is found buried in the sand. It feeds on Diptera

Diptera

Diptera , or true flies, is the order of insects possessing only a single pair of wings on the mesothorax; the metathorax bears a pair of drumstick like structures called the halteres, the remnants of the hind wings. It is a large order, containing an estimated 240,000 species, although under half...

 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 and a cladocera

Cladocera

Cladocera is an order of small crustaceans commonly called water fleas. Around 620 species have been recognised so far, with many more undescribed. They are ubiquitous in inland aquatic habitats, but rare in the oceans. Most are long, with a down-turned head, and a carapace covering the apparently...

ns. A. pulex is a translucent light-pink fish that camouflages well in sand. A. pulex is found in sand banks near the shorelines of clear water and slightly tea-stained streams. Apparently fossorial

Fossorial

A fossorial organism is one that is adapted to digging and life underground such as the badger, the naked mole rat, and the mole salamanders Ambystomatidae...

 by daylight, it is found buried in coarse clear sand at the stream edge, in areas shaded by dense tropical rainforest. The waters are with slow current, pH varying between 5.5–6.2, and temperature between 27.5–28°C (81.5–82.4°F). A. pulex is thought to feed on microscopic fauna like protozoa

Protozoa

Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...

, rotifer

Rotifer

The rotifers make up a phylum of microscopic and near-microscopic pseudocoelomate animals. They were first described by Rev. John Harris in 1696, and other forms were described by Anton van Leeuwenhoek in 1703...

s, and nematode

Nematode

The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...

s since it inhabits interstitial spaces among sand grains in nutrient-poor, clear-water and backwater streams.