The aquatic rat, Ecuador fish-eating rat, fish-eating rat or Ecuadoran ichthyomyine (''Anotomys leander'') is a South American species of semiaquatic rodent in the family Cricetidae. It is the only species in the genus ''Anotomys''. This species is currently considered endangered. It is thought to be nocturnal and feeds on aquatic arthropods and insects. It is found in small ranges along the

Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...

Taxonomy

''Anotomys leander'' is the only member of its genus, which belongs the tribe

Ichthyomyini Ichthyomyini is a tribe of New World rats and mice in the subfamily Sigmodontinae. The species within this tribe share the characteristics of all being carnivorous semiaquatic rodents. *'' Anotomys'' - aquatic rat *'' Chibchanomys'' *''Ichthyomy ...

, subfamily

Sigmodontinae The rodent subfamily Sigmodontinae includes New World rats and mice, with at least 376 species. Many authorities include the Neotominae and Tylomyinae as part of a larger definition of Sigmodontinae. When those genera are included, the specie ...

and family Cricetidae. The ichthyomyines are semiaquatic carnivorous rodents that are found in South America from Mexico to Peru.

Habitat

''A. leander'' has a very small range, the smallest range of the ichthyomyines. Very few specimens have been captured so the full extent of its habitat and range is not completely known; the range is estimated at . The species is found in northern Ecuador along the Andes mountains; however, it has also been found at a single locality in Colombia. Individuals have only been found at elevations of . Their habitat is primarily wetlands that have streams, but also includes grassy paramo and mossy

elfin forest Dwarf forest, elfin forest, or pygmy forest is an uncommon ecosystem featuring miniature trees, inhabited by small species of fauna such as rodents and lizards. They are usually located at high elevations, under conditions of sufficient air humi ...

edge. Every known specimen has been found near running water.

Biology

The aquatic rat possess several distinctive characteristics, many of which can also be found in closely related ichthyomyines. The length of the tail is greater than the length of the body, and they have very large hind feet. They also have reduced or absent pinnae covered by a tuft of white fur. These characteristics are believed to aid in aquatic hunting and movement. For hunting the rodents rely on their

vibrissae Vibrissae (; singular: vibrissa; ), more generally called Whiskers, are a type of stiff, functional hair used by mammals to sense their environment. These hairs are finely specialised for this purpose, whereas other types of hair are coarser ...

(whiskers) to help locate prey along the streams edge. The vibrissae contain a very sensitive and developed

trigeminal nerve In neuroanatomy, the trigeminal nerve ( lit. ''triplet'' nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for sensation in the face and motor functions such as biting and chewin ...

that runs along the infraorbital foramen.

Diet

The diet of this species is not completely known. It is believed to feed on small aquatic arthropods and larvae. A close relative from genus ''

Chibchanomys ''Chibchanomys'' is a genus of rodent in the family Cricetidae The Cricetidae are a family of rodents in the large and complex superfamily Muroidea. It includes true hamsters, voles, lemmings, muskrats, and New World rats and mice. At almost 6 ...

'', also an aquatic ichthyomyine, was found to feed on small fish, arthropods, as well as terrestrial and aquatic insects. This genus hunts along the edge of streams using their vibrissae and once prey is caught the rodent takes it to a safe place (sometimes a burrow) on land to eat.

Karyotype

The

karyotype A karyotype is the general appearance of the complete set of metaphase chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. Karyotyping is the process by which a karyotype is disce ...

has been reported to have

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...

chromosome A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...

count of 2n = 92, but this number may have actually come from a specimen of the related Pittier's crab-eating rat, ''

Ichthyomys pittieri Pittier's crab-eating rat (''Ichthyomys pittieri'') is a species of semiaquatic rodent in the family Cricetidae. It is endemic to Venezuela. The natural habitats of this species are rivers and swamps. Its karyotype has 2n = 92 and FNa = 98. T ...

''. In any case, that value was previously thought to be the highest chromosome number known for a mammal, but it has since been found that the unrelated plains viscacha rat, ''

Tympanoctomys barrerae The plains viscacha rat, plains vizcacha rat, red viscacha rat, or red vizcacha rat (''Tympanoctomys barrerae'') is a species of rodent in the family Octodontidae native to Argentina. It is one of three species in the genus ''Tympanoctomys''. Des ...

'', has 4x = 2n = 102.

Threats

The species is listed as endangered and is threatened by pollution and habitat loss. Their small range makes them vulnerable to habitat loss. Because they rely on a partially aquatic habitat, water pollution, such as oil spills, also poses a serious threat.

References

{{taxonbar, from=Q1282226 Ichthyomyini Endemic fauna of Ecuador Mammals of Ecuador Rodents of South America Vulnerable animals Vulnerable biota of South America Mammals described in 1906 Taxa named by Oldfield Thomas Taxonomy articles created by Polbot