Water Opossum
Encyclopedia
The water opossum also locally known as the yapok, is a marsupial
of the family Didelphidae. It is the only member
of its genus
, Chironectes. This semiaquatic creature is found in and near the freshwater
streams and lakes in Mexico, Central and South America to Argentina
, and is the most aquatic
living marsupial (the lutrine opossum
also has aquatic habits). It is also the only living marsupial in which both sexes have a pouch. The thylacine
, commonly referred to as the Tasmanian tiger, also exhibited this trait, but is now believed to be extinct.
The animal lives in bankside burrows, emerging after dusk to swim and search for fish
, crustacean
s and other aquatic animals, which it eats on the bank.
The yapok of Central and South America is superbly adapted to a life in water. It has long webbed toes on its hindfeet, water-repellant fur, and a pouch that closes during dives. It hunts its aquatic prey of fish, frogs, crustaceans, and rests in a riverbank den by day.
True opossums are unique to North America alone. The word "opossum" was taken from the native Algonquian
word for the animal. Though the yapok, as well as other marsupials in South America and Australia are called "possums", most are not closely related to the Virginia opossum
, and only derive their name by a generally similar shape and appearance.
Being a marsupial and at the same time an aquatic animal, the water opossum has evolved a way to protect its young while swimming. A strong ring of muscle makes the pouch (which opens to the rear) watertight, so the young remain dry, even when the mother is totally immersed in water. The male also has a pouch (although not as watertight as the female's), where he places his genitalia before swimming. This is thought to prevent it from becoming tangled in aquatic vegetation and is probably helpful in streamlining the animal as well.
epoch.
Holocene
subfossil fragments of Chironectes have been discovered in São Paulo
, Brazil. Also, there are fossil specimens from the late Pleistocene
-Recent cave deposits in Minas Gerais
, Brazil as well as from the late Pliocene
in Entre Ríos Province
, Argentina.
Marsupial
Marsupials are an infraclass of mammals, characterized by giving birth to relatively undeveloped young. Close to 70% of the 334 extant species occur in Australia, New Guinea, and nearby islands, with the remaining 100 found in the Americas, primarily in South America, but with thirteen in Central...
of the family Didelphidae. It is the only member
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
of its 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...
, Chironectes. This semiaquatic creature is found in and near the freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
streams and lakes in Mexico, Central and South America to Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
, and is the most aquatic
Aquatic animal
An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...
living marsupial (the lutrine opossum
Lutrine Opossum
The lutrine opossum , also known as the little water opossum or thick-tailed opossum, is an opossum species from South America and is monotypical of the genus Lutreolina. It is found in Brazil, Argentina, Bolivia, Uruguay, Paraguay, Colombia and Guyana...
also has aquatic habits). It is also the only living marsupial in which both sexes have a pouch. The thylacine
Thylacine
The thylacine or ,also ;binomial name: Thylacinus cynocephalus, Greek for "dog-headed pouched one") was the largest known carnivorous marsupial of modern times. It is commonly known as the Tasmanian tiger or the Tasmanian wolf...
, commonly referred to as the Tasmanian tiger, also exhibited this trait, but is now believed to be extinct.
The animal lives in bankside burrows, emerging after dusk to swim and search for fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
, crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s and other aquatic animals, which it eats on the bank.
Origin of the name
The local name for the water opossum, "yapok", probably comes from the name of the Oyapok River in French Guyana.The yapok of Central and South America is superbly adapted to a life in water. It has long webbed toes on its hindfeet, water-repellant fur, and a pouch that closes during dives. It hunts its aquatic prey of fish, frogs, crustaceans, and rests in a riverbank den by day.
True opossums are unique to North America alone. The word "opossum" was taken from the native Algonquian
Algonquian languages
The Algonquian languages also Algonkian) are a subfamily of Native American languages which includes most of the languages in the Algic language family. The name of the Algonquian language family is distinguished from the orthographically similar Algonquin dialect of the Ojibwe language, which is a...
word for the animal. Though the yapok, as well as other marsupials in South America and Australia are called "possums", most are not closely related to the Virginia opossum
Virginia Opossum
The Virginia opossum , commonly known as the North American opossum or tlacuache in Mexico, is the only marsupial found in North America north of Mexico. A solitary and nocturnal animal about the size of a domestic cat, and thus the largest opossum, it is a successful opportunist...
, and only derive their name by a generally similar shape and appearance.
Physical appearance
The yapok is a small opossum, 27-32.5 cm long, with a 36–40 cm long tail. The fur is in a marbled grey and black pattern while the muzzle, eyestripe, and crown are all black. A light band runs across the forehead anterior to the ears, which are rounded and naked. There are sensory facial bristles in tufts above each eye as well as whiskers. The animal's tail, furred and black at the base, is yellow or white at its end. The hindfeet of the yapok are webbed, while the forefeet ("hands") are not. The forefeet can be used to feel for and grab prey as the yapok swims, propelled by its tail and webbed back feet.Aquatic adaptations
The water opossum has several adaptations for its watery lifestyle. It has short, dense fur which is water-repellent. The broad hindfeet are webbed and are used for propulsion through water, moving with alternate strokes. They are symmetrical as well, which distributes force equally along both borders of the webbing; this increases the efficiency of the water opossum's movement through the water. The yapok's long tail also aids in swimming.Being a marsupial and at the same time an aquatic animal, the water opossum has evolved a way to protect its young while swimming. A strong ring of muscle makes the pouch (which opens to the rear) watertight, so the young remain dry, even when the mother is totally immersed in water. The male also has a pouch (although not as watertight as the female's), where he places his genitalia before swimming. This is thought to prevent it from becoming tangled in aquatic vegetation and is probably helpful in streamlining the animal as well.
Reproduction
Yapoks mate in December and a litter of 1-5 young is born 27 weeks later in the nest. By 22 days the offspring are beginning to show some fur, and by 40 days or so their eyes are open, their bodies protruding from the mother's pouch. At 48 days of age, the young opossums detach from the nipples but still nurse and sleep with the mother.Fossil record
The water opossum seems to have a history dating as far back as to the PliocenePliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
epoch.
Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
subfossil fragments of Chironectes have been discovered in São Paulo
São Paulo
São Paulo is the largest city in Brazil, the largest city in the southern hemisphere and South America, and the world's seventh largest city by population. The metropolis is anchor to the São Paulo metropolitan area, ranked as the second-most populous metropolitan area in the Americas and among...
, Brazil. Also, there are fossil specimens from the late Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
-Recent cave deposits in Minas Gerais
Minas Gerais
Minas Gerais is one of the 26 states of Brazil, of which it is the second most populous, the third richest, and the fourth largest in area. Minas Gerais is the Brazilian state with the largest number of Presidents of Brazil, the current one, Dilma Rousseff, being one of them. The capital is the...
, Brazil as well as from the late Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
in Entre Ríos Province
Entre Ríos Province
Entre Ríos is a northeastern province of Argentina, located in the Mesopotamia region. It borders the provinces of Buenos Aires , Corrientes and Santa Fe , and Uruguay in the east....
, Argentina.
Subspecies
- Chironectes minimus argyrodytes
- Chironectes minimus langsdorffi
- Chironectes minimus minimus
- Chironectes minimus panamensis