The web-footed tenrec, Malagasy otter shrew, or aquatic tenrec (''Microgale mergulus'') is the only known

semiaquatic In biology, being semi-aquatic refers to various macroorganisms that live regularly in both aquatic and terrestrial environments. When referring to animals, the term describes those that actively spend part of their daily time in water (in ...

tenrec A tenrec () is a mammal belonging to any species within the afrotherian family Tenrecidae, which is endemic to Madagascar. Tenrecs are a very diverse group, as a result of adaptive radiation, and exhibit convergent evolution, some resemble hed ...

(the related African

otter shrew Potamogalidae is the family of "otter shrews", a group of semiaquatic riverine afrotherian mammals indigenous to sub-Saharan Africa. They are most closely related to the tenrecs of Madagascar, from which they are thought to have split about 47� ...

s have similar habits), and is found in eastern

Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...

, especially in and around

Ranomafana National Park Ranomafana National Park is a national park in southeastern Madagascar, in the Haute Matsiatra and Vatovavy regions. It was established as Madagascar's fourth national park in 1991 following the rediscovery of the greater bamboo lemur (''Hap ...

. It grows to between , and was once thought to be

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

. It feeds on

crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

s, aquatic

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

s, and

crayfish Crayfish are freshwater crustaceans belonging to the infraorder Astacidea, which also contains lobsters. Taxonomically, they are members of the superfamilies Astacoidea and Parastacoidea. They breathe through feather-like gills. Some spe ...

. The population is considered vulnerable. It was formerly placed in the

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...

genus ''Limnogale'', but has been moved to '' Microgale'' based on molecular data showing it to be deeply nested within the latter.

Life history

''Microgale mergulus'' is strictly nocturnal, spending the day in stream side burrows, only emerging at night to hunt. Nocturnal movements appear to be restricted to waterways but include movements away from burrows and diving. Radio collar tracking has shown that some individuals are known to utilize stream channels as much as 1160 meters in length, while others may only patrol 500 meters. In one night a web-footed tenrec may travel 1550 meters along channels in search of food.

Diet

''M. mergulus'' is only known to inhabit stream habitats in eastern Madagascar. While it is no longer classified in the obsolete order of Insectivora, ''M. mergulus'' could very well be designated an insectivore. The bulk of its diet consists of aquatic insects and larvae, with crustaceans (crayfish), small fish, and tadpoles making up the rest. The larvae of insects in the orders Ephemeroptera,

Odonata Odonata is an order of predatory flying insects that includes the dragonflies and damselflies (as well as the '' Epiophlebia'' damsel-dragonflies). The two major groups are distinguished with dragonflies (Anisoptera) usually being bulkier with ...

and

Trichoptera The caddisflies (order Trichoptera) are a group of insects with aquatic larvae and terrestrial adults. There are approximately 14,500 described species, most of which can be divided into the suborders Integripalpia and Annulipalpia on the basis ...

are favored. Diets of individuals inhabiting zero-canopy steams appear to be the same as those living in forested streams.

Phylogeny

The aquatic or web-footed tenrec, ''Microgale mergulus'', and other tenrecs are endemic to Madagascar. They are part of the monophyletic

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

Afrotheria Afrotheria ( from Latin ''Afro-'' "of Africa" + ''theria'' "wild beast") is a superorder of placental mammals, the living members of which belong to groups that are either currently living in Africa or of African origin: golden moles, elephan ...

, which includes placental mammals of diverse anatomies including hyraxes, elephants and mammoths, manatees and dugong, tenrecs, golden moles, elephant shrews, and aardvarks. Genetic sequencing and other methods have confirmed the accuracy and relatedness of this grouping. The web-footed tenrec is one of 22 members of the genus ''Microgale''. Molecular studies have led to its placement in the subfamily

Oryzorictinae Oryzorictinae is a subfamily of tenrecs endemic to the island of Madagascar. It is the largest of three tenrec subfamilies. Oryzorictinae is thought to have split from the lineage of its closest relative, '' Geogale'', about 30 million years ( Ma ...

, along with two species each of the genera ''

Nesogale ''Nesogale'' is a genus of tenrecs, which are a family of afrotherian mammals endemic to Madagascar. On the basis of molecular data indicating its two species form a sister group to the rest of ''Microgale'' (21 extant species), they were transfe ...

'' and '' Oryzorictes''.Nicoll, M., Ratsifandrihamanana, N. (2014), Growth of Madagascar’s protected areas system and its implications for tenrecs (Afrosoricida, Tenrecidae). Afrotherian Conservation. September 2014: 4-8. Published by IUCN, Gland, Switzerland. It is the largest member of this subfamily and likely evolved this increased size in response to its aquatic lifestyle. Ancestral tenrecs are thought to have rafted from mainland Africa to Madagascar in a single event. All tenrecs are thought to descend from a common ancestor that lived 29–37 million years ( Ma) ago They include members of subfamilies

Tenrecinae Tenrecinae is a Tenrecidae, tenrec subfamily endemic to the island of Madagascar. It contains the largest species in the family, ''Tenrec ecaudatus''. All members of the genus possess Spine (zoology), spines, analogous to those of hedgehogs, for ...

and Geogalinae as well as Oryzorictinae. While it is similar in habits to the related equatorial African otter shrews of family

Potamogalidae Potamogalidae is the family of "otter shrews", a group of semiaquatic riverine afrotherian mammals indigenous to sub-Saharan Africa. They are most closely related to the tenrecs of Madagascar, from which they are thought to have split about 47� ...

, their aquatic lifestyles evolved independently from one another. The split between tenrecs and otter shrews has been dated to about 47–53 Ma ago.

Conservation

The aquatic tenrec is currently ranked by the

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

as Vulnerable on the Red List. Due to their specialized habitat requirements and restriction to the island of Madagascar, it is estimated that less than 2,000 km² of suitable habitat remains. Degradation of riparian ecosystems and siltation of streams are the leading threat to the species’. Deforestation is also recognized as a potential cause of decline. However, recent studies have shown healthy populations of ''M. mergulus'' in streams where forest has been cleared or otherwise degraded, as well as non-native plantations. Areas of its habitat which are currently protected include Ranomafana National Park and the Andringitra National Park (1989) and it is also reported in the new Nosy Volo Reserve in the east (2014). Within afrotherian mammals, ''Microgale mergulus'' is typically considered for highest priority conservation priority along with the

giant otter shrew The giant otter shrew (''Potamogale velox'') is a semiaquatic, carnivorous afrotherian mammal. It is found in the main rainforest block of central Africa from Nigeria to Zambia, with a few isolated populations in Kenya and Uganda. It lives in str ...

giant golden mole The giant golden mole (''Chrysospalax trevelyani'') is a small mammal found in Africa. At in length, it is the largest of the golden mole species. This mole (animal), mole has dark, glossy brown fur; the name ''golden'' comes from the Greek lang ...

, northern shrew tenrec and

Nimba otter shrew The Nimba otter shrew (''Micropotamogale lamottei'') is a dwarf otter shrew and belongs to the mammal family Potamogalidae. Otter shrews are shrew-like afrotherian mammals found in sub-Saharan Africa. They are most closely related to the tenrecs ...

, as well as some better-known conservation symbols like the

dugong The dugong (; ''Dugong dugon'') is a marine mammal. It is one of four living species of the order Sirenia, which also includes three species of manatees. It is the only living representative of the once-diverse family Dugongidae; its closest ...

Asian elephant The Asian elephant (''Elephas maximus''), also known as the Asiatic elephant, is the only living ''Elephas'' species. It is the largest living land animal in Asia and the second largest living Elephantidae, elephantid in the world. It is char ...

, and three species of

manatee Manatees (, family (biology), family Trichechidae, genus ''Trichechus'') are large, fully aquatic, mostly herbivory, herbivorous marine mammals sometimes known as sea cows. There are three accepted living species of Trichechidae, representing t ...

s. This priority has been analyzed using two different methods, including phylogenetic diversity (PD) and evolutionary distinctiveness (ED).

References

{{Taxonbar, from1=Q125915299, from2=Q497943 Afrosoricida Endemic fauna of Madagascar Mammals of Madagascar Vulnerable animals Vulnerable biota of Africa Mammals described in 1896 Taxa named by Charles Immanuel Forsyth Major Taxobox binomials not recognized by IUCN