Small otter shrews

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Small otter shrews
Systematics
Subclass : Higher mammals (Eutheria)
Superordinate : Afrotheria
without rank: Afroinsectiphilia
Order : Tenrecus (Afrosoricida)
Family : Otter shrews (Potamogalidae)
Genre : Small otter shrews
Scientific name
Micropotamogale
Heim de Balsac , 1954

The small otter shrews ( Micropotamogale ) are a genus of mammals . which consists of two species, the dwarf otter shrew and the Ruwenzori otter shrew . Together with the great otter shrew , they form the family of the otter shrews (Potamogalidae), the closest relatives of the Tenreks (Tenrecidae). The two species are endemic to the equatorial part of Africa . The distribution areas of the two species are spatially clearly separated from each other. The habitat of the animals includes tropical rainforests interspersed with streams and swamps in mountainous regions. They are small mammals that resemble otters in appearance . They are adapted to a life in the water and feed mainly on crustaceans , insects and smaller vertebrates . However, little information is available about the further way of life. Both the pygmy and the Ruwenzori otter shrew were scientifically described in the mid-1950s, possibly representing two different genera. The population of the pygmy otter shrew is classified as potentially endangered, that of the Ruwenzori otter shrew as possibly safe.

features

Habitus

They are small representatives of the otter shrews that reach a head-to-trunk length of 12 to 20 cm, plus a 9.5 to 15 cm long tail. The weight varies from 32 to 135 g. The dwarf otter shrew ( Micropotamogale lamottei ) is somewhat smaller than the Ruwenzori otter shrew ( Micropotamogale ruwenzorii ). As the name suggests, there is a distant resemblance to otters in appearance . The body of the animals is streamlined, the snout broad and flattened. The coat has a silky sheen, which is caused by the outer hairs with flattened tips. In addition, the top hairs are relatively coarse and the undercoat is extremely dense. On the upper side a dark gray-brown color predominates, the underside is lighter in the Ruwenzori otter shrew, and in the dwarf otter shrew it corresponds to the upper side. The tail is either round in cross-section or only slightly flattened on the sides. Eyes and ears are small. The leathery nasal mirror is characteristic, the nostrils can also be closed by small flaps. Long vibrissae appear on the face and lower jaw . They are arranged in several rows on the upper lip and form a striking wreath of beard. The short and strong limbs have five rays on each of the hands and feet. In the Ruwenzori otter shrew, these are connected to one another by webbed feet, and there is also a fringe of bristly hair on the edges of the hand and foot. These formations are absent in the pygmy otter shrew. However, both species have the overgrown second and third toe rays of the hind foot that are typical of the otter shrews.

Skull and dentition features

The skull of the small otter shrews is between 32.4 and 39.4 mm long, the largest width on the brain skull is 15.5 to 17.8 mm. Generally it is elongated and narrow. Typically for otter shrews, the zygomatic arch does not form a closed arch, and there is also a strong crest . The bit has a total of 40 teeth, the dental formula is: . The first upper and second lower incisors are each enlarged and resemble canine teeth . They act as opponents when grabbing the prey. The subsequent teeth including the canine and the anterior premolars are simply designed. However, there are individual differences between the pygmy and the Ruwenzori otter shrew. In the former, the last incisor (I3) and the anterior premolar (P2) in the upper jaw are significantly more reduced in size than in the latter. As a result, the teeth of the dwarf otter shrew appear more specialized than that of the Ruwenzori otter shrew. The molars have a typical zalambdodontic occlusal surface pattern consisting of three main bumps: the para-, meta- and protoconus (based on the maxillary teeth). The protoconus is well developed, but in the small otter shrews, in contrast to the large otter shrew ( Potamogale velox ), the metaconus clearly merges with the paraconus, the latter forming the main cusp of the molars. The rearmost upper molar is greatly reduced in size.

distribution

Distribution areas of the three species of otter shrews

The pygmy otter shrews are endemic to Africa and occur in two spatially clearly separated areas, which are more than 4000 km apart. The pygmy otter shrew lives in West Africa in the border area of Guinea , Liberia and the Ivory Coast . In contrast, the Ruwenzori shrew can be found in Central Africa in the east of the Democratic Republic of the Congo as well as in Rwanda and possibly also in Uganda . Both species inhabit mountainous regions. They prefer tropical rainforests and mountain forests, their habitats require numerous water veins or swamps.

Way of life

The way of life of the two species of the small otter shrews is as good as unexplored, observations have so far only been made on a few captured individuals. The animals live primarily in forests along rivers, streams and swampy areas. They are good at swimming and diving. However, there are differences between the two species in terms of general locomotion in water. The pygmy otter shrew swims with winding movements of the body and tail, while the ruwenzori otter shrew uses its webbed, large hands and feet to paddle. Your body also undulates, but this does not contribute significantly to progress. Both species are mainly nocturnal. The animals use their own burrows that are padded with plant material as resting places. The diet consists mainly of crabs , insect larvae , fish , worms and small frogs . It is mostly caught in the water and consumed there, but the animals bring larger prey to land. The long vibrissae are used to track down the food. In one night the animals can eat an amount almost equal to their own body weight. Very little is known about reproduction. The gestation period is more than 50 days, the offspring are born naked and blind. A litter of the pygmy otter shrew includes one to four newborns, a female of the Ruwenzori otter shrew carried two embryos to life .

Systematics

Internal systematics of the otter shrews according to Everson et al. 2016
 Tenrecomorpha  
 Potamogalidae  
 Micropotamogale  

 Micropotamogale lamottei


   

 Micropotamogale ruwenzorii



   

 Potamogale



   

 Tenrecidae



Template: Klade / Maintenance / Style

The small otter shrews are a genus belonging to the family of the otter shrews (Potamogalidae). This also includes the great otter shrew ( Potamogale velox ). The otter shrews only occur in equatorial Africa and are adapted to a semi-aquatic way of life. The characteristic features of the family include the fused second and third toe rays, the missing collarbone and the zalambdodonte chewing surface pattern of the molars. The closest relatives of the otter shrews are the Tenreks (Tenrecidae), which in turn are endemic to Madagascar . Molecular genetic studies suggest a separation of the otter shrews and the tenreks in the Lower Eocene around 48.3 million years ago. In the transition from the Upper Eocene to the Lower Oligocene around 33.8 million years ago, the otter shrews split into the two current genus lines. The two species of the small otter shrews diversified in the Lower Miocene around 16.3 million years ago.

There are two types:

Both types are distinguished by their range and the presence of webbed feet.

The genus Micropotamogale was first scientifically described in 1954 by Henri Heim de Balsac together with the pygmy otter shrew . He separated them from the genus Potamogale mainly because of the smaller body size and the more rounded tail. In addition, he worked out differences in the middle ear , since the small otter shrews have a rounded tympanic bladder and a carotid canal . Two years later, after the establishment of the Ruwenzori otter shrew, Heim de Balsac introduced the genus Mesopotamogale for it , which he mainly justified with the pronounced webbed feet. He assigned the Ruwenzori otter shrew a position that mediated between the great otter shrew with its strongly flattened tail and the more generalized dwarf otter shrew with its thin, round cross-section tail. In the period that followed, most scientists shifted mesopotamogals to a subgenus status of micropotamogals , so that this term is hardly used today. However, it is sometimes pointed out that the webbed characteristic of the Ruwenzori otter shrew supports the status of an independent genus.

Threat and protection

The main threats include the loss of habitat due to deforestation and the reduction in water quality due to construction activity. The IUCN lists the pygmy otter shrew as "potentially endangered" ( near threatened ), as iron ore is being mined intensively in its area of ​​distribution in western Africa , which is increasingly restricting the habitat. The Ruwenzori shrew is currently classified as "not endangered" ( least concern ). The IUCN also notes a possible higher risk level for both species. Both the pygmy and the Ruwenzori otter shrew are present in nature reserves.

literature

  • Ronald M. Nowak: Walker's Mammals of the World. 2 volumes. 6th edition. The Johns Hopkins University Press, Baltimore MD et al. 1999, ISBN 0-8018-5789-9 .
  • Peter Vogel: Genus Micropotamogale Pygmy Otter Shrew. In: Jonathan Kingdon, David Happold, Michael Hoffmann, Thomas Butynski, Meredith Happold and Jan Kalina (eds.): Mammals of Africa Volume I. Introductory Chapters and Afrotheria. Bloomsbury, London, 2013, pp. 216-219

Individual evidence

  1. ^ WN Verheyen: Recherches anatomiques sur Micropotamogale ruwenzorii. 1. La morphologie external, les viscères et l'organe génital mâle. Bulletins de la Société Royale de Zoologie d'Anvers 21, 1961, pp. 1-16
  2. ↑ a b c d e f g h Peter Vogel: Genus Micropotamogale Pygmy Otter Shrew. In: Jonathan Kingdon, David Happold, Michael Hoffmann, Thomas Butynski, Meredith Happold and Jan Kalina (eds.): Mammals of Africa Volume I. Introductory Chapters and Afrotheria. Bloomsbury, London, 2013, pp. 216-219
  3. ^ A b Hans-Jürg Kuhn: On the knowledge of Micropotamogale lamottei. Zeitschrift für Mammalskunde 29, 1964, pp. 152-173
  4. ^ Robert J. Asher and Marcelo R. Sánchez-Villagra: Locking Yourself Out: Diversity Among Dentally Zalambdodont Therian Mammals. Journal of Mammalian Evolution. 12 (1/2), 2005, pp. 265-282
  5. ↑ Robert J. Asher: Tenrecoidea. In: Lars Werdelin and William Joseph Sanders (eds.): Cenozoic Mammals of Africa. University of California Press, Berkeley, London, New York, 2010, pp. 99-106
  6. ↑ a b Peter J. Stephenson: Micropotamogale ruwenzorii. The IUCN Red List of Threatened Species 2016. e.T13394A21287768 ( [1] ); last accessed on September 9, 2017
  7. ^ A b Peter J. Stephenson: Micropotamogale lamottei. The IUCN Red List of Threatened Species 2016. e.T13393A21287657 ( [2] ); last accessed on September 9, 2017
  8. ^ U. Rahm: Observations on the first captive mesopotamogal ruwenzorii (Mammalia-Insectivora). Revue Suisse de Zoologie 68 (4), 1961, pp. 73-90
  9. ↑ Peter Vogel: Contribution a l'écologie et a la zoogéographie de Micropotamogale lamottei (Mammalia, Tenrecidae). Revue d'Ecologie (Terre Vie) 38, 1983, pp. 37-49
  10. ↑ a b Kathryn M. Everson, Voahangy Soarimalala, Steven M. Goodman and Link E. Olson: Multiple loci and complete taxonomic sampling resolve the phylogeny and biogeographic history of tenrecs (Mammalia: Tenrecidae) and reveal higher speciation rates in Madagascar's humid forests. Systematic Biology 65 (5), 2016, pp. 890-909 doi: 10.1093 / sysbio / syw034
  11. ^ Henri Heim de Balsac: Un genre inédit et inattendu de Mammifére (Insectivore Tenrecidae) d'Afrique Occidentale. Comptes rendus hebdomadaires des séances de l'Académie des sciences 239, 1954, pp. 102-104 ( [3] )
  12. ^ Henri Heim de Balsac: Morphology divergente des Potamogalinae (Mammifères Insectkivores) en milieu aquatique. Comptes rendus hebdomadaires des séances de l'Académie des sciences 242, 1956, pp. 2257–2258 ( [4] )
  13. ↑ Ch. Guth, Henri Heim de Balsac and M. Lamotte: Recherches sur la morphologie de Micropotamogale lamottei et l'evolution des Potamogalinae. II. Rachis, viscéris, position systématique. Mammalia 24, 1960, pp. 190-216
  14. ^ WN Verheyen: Recherches anatomiques sur Micropotamogale ruwenzorii. 4. Observations ostéologiques et considérations générales. Bulletins de la Société Royale de Zoologie d'Anvers 22, 1961, pp. 1-7

Web links

Commons : Small Otter Shrews ( Micropotamogale )  - Collection of images, videos and audio files