Die Monckton-Schwimmratte (Crossomys moncktoni) ist ein wenig bekanntes, großes Nagetier aus Neuguinea. Sie wurde bisher nur im Hochland des mittleren und östlichen Neuguineas beobachtet, kommt aber möglicherweise auch im Westen der Insel vor.
Die Monckton-Schwimmratte ist ausgezeichnet an das Wasserleben angepasst. Die Kopfrumpflänge beträgt 18 bis 20 Zentimeter, hinzu kommen 21 bis 26 Zentimeter Schwanz. Das Gewicht eines Weibchens betrug 165 Gramm. Das Fell ist oberseits graubraun und unterseits weiß gefärbt. Der Schwanz hat an der Unterseite einen Borstenkamm, ein unter Nagetieren einmaliges Merkmal, das sich ganz ähnlich bei der Wasserspitzmaus findet. Offenbar unterstützt diese Vorrichtung die Ruderfunktion des Schwanzes. Außerdem hat diese Art ein wasserdichtes Fell, vergrößerte Hinterbeine mit Schwimmhäuten, verkleinerte Augen und Ohren. Letzteres hat auch zu dem Namen Earless Water Rat („Ohrlose Schwimmratte“) geführt, der aber irreführend ist, da bei genauerer Betrachtung die Ohren deutlich erkennbar sind.
Die Monckton-Schwimmratte lebt entlang von Bergbächen in Höhen zwischen 600 und 3000 Metern. Sie gräbt Baue in den Flussufern, in denen sie in den Nächten schläft. Tagsüber geht sie auf die Jagd auf Kaulquappen, Würmer und Wasserinsekten.
Systematisch gilt sie als naher Verwandter der Schwimmratten und wird in die Hydromys-Gruppe eingeordnet.
Die IUCN listet die Art als „nicht gefährdet“ (least concern).
Die Monckton-Schwimmratte (Crossomys moncktoni) ist ein wenig bekanntes, großes Nagetier aus Neuguinea. Sie wurde bisher nur im Hochland des mittleren und östlichen Neuguineas beobachtet, kommt aber möglicherweise auch im Westen der Insel vor.
Die Monckton-Schwimmratte ist ausgezeichnet an das Wasserleben angepasst. Die Kopfrumpflänge beträgt 18 bis 20 Zentimeter, hinzu kommen 21 bis 26 Zentimeter Schwanz. Das Gewicht eines Weibchens betrug 165 Gramm. Das Fell ist oberseits graubraun und unterseits weiß gefärbt. Der Schwanz hat an der Unterseite einen Borstenkamm, ein unter Nagetieren einmaliges Merkmal, das sich ganz ähnlich bei der Wasserspitzmaus findet. Offenbar unterstützt diese Vorrichtung die Ruderfunktion des Schwanzes. Außerdem hat diese Art ein wasserdichtes Fell, vergrößerte Hinterbeine mit Schwimmhäuten, verkleinerte Augen und Ohren. Letzteres hat auch zu dem Namen Earless Water Rat („Ohrlose Schwimmratte“) geführt, der aber irreführend ist, da bei genauerer Betrachtung die Ohren deutlich erkennbar sind.
Die Monckton-Schwimmratte lebt entlang von Bergbächen in Höhen zwischen 600 und 3000 Metern. Sie gräbt Baue in den Flussufern, in denen sie in den Nächten schläft. Tagsüber geht sie auf die Jagd auf Kaulquappen, Würmer und Wasserinsekten.
Systematisch gilt sie als naher Verwandter der Schwimmratten und wird in die Hydromys-Gruppe eingeordnet.
Die IUCN listet die Art als „nicht gefährdet“ (least concern).
The earless water rat (Crossomys moncktoni) is a New Guinea rodent, part of the Hydromys group of the subfamily of Old World rats and mice (Murinae). It is the only species of the genus Crossomys. This species is probably most closely related to Baiyankamys.[2] It is still unclear to which species this group is related. It is one of the most aquatically adapted rodents of the world.[2]
It is known as kuypep in the Kalam language of Papua New Guinea.[3]
This animal was first described in 1907 by the British mammalogist Oldfield Thomas, based on a single specimen caught by one Mr. C. A. W. Monckton, after whom the species was named, near Brown River, Central Province, south-east Papua New Guinea.[4] Only in July 1950 a second specimen was captured.[5] Since then, several other examples have been caught in the mountains of eastern New Guinea, but the earless water rat remains a rather rare species. The scientific name means "Monckton's fringed mouse", which refers to the collector of the original specimen (C. A. W. Monckton) and to the fringe of hairs on the tail.[6]
The German mammalogist Hans Rümmler placed this rodent (and Parahydromys asper) in Hydromys,[7] but that has not been accepted generally. Lidicker (1968), who studies the morphology of the phallus of New Guinea rodents, speculated that Crossomys might not be as closely related to Hydromys as was then generally thought.[8] Later on, this was supported by the immunological study of Watts & Baverstock (1994).[9] This study placed Crossomys closer to Leptomys, Pseudohydromys and Xeromys than to Hydromys.
The American mammalogists Guy Musser and Michael Carleton, in their contribution to the authoritative Mammal Species of the World (3rd ed.), divided the group of murine rodents that had before been called "Hydromyinae" or "Hydromyini" in two "divisions":[10] the Xeromys Division (Leptomys, Pseudohydromys and Xeromys) and the Hydromys Division (Crossomys, Hydromys, Microhydromys, Paraleptomys and Parahydromys [Baiyankamys was added later[2]]). According to them, the morphology of Crossomys is more like the Hydromys Division than the Xeromys Division, and therefore they placed it in the Hydromys group. They supported their opinion with an unpublished study of the Australian biologist Ken Aplin, who also placed Crossomys closer to Hydromys.
Helgen (2005) concluded that Crossomys is most closely related to Baiyankamys, which had usually been placed in Hydromys before. Baiyankamys has not been studied genetically. According to his data, the Crossomys-Baiyankamys group is most closely related to Hydromys and Parahydromys, though he did not give material to support his opinion.[2]
The earless water rat is adapted best to a life in water out of all the muroids. It has extremely long hindfeet, the toes of which are webbed completely, strongly reduced forelegs, absent or invisible ears, very small eyes, and a long tail with a row of hairs at the downside. That row starts at each side of the beginning of the tail as a long white row of hairs; these two rows merge at about 50 mm from the beginning of the tail and the row goes on to the end of the tail. In all these characters, it resembles the elegant water shrew (Nectogale elegans), a good example of convergent evolution.[2][6][11]
The back is greyish brown, and the belly is white. The fur is soft and waterproof. The top half of the tail is light grey, and the bottom half is white. The forefeet and claws are very small, but the hindfeet are very large. The upper lip contains a row of short, strong brushes, which may be used for rasping. The external ear (the pinna) is reduced to a small oval that does not or hardly protract above the fur. It is possible that the ear canal can be closed. The brain is rather large, like in many aquatic animals. The nasals are relatively small, just like the palate and the molars. The bullae are small. The rostrum is narrow. The earless water rat is a medium-sized rat, about as large as its close relative Baiyankamys.[2][12] The head-body length is 175 to 200 mm (6.9 to 7.9 in) (based on four specimens), tail length is 212 to 260 mm (8.3 to 10.2 in) (4), hind foot length is 44 to 53 mm (1.7 to 2.1 in) (4), ear length is 1 to 45 mm (0.039 to 1.772 in) (2), and weight 165 g (5.8 ounce avoirdupois) (1).[6] Females have 0+2=4 mammae (no thoracic and two inguinal pairs), the same number as most other Australasian rodents.[6]
The earless water rat and Baiyankamys are related because they share the following characters: tail much longer than head-body length; soft, thick, greyish dorsal coat; long, narrow rostrum with a narrow top; very narrow canines; very narrow mesopterygoid fossae; narrow zygomatic arches with a high squamosal root. B. habbema also has the reduced external ears of the earless water rat.[2]
This animal lives at 1000 to 2700 meters in elevation in Central Cordillera of Papua New Guinea, including the Huon peninsula. The cold, fast-flowing streams of the mountains are its habitat.[6]
During the day it is actively hunting for tadpoles, worms, and river insects (mostly larvae), but at night it sleeps in holes along the river bank. The animal gets only one young at the same time. It is only captured by Telefol hunters when river levels are low.[6]
It is called kwypep by the Kalam tribe (Madang Province), possibly ogoyam in the Telefol language (in Sandaun Province) and momo by the Rofaifo (Southern Highlands Province), although that name is also used for other water rats, like the common Rakali. Some local names can be translated as "water sugar glider", which refers to the similarity of the fur of these two species.[6]
Little is known about the conservation status of this species, although it has the status "least concern" in the IUCN Red List.[1]
The earless water rat (Crossomys moncktoni) is a New Guinea rodent, part of the Hydromys group of the subfamily of Old World rats and mice (Murinae). It is the only species of the genus Crossomys. This species is probably most closely related to Baiyankamys. It is still unclear to which species this group is related. It is one of the most aquatically adapted rodents of the world.
Crossomys moncktoni Crossomys generoko animalia da. Karraskarien barruko Murinae azpifamilia eta Muridae familian sailkatuta dago.
Crossomys moncktoni Crossomys generoko animalia da. Karraskarien barruko Murinae azpifamilia eta Muridae familian sailkatuta dago.
Crossomys moncktoni est la seule espèce du genre Crossomys. C'est un rongeur de la sous-famille des Murinés. Ce sont des rats aquatiques endémiques de Nouvelle-Guinée.
Crossomys moncktoni (Thomas, 1907) è l'unica specie del genere Crossomys (Thomas, 1907), diffusa in Nuova Guinea.[1][2]
L'epiteto generico deriva dalla combinazione della parola greca κροσσός-, frangia e dal suffisso -mys riferito alle forme simili ai topi. Il termine specifico invece è dedicato a Charles Arthur Monckton, il quale catturò l'olotipo il 12 ottobre 1906 presso Serigina, sul fiume Brown, in Papua Nuova Guinea.
Roditore di grandi dimensioni, con lunghezza del corpo tra 175 e 200 mm, la lunghezza della coda tra 212 e 260 mm, la lunghezza del piede tra 44 e 53 mm, la lunghezza delle orecchie tra 1 e 4,5 mm e un peso fino a 165 g.[3]
Il cranio presenta un rostro corto e sottile e una grande e ampia scatola cranica, il palato è breve e fortemente arcuato, le bolle timpaniche sono notevolmente ridotte. Sono presenti due piccoli molari su ogni semi-arcata, ognuno con una caratteristica disposizione delle cuspidi a bacino.
Sono caratterizzati dalla seguente formula dentaria:
2 0 0 1 1 0 0 2 2 0 0 1 1 0 0 2 Totale: 12 1.Incisivi; 2.Canini; 3.Premolari; 4.Molari;La pelliccia è lunga e lucida. Il colore del dorso è grigio cosparso di peli giallo-olivastri lungo la schiena, mentre le parti ventrali sono bianco-argentate, la linea di demarcazione lungo i fianchi è ben definita. Il muso è largo, ricoperto di lunghe vibrisse ispessite e presenta il labbro superiore fortemente rigonfio. Le orecchie sono vestigiali, lunghe soltanto qualche millimetro. Le zampe posteriori hanno cinque dita e sono palmate, mentre quelle anteriori sono piccole, il polso è sottile ed hanno quattro dita. Gli artigli sono piccoli, delicati e fortemente ricurvi. Sono presenti dei cuscinetti plantari larghi e lisci. La coda è più lunga della testa e del corpo, è uniformemente grigia ed ha due frange di lunghi peli bianchi sulla superficie inferiore che si congiungono dopo circa 5 cm dalla base. Il cariotipo è 2n=48 FN=60.
È una specie fortemente adattata alla vita acquatica ed è attiva probabilmente tutto il giorno. Scava tane lungo le sponde dei corsi d'acqua.
È stata osservata nutrirsi di girini e uova di rana.
Le femmine partoriscono un solo piccolo per volta.
Questa specie è diffusa nella cordigliera centrale della Nuova Guinea.
Vive lungo i corsi d'acqua montani vicino ai bordi delle foreste tra i 1.200 e 3.500 metri di altitudine.
La IUCN Red List, considerato che la specie è relativamente diffusa e comune più di quanto originariamente pensato, classifica C.moncktoni come specie a rischio minimo (LC).[1]
Crossomys moncktoni (Thomas, 1907) è l'unica specie del genere Crossomys (Thomas, 1907), diffusa in Nuova Guinea.
귀없는물쥐(Crossomys moncktoni)는 쥐과에 속하는 설치류의 일종이다.[2] 귀없는물쥐속(Crossomys)의 유일종이다. 뉴기니섬의 토착종으로 물쥐군의 일부이다. 바이얀카물쥐속 종과 가장 가까운 것으로 추정하고 있다.[3] 물쥐군 내에서의 관계는 아직 명확하지 않다. 전세계에서 수생 생활에 가장 잘 적응한 설치류 중의 하나이다.[3]
귀없는물쥐는 1907년 영국 포유류학자 토마스(Oldfield Thomas)가 몽크톤(C. A. W. Monckton)이 파푸아뉴기니 남동부 중앙 주의 브라운 강 근처에서 포획한 한 점의 표본을 기초로 발견자의 이름을 따서 처음 기술했다.[4] 두 번째 표본은 1950년 7월에 겨우, 두 번째 표본이 포획되었다.[5] 그 이후 뉴기니 동부 산악 지대에서 몇몇 표본이 포획되었지만, 귀없는물쥐는 여전히 희귀한 종으로 남아있다. 학명은 첫 표본을 수집한 사람의 이름에서 유래했다.[6]
귀없는물쥐는 모두 쥐과 설치류 중에서 수생 생활에 가장 적응한 종이다. 극단적으로 긴 뒷발과 완전한 형태의 물갈퀴가 있는 발가락, 줄어든 강한 앞다리, 거의 없거나 보이지 않는 귀, 아주 작은 눈, 아랫쪽으로 털이 줄지어 난 꼬리를 갖고 있다. 줄은 꼬리 시작 부분에서 양쪽으로 길고 흰 털이 시작된다. 이 두 줄은 꼬리 시작 부분에서 약 50mm 떨어진 곳에서 합쳐지고 꼬리 끝까지 이어진다. 이 모든 특징 때문에 물갈퀴발갯첨서를 닮았으며, 수렴 진화에 대한 훌륭한 예이다.[3][6][7]
