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Facial and Masticatory Muscles |
Authors: Alexandra Sardi and Janelle Cooper Classification: Kingdom: Animalia Common names: Old world rabbit, Domestic rabbit Evolution and Phylogeny: The phylogeny of lagomorphs is still greatly unresolved and under discussion
[1,2,3]. Until the 1980's, the lagomorphs were classified under Rodentia
and grouped under Glires into two families: Duplicidentata and Simplicidentata
[3,4]. In the 1980's, the Glires were supported mostly by morphologists
who recognized the similarities in dentition as reason to group them together.
For example, Glires have absent first lower and upper incisors, absent
upper and lower canines, absent first lower and upper premolars and enlarged
upper and lower incisors [1,3,4]. In the last decade, the resemblance of rodents and lagomorphs has been
dismissed as convergence and new molecular studies have severely challenged
the monophyly of Glires [1]. For years the monophyly of Glires was believed
to be inaccurate. In recent years, new molecular studies with larger datasets
support Glires [1,2]. These are also consistent with recent morphological
studies. Meng and Wyss performed a study using dental, skeletal and a
combined data matrix and obtained five cladograms all of which identified
the Glires [1]. Furthermore, a recent study by Huchon et al compared three
nuclear genes covering the whole rodent and placental diversity and found
that it supported grouping Lagomorpha and Rodentia into Glires [2]. Many studies have also been performed to determine the time when Lagomorpha
and Rodentia diverged. Some of the best preserved specimens of nonrodent
and nonlagomorph Glires are materials from Rhombomylus turpanensis
[1]. This mammal lived in central and eastern Asia during the Eocene and
is believed to be a common ancestor to the Glires [1]. According to the
molecular time-scale, the Lagomorpha appeared about 90 million years ago,
during the late Cretaceous or early Paleocene. This is supported by many
molecular studies but the fossil record places the earliest lagomorphs
in the late Paleocene [1,3,4]. Examples of these early lagomorphs are
Mimolagus and Hsiunnania, from Asia. Hsiunnania,
found in China, is often the preferred lagomorph ancestor due to its low-crowned
molars [3]. More recently, the Ochotonidae [pikas] and Leporinae [hares and rabbits] divided in the Oligocene period in Asia and in North America [3,4,5]. The European old world rabbit, with which this paper is concerned, originated in the Iberian Peninsula and southern France but its domestication has inextricably linked it to humans and spread it throughout the world [4]. The domestic Oryctolagus cuniculus is believed to have originated in French monasteries in the late first millennium. Today, there are sixty-six recognized breeds of O. cuniculus [3]. Appearance: The wild old world rabbit generally has black to light brown coloring and the black-tipped of most hares [4]. It has a dark collar and a tail which is white below and brownish black above. Its underparts are also buffy white. It weighs anywhere between 350 g to 2,250 g., its tail measures 40 cm - 50 mm and a body length of 250-700 mm. Its dental pattern is [i2/1, c0/0, pm3/2, m3/3] [4]. The female is larger than the male but both sexes have thick soft pelage and a naked anal region. The testes are abdominal and descend during breeding season. The many domestic forms of O. cuniculus may differ in coloring and size. Those bred for meat may weigh up to 7.25 kg [4]. All lagomorphs are adapted for speed, hence their long hind legs [2]. Each hind leg has five toes while the forelegs have four. They also have haired patches on the soles of their feet [2]. Geography and Habitat: O. cuniculus was originally found on the Iberian Peninsula and in southern France at the end of the Pleistocene [4]. Eventually humans introduced this species to other parts of the world ranging from Europe to as far as Australia and New Zealand [4]. Today O. cuniculus can be found throughout Western Europe, as far east as Poland and as far south as Ukraine in Eastern Europe, parts of Scandinavia, most of North America, Australia, New Zealand, and in Argentina [4 , p.2]. The domestic rabbit prefers to live in areas that are both dry and warm
with soft earth [2]. These rabbits generally do not live at elevations
more than 1900ft [600m] [2]. Areas such as "fields, meadows, bushes,
and small forests" provide the best living areas [2, p.291]. O.
cuniculus lives above ground, but it is a burrowing animal and
sleeps in an underground den. Many rabbits may live in the same underground
burrow in their own chambers connected by tunnels [4, p.2]. Activity and Behavior: O. cuniculus is a nocturnal animal with a social structure
that includes a male dominance hierarchy [4]. Males may defend their group
of females, which consists of all the females in a breeding group, by
thumping their hind legs on the ground as a warning signal [4]. A breeding
group of females may include all the females in heat in their burrow,
which can range from twenty to thirty other rabbits [4]. The domestic
rabbit has many natural predators such as raccoons, foxes, and domestic
cats and is popular as a game animal [4, p.2]. Throughout history rabbits
have been hunted and bred by humans for use as food as well as for their
fur for various uses such as for clothing [4, p.2]. Locomotion: O. cuniculus has long hind legs and feet that are covered in fur, which make it well adapted for speed [4, p.2]. Its feet give the rabbit "lift and an ability to run in zigzag fashion that surpasses any of its pursuers" [2, p.255]. If necessary, domestic rabbits have the ability to reach speeds up to 77 kilometers per hour" [2, p.255]. The rabbit uses the half-bound as a means for locomotion. The forelimb is not as important as the hind limb, but it still bears a lot of the animal's weight. Diet: Domestic rabbits are primarily herbivores, eating herbs, grasses, and grains [2]. O. cuniculus will also consume leaf buds, bark, stems, branches, and vegetables such as lettuce, beets, and cabbages [4, p.2]. Rabbits are able to adapt to their environments and will eat almost any plant species found in their habitat [2]. They are able to eat such a wide range of plants because of their unusually large caecum. The caecum serves as a fermentation chamber where bacteria break down the cellulose in plants so that rabbits can absorb as many nutrients as possible. Through a process called cecotrophy the rabbit is able to "double digest" its food by consuming fecal material that has not been fully digested [2]. This process also allows the rabbit to extract extra nutrients and vitamins from its food. Reproduction and Ontogeny: Due to their high reproduction rate, the population of rabbits has spread
rapidly and has virtually become and "agricultural pest" in
places such as Australia and New Zealand [4, p.1731]. The breeding season
for O. cuniculus occurs between January and July in the
Northern Hemisphere [1]. In the Southern Hemisphere the breeding season
is the opposite, occurring anywhere between August and February [1, 2].
Female rabbits have the ability to carry "two litters in her uterus
at the same time," a phenomenon known as superfetation [2]. Females
will carry their young for 28-33 days and give birth to litters ranging
"from 1 to 9, averaging 5-6" young per litter [1, p.1730]. Since
females may begin estrus hours after giving birth, they are able to bear
"more than 30 young each year" [1, p.1730]. Newborn rabbits
are "naked, blind, and deaf and weigh about 40-50 grams" [1,
p.1730]. After ten days they open their eyes and are able to leave the
nest after 3 weeks [1]. Females may begin producing young as early as
three months of age[1].
1. Meng et al, "The Osteology of Rhombomylus: Implications for phylogeny
and evolution of glires". Bulletin of the American Museum of Natural
History, Feb 2003, 247 pp. 2. Huchon et al, "Rodent phylogeny and a time scale for the evolution
of glires: Evidence from an extensive taxon sampling using three nuclear
genes." Molecular biology and Evolution, 19 [7]: 1053-1065 July 2002. 3. Anderson, Sydney and Jones, J. Knox Jr.. 1984. Orders and Family of
Recent Mammals of the World. John Wiley and Sons Inc., New York. 4. Grzimek, Bernard. 1990. Grzimek's Encyclopedia of Mammals V. 4. McGraw-Hill,
New Jersey. 5. Novacek, Michael J. 1996. Nature Vol 379 Issue 6536 pp 299, 2p. 6. Nowak, Ronald M. 1999. Walkers's Mammals of the World Volume 2. John's
Hopkins University Press, Baltimore. |
Artwork: Weil, from Stubbs' 1776
"Anatomy of the Horse."
Background free from Eos Development, with
slight color modification.
