Temperature gradient from the urogenital sinus to the pouch in the pregnant marsupial quoll, Dasyurus hallucatus
Introduction
There are at least three distinct methods of transferring the newborn marsupial from the uterus to the teat within the pouch (Gemmell et al., 2002; Nelson and Gemmell, 2004). In marsupials with a forward facing pouch such as the kangaroo and possum, the mother positions her pouch above the urogenital sinus and the expelled newborn crawls upwards to the pouch (Renfree et al., 1989; Veitch et al., 2000). In the bandicoot with a backward facing pouch, the mother positions the urogenital sinus above the pouch. The newborn remain attached to the placenta via the umbilical cord and they slither down to the pouch. With the third group, the dasyurids, the newborn are expelled from the uterus in a column of viscous fluid which they leave to move to the pouch (Nelson and Gemmell, 2003).
The senses that are required by the newborn to make the transfer from the uterus and to locate and attach to a teat are still not fully understood and could differ for the three varying modes of birth. Hartmann (1920) suggested that newborn marsupials orientated themselves away from gravity and that they crawled upwards to the pouch. Cannon et al. (1976) provided further evidence that the vestibular system assisted the newborn to reach the pouch. The newborn marsupial has large open nostrils, functional lungs and sensory cells within the nasal region, all features allowing for the suggestion that the newborn marsupial can sense different odours (Nelson and Gemmell, 2004). Through manipulation of newborn possums while the mother was anaesthetised, it was shown that a young that climbed upwards and past the pouch, turned around and descended into the pouch. If a young was placed above or to the side of the pouch the newborn crawled down or across to the pouch (Veitch et al., 2000). It was concluded that the newborn possum is able to travel from the urogenital sinus to the pouch guided by olfaction and its response to gravity.
In this study, birth in the northern quoll Dasyurus hallucatus has been filmed. The senses used by the newborn to move from the uterus to the pouch are still not fully understood. The aim was to obtain temperatures from the sinus and the pouch to determine if the newborn marsupial used a temperature gradient to assist in the travel to the pouch.
Section snippets
Trapping
Six female quolls were trapped at Shipton's Flat, Queensland, between the 13 and 31 July using Elliot and wire traps approximately 52×23×23 cm, which were baited with oats, peanut paste and either sardines or mince meat. The pregnant quolls were held in cages and examined daily until young were present in the pouch. After trapping, the quolls were housed at Shipton's Flats in individual cages 60×35×40 cm with a nesting box 20×15×15 cm attached to the back wall. The front of the cage was made of
Temperature
In quoll 2 a gradual increase in temperature was obtained during pregnancy from the nose, the sinus, the area between sinus and pouch, and the pouch. However, the gradient observed during pregnancy was not obtained during lactation (Table 1). A similar result was observed with quoll 4 (Table 2). When all the temperatures obtained from the six quolls were examined, a temperature gradient was observed during pregnancy. The temperature at the sinus (28.98 °C) was less than the temperature of the
Discussion
The temperature gradient, that increases from the sinus to the pouch may aid the newborn quolls in reaching the pouch and attaching to the teats. The hairs that form a tunnel between the sinus and the pouch and the arrangement of the hairs in the pouch may also assist the young in the migration from uterus to the pouch.
Three questions were posed by Nelson and Gemmell (2003) after reporting the birth process of the northern quoll. How do the young know when to leave the column when swimming
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