The growth‐stages of the pouch‐young of the Native Cat (Dasyurus viverrinus) together with observations on the anatomy of the new‐born young.*

Abstract

Summary. The biology of the pouch‐young (mammary foetus) is considered in a graded series of stages of Dasyurus commencing with the new‐born, still unattached young and ending with the fully developed animal at the time it leaves the maternal pouch (at the age of 4 to 4 months) and capable of fending for itself. The series has been divided for convenience into seventeen stages, labelled A‐P, and the growth, external appearances and eruption of teeth has been fully considered. The problem of the migration of new‐born young to the pouch, their attachment to the nipples, and the mode of lactation and its duration have been considered, together with some comment of the supposed mammary compressor action of the cremaster muscles. The internal structure of the new‐born Dasyurus has been described in detail, special emphasis being laid on the precocious development of certain structures which are considered necessary adaptational machinery for the insurance of survival of the young in its unusual environment and more particularly those features required for the sole purpose of ensuring its safe arrival in the pouch, its becoming attached to a nipple and the certitude of its receipt of milk without hindrance to its respiration. Notable at birth are (i) the relatively advanced state of the fore‐limbs, (ii) the presence of deciduous claws upon the manual digits and their later replacement by definitive claws, (iii) the presence of the oral shield as a specialization upon the muzzle, (iv) the unique cervical swelling, (v) special features of the tongue and larynx, with the intranasal epiglottis (vi) the reptilian state of the lungs, (vii) the advanced condition of the stomach and duodenum compared with the rest of the gut, (viii) the state of development of brain and sense organs, the olfactory parts being especially forward in development, together with those parts of the nervous system necessary for controlling the movements of the fore‐limb, sucking and respiratory movements, (ix) the indifferent state of the gonads. Throughout comparison has been made with the new‐born of other marsupials, so far as these are known, and features common to them all or peculiar to Dasyurus have been pointed out.

The olfactory system of the tammar wallaby is developed at birth and directs the neonate to its mother's pouch odours

“…Although there are no ethmoturbinates on the day of birth, the MOE appears to be well developed enough to perceive an odour signal and has olfactory knobs on its surface as described in a number of marsupial newborns (Hill & Hill 1955, Hughes et al 1989, Gemmell & Selwood 1994. The G oa -positive receptor cells are connected to the brain before birth, which would allow signal perception and transmission.…”

“…However, since the neonates need to turn through w1808 to reach the teats within the pouch, there must be other signals that guide the young to the teats. There are olfactory sensory cells within the olfactory epithelium at birth so it is likely that olfaction plays a role in directing the young once it is near the pouch entrance (McCrady 1938, Hill & Hill 1955, Lin et al 1988, Hughes et al 1989, Renfree et al 1989.…”

Developmental origins of precocial forelimbs in marsupial neonates

“…Marsupial neonates at birth. Illustrations of (A) Dasyurus viverrinus (see Hill and Hill, 1955) and (B) Trichosurus vulpecula (see Klima and Bangmann, 1987) and whole-mount image of (C) M. domestica, reflecting the variation in the degree of altriciality of newborn marsupials. Illustrations are not to scale.…”

A Histological and Immunohistochemical Analysis of Lymphoid Tissues of the Tasmanian Devil

“…The age in which Hassall's corpuscles appears in marsupials varies within different species (Old et al, 2003). Eastern quolls (Dasyurus viverrinus) had Hassall's corpuscles from 7 days after birth (Hill and Hill, 1955) and stripe-faced dunnarts from 40 days of age (Old et al, 2003). Although only one 3-week-old devil was analyzed, it did show structures resembling Hassall's corpuscles, suggesting that the thymus of this devil had at least matured at this age.…”