Marsupials

AVP and OT are cyclic nonapeptides with a disulphide bridge between the cysteine residues 1 and 6, resulting in a six-amino acid ring and a COOH-terminal a-amidated three-residue tail. OT differs only in two amino acids from AVP lie in position 3, which is essential for OT recqrtor (OTR) stimulation and Leu in position 8. AVP has a Phe in position 3 and an Arg in position 8. Arg 8 is essential for acting upon vasopressin receptors (Fig. 1). Lysipressin, found in pigs and some marsupials, has a Lys in position 8 [1]. 

Figure 6.4. Percent average humidity compared with 6 0 in bone phosphate. The strong association between the two variables across the species of Australian marsupials (data from Ayliffe and Chivas 1990) and North American white-tailed deer (data from Luz ei a/. 1990) indicates that their body water oxygen isotopic composition is strongly determined by the 8"0 in their diet since plant 8 0 varies in negative correlation with humidity.

As explained in Chapter 1, the toxicity of natural xenobiotics has exerted a selection pressure upon living organisms since very early in evolutionary history. There is abundant evidence of compounds produced by plants and animals that are toxic to species other than their own and which are nsed as chemical warfare agents (Chapter 1). Also, as we have seen, wild animals can develop resistance mechanisms to the toxic componnds prodnced by plants. In Anstralia, for example, some marsupials have developed resistance to natnrally occnrring toxins produced by the plants upon which they feed (see Chapter 1, Section 1.2.2). 

Marsupials (6/19) These present no known instances of loss or reduction. The Metatheria (Australian and South American marsupials) differ little in the layout of their VN complex from those of the higher placental mammals (Eutherians) (Broom, 1896 Kratzing, 1984 Poran, 1998). Attention to Australasian forms has until recently predominated [Kratzing, 1978, 1982 and 1984(a)-(c) Salamon, 1996]. A few genera... 

A clear demarcation of the external nose in marsupials and many eutherian mammals presents as a hairless area of skin surrounding the nostrils and the inter-narial space and can include the median part of the upper lip. This typically pigmented zone — the rhinarium — is... 

The early VN neurones migrate by various routes and in mammals become organised into two layers, each with distinct functional attributes (Chaps. 2 and 6). Amongst marsupials, the sensory cells of an opossum appear at about one-week post-conception (Jia and Halpem, 1998). Despite their extremely altricial developmental pattern, the bandicoots dendrites produce sensory processes (Fig. 4.5) on the lumenal border of the VNO at 35 days postnatal, which in the Northern Bandicoot (Isoodon macrourus) is about 50% of pouch life (Kratzing, 1986). 

The developmental changes seen in the immediate postnatal period in altricial rodents and especially in the early stages of marsupials, are an expected outcome of their shortened gestational period, early parturition and consequential dependent status. Regrettably, the relative contribution of the main and accessory chemosensory route(s) cannot be fully assessed. The lesser importance of the AOS (by some tests)... 

Several studies have identified responses that do not involve VN participation, from marsupials to Mouse-lemurs. Where the chosen endpoint is totally unaffected by absence of the organ and in addition is dependent upon MOS activity, then it needs to be classified as VN-independent. Where VN-x results are ambiguous, as already considered for opossums (Monodelphis domestica), further analysis is desirable. For instance, Goats do not use AOS input for mating, only urinalysis, although experiential variables have not been fully explored (Ladewig et al., 1980). Examples of VN independence then exist in both altricial and precocial species. 

Broom R. (1896). Comparative anatomy of the Organ of Jacobson in marsupials. Proc Linn Soc NSW 21, 591-623. 

Kratzing J.E. (1986). Morphological maturation of the olfactory epithelia of Australian marsupials. In Ontogeny of Olfaction (Breipohl W., ed.). Springer, Berlin, pp. 57-70. 

Russell E. (1984). Social behaviour and organisation of marsupials. Mammal Rev 14, 101-154. 

Salamon M. (1996). Olfactory communication in Australian marsupials. In Comparisons of Marsupial and Placental Behaviour (Croft D.B., et al., eds.). Furth, Filander, pp. 46-79. 

Stodart E. (1966). Management and behaviour of breeding groups of the marsupial Perameles nastua in captivity. Aust J Zool 14, 611-623. 

Sussman R. and Raven P. (1978). Pollination by lemurs and marsupials an archaic coevolutionary system. Science 200, 731-736. 

Individuals of sensitive species died after receiving a single dose between 0.05 and 0.2 mg/kg BW, including species of livestock, marsupials, canids, felids, rodents, and foxes. 

Australian mammals, various 1.6-20.0 mg/kg BW Lethal to 8 species of marsupials and 5 species of rodents 9... 

Mcllroy, J.C. 1981b. The sensitivity of Australian animals to 1080 poison. II. Marsupial and eutherian carnivores. Austral. Wildl. Res. 8 385-399. 

Spotted-tailed quoll, Dasyurus maculatus Familiar Marsupial predator Since murid arrival0 25.2 2.20 BFP... 

Tasmanian devil, Sarcophilus harrisii Unfamiliar Marsupial predator Until 3000 yrs agof 19.9 1.05 LPKS... 

Rodent visitation rates to odour stations decreased in the presence of predator faeces, compared to blank and novel odours. The response to different predators varied seasonally, and encompassed avoidance of familiar and unfamiliar faecal odours from marsupial and eutherian predators. This study supports the scat avoidance hypothesis (sensu Banks et al. 2003), which predicts that faeces are a useful indicator of predator presence, and I thus argue that, at least in the present context, faecal odours could be a good cue of predator presence for rainforest species. 

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