In marsupials

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... 

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

The vomeronasal system, also known as the accessory olfactory system, consists of chemoreceptors, organized into the VNO, the vomeronasal nerve, its terminal, the accessory olfactory bulb, and more central pathways. First described by Jacobson in 1811, the VNO has been studied intensely. We now know how stimuli reach it and what behaviors it mediates. The VNO occurs in amphibians, reptiles, and mammals. Among mammals, it is best developed in marsupials and monotremes. In birds it only appears during embryogenesis. The VNO and its function are best known for squamate reptiles, particularly snakes, and rodents and ungulates among the mammals. 

Retinal cells in marsupials are generated in two phases. The first cells to generate are the ganglion cells,... 

Generally we find much similarity in the structure of the olfactory systems of marsupials and placentals. Therefore, marsupials should be considered excellent models for certain types of behavioural research and must be included in any general model of mammalian behavior. In this context it would be very valuable to further investigate the use of olfactory communication in marsupials which could give us additional insights into the function of olfactory signals in all mammals. 

The major objective of this chapter is to summarize existing information on chemical communication in marsupials. To do this, the gray opposum will be used as a model. Aspects of olfactory communication in a variety of other marsupials, and in monotremes, also will be addressed. 

CHARACTERISTICS OF SCENT MARKING BEHAVIOR IN MARSUPIALS AND MONOTREMES Scent Marking in Gray Opossums... 

Scent-marking in marsupials. In addition to using specific anal-cloacal, and sternal glands, marsupials use saliva, urine and feces in chemical communication (Eisenberg and Golani, 1977). Other specific glands, such as frontal glands and parts of the body (such as the flank), are also used (Schultze-Westrum, 1965, 1969 Fadem and Cole, 1985). 

The use of chemical communication in maternal-young interactions in marsupials and monotremes. As previously noted, marsupials and mono-tremes are born (hatched) at a very early stage of development and have an extended period of development outside of the body of the mother. 

Fibers from these olfactory sense cells which are present in the olfactory epithelium, enter the olfactory bulbs. In contrast to the absence of differentiated organs in other sensory systems, the differentiation of the olfactory system at hatching suggests that in monotremes as in marsupials, sense of smell plays a part in location of the maternal teat (Griffiths, 1978). 

The hormonal control of the estrous cycle and ovulation is similar in eutherian and marsupial mammals (Sutherland et al., 1980). However, in marsupials, gestation is always shorter than the estroUs cycle and pregnancy does not interrupt the cyclic recurrence of estrus (Sharman, 1970). Spontaneous ovulation appears to be the rule in marsupials and the estrous cycle of polyestrous species is approximately one month in length (Tyndale-Biscoe, 1973). The effects of social factors on reproduction in female marsupials have not heretofore been examined systematically, in part because it has been difficult to maintain and breed... 

In addition to being intrisically of interest, study of behavioral, anatomical and physiological aspects of olfaction in marsupials can contribute in a unique manner to our knowledge and understanding of the evolution of chemical communication within the Class Mammalia. 

Ganslosser, V. U., 1982, Social structure and communication in marsupials, Zool. Anz. Jena., 209 294. 

Johnson, J. I., Jr., 1977, Central nervous system in marsupials, in "Biology of Marsupials," D. Hunsaker, ed., Academic Press, New York. 

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