Human babies and other young mammals prefer food odours and flavours of their mother's diet during pregnancy as well as their mother's individually distinctive odour. Newborn mice also prefer the individual odours of more closely related-even unfamiliar-lactating females. If exposure to in utero odorantswhich include metabolites from the mother's diet and the foetus's genetically determined individual odour-helps shape the neuroanatomical development of the olfactory bulb, this could influence the perception of such biologically important odours that are preferred after birth. We exposed gene-targeted mice during gestation and nursing to odorants that activate GFP-tagged olfactory receptors (ORs) and then measured the effects on the size of tagged glomeruli in the olfactory bulb where axons from olfactory sensory neurons (OSNs) coalesce by OR type. We found significantly larger tagged glomeruli in mice exposed to these activating odorants in amniotic fluid, and later in mother's milk, as well as significant preferences for the activating odour. Larger glomeruli comprising OSNs that respond to consistently encountered odorants should enhance detection and discrimination of these subsequently preferred odours, which in nature would facilitate selection of palatable foods and kin recognition, through similarities in individual odours of relatives.

With 1 figure in the text)Complete burrow systems of the mole rat Spalux ehrenhergi (Rodentia; Spalacidae), from two sites on Mount Carmel in Israel, with different soil types (terra-rossa and rendzina), were excavated and described here for the first time.A comparison was made of burrow structure patterns in the two soils and of the sexes, with special attention to the features of the feeding tunnels.The pattern in the rendzina revealed longer burrows with a longer main tunnel and fewer branches per metre of the main tunnel, while the pattern in the terra-rossa revealed shorter burrows with a shorter main tunnel and a relatively higher number of branches. These differences can primarily be related to the different levels of food availability, which is higher in the terrarossa. It is suggested that each of the patterns reflects the mole rat's ability to optimize foraging efficiency in accordance with its given food availability.The average total length of the males' burrows was much greater than those of the females' burrows in the rendzina soil. It appears that food requirements determine different burrow features of the sexes rather than reproduction requirements.Other tunnel features (e.g. structural complexity, depth and width, segment length and spatial arrangement) and the factors which may affect them, as well as burrow structure of young mole rats and evidence of the underground dispersion of young mole rats, were presented and discussed.Many similarities were found in a comparison of S. ehrenhergi burrow features with those of other solitary subterranean rodents.

The adaptive value of sound signal characteristics for transmission in the underground tunnel ecotope was tested using tunnels of the solitary territorial subterranean mole rats. We analyzed the propagation of synthetic calls with various frequencies through natural tunnels along different distances. Here we present evidence that sound propagation proved efficient only across short distances (a few meters). The least attenuation of sounds occurred at low frequencies. The 440 Hz sound was transmitted better than the lower (220 Hz) or higher (880, 1760, 3520 Hz) tested frequencies. These characteristics matched perfectly with the mole rat features of vocalization and hearing, thus reflecting the operation of natural selection for adaptive vocal communication in the underground tunnel ecotope.

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The involvement of the Harderian gland, atrophied eyes, and melatonin in the perception of photoperiodic changes has been studied in the mole rat, a fossorial blind mammal the thermoregulatory capacity of which is photoperiod-dependent. When transferred from a long photoperiod to a short one, mole rats increase their resistance to cold, a perfectly reversible phenomenon. After 2 weeks under short photoperiod the thermoregulatory capacities of animals without Harderian glands are less than those of the controls. The Harderian gland appears thus to be implicated in the detection of photoperiodic changes. After 5 weeks, however, the Harderianectomized animals had perfectly integrated the photoperiodic change, so demonstrating that other photoreceptor organs exist. The atrophied eyes, which, under these conditions, do not seem to play an important role, are involved when the animals are transferred from short photoperiod to long photoperiod. Melatonin, but not 5-methoxytryptamine, appears to be a crucial compound in such a phenomenon. These results, which demonstrate that in mammals (at least in the mole rat, as in nonmammalian vertebrates), nonocular photoreceptors exist, suggest that the mechanism by which mammals integrate photoperiodic changes is not the same when the animals are transferred from long to short photoperiod as when transferred from short photoperiod to long photoperiod.

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