Mole rats

Rodentia (4/30) Of the 2000 or so species, none is suspected of loss. Even a highly fossorial form, the murine Mole Rat, maintains an AOS capacity (Heth, 1995 Zuri, 1998). A promising candidate, the subterranean and eusocial Naked Mole Rat (Batherygidae), shows little or no chemosensory contribution to reproductive regulation (Lacey, 1991 Faulkes et al., 1993). The role of its AOS remains to be discovered, possibly the outbreeding (dispersive) morph is the best candidate type (O Riain et al., 1996). 

Bioassay of alternate molecular forms supports the view that the ORs are capable of resolving isomeric distinctions in neutral (non-biological) odourants. Stereochemical pairs of odours were tested for differential sensitivities in the blind subterranean mole rat (Spalax ehrenbergi). The subjects responded to one enantiomer, but not to its stereoisomer. Both sexes were attracted to the odour of R-(-)-carvone but unresponsive to S-(+)-carvone in contrast, males and females were repelled by the odour of (+)-citronellol, but not by (-)-citronellol (Heth et al., 1992). The lack of responsiveness by mole rats could be central due to lack of salience, or peripheral due to hyposmia/anosmia for one isomer. Both carvones have distinct odours for the human nose. 

Faulkes C.G. and Abbott D.H. (1993). Evidence that primer pheromones do not cause social suppression of reproduction in male and female Naked Mole Rats (H. glaber). J Reprod Fertil 99, 225-230. 

Heth G., Nevo E., Ikan R., Weinstein Y., et ai. (1992). Differential olfactory perception of enantiomeric compounds by blind subterranean mole rats (Spalax ehrenbergi). Experientia 48, 897-902. 

Heth G. and Todrank J. (1995). Assessing chemosensory perception in subterranean mole rats different responses to smelling versus touching odorous stimuli. Anim Behav 49, 1009-1015. 

Jarvis J.U.M. (1991). Reproduction of naked mole rats. In The Biology of the Naked Mole-Rat (Sherman P., Jarvis M. and Alexander R., eds.). Princeton University Press, pp. 384-325. 

Nevo E., Bodmer M. and Heth G. (1976). Olfactory discrimination as an isolating mechanism in speciating mole rats. Experientia 32, 1511-1512. 

Smith T.E., Faulkes C.G. and Abbott D.H. (1997). Combined olfactory contact with the parent colony and direct contact with nonbreeding animals does not maintain suppression of ovulation in female naked mole-rats (Heterocephalus glaber). Horm Behav 31, 277-288. 

Zuri I., Fishelson L. and Terkel J. (1998). Morphology and cytology of the nasal ca and vomeronasal organ in juvenile and adult blind Mole rats (Spalax ehrenbe Anat Rec 251, 460-471. 

O Riain, M.J. and Jarvis, J.U.M. (1997) Colony member recognition and xenophobia in the naked mole-rat. Anim. Behav. 53, 187-198. 

Ryan and Lacy 2003), and primates (Smith 1995 Soltis, Mitsunaga, Shimizu, Yanagihara and Nozaki 1999). This preference can be very strongly expressed females of some species choose not to mate at all when no unrelated males are available (woodpeckers Koenig, Stanback and Haydock 1999 mole rats Cooney and Bennett 2000 meerkats O Riain, Bennett, Brotherton, Mcllrath and Clutton-Brock 2000). 

Mole rats of the superspecies Spalax ehrenbergi occur in four main chromosome forms 2n = 52, 54, 58, and 60. Females of two of these forms (52 and 58) were given choices between soiled bedding (or urine) from males of a homochromoso-mal or a heterochromosomal form. The females were estrous or diestrous. Only estrous females preferred soiled bedding and urine of homochromosomal males, measured in time spent near the odor samples. Diestrous females showed no preference (Nevo etal, 1976). 

Discrimination of species odors, and hy inference, reproductive isolation between species by means of odors, has been demonstrated for many species. Early examples are bank voles, Ckthrionomysglareolus (Godfrey, 1958), Peromyscus spp. (Moore, 1965 Doty, 1972),M sspp. (Bowers and Alexander, 1967), andger-bils (Dagg and Windsor, 1971). Male naked mole rats (superspecies Spalax ehren-hergi, Spalacidae) preferred odors from estrous females of their own to a different karyotype in a two-choice apparatus. The odors used were those of soiled bedding and urine from females (Nevo etah, 1976). 

All these features parallel those found in eusocial insects, and the naked mole-rat has been recognized as the only eusocial vertebrate (Jarvis, 1981). Naked mole-rats resemble termites more than hymenopterans they are diploid, male and females form the worker castes, the young contribute to the colony labor, some workers reproduce if the breeding female is removed, and theyoung obtain food by coprophagy (Jarvis, 1981). A similar social system exists in the Damara-land mole-rat, Cryptomys damarensis (Bennett and Jarvis, 1988). 

Bennett, N. and Jarvis, J. U. M. (1988). The social structure and reproductive biology of colonies of the mole-rat, Cryptomys damareasis (Rodentia, Bathyersidae). JournaZ of Mammalogy 69,293-302. 

Humans,mole rats" and squirrel monkeys" can distinguish between suprathreshold concentrations of the two enantiomers of carvone. The (47 )(—)-carvone is detected at lower concentrations than the (45) (-l-)-carvone by humans. At equivalent suprathreshold concentrations some individuals perceive (45) (-f)-carvone to be more intense than its... 

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Mole-rats are well-adapted to life underground. Their eyes are much reduced, as is the visual center in the brain, suggesting that sight does not play much of a role in their dark, subterranean environment, hi fact, it is not clear whether some mole-rat species can perceive light at... 

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