Female reproductive responses to photoperiod and male odours in the subterranean rodentCtenomys talarum

Abstract

The propitious timing of reproductive efforts favours the survival of both parents and the offspring at the time when conditions and/or resources to support the care and rearing of offspring are assured (Bronson 1989, Ims 1990. Reproduction is controlled by physiological interactions mediated by hormones which are ultimately induced by environmental and social factors including photoperiod, temperature, [73] Acta Theriologica 53 (1): 73-85, 2008. . 2008. Female reproductive responses to photoperiod and male odours in the subterranean rodent Ctenomys talarum. Acta Theriologica 53: 73-85.The tuco-tuco Ctenomys talarum Thomas, 1898 is a solitary subterranean rodent that breeds seasonally in coastal sand-dune grasslands from Argentina. We assessed whether short-day photoperiod determines the onset of reproduction by an increase in female's receptivity and whether male odour interacts with photoperiod as a cue by producing a greater response in receptivity. Receptivity was measured by an increase in the percentage of vaginal epithelial cells, particularly cornified cells. Females were trapped during their non-reproductive season (summer-long days) and randomly assigned to different day-length experimental groups: constant summer (CS), early winter (EW), and natural (NA) photoperiod. We examined the vaginal epithelium using vaginal smears during the first experimental phase (120 days) to test the effect of photoperiod. In the second experimental phase (15 days), we presented the females with male-soiled shavings to test the effect of photoperiod and male odor. Ctenomys talarum females showed some evidence of reproductive responsiveness to photoperiodic cuing. The proportion of epithelial cells peaked earlier in females when winter day-length was advanced than in females under natural photoperiod. Contrary to that expected, male odours did not stimulate female receptivity. These results suggest that, while photoperiod may participate in regulating reproduction, the integration of other environmental and social factors, as well as the identification of bodily conditions that lead to differences in individual response needs further consideration.

Source Odor, Intensity, and Exposure Pattern Affect Antipredatory Responses in the Subterranean Rodent Ctenomys talarum

“…Also, and coincident with a general view that considers that predator detection abilities might be tightly correlated with other chemosensory abilities (Kats & Dill ), individuals of C. talarum that rely on chemical signals for individual, sexual and reproductive‐state recognition and food detection (Zenuto et al. ; Schleich & Zenuto ; Fanjul & Zenuto ; Zenuto ) are also good at detecting and discriminating predator odors.…”

Female reproductive behaviour, ovarian hormones and vaginal cytology of the induced ovulator, Ctenomys talarum

“…Females familiarised with male odours showed some reduction of their aggression during courtship but preferred unfamiliar males as mates (Zenuto et al 2007). Male odours did not stimulate changes in vaginal smear parameters indicative of receptive condition in females (Fanjul and Zenuto 2008b). Still, male chemical cues or even body contact could cause enhanced follicular development not detected in vaginal smears, as it was found for the social C. hottentotus pretoriae (Malherbe et al 2004).…”

“…Indeed, several findings support copulamediated mode of ovulation. Females did not show spontaneous vaginal oestrus over a 6-month period (Fanjul and Zenuto 2008b). Penile morphology is characterised by the presence of spines and spikes (Balbontin et al 1996), consistent to induced ovulation (Parag et al 2006).…”

Reproductive biology of Río Negro tuco-tuco, Ctenomys rionegrensis (Rodentia: Octodontidae)

“…Estrous cycles in captive females were produced without male contact, suggesting that estrous occur spontaneously. However, like C. talarum, a high proportion of females did not exhibit estrous cycles (Fanjul and Zenuto 2008b). The individual variability in females responses suggests that reproduction is controlled by physiological interactions which are ultimately induced by environmental and social factors.…”

“…Mainly in the Argentinean species C. mendocinus (Rosi et al 1992(Rosi et al , 1996 and C. talarum (Pearson et al 1968;Malizia andBusch 1991, 1997;Malizia 1998;Zenuto et al 1999Zenuto et al , 2002aFanjul et al 2006) female reproductive parameters like pregnancy frequency and duration, litter size, and reproductive seasonality have been reported. Except in C. talarum (Malizia 1998;Fanjul et al 2006;Fanjul and Zenuto 2008b) most of such studies are based on data obtained from autopsied animals because their subterranean habits prevent or make difficult direct behavioural studies in wild populations. However, a non-invasive study of the external features and vaginal cytology, combined with a long-time field study would allow us to determine accurately and to monitor reproductive status in females across time.…”