Seasonal reproduction in the highveld mole-rat, Cryptomys hottentotus pretoriae (Rodentia: Bathyergidae)

Abstract

The highveld mole-rat, Cryptomys hottentotus pretoriae, is a cooperatively breeding rodent that exhibits seasonal breeding and a reproductive division of labour. Body mass, reproductive-tract morphometrics, ovarian histology, and plasma oestrogen and progesterone concentrations were studied for both reproductive and non-reproductive females from 55 colonies, the main objective being to determine the inclination of this species towards seasonal breeding. Offspring are born from July through to November. However, qualitative analysis of ovarian histology revealed that reproductive females retain the potential for ovulation and subsequent production of corpora lutea during the late-summer nonbreeding period (December-March). Seasonal differences were found in ovarian morphometrics and hormone concentrations that are associated with enhanced follicular activation in April and May and subsequent conceptions from July through to November during the breeding period. The nonbreeding period coincides with maximal dispersal opportunities in the summer-rainfall areas inhabited by the highveld mole-rat. Body mass, reproductive-tract morphometrics, testicular histology, and plasma testosterone concentrations were determined for reproductive and non-reproductive males from 37 colonies. Available evidence suggests that there is a gradual increase in testicular mass for reproductive males as the breeding season approaches, but after September the testicular parameters fall. Seminiferous-tubule diameter was significantly greater in reproductive males but exhibited no seasonal variation. Testosterone concentrations were higher in reproductive males. Current data support a lack of gonadal regression in males during the nonbreeding season.Résumé : Le rat-taupe Cryptomys hottentotus pretoriae est un rongeur qui se reproduit de façon coopérative, dont la reproduction est saisonnière et qui pratique la répartition des tâches reliées à la reproduction. Nous avons déterminé la masse du corps, la morphométrie du système reproducteur, l'histologie des ovaires et les concentrations plasmatiques d'oestrogène et de progestérone chez des femelles reproductrices et non reproductrices de 55 colonies, dans le but de vérifier la tendance à une reproduction saisonnière chez cette espèce. Les petits naissent entre le début de juillet et la fin de novembre. Cependant, une analyse qualitative de l'histologie des ovaires démontre que les femelles reproductrices gardent leur potentiel d'ovulation et restent capables de produire ensuite des corps jaunes pendant la saison non reproductive en fin d'été (décembre à mars). Il existe des différences saisonnières dans les mesures morphométriques de l'ovaire et les concentrations hormonales, différences associées à la plus grande activité folliculaire en avril et en mai et aux conceptions subséquentes de juillet à la fin de novembre au cours de la période reproductive. La période non reproductive coïncide avec les probabilités maximales de dispersion dans les régions à pluies estivales habitées par le rat-taupe...

Field Evidence for Colony Size and Aseasonality of Breeding and in Ansell's Mole-Rat,Fukomys anselli(Rodentia: Bathyergidae)

“…It is, however, noteworthy that within the more southerly occurring genus of Cryptomys, reproduction appears to be strictly seasonal, e.g. Cryptomys h. hottentotus (Spinks et al 1997(Spinks et al , 1999 and Cryptomys h. pretoriae (Janse van Rensburg et al 2002).…”

Relations between social status and the gonadotrophin‐releasing hormone system in females of two cooperatively breeding species of African mole‐rats, Cryptomys hottentotus hottentotus and Cryptomys hottentotus pretoriae: Neuroanatomical and neuroendocrinological studies

“…Common mole-rats were collected from Kamieskroon (30°S, 17°E, South Africa) and highveld mole-rats from the Pretoria area (26°S , 28°E, South Africa). From 2000 to 2002, entire colonies were trapped both during and out of the breeding season (i.e., the period in which mating, gestation, parturition, and lactation take place; Spinks et al, 1997Spinks et al, , 1999Janse van Rensburg et al, 2002). In the common mole-rat, pups are born from late November to January (Spinks et al, , 1999; the highveld mole-rat breeds from April to September (Janse van Rensburg et al, 2002).…”

“…These are the only social bathyergids known to restrict breeding to a particular season (Janse van Rensburg et al, 2002;Jarvis and Bennett, 1991); furthermore, in the subordinate colony members of these species, reproduction is suppressed throughout the year, as long as they remain within the confines of their natal colony (Bennett, 1989;Moolman et al, 1998). In female highveld mole-rats, the suppression of reproductive functions in the subordinates is associated with reduced pituitary sensitivity to GnRH ( Van der Walt, et al, 2001); this is not the case in the subordinate female common molerats (Spinks et al, 2000a).…”

Field evidence for aseasonality of reproduction and colony size in the Afrotropical giant mole-rat Fukomys mechowii (Rodentia: Bathyergidae)

“…Georychus capensis, Bathyergus suillus, Bathyergus janetta and Heliophobius argenteocinereus (Sumbera et al 2003;Hart et al 2006;Oosthuizen & Bennett 2007), and social, e.g. Cryptomys and Fukomys (Bennett & Jarvis 1988a;Bennett 1989;Burda 1989;Spinks et al 1997Spinks et al , 1999Janse van Rensburg et al 2002. Until recently, the only published information on the reproduction of the giant mole-rat was derived from laboratory studies (Bennett & Aguilar 1995;Scharff et al 1999) and one small field study (Scharff et al 2001) in which reproduction was suggested to take place throughout the year, or from anecdotal reports from Ansell (1978) who captured young animals throughout the year.…”

“…To date, all the studied species within the genus Fukomys have been reported to be aseasonal breeders producing offspring throughout the year: F. damarensis (Bennett & Jarvis 1988a,b;Bennett & Faulkes 2000), F. darlingi (Bennett et al 1994) and F. anselli (Burda 1989) By contrast, within the more southerly occurring genus Cryptomys, reproduction appears to be more seasonal, e.g. Cryptomys h. hottentotus (Spinks et al 1997(Spinks et al , 1999 and Cryptomys h. pretoriae (Janse van Rensburg et al 2002).…”