M. van der Merwe

Are non‐reproductive male highveld mole‐rats, Cryptomys hottentotus pretoriae physiologically suppressed while in the confines of the natal colony?

The highveld mole-rat, Cryptomys hottentous pretoriae is a social, subterranean, co-operative breeder with a high reproductive skew. The relationship between reproductive status and reproductive physiology in male highveld mole-rats was investigated. Testicular morphometrics, histological parameters, plasma testosterone concentrations and sperm motility parameters were studied in 31 males (14 reproductive and 17 non-reproductive males). Reproductive males were significantly larger than non-reproductive males, with testicular mass and volume corrected for body mass considerably larger for the reproductive males. Circulating plasma testosterone concentrations of reproductive males were not significantly higher than non-reproductive males (reproductive males 10.3±1.8 nmol l−1vs non-reproductive males 7.3±1.74 nmol l−1). Sperm motility parameters were measured, but no significant differences were found between reproductive and non-reproductive males. All 14 reproductive males had motile sperm, whereas 13 of the 17 (76%) of non-reproductive males possessed motile sperm. A typical ejaculate of a reproductive male contains 48.3% motile sperm characterized by a high percentage of flagellar defects, whereas the non-reproductive male has an ejaculate containing 45.6% motile sperm with a high percentage of head defects. It is apparent that non-reproductive males are not physiologically suppressed from reproducing. Moreover, the non-reproductive males are excluded from incestuous matings as a result of being the offspring of the reproductive female.

Aseasonal reproduction in the Hottentot golden mole, Amblysomus hottentotus (Afrosoricida: Chrysochloridae) from KwaZulu-Natal, South Africa

The Hottentot golden mole, Amblysomus hottentotus, is a subterranean mammal that exhibits aseasonal breeding. Reproductive organs of golden moles that had been killed on a monthly basis over a period of one year were examined. Reproductive tract measurements and body mass of each individual was measured and ovarian and testicular histology investigated. Body mass of males was significantly higher than that of females. Ovarian and testicular volume as well as seminiferous tubule diameter did not vary statistically on a seasonal basis. Graafian follicles and corpora lutea were present in the ovaries for nine months of the year, suggesting that ovulation can occur in any month. Despite the lack of seasonality, there appears to be enhanced follicular development during the warm, wet summer months. The litters tend to be small, mean ± S.E.: 2.0 ± 0.1 (range 1.0–3.0).

A general model of population growth in the hyrax procavia capensis

Abstract A study of an expanding hyrax population when the parameters of such a sub-population provided demographic parameters which were used to construct a model of population growth. The model simulates the observed growth of the population and its stabilization once an increasing death-rate factor, dependent on population size, was incorporated. The hyrax is dependent on shelter for protection from predation, and a biological evaluation of the model suggests that shelter is the limiting factor in population growth and control of predation effects. The study population is not limited by food, but comparisons with populations from semi-arid environments, where food shortage necessitates movements away from shelter thereby increasing predator susceptibility, suggest that the model has general application to population growth in this species.

Growth of ovarian follicles in the Natal clinging bat

Growth and atresia of the ovarian follicles of Miniopterus schreibersi natalensis (A. Smith, 1834) were studied from females collected on the southern Transvaal Highveld. In this hibernating subspecies no storage of sperm or delayed ovulation occur and females enter hibernation in a pregant condition. Only one Graafian follicle develops, which is characterized by a large antrum with the ovum-bearing mass of cells occupying only a relatively small portion of the antrum. Many follicles develop to a medium size before undergoing regression. Basically two types of regression occur; usually destruction of the stratum granulosum takes place before the oocyte is affected. The reverse condition was also observed but was very uncommon. Corpora lutea atretica resulting from the luteinization of medium-sized Graafian follicles were commonly found.

Seasonal changes in the ovarian structure of the cape fur seal (Arctocephalus pusillus pusillus)

The annual reproductive cycle of the female Cape fur seal (Arctocephalus pusillus pusillus) was described by noting monthly gross changes in ovaries from 159 females, histological changes in 46 females and placental scars in 119 females. The size and weight of an ovary containing a corpus luteum was significantly greater than that of an ovary containing a corpus albicans for most of the year, the latter only approaching, or exceeding the former during the breeding season. Follicular activity initially increased in ovaries containing either a corpus luteum or a corpus albicans; however, it declined in the ovary containing a corpus luteum after implantation, while in that containing a corpus albicans it increased, reaching a maximum in December of 32.0 ± 10.08 follicles, averaging 5.41 ± 0.73 mm. The corpus luteum increased in size following ovulation, attaining a maximum size of 22.28 ± 3.38 mm in August (eight months after ovulation). Thereafter, it gradually decreased in size, generally becoming invisible to the naked eye by 30–32 months after ovulation. Luteal cells increased until seven months after ovulation, reaching a maximum size of 34.36 ± 1.26 μm before regressing, disappearing from the corpus luteum by 18 months after ovulation. Using placental scarring and CA counts in 119 females, a pregnancy rate of 77.4% was calculated, with 6.5% abortions and 16.1% non-implantations making up the remainder.

Aspects of the histology of reproduction in the female Angolan free‐tailed bat Mops condylurus (Microchiroptera: Molossidae) in Mpumalanga, South Africa

The reproductive pattern of the female Angolan free-tailed bat Mops condylurus (A. Smith, 1933) was investigated at two localities in Mpumalanga. Female Angolan free-tailed bats displayed a seasonal bimodally polyoestrous reproductive pattern. Parturition in December was followed closely by a post-partum oestrus. Ovarian follicle and endometrium cycles also closely followed the breeding season. The reproductive tract displayed complete dextral dominance with the right ovary and uterus being functionally dominant. Luteal activity was maintained throughout pregnancy and healthy corpora lutea were observed until late in pregnancy. Shedding of the zona pellucida occurred in the oviduct in the region of the ampulla–isthmus junction. The embryo entered the uterus as a morula, where it was transformed into a unilaminar, free-lying blastocyst. A unique feature of the pre-implantation uterus was the formation of a distinct decidua at the implantation site on the mesometrial side. Implantation in the Angolan free-tailed bat was centric and superficial. First attachment of the trophoblast to the endometrium was mesometrial. The formation of a pre-placental pad of trophoblast cells was also initiated on the mesometrial side, while orientation of the embryonic disc was anti-mesometrial. Placental development occurred in the abembryonic hemisphere. Proliferation of the trophoblast over the embryonic hemisphere was slow and a bilaminar arrangement of the trophoblast was not observed in this region until after the primitive streak stage.

Schizamniogenesis in the rusty bat, Pipistrellus rusticus

Rusty bats are seasonally monoestrous, carrying a single foetus in each of the two uterine horns. Implantation is superficial with amniogenesis initiated very early during embryogenesis. Contrary to most other bat species where the amnion is formed by folding, it is formed by cavitation in the rusty bat.

Morphology and distribution of sweat glands in the Cape fur seal, Arctocephalus pusillus pusillus (Carnivora : Otariidae)

The present study examined whether sweat glands are present in the skin of the Cape fur seal, Arctocephalus pusillus pusillus. Sweat glands have an important role in thermoregulation; the presence or absence of sweat glands in the fur-covered and naked skin areas of the Cape fur seal was investigated using standard histological procedures and light and scanning electron microscopy. Sweat glands were present in both fur-covered and naked skin areas. The skin layers in the naked skin areas were thicker than those in the fur-covered areas, presumably to protect them against abrasions in the absence of hair. The density of apocrine sweat glands did not differ among the body regions; however, both apocrine and eccrine sweat glands were larger in naked skin areas than in fur-covered areas. This increased size of the glands suggests a more active role for the glands in the naked skin areas, and a higher heat-loss capability through evaporative cooling in these body regions.

Reproductive biology of the Cape serotine bat, Eptesicus capensis in the Transvaal, South Africa

The reproductive biology of the Cape serotine bat, Eptesicus capensis, was investigated histologically. The study was based on 67 specimens collected over a six-year period. This species is seasonally monoestrous, normally giving birth to twins during November. Spermatogenesis peaks during autumn (March-May) when masses of spermatozoa are released into the epididymides, and spermatozoa are present in the epididymides from March to October. Copulations are initiated during this period from the end of March to the beginning of April, with the first ovulations occurring during August. During the pre-ovulation period leucocytes are commonly found within the uterine lumen and uterine glands of females.

Polytocy in the Cape serotine bat Eptesicus capensis (A. Smith 1829) from the Southern African subregion

Polytocy is described in the Cape serotine bat, Eptesicus capensis, and discussed in relation to the occurrence of multiple births in other microchiropteran bat species in the southern African subregion. Although twins appear to be characteristic of the Cape serotine bat, triplets and even the occasional quadruplets occur.