Steroidogenic correlates of pregnancy in the rock hyrax (Procavia capensis)

In pregnant rock hyraxes isolated leucocytes metabolise both [3H]pregnenolone and [3H]progesterone while whole blood, erythrocytes and an erythrocyte/leucocyte mixture only metabolised [3H]progesterone. Plasma displayed no tendency to metabolically convert any one of these two steroids. In whole blood [3H]progesterone appears to be converted to 5alpha-pregnane-3,20-dione and a compound with chromatographic properties similar to that of 5alpha-pregnan-3alpha-ol-20-one. 5Alpha-pregnane-3,20-dione exhibited a high relative binding affinity for the uterine progesterone eceptor (94%), but 5alpha-pregnan-3alpha-ol-20-one displayed very little affinity for the same receptor (0.4%). 5Alpha-pregnane-3,20-dione may therefore aid in the maintenance of pregnancy. Corpora lutea metabolised progesterone to 17alpha-hydroxyprogesterone, a compound exhibiting no progestational function because of its low relative binding affinity for the uterine progesterone receptor (2%). Progesterone appears to be the main product of the corpus luteum. However, 5alpha-pregnane-3,20-dione circulated at concentrations approximately 8.5 times higher than progesterone, probably due to the metabolic conversion of progesterone to 5alpha-pregnane-3,20-dione by the blood. We conclude that in the hyrax progesterone, produced by the corpora lutea, enters the circulation, where it is reduced to 5alpha-pregnanes. 5Alpha-pregane-3,20-dione may then be transported to the uterus where it binds to the progesterone receptor to assist in the maintenance of pregnancy. This mechanism appears to be analogous to that of the African elephant which is phylogenetically related to the hyrax, except that in the elephant the 5alpha-reduced metabolites are produced by luteal tissue and not the blood.     

Geographic mitochondrial DNA variation in the rock hyrax, Procavia capensis.

Restriction-fragment-length polymorphisms in mitochondrial DNA (mtDNA) were used to evaluate geographic population genetic structure in the rock hyrax, Procavia capensis, a species which occurs widely, though restricted to rocky habitat, throughout South Africa. Ten restriction endonucleases were employed to assay mtDNAs from 55 specimens representing 10 localities. Haplotypes showed strong geographic patterning, and estimates of nucleotide sequence divergence indicate two major clades thought to be dispersing along separate routes. The divergence time of approximately 2 Myr between clades is relatively high for intraspecific variation. We speculate that the marked genetic break distinguishing the northwestern populations from those constituting the south/central clade may be indicative of two species in what has conventionally been regarded as P. capensis.     

Electron microscopic structure and innervation of the carotid baroreceptor region in the rock hyrax (Procavia capensis).

Semi-thin plastic sections reveal that the carotid baroreceptor region in the rock hyrax comprising the origin of the internal carotid artery has a preponderantly elastic structure and a thick tunica adventitia. In contrast, the common carotid artery has a musculoelastic structure, whereas the cranial segment of the internal carotid artery (immediately distal to the baroreceptor areas) shows the features of a muscular artery. Electron microscopy discloses the presence of sensory nerve endings within the parts of the tunica adventitia adjoining the preponderantly elastic zone of the internal carotid artery. These nerve endings are characterized by varicose regions containing a large quantity of mitochondria. Bundles of collagen fibers in the tunica adventitia form convolutions or whorls around the nerve terminals and often terminate on the surface of the elastic fibers or into the basement membranes of the neuronal profiles. The large content of elastic tissue in the tunica media of the baroreceptor region may render the vessel wall highly distensible to intraluminal pressure changes. This, in turn, would facilitate the transmission of the stimulus intensity to the sensory nerve terminals located in the tunica adventitia. It is suggested that the stretching of elastic fibers may form the main mechanical event leading to the distortion of the associated nerve terminals. However, a change in the geometrical configuration of the bundles of collagen under the influence of the elastic fibers may provide a better insight into the mechanisms of distortion of the baroreceptors related to and/or in contact with collagen fibers.     

Age determination and body growth of the Common duiker Sylvicapra grimmia(Mammalia)

Age determination in the Common duiker Sylvicapra grimmia was investigated by analysis of tooth eruption and replacement sequence, incremental lines of tooth cementum and tooth wear in a unique collection of 48 known-age skulls, and also by analysis by post-natal body growth in known-age duiker. In both the mandible and maxilla, permanent molariform teeth were fully erupted and in wear by 26 months of age. There was little variation in the age of eruption and replacement of all molariform teeth, making this a particularly useful feature of the duiker for age determination purposes. In contrast, the variability in eruption of the incisiforms, coupled with the difficulty in distinguishing deciduous incisiforms from the permanent counterparts, placed an unexpected limitation on the use of these teeth. Although the apparent linear relationship between tooth attrition and age has potential for further investigation as an age determination technique, the cementum annuli were not correlated with chronological age. Theoretical Von Bertalanffy equations were used to analyse body growth with age. It was concluded that because the asymptote of growth was reached at such an early age, and because there is so much individual variation in growth, body growth, including horn growth, is of very limited value for age determination. Female duiker were significantly larger than males.     

The reproductive system of male rock hyrax (Procavia and Heterohyrax)

The male genitalia of the rock hyrax (Procavia and Heterohyrax) are described. Features of the gross anatomy and histology of the testes and male accessory organs are presented, and comparison is made between the sexually active and sexually quiescent animal.
Microscopical observations have revealed the main area of storage of spermatozoa in this mammal and partly on these grounds, a new nomenclature for different parts of the reproductive system is proposed. Seasonal variations in male sexual activity in these mammals are also discussed, in addition to anatomical considerations.     

The ontogenesis of the tympanic region of the Procaviidae (Mammalia: Hyracoidea)

Lindahl (1948) has described the early ontogenesis of 14 fetal stages of Procavia capensis. The oldest fetus of his series has had a headlength of 20 mm. It is the series with which the present account on the development of the tympanic region in hyracoids starts. Further middle to late fetuses have been studied by means of serial sections or macroscopic preparations. First 5 different ontogenetic stages are described, and then we follow the development of different organs in their ontogenesis. Results: 1. The development of the tympanic region is almost completed at birth, except for the external meatus. The bulla tympani is fully ossified. 2. The entotympanic forms the medial and rostral part of the Bulla tympani. Its anlage is first met at a headlength of 31 mm. From the very beginning, it is fused with the tubal cartilage. Hyracoids do not have a caudal entotympanic. The cartilaginous mass-taken for a caudal entotympanic by Van der Klaauw (1926)-is actually a tympanic process of the petrosal. Extensive discussion reveals that the structures named entotympanics in some eutherians are most likely not homologous. 3. It is almost impossible to separate the entotympanic from the tympanic in neonates already. This is due to the surprising fact that the tympanic produces secondary cartilage at the suture between the 2 elements. 4. A gonial is lacking in hyracoids; instead the malleus is fixed in a peculiar way at the tympanic. 5. According to Lindahl (1948), the stapedial artery exists till a fetal headlength of 14 mm. Then the artery obliterates but the crura stapedis with the stapedial foramen persist. 6. Hyracoids possess a tympanohyal which changes its relation to the facial nerve during ontogenesis. 7. The development of the Eustachian sac (Diverticulum tubae auditivae) is described and compared with its development in the horse, based on the few data available in literature. 8. The internal carotid artery changes its course during its ontogenesis. Up to late stages it passes over the caudal part of the Eustachian sac and along the medial side of the Bulla tympani. A sulcus caroticus might still be seen in neonates. It is only in postnatal development that it looses the course along the bulla and passes along the mediocaudal side of the Eustachian sac. 9. The formation of the Recessus meatus acustici externi in exactly takes place the way described only once by Hammar (1902). The cavitation of the recessus occurs independently of the cavity of the external meatus.     

Ecology of Physaloptera capensis (Nematoda : Spiruroidea) infecting the Springhare Pedetes capensis (Mammalia) in Botswana

Incidence and intensity of the stomach nematode Physaloptera capensis in relation to the age, sex, reproductive status, physical condition, density and habitat of its host, the Springhare, were investigated in the Republic of Botswana (August 1971-August 1973). All data indicate that this nematode is a benign parasite of the Springhare. Infections were not randomly distributed within the Springhare population. Mean number of worms per Springhare was 83 and 34% of all Springhares were parasitized. Adults, females and lactating females showed significantly heavier infections than juveniles, males and non-lactating females, respectively. Infection was directly associated with the amount of grass cover in the Springhares' habitat but independent of the density and physical condition of Springhares. Possible causes of differences in rates of infection among Springhares of different age/reproductive classes and from populations of different density are mentioned. It is suggested that numbers of P. capensis may be regulated mainly by density-independent environmental factors operating upon rates of transmission.     

Age determination, age structure, and longevity in the mole Scalopus aquaticus (Mammalia: Insectivora)

Three hundred and eighty-two moles, Scalopus aquaticus , were collected from 16 sampling grids located within a 23 km² area in South Carolina, USA. Age of moles was determined using tooth wear. Both the mean and median ages of trapped moles were c. two years; the oldest mole was in its seventh year of life. More than 50% of the individuals are estimated to die during the first six months of life; adult survivorship was relatively high and age-dependent. There was differential mortality between the sexes, and females lived longer than males. Scalopus aquaticus in South Carolina lived c. 1.2 times longer than the maximum lifespan predicted on the basis of body mass. Pooled samples of moles yielded the expected age distribution, with fewer individuals occurring in successively older age classes. However, based on bootstrap estimates of the variance in age structure, samples from some grids contained significantly more young or old individuals than expected due to sampling error. Mole populations appear not to be in demographic equilibrium at this local scale, but instead conform more closely to a metapopulation-type of structure.     

Scale-dependent foraging costs: habitat use by rock hyraxes (Procavia capensis) determined using giving-up densities

Individuals select for habitats at different scales. Can a species’ response to different spatial and temporal heterogeneities be placed in a common currency? Is it possible to rank the relative importance of different habitat features on the organism's behavior and ecology? Do the effects of different spatial and temporal heterogeneities interact in predictable ways? To address these questions, we quantified hyrax habitat use at a series of rocky outcrops (koppies) and an isolated gorge in Augrabies Falls National Park, South Africa. We measured the hyraxes’ perceptions of feeding opportunities and costs using giving‐up densities (GUDs) within experimental food patches. At very small spatial scales (2–3 m), we tested whether hyraxes have lower GUDs under cover (shrubs or rocks) or 2–3 m away in the open. Hyraxes valued cover highly, consistently showing lower GUDs in cover microhabitats. This preference did not result from differences in energetic costs, as hyraxes did not track sun in winter or shade in summer. At moderate spatial scales (10–80 m), we tested whether hyraxes act as central place foragers with lower GUDs closer to their dens. GUDs increased with increasing distance to dens at four koppies, but not at the gorge. At larger spatial scales, preferences differed between colonies based on differences in habitat structure, with hyraxes on similar structures (koppies) behaving similarly. We evaluated how foraging costs varied with temporal heterogeneity within the day, among days, and among seasons. Hyraxes showed their lowest GUDs in the early mornings and late afternoons. Hyraxes shifted foraging locations among days, which may result from sentinels shifting location on consecutive days and/or hyraxes managing their food. Differences between GUDs during the various sample periods were not seasonally correlated. We conclude that spatial and temporal habitat utilization by hyraxes may be driven more by predation risk rather than other costs.     

The occurrence of abnormal sperm in the cauda epididymis of Rhinolophus capensis (Mammalia: Chiroptera)

The spermatozoa of Rhinolophus capensis are stored in the cauda epididymidis for about 10 months, 4 months prior to copulation and 6 months after copulation. Electron microscopy has shown the occurrence of sperm defects (mitochondrial proliferation, bending and coiling of the tail, and Dag defect) throughout the period of sperm storage. However, these defects are more common during the postcopulation period, when excess spermatozoa are being removed, suggesting that they may be associated with sperm degradation.     

Mitochondrial DNA Phylogeography and Comparative Cytogenetics of the Springhare, Pedetes capensis (Mammalia: Rodentia)

Variation in mitochondrial DNA (mtDNA) was used together with comparative cytogenetics to examine the evolutionary history and taxonomic status of an African hystricomorphous rodent, the springhare Pedetes capensis. The mtDNA phylogeographic structure showed that the majority of the southern African populations (P. c. capensis) are characterized by unique but closely related maternal lineages. Based on restriction endonuclease fragment analysis, the east African populations (P. c. surdaster) appear more structured and are distinguished from those in southern Africa by an average sequence divergence of 5.52% (±1.4%). This marked divergence is concordant with results of the cytogenetic study. Specimens from southern Africa have 2n = 38, and those from east Africa 2n = 40. The change in diploid number is due to a single centric fusion. It is suggested that the closure of the Brachystegia or miombo woodland (20,000–10,000 B.P.), which delimits contemporary springhare ranges, may have been too recent to account for the accumulated genetic differences that distinguish these taxa. While rifting and associated habitat changes in east Africa can be invoked to explain genetic structure in this region, the southern African springhare populations, which have a high incidence of locality-specific haplotypes, show a shallow phylogeographic structure, in keeping with a relatively recent range expansion from smaller source populations. Given the magnitude of genetic, morphological, and ethological differences between the two geographic isolates, we believe that there is strong support for the elevation of the east African and southern African springhare populations to full species status, thus supporting earlier taxonomic treatments of this rodent.