Effects of supplementary food on the winter inhibition of reproduction in male and female four-striped field mice (Rhabdomys pumilio).

The effects of winter food supplementation on reproduction in the seasonally breeding four-striped field mouse Rhabdomys pumilio were investigated at Mountain Zebra National Park in the Eastern Cape Province of South Africa. On both control and supplemented grids, reproductive activity in females was inhibited; no pregnant females were collected and juveniles were only present in the first winter month. The provision of additional food resulted in an increase in body mass and mass of the male and female reproductive organs. However, all males, from both grids, were spermatogenically active. Ovarian activity was not stimulated by the provision of additional food, but the development of the uterus was and the endometrium was thicker and more vascularised in mice from the supplemented grid than from the control grid. We conclude that seasonal reproduction in R. pumilio is controlled by the females, in which reproductive activity is inhibited in winter. However, the provision of supplementary food was not sufficient to override the reproductive inhibition.

The effect of prolonged cold storage of eland (Taurotragus oryx) cauda epididymides on the spermatozoa: possible implications for the conservation of biodiversity.

The objectives of this study were to investigate the effects of prolonged storage of cauda epididymides at 4 degrees C on spermatozoa, and to determine the practicality of utilising epididymal sperm, harvested from testes collected during routine culling of game animals, in assisted reproductive technologies. Testes from eland (Taurotragus oryx) were collected and epididymides removed and maintained at 4 degrees C. Sperm motility, viability, morphology and membrane integrity were examined at 12 h intervals for 108 h. Sperm motility and viability were significantly lower at the end of the experiment than at the start (P < 0.05) and there was individual variation in the rate at which motility and viability declined. The total number of normal sperm decreased significantly with prolonged storage at 4 degrees C. Midpiece defects were the most common and head and tail abnormalities were rare. A significant decrease in acrosomal and nuclear membrane integrity was observed with prolonged cold storage but there was no significant change in cell membrane integrity. However, about 30% of epididymal sperm survived for 3 days at 4 degrees C and more than 10% survived for 4 days, and it should be possible to use sperm from culled animals in some assisted reproductive technologies.

The effects of melatonin on sperm motility in vitro in Wistar rats.

The effects of physiological concentrations of melatonin on motility of spermatozoa from Wistar rats were assessed in vitro. Melatonin had dose-dependent negative effects on sperm forward progression, the quality of sperm motility and on a sperm motility index. Some, but not all of these effects were due to ethanol (0.5% final concentration) which was used as a solvent for melatonin. Addition of ethanol to the incubation medium altered the pH, and increased pH had a significant negative effect on all aspects of sperm motility. Finally, the overlay of oil, which is a routine part of many sperm culture systems, had an ameliorating effect that was probably because of the lipophilic nature of melatonin.

Gender differences in the inhibitory effects of a reduction in ambient temperature and a reduction in food quantity on reproduction in the Southern African rodent, Rhabdomys pumilio.

The effects of a reduction in ambient temperature (from 26 degrees C to 15 degrees C) and a 10% reduction in daily food consumption on reproductively active male and female four-striped field mice ( Rhabdomys pumilio) were investigated. In male R. pumilio, both reduced ambient temperature and a reduction in food quantity had an inhibitory effect on spermatogenesis and on size of the reproductive organs, and this was greatest when the two factors were combined and the effect of fat was removed. Female R. pumilio responded differently and reproduction was inhibited by a reduction in food quantity, irrespective of ambient temperature. The masses of the ovaries and uterus, the numbers of developing follicles and corpora lutea, and the development of the uterine wall were all reduced by food deprivation at 26 degrees C to levels similar to those that resulted from a reduction in ambient temperature to 15 degrees C with a reduction in food quantity. It is concluded that reproduction in R. pumilio from the Eastern Cape Province of South Africa is opportunistic, that reproduction will be inhibited by an energetic challenge and that there is sexual dimorphism in the response to ambient temperature and food supply.

Short day length alone does not inhibit spermatogenesis in the seasonally breeding four-striped field mouse (Rhabdomys pumilio).

This study was an examination of the effect of photoperiod on spermatogenesis and the accessory glands of the four-striped field mouse (Rhabdomys pumilio), a seasonally breeding rodent that occurs through Southern Africa. Adult scrotal males were exposed to either short day length (10L:14D), long day length (14L:10D), or natural photoperiod in constant-environment rooms (25 degrees C, 41% humidity; food and water ad libitum) for 8 wk in late summer, when males in the wild were spermatogenically active, and in mid-winter, when they were inactive. In neither experiment did prolonged exposure to short day length or naturally decreasing day length inhibit spermatogenic activity, and we conclude that the normal cessation of spermatogenesis that occurs in most male four-striped field mice in winter is not stimulated by day length alone.

The 'hybrid' character of the gametes and reproductive tracts of the African shrew, Myosorex varius, supports its classification in the Crocidosoricinae.

The Soricidae are generally considered to comprise two subfamilies--Crocidurinae and Soricinae--each of which has distinctive reproductive characteristics. Although Myosorex varius is classified as a crocidurine, the features of its reproductive system call that classification into question. Compared with three other shrew genera, Myosorex exhibited a number of specific features including a relatively prolonged time (about 22 h) for ovulation to be induced by hCG injection and the smallest diameter (75 microns) recorded for any mammal egg. Moreover, the relative testis mass and the number of epididymal spermatozoa were somewhat greater than in some other shrews studied recently. However, many reproductive features in Myosorex have a 'hybrid' character. The glans penis has spines similar to those evident in crocidurines but absent in soricines, yet the accessory sperm storage site, midway along the vas deferens, is similar to that in soricine shrews. The ultrastructure of Myosorex spermatozoa was primarily soricine, despite an unduly large acrosome, which reaches its apogee in the Crocidurinae. Whereas the Fallopian tube displays a crocidurine-type isthmus characterized by deep crypts throughout, the ampulla is richly endowed with ciliated crypts, which in soricines contain spermatozoa. The first polar body persists in the Myosorex ovum, as it does in the soricines Cryptotis and Blarina, but not in the crocidurine Suncus and Crocidura. However, the cumulus oophorus of Myosorex appears largely crocidurine by virtue of its persistent intercellular junctions, long term stability, and the absence of a matrix, lacking only the unique perizonal space that finally characterizes the cumulus of the crocidurines, Suncus and Crocidura. The 'hybrid' character of the reproductive system of Myosorex is more consistent with the proposal that the genus is a survivor of a primitive subfamily--the Crocidosoricinae--from which present day Soricinae and Crocidurinae have arisen.

African bats: evolution of reproductive patterns and delays.

Patterns of reproduction in African bats can be compared in three taxon-based groups: fruit bats (Megachiroptera), freetailed bats (Microchiroptera: Molossidae) and the nonmolossid Microchiroptera. In the fruit bats and nonmolossid Microchiroptera there is a trend from either seasonal or aseasonal polyestry, with prolonged or continuous spermatogenesis in the tropics, towards seasonal monestry and seasonal spermatogenesis at more temperate latitudes. Reproductive delays (sperm storage, delayed implantation and delayed development) are rare at tropical latitudes, but are the norm in the nonmolossid Microchiroptera away from the tropics. The molossids are mostly polyestrous at tropical and temperate latitudes, although the duration of the reproductive season decreases with increasing latitude. The molossids appear to have escaped the constraints that affect reproduction of the other Microchiroptera. We propose that this may be due to their flight capabilities and foraging behavior, which give them access to year-round food, and to the thermal characteristics of their roots. We suggest that the ancestral reproductive pattern of the Chiroptera was probably aseasonal or seasonal polyestry, as seen in extant tropical species, and therefore that reproductive cycles have evolved from the polyestrous to the monestrous condition. Short periods of reproductive delay occur in some species of tropical bats; we suggest that these reproductive delays originally were not adaptations to temperate latitudes but rather to the long dry season, which is characteristic of African tropical latitudes. With the move away from the tropics, selective pressures, acting on the timing of lactation and spermatogenesis, would have ensured that these processes continued to occur in the warm wet season, and that the length of the reproductive delay increased. This model accommodates the probable evolutionary origin of bats and links the evolution and development of reproductive delays to the differences in climate that occur with changes in latitude. There is evidence that mate choice and sperm competition may be important to modern bats, but we believe that they need not be involved as causal factors in the evolution of reproductive delays, which can be adequately explained using purely energetic arguments.

Rainfall, food abundance and timing of parturition in African bats.

We used published results from studies in Africa to test the hypothesis that the timing of parturition in the Chiroptera is constrained by rainfall. Comparison of year-round rainfall and insect data at various latitudes showed that insect abundance peaks approximately a month after peak rainfall. A similar comparison of parturition time to rainfall showed that with the possible exception of the molossids, the Microchiroptera commonly give birth a month before peak rainfall. With an average 6-week lactation period in the Microchiroptera, the timing of parturition is such that young bats are weaned just before the period of maximum insect abundance. We suggest that the needs of the young in this post-weaning period may be more important than the energetic demands of lactation on the mother in determining the timing of parturition on an evolutionary scale. A similar conclusion is implied for the African Megachiroptera, but there is insufficient information on their reproduction to adequately test the main hypothesis for these bats.

Failure of the estrous cycle and spermatogenesis to respond to day length in a subtropical African rodent, the pouched mouse (Saccostomus campestris).

Little is known about the role of photoperiod in the control of reproduction in mammals from the tropics in general and, in particular, from the Afrotropics. The present study examined the reproductive photosensitivity of the pouched mouse (Saccostomus campestris: Cricetidae), a small, seasonally breeding rodent that occurs from about 12 degrees S to 33 degrees S in Africa. Groups of 10 laboratory-bred male pouched mice were exposed to either long-day (16L:8D) or short-day (8L:16D) conditions for 14 wk, after which they were killed and the spermatogenic activity of the testes was assessed histologically. A group of 10 adult, multiparous females were exposed to long-day conditions for 3 mo, after which the lengths of five consecutive estrous cycles were measured. Thereafter, day length was reduced to 10L:14D, and after 16 days acclimation, the lengths of five estrous cycles were measured. Finally, day length was reduced to 8L:16D, and after 33 days, the lengths of five estrous cycles were measured. Day length had no influence on body size, testis size, or the histology of the testis, and all specimens were actively producing spermatozoa. The length of the estrous cycle (4.0 +/- 0.3 days under long-day conditions) did not change significantly with the decrease in photoperiod. In a third experiment, 14 multiparous and six nulliparous females that had been maintained under short-day conditions for 33 days were mated and successfully reared litters.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of prolactin and hCG treatment on luteal activity and the conceptus during delayed implantation in Schreibers' long-fingered bat (Miniopterus schreibersii).

In Schreibers' long-fingered bat (Miniopterus schreibersii) from South Africa, implantation is delayed from May to August during which time the corpus luteum is inactive and plasma progesterone and LH concentrations low. Treatment of pregnant long-fingered bats with exogenous prolactin for 10 days in early delayed implantation (May) resulted in changes in luteal ultrastructure that were consistent with increased steroidogenesis, high plasma progesterone concentrations and the initiation of implantation. Treatment of bats with hCG for 10 days in early delayed implantation induced similar changes in luteal ultrastructure and plasma progesterone concentrations, but did not initiate implantation. Treatment with exogenous progesterone during early delayed implantation had no influence on the corpus luteum or the conceptus. We conclude that prolactin is the most important pituitary hormone in the control of delayed implantation, although the route via which it induces implantation is unknown.

Thermal preference of Schreiber's long-fingered (Miniopterus schreiberisii) and Cape horseshoe (Rhinolophus capensis) bats.

Thermal preference in a temperature gradient was investigated in Schreibers' long-fingered (Miniopterus schreibersii) and Cape horseshoe (Rhinolophus capensis) bats in relation to their roost temperatures. Both species selected a wide range of temperatures but R. capensis selected a narrower range and most frequently selected temperatures were 2-3 degrees C lower than M. schreibersii. There was some evidence of seasonal changes in temperature preference in M. schreibersii but not in R. capensis. However, euthermic bats of both species consistently selected higher temperatures than those that entered torpor. Roost temperatures were within the range selected for torpor in the laboratory but euthermic bats selected higher temperatures in the laboratory than those available to them in their roost. M. schreibersii has a wide geographical distribution and appears able to adapt its temperature preferences to those prevailing in available roosts. R. capensis is endemic to the Cape Province, South Africa, but its thermal preferences do not appear to be a factor limiting its distribution.

Spermatozoon structure of eight species of South African holothurians (Echinodermata).

Transmission electron microscopy of the spermatozoa of eight species (from seven genera) of holothurians has shown that each species has a sperm with unique dimensions, indicating that spermatozoon morphology can be used as a taxonomic character. However, although the structure of the sperm is species-specific, all sperm have a similar appearance which is typical of holothurians. The sperm head is composed of a spheroidal nucleus (about 2 µm diameter) which has a large anterior fossa housing the approximately spherical acrosome. The acrosome is differentiated internally and surrounded by periacrosomal material. The mid-piece consists of a single mitochondrion with lamellar cristae which surrounds the eccentrically positioned centrioles. The conservative form and arrangement of the sperm organelles suggest that sperm morphology cannot be used for phylogenetic investigations within this taxon.

Plasma progesterone and luteinizing hormone concentrations and the role of the corpus luteum and LH gonadotrophs in the control of delayed implantation in Schreibers' long-fingered bat (Miniopterus schreibersii).

In Schreibers' long-fingered bat from South Africa (approximately 33 degrees S) copulation, ovulation and fertilization occurred in April and May, implantation was delayed until August, and parturition occurred in December. Delayed implantation coincided with winter, during which the bats remained active, only entering prolonged periods of torpor during particularly cold spells. Plasma progesterone concentration was low during non-pregnancy (1.54 ng/ml) and during delayed implantation (1.67 ng/ml), and thereafter increased to reach a peak mean of 64.82 ng/ml in late pregnancy. Changes in size and ultrastructure of the luteal cells indicated periods of steroidogenesis just after formation of the corpus luteum, and for about 2 months after implantation; reduced steroidogenic activity during delayed implantation; and luteolysis in the last 2 months of pregnancy. Plasma luteinizing hormone (LH) concentration and pituitary LH-beta immunoreactivity were highest during follicular development and peaked just before ovulation. During early delayed implantation, plasma LH concentration was low, and both plasma LH and pituitary LH-beta immunoreactivity increased from July, reaching peaks in late pregnancy. LH may be required to activate the corpus luteum and terminate delayed implantation, or, as in some small carnivores, it may be required for luteal maintenance.

Patterns of Leydig cell and LH gonadotroph activity, and plasma testosterone concentrations in the seasonally reproducing Schreibers' long-fingered bat (Miniopterus schreibersii).

Spermatogenesis in Schreibers' long-fingered bat from approximately 33 degrees S in South Africa was seasonal, and occurred in the 3 months (February-April) preceding ovulation. The ultrastructure of the Leydig cells indicated a period of increased steroidogenesis at this time, and plasma testosterone concentrations were elevated from March to May (10.3 ng/ml). The reproductive accessory glands were secretorily active between March and May, and copulation occurred at the end of this period of activity. Changes in LH-beta immunoreactivity suggest that the LH gonadotrophs were secretorily active 1 month before the onset of spermatogenesis and that peak activity coincided with peak plasma testosterone concentrations, spermiogenesis and spermiation. During winter (May-August) there was no reproductive activity and the bats remained active, only entering prolonged periods of torpor during particularly cold spells. A secondary elevation in plasma testosterone concentration, during reproductive inactivity (October; 9.3 ng/ml), was not accompanied by any change in Leydig cell ultrastructure, and the biological significance of this peak is unknown. Such synchronous activity of the pituitary, Leydig cells, seminiferous epithelium and accessory glands is associated with the typical reproductive cycle of long-fingered bats in which copulation and fertilization are restricted to a brief period at the end of summer, and in which neither sperm storage nor a prolonged period of copulation occur.

Ultrastructure of the sperm and spermatogenesis in five South African species of the trochid genus Oxystele (Mollusca, Prosobranchia).

Sperm of Oxystele are of the primitive type, which is typical of molluscs using external fertilization. They comprise a head, which is composed of a barrel-shaped nucleus and large conical acrosome; a midpiece of five or six spherical mitochondria; and a tail, with a 9 + 2 arrangement of microtubules. The morphology of the sperm broadly resembles that of the sperm of other trochids as well as that of the sperm of the Pleurotomariidae, Haliotidae, and Fissurellidae but differs considerably from that of the Patellidae. Each of the five species examined was found to have a different sperm morphology. Our results support the suggestion of Heller and Dempster (in preparation) that Oxystele variegata Anton actually consists of two sympatric species. The morphological changes that occur during spermatogenesis are very similar in all species and resemble descriptions given for other molluscs with primitive sperm.

Ultrastructural changes in the seminiferous epithelium of two seasonally reproducing bats (Mammalia: Chiroptera).

The Sertoli cells of the Cape horseshoe bat (Rhinolophus capensis) and Schreiber's long-fingered bat (Miniopterus schreibersii) undergo marked changes in ultrastructure related to stages in the spermatogenic cycle. The amount of lipid stored in the Sertoli cells varies annually and is at a maximum from just after spermiation to early in the following spermatogenic cycle. During spermatogenesis, the diameter of the lipid droplets decreases, reaching a minimum prior to spermiation. Sertoli cells exhibit a marked apicobasal differentiation, particularly in the vicinity of developing late spermatids, where the cytoplasm of the Sertoli cell is packed with smooth endoplasmic reticulum. The possible roles of lipid droplets and smooth endoplasmic reticulum. The possible roles of lipid droplets and smooth endoplasmic reticulum in steroidogenesis by Sertoli cells are discussed. Junctional complexes occur between Sertoli cells and spermatogonia, are apparently absent from between Sertoli cells and spermatocytes, and are restricted to the region of the developing acrosome in the spermatids. Annulate lamellae, which occur commonly in the developing germinal cells and less frequently in the Sertoli cells, may be associated with the production of microtubules, which are present in both spermatids and Sertoli cells.

Fine structure of the neck of epididymal spermatozoa of Schreiber's long-fingered bat (Chiroptera: Mammalia).

The structure of the spermatozoon of the long-fingered bat (Miniopterus schreibersii) was studied using transmission electron microscopy. The neck is characterized by two asymmetrically arranged features that allow the orientation of sections in different planes and therefore aid the interpretation of the structure. There are six segmented columns, two major and four minor, in the anterior 79% of the neck, and it is only posterior to this that the major columns split. One major column is associated with doublets 9, 1, and 2, and the other major column, with doublets 5 and 6. The proximal centriole is surrounded by the capitulum and segmented columns, and the distal centriole persists and is apparent in both longitudinal and transverse sections. The central pair of microtubules pass through the distal centriole and terminate at the proximal centriole. A line drawn through the two central microtubules divides the head into left and right halves. Development of the neck begins during early spermiogenesis at which time the two centrioles are associated with the production of the capitulum, segmented columns, and axoneme complex.

A comparison of the structure of the spermatozoa and spermatogenesis of 16 species of patellid limpet (Mollusca: Gastropoda: Archaeogastropoda).

Light and transmission electron microscopy of the spermatozoa and spermatogenesis of 16 species (in three genera, Patella, Helcion, Cellana) of patellid limpet have shown that head lengths of the sperm range from 3 to 13 µm, and each species has a sperm with a unique morphology, indicating that the spermatozoa can be used as a taxonomic character. Although spermatozoon structure is species specific, five types can be recognized, based on the size, shape, and structure of the nucleus and acrosome. The occurrence of five morphological types of sperm, one of which (Cellana capensis) is particularly different from other patellids, suggests that the taxonomy of the family Patellidae be re-examined. The morphological changes that occur during spermatogenesis are very similar in all species, although two patterns of chromatin condensation are found. Those species with sperm that have short squat nuclei (length:breadth < 3.5:1) have a granular pattern of condensation. Species with sperm that have more elongate nuclei (length:breadth > 5:1) have an initial granular phase followed by the formation of chromatin fibrils. These fibrils become organized along the long axis of the elongating nucleus. The absence of a manchette suggests that nuclear elongation is brought about from within the nucleus.

Seasonal changes in plasma testosterone concentrations and Leydig cell and accessory gland activity in the Cape horseshoe bat (Rhinolophus capensis).

Male Cape horseshoe bats were studied in the Cape Province of South Africa (33 degrees 17'S, 26 degrees 25'E) between January 1983 and June 1985. The reproductive cycle is characterized by reactivation of the seminiferous tubules in early summer (October) after a 4-month (June to September) period of winter inactivity. Spermiogenesis occurred between January and April, and spermatozoa were released to the epididymides in April and May. Spermiogenesis was associated with Leydig cell activity and increasing plasma testosterone concentrations. At this time components of the reproductive accessory glands became secretorily active or showed increasing secretory activity. During winter Leydig cells were secretorily inactive and plasma testosterone concentrations dropped, but components of the accessory complex remained active. There was a second period of Leydig cell secretory activity and increasing and peak plasma testosterone values in late winter/early summer which may be associated with copulation or the initiation of a new cycle of spermatogenesis.