Aspects of reproduction in female Ross seals (Ommatophoca rossii)

Ovaries were collected from 26 Ross seals shot in the King Haakon VII Sea south of the 60 degrees latitude during 3 periods, between 12 January and 2 February 1980-1982. The structure of the ovaries resembled that of other pinnipeds. A corpus luteum was found in 18 of 26 females, which therefore were regarded as reproductive. However, no females were lactating or visibly pregnant (presence of fetus in the uterus). Of the remaining 8 females (non-reproductive), 3 had neither a corpus luteum nor a corpus albicans. Ovulation did not alternate between ovaries in 4 of 10 females. Ovarian weight was greater in reproductive females than in non-reproductive females, and was also correlated with presence of a corpus luteum. Follicular development was more advanced in reproductive females than in non-reproductive females, and it was also more pronounced in the ovary containing a corpus luteum. The finding of a high percentage of females with a corpus luteum, but with no fetus in the uterus, together with histological characteristics of the ovarian structures in the present study, and earlier published data on mating, pupping and moulting, provide circumstantial evidence for delayed implantation in Ross seals.     

Changes in progesterone concentrations in the Japanese long-fingered bat, Miniopterus schreibersii fuliginosus

In the Japanese long-fingered bat, when compared with the baseline values during non-pregnancy in the autumn, plasma progesterone concentrations were not significantly elevated during the delayed implantation stage that begins before the bats enter hibernation. However, progesterone concentrations were significantly lower during the delayed development stage that occurs during hibernation and rose significantly during the rapid embryogenesis that occurs after arousal from hibernation in the spring. Changes in the corpus luteum volume corresponded closely with those of plasma progesterone values. Maintenance of gravid females at 25 degrees C for 2 weeks in winter resulted in significant increases in the plasma progesterone concentration and the corpus luteum volume.     

On the occurence of a short period of delayed implantation in Schreibers'long-fingered bat (Miniopterus schreibersii) from a tropical latitude in Zimbabwe

Mating in Schrcibers'long-fingered bat ( Miniopterus schreibersii ) from central Zimbabwe (18°S) occurred between mid-April and mid-May, after a five-month period of spermatogenesis. Implantation was delayed until early July and parturition occurred between late October and mid-November, about four months after implantation and six to seven months after fertilization. The timing and length of gestation at 18°S are similar to that described for M. schreibersii from Zaire (11σS) and when these date are compared with those for the same species from higher latitudes in Africa, it is apparent that there is a small, but distinct, increase in the total length of pregnancy and the length of delayed implantation with increasing latitude. The reproductive bilogy of Miniopterus schreibersii from Africa and France differs fundamentally from that of the same species from Australia and Japan, and it is suggested that studies of the relationship between latitude and duration of delayed implantation should be based on comparisons within single species from different latitudes on the same continent, and that comparisons between species and between continents should be avoided.     

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.     

Formation and fate of the corpus luteum in the Dusky leaf monkey (Presbytis obscura)

The formation and fate of the corpus luteum have been described for a previously un researched species of South-east Asian colobine, the Dusky leaf monkey, Presbytis obscura. Histological material from 44 wild female monkeys collected at various stages of the menstrual cycle, pregnancy and lactation over a 12-month period was available for study. The corpus luteum of the menstrual cycle was a cystic structure and consisted of a thin rim of luteal tissue surrounding a central cavity filled with a meshwork of fibrin. At the end of the luteal phase the corpus luteum either degenerated into a corpus albicans, or became transformed into a corpus aberrans. Corpora aberrantia have previously only been described in the ovaries of the rhesus monkey, where they may persist for many months. Ultimately the corpus aberrans may also degenerate into a corpus albicans. Small corpora lutea atretica were observed during early pregnancy but there was no evidence of corpora lutea accessoria. Anovulatory cycles were common amongst the females included in this study and may play a role in limiting the growth of troops in their natural environment. Comparisons have been drawn between the findings presented here and those published for other species of catarrhine primate.     

Reproduction in the common porpoise (Phocoena phocoena) of the North Atlantic

Examination of the reproductive organs from 137 Common porpoises ( Phocoena phocoena ) from the Gulf of St Lawrence, the Bay of Fundy and British waters has enabled observations to be made on reproductive events. Birth in Canadian waters occurs mainly in June and July: mating takes place from june to August . The evidence indicates that females do not become pregnant every year. Birth length is 80 to 90cm; juveniles attain a length of 100 to 110 cm after three to four months. Sexual maturity is reached at a length of about 133 cm in males and 145 cm in females, probably in their third or fourth year. The corpus luteum persists throughout gestation and retrogresses from their histological characteristics. One kind possesses much acellular material and is probably a corpus albicans gravitadionis; the other consists of a mass of obliterated vessels and is the remains either of a corpus luteum of an infertile ovulation or of a lutealized follicle. Evidence indicates that there is seasonal testicular activity, reaching a maximum during July and subsiding in late August.     

Morphological changes in the corpus luteum of tuatara (Sphenodon punctatus) during gravidity

Tuatara (Sphenodon spp.) are rare reptiles, members of the reptilian order Sphenodontida, inhabiting small offshore islands of New Zealand. Females usually require about three years to yolk a clutch of eggs followed by an 8-month period of in utero egg shelling. As in other vertebrates, the post-ovulatory follicle forms a transitory endocrine structure, the corpus luteum. The tuatara Sphenodon punctatus exhibits a corpus luteum having several unusual morphological features as compared to turtles and squamate reptiles. Like the crocodilians, the tuatara has a corpus luteum in which the luteal cell mass never fills the central cavity and in which the thecal fibroblasts do not close the ovulation aperture. As in all oviparous reptiles examined, however, the corpus luteum appears to persist throughout gravidity based on its histological appearance. During gravidity, plasma progesterone concentrations are detectable, even though gravidity lasts an exceptionally long time (8 months) for an oviparous species. Luteolysis is initiated within two months following oviposition. The initial stages of luteolysis appear rapid, but luteal scar tissue is apparent in the ovaries of all adult females we examined and probably persists for many years post-oviposition. J Morphol 232:79–91, 1997. © 1997 Wiley-Liss, Inc.     

The biology and evolution of the reproductive cycle of Miniopterus schreibersii and M. australis (Chiroptera: Vespertilionidae)

The reproductive biology of Miniopterus schreibersii and M. australis was studied at latitude 28·5°S, in eastern Australia. Comparison was made with material from 23·5°S to 37°S.
Both species are monoestrous and monotocous. Ovulation is from the left ovary and implantation is in the right cornu. At latitude 28·5°S, a "silent heat" precedes behavioural oestrus and fertilization by two months in M. schreibersii and three months in M. australis. In M. schreibersii copulation and fertilization occur in late May and early June, immediately after a relatively short period of spermatogenesis and about one month after the release of sperm to the epididymides. During winter, implantation of the blastocyst stage is delayed. The male accessory glands involute but a store of epididymal sperm is retained. Implantation occurs in August and birth is in December.
M. australis conceives in mid-August, after an extended period of spermatogenesis which ceases four to six weeks prior to copulation. An epididymal sperm store is present some 21/2 months prior to insemination. Implantation has occurred by mid-September and parturition takes place in December.
Comparative data from other latitudes in eastern Australia show no differences in the timing of a reproductive events of M. australis between 23·5°S and 31°S. In M. schreibersii in South Australia (37°S) mating occurs in April and May. Plasticity in the timing of parturition (October to December) and other anomalies of this population are discussed.
The data suggest that evolutionary hypotheses involving extrapolation from one species to the other are questionable and that a more complex and varied adaptive response to climate may exist than has hitherto been supposed.     

Plasma progesterone levels during pregnancy in the little brown bat Myotis lucifugus (Vespertilionidae)

Plasma progesterone was measured by radioimmunoassay in individual female Myotis lucifugus throughout pregnancy and lactation. Progesterone levels, which averaged 6.7 +/- 0.7 ng/ml in late hibernation, rose to a mean of 18.9 +/- 6.7 ng/ml in unimplanted bats collected in the first two weeks after arrival at a maternity roost. Analysis of progesterone levels in bats in which the developmental stage of the embryo was known revealed two sharp, transient increases in plasma progesterone during the preimplantation period. The first, with values of 30-45 ng/ml, occurred at ovulation. The second, with values of 20-30 ng/ml, coincided with blastocyst formation. Progesterone levels increased exponentially from a mean of 7.4 +/- 1.0 ng/ml during early implantation to peak values of 100-200 ng/ml (means = 136.2 +/- 15.6) in the last two weeks of pregnancy, and showed no evidence of either a midpregnancy or prepartum decline. Despite involution of the corpus luteum at the end of pregnancy, progesterone levels averaged 9.0 +/- 1.0 ng/ml during lactation and did not decline until the end of lactation. In bats undergoing abortion, mean levels of plasma progesterone were already less than 6 ng/ml, equivalent to levels in nonbreeding females. The results indicate that the progesterone profile of pregnant M. lucifugus, though generally resembling those of other bats, exhibits several distinctive features. The sharp rise in plasma progesterone coinciding with blastocyst formation has not been reported in other mammals and suggests a possible role of progesterone in the cavitation process. In addition, peak values of plasma progesterone in late pregnancy were conspicuously higher than levels reported in other verpertilionid bats. The levels did not appear to fall before parturition, although such falls have been reported in other bats.     

Rescue of the corpus luteum in human pregnancy

Rescue of the corpus luteum from its programmed senescence maintains progesterone production required for pregnancy. In primates, chorionic gonadotropin produced by the developing conceptus acts as the primary luteotrophic signal. The purpose of this research was to assess corpus luteum rescue by examining changes in daily urinary progesterone metabolite levels during the first week after implantation. We determined the variability in progesterone metabolite profiles and evaluated its relationship to early pregnancy loss in 120 naturally conceived human pregnancies, including 43 early pregnancy losses. In other primates, an abrupt increase in the progesterone metabolite occurs at the time of implantation. This pattern occurred in an estimated 45% of the pregnancies in the present study. In the remaining pregnancies, there was a delayed rise (18%), neither a rise or decline (22%), or a decline (15%) during the week after implantation. The estimated rate of early pregnancy loss increased across these categories (from 5% loss with an abrupt rise at implantation to 100% loss with progesterone metabolite decline). Low urinary hCG levels in early pregnancy were significant determinants of a decline in postimplantation progesterone metabolite. However, preimplantation steroid metabolite levels were not significant, suggesting no inherent problem with the corpus luteum. Examination of individual progesterone metabolite profiles in relation to hCG profiles also indicated that few losses were caused by corpus luteum failure. Delineating the functional importance of an abrupt progesterone rise at the time of implantation may provide new strategies for promoting successful implantation in assisted reproduction.     

Reproduction in the Indian pigmy pipistrelle bat, PipistreUus mimus

PipistreUus mimus Wroughton exhibits a clearly defined breeding season at Varanasi (25°N, 83°E). Morphological specializations of the Graafian follicles consist of a hypertrophied discus proligerus resulting in the reduced antral cavity, and post-partum oestrus. The females appear to store spermatozoa in their genital tracts during November and December. Other interesting features associated with reproduction in this species are that the corpus luteum regressed soon after implantation and there is a very short period of lactation.     

Factors Affecting Date of Implantation,Parturition, and Den Entry Estimated from Activity and Body Temperature in Free-Ranging Brown Bears

Knowledge of factors influencing the timing of reproduction is important for animal conservation and management. Brown bears (Ursus arctos) are able to vary the birth date of their cubs in response to their fat stores, but little information is available about the timing of implantation and parturition in free-ranging brown bears. Body temperature and activity of pregnant brown bears is higher during the gestation period than during the rest of hibernation and drops at parturition. We compared mean daily body temperature and activity levels of pregnant and nonpregnant females during preimplantation, gestation, and lactation. Additionally we tested whether age, litter size, primiparity, environmental conditions, and the start of hibernation influence the timing of parturition. The mean date of implantation was 1 December (SD = 12), the mean date of parturition was 26 January (SD = 12), and the mean duration of the gestation period was 56 days (SD = 2). The body temperature of pregnant females was higher during the gestation and lactation periods than that of nonpregnant bears. The body temperature of pregnant females decreased during the gestation period. Activity recordings were also used to determine the date of parturition. The parturition dates calculated with activity and body temperature data did not differ significantly and were the same in 50% of the females. Older females started hibernation earlier. The start of hibernation was earlier during years with favorable environmental conditions. Dates of parturition were later during years with good environmental conditions which was unexpected. We suggest that free-ranging pregnant brown bears in areas with high levels of human activities at the beginning of the denning period, as in our study area, might prioritize investing energy in early denning than in early parturition during years with favorable environmental conditions, as a strategy to prevent disturbances caused by human.     

Morphology of the reproductive tract in a lizard exhibiting incipient viviparity (Sphenomorphus fragilis) and its implications for the evolution of the reptilian placenta

The morphology of the female reproductive tract and corpus luteum is examined in Sphenomorphus fragilis, a lizard from the lowland regions of New Guinea exhibiting incipient viviparity. Females oviposit eggs that hatch either immediately or within a few hours. Corpora lutea form from ovulated follicles and decrease in diameter as embryonic development progresses. The oviduct from vitellogenic females is sparsely populated with well developed uterine glands containing secretory granules. The eggs are covered with a relatively thin shell (10 μm thick) composed of an inner boundary layer and proteinacous fibers. The secreted shell is complete by early neurulation. Shell morphology does not change throughout the remainder of the in utero incubation period. A well vascularized uterus and chorioallantoic membrane provide simple placentation. These findings suggest that the reduction in shell thickness associated with the evolution of a placenta is due to a decrease in the number of shell glands in the uterus and is not a delay or inhibition of the shelling process per se. This hypothesis further suggests that the selective forces favoring shell gland loss act on the vitellogenic female during gland recruitment which occurs prior to ovulation and not on the pregnant female. © 1992 Wiley-Liss, Inc.     

Morphological changes of the ovary and hormonal changes through the ovarian cycle of the common marmoset (Callithrix jacchus)

Laparoscopic observations of morphological changes of the ovary during the ovarian cycle in conjunction with radioimmunoassay of serum progesterone and estradiol-17β was investigated as a method of monitoring the ovarian cycle in the common marmoset. In the common marmoset, plural follicles first appeared in each ovary five days prior to ovulation. At three to four days prior to ovulation one or two follicles developed into translucent blisters on the surface of the ovary. As the follicles filled with follicular fluid, they became larger and clearer until one to two days prior to ovulation, at which time they formed well defined, transparent bubbles protruding from the surface of the ovary. After ovulation, the ovulation point could be detected at the center of the follicle, sometimes surrounded by a corpus of engorged blood vessels. Ovulations of the plural follicles were not simultaneous, and due to the time lag ovulations took at least 12 to 20 hrs in four out of seven animals examined. After two to five days of ovulation the corpus hemorragicum, a bright red protrusion made of tissue and blood disrupted by ovulation, was found. Subsequently, the color of the formatted corpus luteum changed from dark-red to yellow then to yellow white. While the corpus luteum remained reddish in color serum progesterone was maintained at as high levels as in the luteal phase. There was no mature follicle or corpus luteum in subordinate female ovaries.     

Copulatory behavior unaccompanied by ovulation in the Japanese monkey (Macaca fuscata)

Copulatory behavior unrelated to conception is sometimes observed in some non-human primates including the Japanese monkey. In the present study, the authors examined whether a mature follicle or a newly formed fresh corpus luteum was observed in the ovaries of female Japanese monkeys which displayed the copulatory behavior unrelated to conception. Post-conception copulatory behaviors were observed in three out of four females usually kept in individual cages in an air-conditioned room, and in two out of three females without infants kept in an outdoor group cage. However, neither a mature Graafian follicle nor a fresh corpus luteum formed newly after conception was observed in any of these females by laparoscopic examinations conducted immediately after termination of the copulatory behavior. In females with infants born in the preceding birth season, copulatory behaviors were observed in three out of four females kept in the outdoor group cage, and in two out of four females in a free-ranging troop. Ovulation was confirmed in one case out of the three kept in the outdoor group cage, but neither a mature follicle nor a newly formed corpus luteum was observed in the remaining four females. These findings suggest that copulatory behavior in the Japanese monkey is not always controlled by the development of a follicle or ovulation in the ovary.     

Gonadal activity in some Bottlenose dolphins (Tursiops truncatus)

Details are given of the characteristics of the ovaries and testes of young and adult dolphins, Tursiops truncatus , all of which had been caught off Florida or Mississippi. Most had been in captivity for periods varying from a few days to ten years. Birth takes place most commonly during February to May and September to November. Length of neonates is between 98 and 126 cm. The state of activity of the gonads suggests that sexual maturity is reached in females at a length of over 220 cm and probably in their fifth year. Males do not become sexually active until about 260 cm in length and at an estimated age of at least ten years. Plasma testosterone levels are highest in a captive fertile male during April and May and October and November. The corpus luteum persists throughout the 12-month gestation period and also appears to persist as a corpus albicans for the dolphin's life span. The left ovary is usually larger than the right and twice as many corpora are found in the left as in the right ovary. No evidence of regular, cyclic ovulation is detected and it is concluded that ovulation is induced in Tursiops.     

Hormonal independence of courtship behavior in the male garter snake

Garter snakes exhibit a dissociated reproductive tactic in which gonadal activity is minimal at the time of mating, increasing only after the breeding season has ended. Experiments are presented demonstrating that neither short-term nor longterm castration affects courtship behavior in adult male red-sided garter snakes (Thamnophis sirtalis parietalis). So long as males have passed through a low-temperature dormancy period (hibernation), castration either shortly after emergence in the spring, or before entering winter dormancy in the fall, does not prevent the display of intense courtship behavior on emergence. Similarly, males castrated during mating activity the previous spring prior to the annual testicular growth phase actively courted females on emergence from hibernation. Males adrenalectomized and castrated during low-temperature dormancy also courted females on emergence. Hypophysectomy during or before low-temperature dormancy did not prevent males from displaying high-intensity courtship behavior on emergence from hibernation. Treatment with sex steroid hormones, as well as hypothalamic and pituitary hormones, and a variety of neural and metabolic affectors also fails to elicit courtship behavior in noncourting males during the summer. It was concluded that causal mechanisms controlling courtship behavior in the red-sided garter snake are fundamentally different, at least at the physiological level, from those mechanisms described for many laboratory and domesticated species.     

Reproductive synchrony and annual variation in foetal growth rate in the long-fingered bat (Miniopterus schreibersii)

Mating in the long-fingered bat (Miniopterus schreibersii) from the East Cape region of South Africa occurred during a four-week period in April and May, and implantation was delayed until August. Analyses of foetal age and estimated dates of conception indicate that after implantation, the progression of pregnancy within the population was synchronous both within and between years. It is suggested that implantation, probably initiated by increasing day length, occurred at about the same time throughout the population and thus synchronized reproduction. In the final month of pregnancy foetal growth rate and, consequently, the timing of parturition in the three years of the study varied. These variations were correlated with variations in rainfall and it is suggested that the failure of the November rains in 1990 would have caused a reduction in insect abundance and that this was responsible for the decrease in foetal growth rate and the delay in parturition.     

REPRODUCTION IN THE FEMALE SUBANTARCTIC FUR SEAL, ARCTOCEPHALUS TROPICALIS

The reproductive tracts of 89 female subantarctic fur seals, taken at Gough Island between November 1977 and October 1978, were examined. Females started ovulating at age 4 yr and all 6-yr-old females were sexually mature. They are mono-ovulatory, alternating between ovaries, and only single embryos were found. Females older than 13 yr ( n = 11) showed poor follicular development and some failed to ovulate. The gestation period (first recorded ovulation to first recorded birth) was 360 d, while delayed implantation (first recorded ovulation to first recorded implantation) lasted for 139 days. Follicle numbers in the functional ovary declined sharply after ovulation while the corpus luteum increased in size until at least 1 mo prior to parturition. The number of follicles in the contralateral ovary increased after midwinter (June/July), and the mean size of the largest follicles peaked prior to ovulation in December. The mean size of the largest follicles increased in both ovaries near implantation time, after reaching a low subsequent to, ovulation. The regressing corpus albicans, conspicuous for approximately 3 mo after parturition, could not be detected macroscopically within one year postpartum. Subantarctic fur seals at Gough Island have a distinct postreproductive class of older females. The pregnancy rate for all females ≥4 yr of age was 79%, and it was 84.5% for the sexually mature group of ≥6 yr of age, while the mean age at puberty was 4.80 yr.     

Relationship between uterine morphology and peripheral concentrations of sex steroid hormone in wild Japanese black bears (Ursus thibetanus japonicus)

Developing a better understanding of the reproductive physiology and breeding condition peculiar to wild Japanese black bears (Ursus thibetanus japonicus) is crucial for estimation of their habitat distribution. The aim of this study was to clarify the changes in morphology of the genital organs, cellular proliferation in the endometrium and sex steroid hormone concentrations along with the reproductive cycle in Japanese black bears. Samples were collected from a total of 24 female Japanese black bears (1-15 presumptive years old) that were caught in the wild in Iwate prefecture during the period between August 1999 and September 2005. Twenty-two out of the 24 animals were hunted from May to October. The ovaries from the 24 animals and the uteri from 23 animals were observed macroscopically and histologically to examine the relationship between morphology of the genital organs and the month of the year the animal was caught. The staining pattern of proliferating cell nuclear antigen (PCNA) in the endometrium was characterised. Peripheral concentrations of oestradiol-17beta and progesterone were determined by radioimmunoassay. All the animals that had a corpus luteum (n=12) were captured from August to October. The thickness of the endometrium in the animals captured from August to October (n=16) was significantly greater than those in animals captured from May to July (n=5) (P<0.05). From August to October, the thickness of the endometrium and the ratio of the area of the uterine glands to the area of the endometrium in the animals with a corpus luteum (n=12) were significantly greater than those without a corpus luteum (n=4) (P<0.01). Positive PCNA staining was only observed in the uteri of two animals captured in May. There was a significantly positive correlation between plasma progesterone concentrations and the thickness of the endometrium (rho=0.589, P<0.05). There were also significantly positive correlations between the progesterone to oestradiol-17beta ratio (P4/E2 ratio) and the thickness of the endometrium (rho=0.710, P<0.05), and between the P4/E2 ratio and the ratio of the uterine gland area in the endometrium (rho=0.626, P<0.01). These data suggest that the corpus luteum is formed during or just after the breeding season and that the cells in the endometrium and the uterine glands, which proliferate in the early breeding season, grow and develop under the influence of progesterone and oestradiol-17beta during the period of delayed implantation in Japanese black bears.