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P. A. RACEY and D. M. POTTS

Summary.

Spermatozoa distend the uterus of the overwintering pipistrelle bat and their relationship with the uterine epithelium has been examined. The epithelium actively secretes PAS-positive material and spermatozoa are found orientated with their heads directed towards it over large areas. Electron microscopy has revealed that microvilli originating from the epithelial cells are commonly in contact with the cell membrane of the spermatozoa. It is suggested that this contact may constitute one of the pathways by which nutrient material from the endometrium is transferred to the stored spermatozoa and may account, in part, for the prolonged survival of the spermatozoa in this species. The relationship between spermatozoa and their storage organs is briefly reviewed.

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P. A. Racey and Susan M. Swift

Summary. Gestation length in a colony of pipistrelle bats varied by 10 days in two consecutive years when the weather conditions during early gestation differed appreciably. Plasma progesterone concentrations and corpus luteum volume increased during pregnancy to reach a maximum about 6 days before the first births. Pipistrelles maintained high body temperatures during pregnancy if the food supply was adequate. The rate of fetal development therefore appears to be determined by maternal body temperature, which becomes reduced by shortage of food in cold weather.

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M. E. Nicoll and P. A. Racey

Summary. Reproduction in female tenrecs was studied on Praslin Island (4°20′S, 55°45′E) in the Seychelles from November 1977 to September 1980. Dissection and histological examination of reproductive tracts revealed that each ovary is encapsulated in a bursa. Polyovular follicles were abundant and contained up to 5 oocytes. The occurrence of more implanted fetuses than corpora lutea (CL) indicated successful polyovuly in 25% of pregnancies. No antrum was observed during follicular growth at oestrus, and follicles were relatively small at maturation, reaching a maximum diameter of 570μm. Ovulation involves a gentle extrusion of the granulosa and ovum into the periovarian space. Spermatozoa were abundant in the female reproductive tract including the periovarian space at oestrus. Spermatozoa penetrated the loosely-packed theca of mature follicles and were present in CL, indicating that intrafollicular fertilization may occur. The relatively small CL formed by eversion, reaching a maximum size after implantation. Fusion of up to four CL occurred in the ovaries of 41% of pregnant females. Polyovulation in the tenrec was confirmed by the occurrence of 10·4 ± 0·5 (mean ± s.e.m.) CL and 9·7 ± 0·5 (mean ± s.e.m.) implantations. Resorption occurred in 74% of 19 dissectable pregnancies, occurring in both uterine horns in 26% of pregnancies. Coefficients of variation in weights of fetuses in each litter were 10·0–26·8%, with the largest value corresponding to 273% variation in fetus weights. Litter size in the Seychelles tenrecs was smaller than in the same species in Madagascar (17·1 ± 1·9 implantations) where the tenrec is native.

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P. I. Webb, J. R. Speakman and P. A. Racey

Summary. Oxygen consumption and evaporation were measured in a single pregnant pipistrelle bat during labour and parturition of twins, using an open-flow respirometry system. During 233 min of measurements, three distinct phases were noted, which we suggest represent prelabour, labour and grooming or suckling the young.

On the basis of this hypothesis, during labour and parturition, oxygen consumption was a maximum of 8·9% of daily energy expenditure, evaporation was 2·7% of daily water turnover, and total water loss was 5·5% of daily water turnover in free-living bats in early lactation.

We estimated that, for the mother and young combined, oxygen consumption associated with grooming and suckling would be equivalent to 37·5% of daily energy expenditure of the mother, if carried out continuously. Similarly, evaporation due to grooming and suckling would be equivalent to 16·4% of daily water turnover.

In terms of daily energy expenditure and daily water turnover, labour and parturition are therefore cheap, but grooming and suckling (even ignoring costs in terms of losses in the milk) are expensive.

Keywords: bat; labour; parturition; oxygen consumption; evaporation

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P. A. Racey, T. A. Uchida, T. Mori, M. I. Avery and M. B. Fenton

Summary. Copulation lasted for up to 46 min in little brown bats. Spermatozoa were stored in both the uterus and the utero-tubal junction, although intimate relationships between spermatozoa and the epithelium were particularly evident in the utero-tubal junction, and were established at the beginning of the period of sperm storage. Polymorphonuclear leucocytes were present in all uteri irrespective of whether or not they had been inseminated but were not generally present in the utero-tubal junction or oviduct. Engulfment of spermatozoa by the epithelial cells of the utero-tubal junction and by polymorphonuclear leucocytes in the uterine glands was evident soon after copulation. It is suggested that this may effect the removal of defective spermatozoa and allow luminal spermatozoa access to the spatially restricted storage sites.

Uninseminated female bats attempted to elicit copulation from torpid males, and were also observed adjacent to copulating pairs. Female bats also uttered copulation calls.

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I. C. Lamb, W. Strachan, G. Henderson, T. Atkinson, W. Lawson, G. G. Partridge, M. F. Fuller and P. A. Racey

Summary. Primiparous crossbred does were remated on Day 1 (n = 15) or 14 (n = 25) post partum and killed on Day 10 post coitum to assess their fertility. Blood samples were taken during the pre- (0–12 h post coitum) and post- (1–10 days post coitum) ovulatory periods and plasma was assayed for luteinizing hormone (LH), prolactin, oestradiol-17β and progesterone. Ovulation response was significantly greater (P < 0·01) and ovulation rate significantly lower (P < 0·001) in does mated on Day 1 than in those mated on Day 14 post partum. Does failing to ovulate on Day 14 post partum exhibited no preovulatory LH surge and had significantly lower (P < 0·05) premating concentrations of oestradiol-17β and prolactin than those ovulating at this time. No significant differences in hormone concentrations were observed during the preovulatory period between does ovulating on Days 1 and 14 post partum, with the exception of oestradiol-17β. Concentrations of this hormone were significantly lower (P < 0·01) in does mated on Day 1, at 1 h post coitum. We conclude that (i) fertility was affected by the remating interval after parturition, (ii) ovulation failure was associated with an absence of the preovulatory LH surge and a reduction in premating concentrations of oestradiol-17β and prolactin and (iii) the lower ovulation rate in early lactation was apparently caused by a reduction in ovarian competence to respond to the gonadotrophic stimulus.

Keywords: rabbit; remating; prolactin; oestradiol; progesterone