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P. A. RACEY

The viability of spermatozoa after prolonged storage in the female reproductive tract has been established in several species of hibernating bats (Wimsatt, 1944; Hiraiwa & Uchida, 1956; Racey & Kleiman, 1970). Spermatozoa are, however, also stored in the cauda epididymidis of male bats during winter (Courrier, 1927). Although mating is initiated soon after the completion of spermatogenesis in late summer, its occurrence has frequently been reported during winter (Wimsatt, 1945) and spring (Moffat, 1922), and Strelkov (1962) showed that an increasing proportion of four vespertilionid species were inseminated as hibernation progressed.

Investigation of the viability of spermatozoa stored in the cauda epididymidis of hibernating bats has only recently become possible now that one species, the noctule (Nyctalus noctula), is maintained and bred in the laboratory

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P. A. RACEY

Summary.

The reliability of palpation, weighing, radiography and the state of the nipples is discussed in relation to the determination of pregnancy in the pipistrelle.

In two series of pregnant pipistrelles, the mean length of gestation has been extended by the induction of torpor at different stages during pregnancy and this extension is in good agreement with the period of torpor. Pregnancy is thought to be extended in response to adverse conditions in the natural environment, and the present concept of a standard gestation period for these heterothermic animals is therefore questioned.

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P. A. Racey

Summary. Seasonal changes in testicular and plasma testosterone levels and in androgen-dependent organs were determined in moles breeding at 53°N. Although the testes contain up to 30 times more testosterone during spermatogenesis than during sexual quiescence, appreciable quantities of this hormone are present during late summer and early autumn. Annual spermatogenesis lasts for only 2 months, but in some moles spermatozoa remain in the epididymis for up to 3 months after the testes have begun to involute, and may therefore be available to inseminate females coming into a second oestrus.

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P. A. RACEY

Summary.

Spermatogenesis took place in noctule bats during summer; spermatozoa were released from the testis in August and September, and the testes then involuted. Although no more spermatozoa were produced, they continued to be stored in the cauda epididymidis for the duration of winter.

The testosterone content of the testes rose with the progress of spermatogenesis from 10 ng/pair in May to 847 ng/pair in August. The concentration of the hormone in the blood plasma paralleled this increase, rising from 4·7 ng/ml to 134 ng/ml over the same period. Testosterone levels were maintained during autumn, when most mating took place, but decreased during the subsequent winter period of sperm storage. The weights of the accessory glands and their fructose content were maintained over this period.

It appears that the maintenance of active accessory glands of reproduction and of fertile spermatozoa in the epididymis has a comparatively low androgen requirement in noctule bats.

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P. A. Racey

The prolonged storage of spermatozoa by bats was first reported by Pagenstecher in 1859, and subsequently attracted the attention of several early comparative anatomists and histologists whose work has been thoroughly reviewed by Hartman (1933). Hartman was initially sceptical about the fertilizing capacity of the stored spermatozoa (Hartman & Cuyler, 1927) and it was left to Wimsatt (1942, 1944) to undertake the first critical experiments of isolating inseminated females from males and observing the developing embryo in the reproductive tract after arousal from hibernation in spring. Further work, reviewed by Wimsatt (1969), has shown that sperm storage is one facet of the complex reproductive adaptations of bats living in temperate latitudes where a period of hibernation occurs during prolonged oestrus.

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P. A. Racey

Wellcome Institute of Comparative Physiology, Zoological Society of London, Regent's Park, London NW1 4RY, U.K.

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Fumie Suzuki and P. A. Racey

Summary. In sexually active common shrews (Sorex araneus) the rete testis is a simple sac-like structure situated superficially between the equator and the anterior pole of the testis, and its epithelium contains glycogen-rich cells. In the ductuli efferentes, the tight junctions of the epithelial cells are poorly developed. The epididymis can be divided cytologically into initial, middle and terminal segments, and some variations are apparent in the fine structure of the principal cells throughout the duct. In the initial segment and in the most proximal part of the middle segment, mitochondrion-rich cells occur sporadically in the epithelium. The ductus deferens is divided into three anatomical regions, a tortuous pars epididymica, a straight middle portion, and an ampullary region. The distal half of the straight portion is distended, and appears to function, together with the terminal segment of the epididymis, as a sperm reservoir.

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Fumie Suzuki and P. A. Racey

Summary. Seasonal changes of the testicular interstitial tissue were studied by electron microscopy. During the breeding season in spring, clusters of Leydig cells are surrounded by wide lymphatic sinusoids. In sexually quiescent moles, these sinusoids collapse, and the abundant Leydig cells become closely packed and occupy most of the testis. During sexual activity, the Leydig cells contain abundant smooth endoplasmic reticulum (SER), mitochondria with tubular cristae, and lipid droplets. Some areas of the cytoplasm are occupied exclusively by tubular SER, arranged in parallel. During regression the SER appears tortuous, and large lipid droplets are found in the cytoplasm, although these gradually become smaller. During the long period of sexual quiescence, the size and abundance of Leydig cells and the appearance of SER, lipid droplets and mitochondria were similar to those observed during sexual activity.

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Fumie Suzuki and P. A. Racey

Summary.

The epididymis of the European mole (Talpa europaea) was studied by light and electron microscopy. In the sexually active animal, spermatozoa mature during their passage through the epididymis and the structure of the cells lining the duct suggests a clear regional division into initial, middle and terminal segments. Numerous intra-epithelial vesicles were present in the distal part of the middle segment of sexually active moles and the lining epithelium in the terminal segment appeared to be secretory.

Variation in the sensitivity of different regions of the epididymis to androgens was apparent : the principal cells of the initial segment were morphologically active only during the peak of the breeding season in spring, while the cells of the terminal segment became active earlier and remained so for longer. During sexual regression, many autophagic vacuoles were found in the principal cells, and these became transformed into lipofuscin pigment granules. Cells heavily laden with these granules appeared concurrently in the lining epithelium. It is suggested that such cells may be involved in the regression of principal cells by means of heterophagic activity. A similar situation was also observed, but to a lesser extent, at the beginning of the breeding season.

Outside the breeding season, the organelles of the principal cells were poorly developed throughout the epididymis, and lipofuscin pigment granules remained in the principal and basal cells of adults. Such granules were seldom seen in immature animals.

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P. A. Fowler and P. A. Racey

Summary. Simultaneous telemetry of the body and testis temperatures of 8 hedgehogs was carried out during hibernation and during sexual reactivation in spring. Between October and January, when the testes were involuted, the body/testis temperature differential was variable, with mean daily testis temperatures up to 1°C warmer than body temperatures. From mid-February onwards, when plasma testosterone approached maximal concentrations, mean testicular temperatures stabilized 1 ·4 ± 0·2°C below body temperatures. During spermatogenesis testicular temperature of hedgehogs was significantly lower than body temperature. Over the euthermic body temperature range of 34·7–36·2°C, testicular temperatures varied from 34·0 to 34·9°C. Only at body temperatures over 36·2°C did testicular temperature reach 35°C. During spermatogenesis hedgehog testis temperatures are similar to those of many scrotal mammals.