Evidence that the photoperiod controls the annual changes in testosterone secretion, testicular and body weight in subtropical male goats

The aim of this study was to determine whether the reproductive seasonality of local male goats from subtropical Mexico (26 degrees N) is controlled by photoperiod. The control group (n = 7) remained in an open shed under natural daylight. The two experimental groups (n = 6 each) were placed in light-proof buildings and exposed for 2 years (yr) to alternations of 3 months (mo) of long days and 3 mo of short days. One group was first exposed to long days and the other one to short days. Body and testicular weights were determined every 2 wk. Blood samples were obtained weekly to determine testosterone plasma concentrations. In the control group, the body weight exhibited variations (P < 0.0001) and it increased during the non-breeding season. In both treated groups, long days stimulated weight gain and short days inhibited it (P < 0.0001). In the control group, testicular weight displayed variations (P < 0.0001), and high values were registered in June. In the treated groups, a testicular weight reduction occurred 6-9 mo after the onset of the study. Afterwards, the changes in testicular size varied according to daylength (P < 0.01). The pattern of plasma testosterone concentration in the control group varied over the study (P < 0.0001) and the levels were higher from May-June to November. In both treated groups, the changes in testosterone secretion occurred according to photoperiod changes (P < 0.0001). Short days enhanced testosterone secretion one photoperiodic cycle after the onset of the study and long days inhibited it. Local male goats from subtropical Mexico are sensitive to photoperiodic changes and this environmental cue may control the timing of the breeding season in natural conditions.     

Annual cycle of liveweight and reproductive changes of farmed male fallow deer (Dama dama) and the effect of daily oral administration of melatonin in summer on the attainment of seasonal fertility

Entire bucks (N = 7) exhibited pronounced liveweight gains over spring and summer months (October-February), to reach a peak mean weight of 59.8 kg, and rapid liveweight losses over the rutting period (April-May) with a minimum mean liveweight of 54.2 kg. Mean neck girth and serum testosterone levels increased during late summer (January-March) and peaked at 387 mm and 12 ng/ml respectively immediately before the onset of the rut (April). Thereafter both measures declined during winter and spring months (June-December). Bucks castrated prepubertally (N = 11) exhibited similar but less pronounced changes in mean liveweight and neck girth, in the absence of any change in testosterone secretion. Peak mean testicular diameter of entire bucks (39 mm) occurred immediately before the rut and was followed by testicular regression over winter and spring months (June-November), such that the testes attained their minimum mean size of 18 mm diameter in early summer (November). Motile spermatozoa were absent from ejaculates collected in summer (November 1983, 1984; January 1984). However, ejaculates collected pre-rut (late March), immediately post-rut (June) and in early spring (September) contained successively increasing numbers of motile spermatozoa. A further 14 polled, entire bucks were given orally 5 mg (N = 7; Group A) or 20 mg (N = 7; Group B) melatonin at 15:30 h daily from 1 December 1983 to 14 January 1984 (45 days). Seven control bucks (Group C) received vehicle ration only. The measurements taken for bucks in Groups A and B were not significantly different (P greater than 0.1) on any sampling date and the data for these 2 groups were pooled. Mean serum testosterone concentrations and mean ejaculate volume were not significantly different between melatonin-treated and control bucks on any sampling date, although other measures exhibited significant differences (P less than 0.05) at various treatment or post-treatment dates: melatonin-treated bucks showed a transiently greater increase in neck muscle development during and immediately after treatment, a slight retardation of liveweight gain between 45 and 75 days after treatment, an earlier peak in maximum mean testicular diameter and an earlier onset of sperm presence in ejaculates.     

Season of birth modifies puberty in female and male goats raised under subtropical conditions

In seasonal goats and sheep breeds, onset of puberty is modified by the season of birth. As adult does and bucks from subtropical Mexico display seasonal variation in their reproductive behaviour, this study was carried out to determine the effect of season of birth on puberty. Three groups of each sex born in January, May and October were used. During the seasons, does and bucks were weaned at an age of 30 days and offered ad libitum alfalfa hay and 100 g of commercial concentrate. In the female kids, the onset of ovulatory activity was determined by progesterone plasma concentrations once in a week from 3 months of age until the onset of puberty. In the male kids, the onset of puberty was individually recorded by observing the ability to mount and intromit an induced oestrous female goat aged 3 months and the presence of spermatozoa in the ejaculate obtained in an artificial vagina 1 week after the first mount. In female kids, there was an effect of the season on the date of first ovulation (P < 0.001). In the May group, ovulatory activity commenced at an earlier age (201 ± 3 days) compared with January (264 ± 5 days) and October (344 ± 5 days) groups (P < 0.001). In the January group also, the ovulatory activity commenced earlier than the October group (P < 0.001). In males, an effect of the season of birth on the first mounting was observed (P < 0.001). The male kids that were born in May (111 ± 3) and October (112 ± 5 days) attained puberty earlier than those born in January (131 ± 4 days; P < 0.001). The time of onset of puberty did not differ between groups of May and October. All males showed the presence of spermatozoa in the first ejaculate obtained 1 week after the first mount. The spermatozoa in all ejaculates were immobile. It was concluded that the season of birth modified the onset of puberty in both genders, but these modifications were more pronounced in the female than in the male kid goats.     

Continuous light after a long-day treatment is equivalent to melatonin implants to stimulate testosterone secretion in Alpine male goats

In rams, artificial long days followed by continuous light stimulate testosterone secretion during the non-breeding season. The objective of this study was to determine whether artificial long days followed by continuous light could stimulate testosterone secretion in Alpine bucks as well as in those exposed to long days followed by a melatonin treatment. All bucks were kept in shaded open pens. Control males were exposed to natural photoperiod conditions (n=5). Males of the two experimental groups were exposed to 2.5 months of long days from 1 December (n=5 each). On 16 February, one group of males was exposed to 24 h of light per day until 30 June; the other group was exposed to natural variations of photoperiod and received two s.c. melatonin implants. Testicular weight was determined every 2 weeks, and the plasma testosterone concentrations once a week. In the control and the two photoperiodic-treated groups, a treatment×time interaction was detected for testicular weight and plasma testosterone concentrations (P<0.001). In control bucks, testicular weight increased from January and peaked in June, whereas in both photoperiodic-treated groups, this variable increased from January, but peaked in April, when the values were higher than in controls (P<0.05). In the control group, plasma testosterone concentrations remained low from January to June, whereas in both photoperiodic-treated groups, this variable remained low from January to March; thereafter, these levels increased in both photoperiodic-treated groups, and were higher than controls in April and May (P<0.05). We conclude that continuous light after a long-day treatment stimulate testosterone secretion in Alpine male goats during the non-breeding season as well as the long days followed by a melatonin treatment. Therefore, continuous light could replace the implants of melatonin.     

Seasonal variation in serum testosterone, testicular volume, and semen characteristics in the coyote (Canis latrans)

The coyote is a seasonally breeding mammal, with most copulations occurring between December and April (depending on location). The objective of this study was to characterize seasonal changes in serum testosterone concentrations, testicular volume, and ejaculate quantity and quality in captive male coyotes. There were seasonal differences in testicular volume, with the greatest volume (20.2+/-5.4cm2), mean+/-S.E.M.) in February, corresponding with peak breeding season. Circulating serum testosterone concentrations peaked (3.31+/-0.9 ng/mL) during January and were positively correlated (P< or =0.001, r=0.413) with testicular volume. Ejaculate volume (1.67+/-0.4 mL) and sperm concentration (549.2 x 10(6)+/-297.7 spermatozoa/mL) both peaked during January and February, consistent with the height of the breeding season. Ejaculate volume and sperm concentrations were positively correlated with testicular size (r=0.679, P< or =0.001 and r=0.499, P< or =0.001, respectively) and with serum testosterone concentrations (r=0.368, P< or =0.01 and r=0.208, P< or =0.05). Progressively motile, viable, and morphologically normal spermatozoa fluctuated seasonally, peaked (90.4+/-4.5, 84.8+/-4.1, and 87.9+/-2.9%) during the breeding season, and then subsequently declined (period of aspermatogenesis). All three of these end points were positively correlated with testicular size (r=0.589, P< or =0.001; r=0.586, P< or =0.001; and r=0.469; P< or =0.001) and serum testosterone (r=0.167, P< or =0.05; r=0.190, P< or =0.05; and r=0.221, P< or =0.01). In conclusion, there were intricate relationships among testosterone concentrations, testicular volume, and the production of both functionally intact and morphologically normal spermatozoa.     

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.     

Age-related changes in body weight,scrotal size and plasma testosterone levels in buffalo bulls (Bubalus bubalis)

Body weight, testicle size and peripheral testosterone concentrations were measured in 35 water buffalo bulls at 5, 15, 17, 21, 25 and 38 months of age. These parameters were studied in all animals during the same month (October), so the changes due to age were independent of changes in photoperiod and temperature. Body weight increased linearly with age. The testicular size measured in terms of scrotal circumference as related to age, showed a curvilinear increase; the average rate of testicular growth was maximum between 15 and 25 months. Plasma testosterone levels were low between 5 and 21 months. A significant rise in plasma concentration of testosterone was observed at 25 months reaching peak levels at 38 months. The mean age of sexually mature bulls at the time of first ejaculation of semen with motile sperm, was 24.9±0.9 months (n=9). It has been concluded that in the Nili-Ravi buffalo bulls the sexually quiescent period (prepubertal) extends up to 15 months of age and sexual maturation as indicated by the presence of motile sperm in the ejaculate is attained at about 25 months.     

Seminal carnitine and acetylcarnitine content and carnitine acetyltransferase activity in young Maremmano stallions

The reproductive characteristics and seminal carnitine and acetylcarnitine content as well as carnitine acetyltransferase activity of young Maremmano stallions (n=25) are reported. The stallions were subjected to semen collection in November and January; in each trial two ejaculates were collected 1h apart. The total motile morphologically normal spermatozoa (TMMNS) and the progressively motile spermatozoa at collection and during storage at +4 degrees C were evaluated. Seminal L-carnitine (LC), acetylcarnitine (AC), pyruvate and lactate were measured using spectrophotometric methods, whereas carnitine acetyltransferase activity was measured by radioenzymatic methods. Since there were no major significant differences in seminal and biochemical characteristics between the November and January trials, data were also pooled for the first and second ejaculates. Significant differences (P<0.001) were observed between the first and second ejaculates for sperm count (0.249+/-0.025 versus 0.133+/-0.014x10(9)/ml), total number spermatozoa by ejaculate (12.81+/-1.23 versus 6.36+/-0.77x10(9)), progressively motile spermatozoa (48.6+/-3.0 versus 52.6+/-3.0%) and TMMNS (3.35+/-0.50 versus 2.02+/-0.37x10(9)). In the raw semen the LC and AC were significantly higher in the first ejaculate than in the second (P<0.001), whereas, pyruvate and pyruvate/lactate ratio were higher in the second ejaculate (P<0.05). Seminal plasma AC and LC concentrations resulted higher in the first ejaculate (P<0.001). The pyruvate/lactate ratio was higher in the second ejaculate (P<0.05). Both raw semen and seminal plasma LC and AC concentrations were positively correlated with spermatozoa concentration (P<0.01); in raw semen AC was also correlated to TMMNS (P<0.01). Lactate levels of raw semen was correlated to progressively motile spermatozoa after storage (P<0.01). In the second ejaculate, significant correlations were also observed among AC/LC ratio in raw semen and progressively motile spermatozoa after 48 and 72h of refrigeration. Furthermore, AC levels were correlated to lactate concentration. The positive correlation between LC, AC and spermatozoa concentration, and between AC and TMMNS indicated carnitine as potential semen quality marker. Moreover, the correlation between AC/LC ratio and progressive spermatozoa motility after refrigeration, suggests that carnitine may contribute towards improving the maintenance of spermatozoa viability during in vitro storage.     

Length of postpartum anestrus in goats in subtropical Mexico: effect of season of parturition and duration of nursing

The aim of this study was to determine whether season of birth and length of nursing affected the duration of postpartum anestrus in Creole female goats maintained on a constant plane of nutrition in subtropical Mexico. Three experiments were conducted in the Laguna region in the State of Coahuila, Mexico (26 degrees N). In the first experiment, 34 goats gave birth in January; in the second, 31 females gave birth in May; and in the third, 22 goats kidded in October. At parturition, females were allocated to 1 of 3 groups based on body weight and date of parturition: kids were weaned at 2, 30 or 90 d according to their group. After weaning, females were milked manually once a day until the end of the study. All animals were kept in a shed and were fed alfalfa ad libitum and given 200 g of concentrate daily. Starting 1 wk after parturition, estrous behavior was detected twice daily using an apron-bearing male, and blood samples were obtained twice weekly to determine ovarian activity from the plasma progesterone levels. A strong effect of month of parturition was found on the duration of postpartum anestrus (P < 0.0001), which was longer in females kidding in January (about 200 d) than in those kidding in May (about 100 d) or October (about 50 d). A tendency for an interaction between season of parturition and length of nursing was observed in the length of anovulation (P < 0.07): for parturition in October, anestrus was longer when kids were weaned after 90 d than after 2 or 30 d (P < 0.01). Season of parturition also affected dates of reinitiation of ovulatory and estrous activity (P < 0.001). Proportions of normal, short and long cycles and of associations between estrous and ovulations were not influenced by season of parturition or the age of weaning. These data demonstrate that in subtropical latitudes, season of parturition can dramatically influence the duration of postpartum anestrus independently of the availability of food.     

Testicular endocrine function, seasonality and semen quality of the stallion

To gain further information on gonadal function of the stallion, concentrations of testicular steroids in blood plasma (bpl) and seminal plasma (spl) and their distribution in the ejaculate were determined. Blood and semen samples from a total of 11 stallions were collected from November to July. Estrone (E1), estrone sulfate (E1S), estradiol-17beta (E2beta) and testosterone (T) were determined in bpl and spl, and in addition androstenedione (A), dehydroepiandrosterone (DHEA) and 5alpha-dihydrotestosterone (5alpha-DHT) were measured in spl. At certain points of time, aliquots of an ejaculate were centrifuged, washed and the distribution of E1, E1S, E2beta and T into seminal plasma and the sperm fraction was assessed. Hormone assay was by RIA, partly after prior separation by HPLC. Mean concentrations (X(g) x DF) were as follows: E2beta (bpl) 31.1 (1.16), (spl) 24.2 (1.42) pg ml(-1); E1 (bpl) 143.3 (1.21), (spl) 117.7 (1.53) pg ml(-1); E1S (bpl) 157.3 (1.44), (spl) 2.92 (1.42) ng ml(-1); T (bpl) 570.6 (1.43), (spl) 23.1 (1.68) pg ml(-1); A (spl) 17.9 (1.39) pg ml(-1); DHEH (spl) 12.4 (1.51) pg ml(-1); 5alpha-DHT (spl) 9.7 (1.29) pg ml(-1). Except for E2beta and A in seminal plasma, a seasonal pattern was established for all other steroids with lowest mean values occurring from November to April. From the semen parameters determined, only motility was correlated to season. There was a higher correlation among oestrogen in blp than in spl and the only correlation identified between oestrogenic and androgenic steroids was between T and E2beta in blp. In spl, T was correlated with A and 5alpha-DHT. T was the dominant free steroid in bpl while it was E1 in spl; T and E1S concentrations were about 23- and 54-fold lower in spl compared to bpl with E1S, however, showing the highest absolute values in both fluids. In the fractionated ejaculate an association of free oestrogens, particularly E2beta, with spermatozoa was observed.     

Seasonal changes in epididymis and the effects of FSH and testosterone in the spiny-tailed lizard,Uromastix hardwicki

Seasonal changes in epididymal weight and histology were studied in relation to testicular function in the adult spiny-tailed lizard, Uromastix hardwicki, over a period of 1 year. The eipdidymal weights, tubular diameter, and epithelial height increased in March, reaching a peak in April. This peak coincided with sperm maturation, elevated plasma testosterone levels, and release of sperm into the epididymis. The epididymal weights decreased in May following a sudden regression of the testis early in the month. The epididymal weights decreased further during June and remained low until February. The diameter of the duct and the height of the epithelial cells also decreased in May and the epididymal epithelium maintained a low histological profile from June to February. The fall testicular recrudescence was not accompanied by a change either in the weight or the histological structure of the epididymis. Administration of oFSH (0.1 mg) daily for 7 days during the sexually quiescent period induced a significant increase in the weight of the epididymis and epithelial height of the duct. Administration of testosterone alone, (2.0 mg) daily for the same period and under identical conditions, did not induce a change in the weight of epididymis or its histology. A possible permissive role of gonadotrophin in the hormonal regulation of the lizard epididymis has been suggested.     

Seasonally activated spermatogenesis is correlated with increased testicular production of testosterone and epidermal growth factor in mink (Mustela vison)

Seasonal changes in spermatogenesis were studied with respect to testicular production of both testosterone and epidermal growth factor (EGF) in mink. The testes were collected in November (n = 15; testis recrudescence), February (n = 15; before breeding season), March (n = 14; breeding season), and May (n = 11; testis involution) and the following parameters of testicular activity were quantified: testicular mass, number of testicular spermatozoa, percentages of haploid, diploid, and tetraploid (G2/M-phase) cells and content of testosterone and EGF. The growth factor was immunohistochemically localized in the parenchyma. Testis mass, spermatogenic activity, and the production of both testosterone and EGF were maximal in March, but were not significantly different from the levels in February. The correlation between testis weight and sperm per testis was r = 0.825 (P < 0.001). Testosterone and EGF levels were correlated to each other (r = 0.78; P < 0.001) and had significant positive correlations to testis mass, number of sperm and proportion of haploid cells; and negative correlations to percentages of mitotic cells. EGF was localized in interstitial cells and in the luminal region of seminiferous tubules, where it occurred during the last steps of spermiogenesis. We inferred that intensified seasonal spermatogenesis was stimulated by testosterone and by autocrine/paracrine effects of EGF.     

Investigations on reproductive physiology in the male Eurasian lynx (Lynx lynx)

This study characterized (in vivo) morphological and functional parameters of reproductive organs of adult male lynx (n = 3) prior to, during, and after the breeding season (n = 3). Size and morphology of the reproductive tract were monitored by transcutaneous (testes) and transrectal (accessory sex glands) ultrasonography. Semen was collected by electroejaculation. Ejaculate volume, sperm number, motility, and morphology of spermatozoa as well as testosterone concentrations in blood serum and feces were evaluated. The testes and prostate had seasonal changes in size and echotexture. The mean (+/- S.D.) maximum and minimum testicular volume were 2.8 +/- 0.8 cm3 and 1.5 +/- 0.3 cm3, respectively. Fecal testosterone concentrations were highest in February (1240 +/- 393 ng/g feces), with a second increase in May (971 +/- 202 ng/g feces), but concentrations were lowest in January (481 +/- 52.9 ng/g feces). Ejaculate volume, total sperm number and percentage of motile, and intact spermatozoa were maximal in March (the middle of the breeding season). In one of the eight litters, multiple paternity was proven; however, in the remaining seven litters, all 16 cubs were sired by the same male. This particular male had the most developed and active testes and best semen quality, which may be important for sperm competition.     

Seasonal changes in plasma testosterone and ejaculatory capacity in squirrel monkeys (Saimiri sciureus)

Seasonal changes in body weight, plasma testosterone and ejaculatory capacity were observed in five intact and two testosterone-implanted castrated squirrel monkeys for a total of 13 months. Electroejaculation was employed for obtaining data concerning ejaculation. In the intact animals, there were significant increases in body weight, ejaculate volume and plasma testosterone during the breeding season. With the exception of one animal, there was also a decrease in ejaculation latency during the season. Seasonal differences in the sperm count and sperm motility were not observed. Testosterone-implanted castrates showed changes in both ejaculate volume and ejaculation latency similar to those seen in intact monkeys during the breeding season. The body weight and plasma testosterone of the castrates remained quite constant throughout the year. Supported by NIH grants HD 00778, MH 21178 and MH 23645.     

FUNCTIONAL REDUCTION OF THE SOUTHERN MINKE WHALE (BALAENOPTERA ACUTOROSTRATA) TESTIS DURING THE FEEDING SEASON

Seasonal variation in reproductive activity in the male southern minke whales was investigated. The animals were killed and collected during the feeding season (December-March) in the Antarctic Ocean in the eastern part of Area III (35°E-70°E, south of 60°S) and Area IV (70°E-130°E, south of 60°S). Blood samples, testes, epididymides, and vasa deferentia were collected from 62 males, which had testes weighing over 400 g each. Changes in testicular morphology and plasma testosterone, estradiol-17β and LH concentrations measured by enzyme immunoassay were investigated. Reduction of testicular function associated with different capture periods was found in the summer season. From December to March, body length and body weight remained steady, but decreases in testicular weight, epididymal weight, and testicular volume were found in February. During the same period, plasma testosterone concentration also declined. A significant decrease in the number of germ cells continued during the period of feeding season. An increase in area of seminiferous tubule tended to proceed in a number of germ cells. These changes reflected the percentage of spermatozoa in the vasa deferentia ; in particular, motile spermatozoa were observed in December. Based on morphological observation, spermatogenesis had also declined. These results indicate regulation of testicular function by testosterone, as in terrestrial mammals. A gradual decrease of testicular function occurred during December-January.     

Seasonal variation in reproductive physiological status in the Iberian ibex (Capra pyrenaica) and its relationship with sperm freezability

The present work examines the relationship between seasonal changes in testicular function, accessory gland size, and horn growth in Iberian ibexes, as well as the relationship between these changes and the resistance of ibex spermatozoa to freezing-thawing. The size of the bulbourethral glands and seminal vesicles showed pronounced monthly variation (P < 0.001), which was correlated positively with the plasma testosterone concentration (P < 0.001) and scrotal circumference (P < 0.001). The size of the accessory sex glands peaked during the autumn. Overall, semen quality was markedly improved during autumn and winter. When horn growth was at a minimum during autumn and winter, semen quality and accessory gland size were all increased compared to in spring and summer. However, increased plasma testosterone levels in the autumn were strongly associated with reduced sperm freezability; thus, the cryosurvival of spermatozoa collected during the autumn was poorer than at other times of the year. In winter, however, when the plasma testosterone concentration fell to baseline, the negative effects of cryopreservation on the percentage of motile spermatozoa and on the integrity of the plasma membrane of frozen-thawed sperm cells were significantly less intense (P < 0.05). These findings show a clear relationship between the functional and morphological status of the different parts of the reproductive tract that optimises reproductive function during the breeding season in the ibex male. They also show that winter is the most suitable season for the collection and cryopreservation of ibex spermatozoa.     

Effects of season and breed on sperm acrosin activity and semen quality of boars

Acrosin activity and semen quality (sperm concentration, ejaculate volume and number of spermatozoa) were assessed from March 1997 to March 1998 in semen of Large White, Pietrain and Duroc x Pietrain boars. Semen quality varied with season, including high production of spermatozoa in autumn and winter and low production in summer. Semen quality also differed across breeds. Acrosin activity of boar spermatozoa was not affected by breed (range 3.16-3.32 mU/10(6) spermatozoa), but exhibited distinct seasonal changes. Monthly changes in acrosin activity were parallel to changes in number of sperm in the ejaculate from November to March. On the other hand, dramatic changes in acrosin activity between July and October (range 1.85-4.59 mU/10(6) spermatozoa) were not paralleled by similar changes in number of ejaculated sperm. These fluctuations in acrosin activity may reflect either changes in sperm acrosin production or disturbances to sperm membranes, probably related to effects of high summer temperatures during spermatogenesis. Results confirmed seasonal and breed-related differences in boar semen quality characteristics.     

Testicular mitosis, meiosis and apoptosis in mink (Mustela vison) during breeding and non-breeding seasons

Testes of mink were compared between the breeding (March) and non-breeding seasons with the start (November) and cessation (May) of spermatogenic activity. Testicular mass and spermatozoa per gram testis were assessed. Percentages of haploid (1C), diploid (2C) and tetraploid (4C) cells were monitored using DNA flow cytometry and the proportions of somatic and spermatogenetic cells were determined after selective labelling of somatic cells with a vimentin antibody. Apoptosis was examined by cell death detection ELISA, and testosterone concentrations were measured with an enzyme-immunoassay. The significantly higher testis mass during the breeding period coincided with higher numbers of testicular spermatozoa per gram testis and peak of testicular testosterone concentration in comparison with non-breeding periods. The proportions of 1C, 2C and 4C cells showed corresponding strong differences between these periods with the maximum of 1C cells during breeding. The proportions of testicular cells in G2-M phase of mitosis were very low during the period of peak spermatogenesis; they were markedly increased in the time of autumnal resumption in November but were even higher during testis involution in May. However. the meiotic transformation (1C:4C ratio) is maximal in March. The total as well as the relative proportions of spermatogenic and somatic cells differed significantly not only between breeding and non-breeding periods but also between the periods at the start and at the end of active spermatogenesis. The intensity of apoptosis was also seasonally dependent. The highest level in March indicates a stimulated apoptosis even during the breeding period. In conclusion, the production of spermatozoa in mink is intensified by enlargement of gonads as well as enhanced efficiency of spermatogenesis during breeding. In this time, the testosterone concentration and the meiotic transformation show high levels, but the mitotic activity of spermatogenic cells is already significantly diminished and an intensified apoptosis seems to precede the forthcoming testis involution after breeding. The results suggest that the regulation of seasonal testicular activity is characterised by co-ordinated shifts in the relationships between mitosis, meiosis, apoptosis and testosterone production.     

Seasonal spermatogenic cycle and morphology of germ cells in the viviparous lizard Mabuya brachypoda (Squamata,Scincidae)

We describe seasonal variations of the histology of the seminiferous tubules and efferent ducts of the tropical, viviparous skink, Mabuya brachypoda, throughout the year. The specimens were collected monthly, in Nacajuca, Tabasco state, Mexico. The results revealed strong annual variations in testicular volume, stages of the germ cells, and diameter and height of the epithelia of seminiferous tubules and efferent ducts. Recrudescence was detected from November to December, when initial mitotic activity of spermatogonia in the seminiferous tubules were observed, coinciding with the decrease of temperature, photoperiod and rainy season. From January to February, early spermatogenesis continued and early primary and secondary spermatocytes were developing within the seminiferous epithelium. From March through April, numerous spermatids in metamorphosis were observed. Spermiogenesis was completed from May through July, which coincided with an increase in temperature, photoperiod, and rainfall. Regression occurred from August through September when testicular volume and spermatogenic activity decreased. During this time, the seminiferous epithelium decreased in thickness, and germ cell recruitment ceased, only Sertoli cells and spermatogonia were present in the epithelium. Throughout testicular regression spermatocytes and spermatids disappeared and the presence of cellular debris, and scattered spermatozoa were observed in the lumen. The regressed testes presented the total suspension of spermatogenesis. During October, the seminiferous tubules contained only spermatogonia and Sertoli cells, and the size of the lumen was reduced, giving the appearance that it was occluded. In concert with testis development, the efferent ducts were packed with spermatozoa from May through August. The epididymis was devoid of spermatozoa by September. M. brachypoda exhibited a prenuptial pattern, in which spermatogenesis preceded the mating season. The seasonal cycle variations of spermatogenesis in M. brachypoda are the result of a single extended spermiation event, which is characteristic of reptilian species. J. Morphol. © 2012 Wiley Periodicals, Inc.     

Spermatozoa output, testicular sperm reserve and epididymal storage capacity of the Red Sokoto goats indigenous to northern Nigeria

Fifteen Red Sokoto goats (bucks) aged 2 to 2 1 2 years with a mean body weight of 17.80+/-1.24 kg were used for studying daily spermatozea output, testicular and epididymal sperm reserves. Semen ejaculates were obtained from each buck and evaluated daily for six weeks. Semen characteristics were as follows: volume, 0.72+/-0.91ml; colour, milky/creamy; sperm concentration/ml, 0.61+/-0.05 x 10(9); mass motility, 3.80+/-0.33; individual metility, 77.50+/-5.60; and normal sperm morphology, 80.00+/-10.50. Mean scretal circumference was 21.80+/-0.29. Mean testicular and spididymal (capita, corpora and caudas) weights (gm) were 83.74+/-5.33, 7.27+/-0.63, 2.22+/-0.23 and 6.13+/-0.73 respectively. Corresponding sperm reserves were 44.32+/-5.79, 8.82+/-1.95, 4.99+/-0.86 and 45.64+/-7.87 x 10(9). Scrotal circumference was positively correlated to testicular weight (r = 0.86), testicular spermatids (r = 0.77), and caudas spermatozoa (r = 0.83).