Testicular Sperm Reserves Research Articles

Evaluation of the cell population of the seminiferous epithelium and spermatic indexes of the bat Sturnira lilium (Chiroptera: Phyllostomidae).

Due to the scarcity of information about patterns of spermatogenesis in bats, this study aimed to provide information on the testicular activity of the bat Sturnira lilium along the annual seasons. Thus, a series of morphometrical and stereological analyses were made using the testes of adult S. lilium in order to achieve a better understanding of the sperm production dynamics. Light and transmission electron microscopy analyses were performed in testicular fragments of animals captured during dry and rainy seasons. The testes followed the pattern of organization described for other mammals, and there were no morphological differences between organs collected either in dry or in rainy seasons. Each tubular cross-section in stage 1 was made of 0.5 type-A spermatogonia, 4.4 primary spermatocytes in preleptotene/leptotene, 3.7 in zygotene, 11.9 in pachytene, 35.6 round spermatids and 8.5 Sertoli cells. The mitotic and meiotic indexes were 15.4 and 2.9 cells, respectively, while the spermatogenesis yield was 68.7 cells. The testicular sperm reserves was 37.61×106 cells, and daily sperm production per gram of testis averaged 209.68×106 cells, both highest averages occurring in the rainy season. S. lilium male bats have a continuous reproductive pattern, high spermatogenesis yield and low support capacity by the Sertoli cells.

Effects of alcohol consumption on the haematology and testis of mice experimentally infected with Trypanosoma brucei

Forty 6-week-old inbred albino mice were used to study the effect of alcohol consumption on haematology and testis of mice experimentally infected with Trypanosoma brucei (T. b. brucei). The forty mice were divided into four groups of 10 mice each. Groups 1 and 3 mice received graded levels of ethanol at 10, 20 and 30 % (v/v) in water for 1 week, 2 weeks and the rest of the experimental period, respectively. At day 29 of the experiment, mice in groups 1 and 2 (non-alcohol exposed) were infected intraperitoneally with 1.0 × 106 T. brucei in PBS-diluted blood. Group 4 mice served as control and were neither given alcohol nor infected with trypanosomes. The animals in all the groups were given water and commercial diet ad libitum. The alcohol-exposed infected mice had significantly (P < 0.01) higher levels of parasitaemia than the non-alcohol-exposed infected group. The control group had significantly (P < 0.01) higher body weights, packed cell volume, red blood cell, white blood cell counts and testicular sperm reserve than the other groups. These parameters were significantly (P < 0.01) lowest in the alcohol-exposed infected group when compared with the other groups. Microscopically, degeneration and necrosis of spermatogenic cells were observed in seminiferous tubules of the testes of alcohol-exposed and T. brucei-infected mice. Sections of testes of the mice exposed to alcohol alone and non-alcohol-exposed T. brucei-infected mice had seminiferous tubules with poor development of spermatogenic cells. It was concluded that alcohol exposure markedly increased the deleterious effects of T. brucei considering the increases in the haematological values and various lesions produced in testes of the experimental mice.

Effects of aqueous garlic (Allium sativum) extract on testicular morphology and function in lead nitrate (Pb(NO3)2)-treated albino rats

This study investigated the effects of aqueous garlic extract (Allium sativum) on testicular morphology and function in lead nitrate (Pb(NO3)2)-treated albino rats. Twenty four male albino rats, divided randomly into four groups of six rats per group, were used. Group A rats served as the control and received neither Pb(NO3)2 nor aqueous garlic extract (AGE) treatment. The treatments to the remaining three rat groups were as follows: group B, 300 mg/kg body weight of AGE; group C, 2 mg/kg body weight of Pb(NO3)2; and group D, 2 mg/kg body weight of Pb(NO3)2, and 300 mg/kg body weight of AGE 2 h later. Both the AGE and Pb(NO3)2 were orally given to these rats every 48 h for a period of 6 weeks. The testicular and epididymal (left and right sides) sperm reserves and the histomorphological features of the testes of the rats in the treatment groups were compared to the control rats. Results showed that testicular and epididymal sperm reserves were significantly (P < 0.05) reduced in rats that received only Pb(NO3)2 treatment. AGE ameliorated the changes in testicular morphology and function associated with Pb(NO3)2 treatment in group D rats. Garlic in this study enhanced spermatogenesis as evidenced from the significant (P < 0.05) increase in the epididymal (left and right sides) sperm reserves of the group B rats. This implies that garlic may serve as an agent that could be used in improving male fertility.

Testicular morphology and antispermatogenic effects of 2,4-dichlorophenoxyacetic acid (2,4-D) in male West African Dwarf (WAD) goats

This study investigated the testicular morphology as well as the gonadal and extra-gonadal sperm reserves of West African Dwarf (WAD) goats exposed to graded levels of 2,4-dichlorophenoxyacetic acid (2,4-D). Twenty male WAD goats of five goats per group were used for this study. Goats in groups A, B and C received low [75 mg/kg body weight (BW)], medium (100 mg/kg BW) and high (125 mg/kg BW) dose levels of 2,4-D, respectively. The group D goats served as the control. On day 112, goats in the four groups were sacrificed and the testicular and epididymal sperm reserves were determined. Histopathologic changes in the testis of the 2,4-D-exposed and control goats were also assessed. The mean number of spermatozoa in the testes and the various segments of the epididymides decreased significantly (p < 0.05) in all the treatment groups relative to the control. Combined testicular sperm reserve per millilitre for the treatment groups (group A—19.61 ± 2.63 × 108, group B—12.02 ± 1.02 × 108 and group C—9.95 ± 0.97 × 108) reduced significantly (p < 0.05) relative to the mean value (23.52 ± 4.43 × 108) of the control—group D. The total epididymal sperm reserve per millilitre in the treatment groups (group A—24.25 ± 4.19 × 108, group B—17.18 ± 2.57 × 108 and group C—17.88 ± 2.89 × 108) was also found to be significantly (p < 0.05) lower than the mean value (40.85 ± 11.24 × 108) for the control—group D. This reduction in the testicular and epididymal sperm counts of the 2,4-D-exposed WAD goats in this study suggest disruption in spermatogenic activity, which may lead to low productivity. Variable degrees of circulatory disturbances were observed in the testis sections of 2,4-D-exposed goats.

Testicular biometry and epididymal sperm reserve in local sheep of Kashmir valley

Testes with intact epididymis were collected from 10 adult local ram immediately after slaughter at abattoir. Measurements of testes and epididymis were taken as per standard procedure. Sperm reserve from three different segments of the epididymis was determined. Length, Breadth and thickness of the left testes and epididymis were slightly more than right one although no significant difference was recorded between the two. Testicular circumference was also found higher for left one than right. Total epididymal sperm reserve recorded was 36.24±0.68 billion, which comprised 15.64±0.42, 0.23±0.02 and 20.37±0.77 billion for caput, corpus and cauda epididymis respectively.

Gonadal and extra-gonadal sperm reserves and sperm production of pubertal rabbits fed dietary fumonisin B 1

The influence of fumonisin B 1 (a mycotoxin produced by Fusarium verticillioides) on sperm reserves and production of crossbred pubertal rabbits was studied using an experimental model that lasted 28 weeks. Forty-eight male rabbits, 7 weeks old and with average weight of 757.50 ± 0.50 g, were allotted to four dietary fumonisin B 1 concentrations of 0.13, 5.0, 7.5 and 10.0 mg kg −1 constituting diets 1 (control), 2, 3 and 4, respectively. The paired testes weight of rabbits fed diet 3 was significantly ( P < 0.05) higher than those fed diet 2 and the control. However, the epididymal weight was significantly ( P < 0.05) lower in rabbits fed the control diet as compared to others on test diets. The gonadal sperm reserves of the animals were significantly ( P < 0.05) reduced by the toxin with increased concentrations of the toxin in the diets. The sperm reserves per testis and per gram testis were significantly ( P < 0.05) higher in the control rabbits than those fed diets 3 and 4. The sperm reserves in caput, corpus and caudal epididymis declined significantly with each increase in the fumonisin concentration in the diets. The number of spermatozoa in total caput, corpus and cauda was significantly ( P < 0.05) higher in rabbits fed the control diet and the least in rabbits fed diet 4 containing 10.0 mg fumonisin B 1/kg. Extra-gonadal sperm reserves significantly decreased ( P < 0.05) in rabbits fed diets 3 and 4 compared to the control. The daily sperm production of the animals fed diets 2, 3 and 4 declined significantly to 67, 59 and 36% relative to those animals fed the control diet. This study suggests that exposure of breeding male rabbits to diets contaminated with fumonisin B 1 up to 7.5 mg fumonisin B 1/kg will depress testicular and epididymal sperm reserves and sperm production and potentially impair reproduction in the animals.

Effect of experimental feeding of Codiaeum variegatum leaves on growth, hematology, gonadal, and extra-gonadal sperm reserves of adult albino rats

Twenty-four male adult albino rats, weighing between 130 and 239 g, were randomly divided into four groups of six rats per group (A to D). The rats were fed either normal pelleted commercial feed containing 14.5% crude protein alone (group A) or feed supplemented with pulverized dry leaves of Codiaeum variegatum (garden croton) at the levels of 0.25% (B), 0.5% (C), and 1.0% (D). All four groups of rats were fed for 12 weeks, during which period clean water was provided ad libitum. Every 2 weeks, body weights of individual rats were taken and blood collected for hematology (packed cell volume (PCV), total and differential leukocyte counts). Hemoglobin concentration was determined at 4-week intervals. At the end of the 12-week study period, all rats were sacrificed; testes and epididymes of individual rats were weighed separately to calculate the organosomatic index for both organs. Thereafter, testicular and epididymal sperm counts were performed. Supplementing rat feed with C. variegatum leaves in treated groups (B, C, and D) resulted in reduced weight gain such that by the 12th week of study, the mean body weight of group D rats was significantly lower than that of the unsupplemented control (group A) rats. The testicular and epididymal organosomatic index for the different treatment groups were not significantly (P > 0. 05) different from the mean values for group A rats. The hematological evaluation of the rats showed that supplementation at any of the level used did not significantly (P > 0. 05) alter the mean PCV values. The mean total leukocyte and the mean absolute neutrophil counts (by the fourth week) for the treated groups were significantly (P 0.05) from the mean values for the control group. On the other hand, the mean epididymal sperm counts for the treated rat groups were significantly (P < 0. 05) lower than the mean values for the control in a dose-dependent pattern. This study has shown that feeding male rats in particular and probably other animals in general on the leaves of garden croton at a level as low as 0.25% level of supplementation has the tendency to stimulate the immune function of animals but could severely reduce the testicular and epididymal sperm reserve counts, thereby reducing the reproductive efficiency of male animals. These results recommend further studies in respect to the immunostimulating and spermatotoxic properties of the leaves of this plant.

Cell population indexes of spermatogenic yield and testicular sperm reserves in adult jaguars ( Panthera onca)

The intrinsic yield of spermatogenesis and supporting capacity of Sertoli cells are the desirable indicators of sperm production in a species. The objective of the present study was to quantify intrinsic yield and the Sertoli cell index in the spermatogenic process and estimate testicular sperm reserves by histological assessment of fragments obtained by testicular biopsy of five adult jaguars in captivity. The testicular fragments were fixed in 4% glutaric aldehyde, dehydrated at increasing alcohol concentrations, included into hydroxyethyl methacrylate, and were cut into 4 μm thickness. In the seminiferous epithelium of the jaguar, 9.2 primary spermatocytes in pre-leptotene were produced by “A” spermatogonia. During the meiotic divisions only 3.2 spermatids were produced by a primary spermatocyte. The general spermatogenic yield of the jaguar was about 23.4 cells and each Sertoli cell was able to maintain about 19.2 germ cells, 11 of them were round spermatids. In each seminiferous epithelium cycle about 166 million spermatozoa were produced by each gram of testicular tissue. In adult jaguars, the general spermatogenic yield was similar to the yield observed in pumas, greater than that observed for the domestic cat, but less compared to most domestic animals.

Testicular and epididymal sperm reserves and sperm production of pubertal boars fed dietary fumonisin B 1

Twenty-four male Large White weaning pigs of 8–9 weeks of age averaging 6.94 ± 0.26 kg were used to evaluate the effect of dietary fumonisin B 1 (FB 1) on sperm reserves and production of pubertal boars. The animals were randomly assigned to 4 diets containing 0.2, 5.0, 10.0 and 15.0 mg FB 1/kg constituting the control, diets 1, 2 and 3, respectively, in a 6-month feeding trial. Dietary FB 1 above 5 mg/kg significantly ( P < 0.05) reduced testicular and epididymal sperm reserves as well as the daily sperm production (DSP) per boar. The total caudal sperm reserves of the animals on diets 2 and 3 were about 70% of those on the control diet. The DSP of the animals on the control diet and diet 1 were significantly ( P < 0.05) higher than those on diets 2 and 3. The study revealed that male weaning pigs for breeding should not be exposed to dietary FB 1 higher than 5 mg/kg for no suppression in sperm production and reproductive performance.

The Effect Of Hexane Extract Of &lt;i&gt;Azidirachta indica&lt;/i&gt; Leaves On testicular Sperm Reserve In Mice

The 50% lethal dose (LD50) of hexane leaf extract of A indica solubilized in 10% tween 20 was determined as 182mg/kg body weight. 25 adult male albino mice (34.1 - 53) were randomly divided into five groups containing five mice each. The mice in groups 1-1V were given graded doses of the extract @ 1,7,3,3,6,7 and 8.33mg/kg body weight respectively by intraperitoneal route. They were treated 3 times a week for four consecutive weeks. Group V mice, which served as control received corresponding volumes of 10% tween 20 solutions. The animals were weighed, sacrificed and the testes weighed. The left testis was macerated in 2mls of semen diluting fluid until a homogenous mixture was formed. Improved Neubauer's chamber was used to determine the testicular sperm reserve. The right testis, liver, kidney and spleen were routinely prepared for light microscopy. The control mice had significantly higher (P

Male reproductive function is not affected in prolactin receptor-deficient mice.

Mice with a targeted disruption of the prolactin (PRL) receptor gene were used to study the physiological role of PRL in the control of the male reproductive function. Fertility parameters as well as body and reproductive organ weights (epididymis and testes) were unaffected in PRL receptor knockout mice. Testicular histology and sperm reserves were also normal. Compared with wild-type animals, knockout mice had no significant difference in basal plasma LH, FSH, and testosterone levels, and the weight of seminal vesicles and prostate was unaffected. Moreover, no alteration was detected in human chorionic gonadotropin-induced testosterone levels. It is concluded that the absence of PRL signaling is not detrimental to male testicular function and to fertility in the mouse.

Effect of dietary selenium and vitamin E on spermatogenic development in boars.

An experiment involving a total of 61 crossbred boars evaluated the effects of dietary Se and vitamin E on spermatogenic development at various stages of sexual development and the prostaglandin F2alpha (PGF2alpha) content in the seminal vesicle and prostate glands at 18 mo of age. The experiment from 5.4 to 9 mo of age was conducted as a 2 x 2 factorial in a randomized complete block design. Dietary Se at 0 or .5 ppm was the first factor and vitamin E at 0 or 220 IU/kg diet was the second. From 9 to 18 mo of age, a group of sexually active and inactive boars was a third factor. Treatment diets were fed from weaning (28 d of age) to the end of the experiment. Three boars per treatment group at 5.4 (105 kg BW), 6.2 (130 kg BW), and 9.0 (150 kg BW) mo of age were killed and the testes collected. From 9 to 18 mo of age, three boars from each dietary treatment group were used for semen collection, and another set of three to four boars from each treatment group remained sexually inactive. At 18 mo, both sets of boars were killed and their testes, prostates, and seminal vesicles were collected. The testis at each age was evaluated for sperm reserve numbers and germ and Sertoli cell populations. At 5.4 or 6.2 mo of age, testicular sperm reserves were not affected by dietary Se (P > .15), at 9.0 mo of age there was a trend for a higher (P < .10) number of sperm reserves, and by 18 mo of age the Se-fed boars had higher (P < .01) numbers of sperm reserves. Vitamin E had no effect (P > .15) on testicular sperm reserves at any age period. Boars fed dietary Se had a greater number of Sertoli cells (P < .01) and round spermatids (P < .01) at 6.2 mo of age, but by 18 mo of age the boars fed Se had more Sertoli cells (P < .05), more secondary spermatocytes (P < .01), and more round spermatids (P < .05). Vitamin E did not affect Sertoli or germ cell populations at the various ages. Boars at 18 mo of age had lower PGF2alpha concentrations in the prostate (P < .05) and seminal vesicles (P < .01) when vitamin E was fed, whereas Se had no effect. Sexually active boars had lower PGF2alpha concentrations in the seminal vesicles (P < .01) than sexually inactive boars, but there was no effect (P > .15) of sexual activity on the number of Sertoli cells, primary or secondary spermatocytes, or round spermatids. Our results indicate that Se has a role in establishing the number of boar spermatozoal reserves and Sertoli cells, whereas supplemental vitamin E did not affect these criteria.

Testicular and epididymal sperm content in grazing Cashmere bucks: seasonal variation and prediction from measurements in vivo

Each month, for 15 months, the testes and epididymides were recovered from five Australian cashmere bucks selected at random from a group of mature bucks (initial n = 116) at pasture (location 29 degrees S, 153 degrees E). The extent of seasonal change in testicular and epididymal sperm reserves was determined and indirect methods for predicting these reserves were developed. Paired testicular weight exhibited clear seasonal variation from 137 g in August to 269 g in February. The total elongated spermatid content of the testes, determined by homogenization, showed a very similar seasonal pattern, ranging from 13.8 x 10(9) in September to 36.2 x 10(9) in March. Seasonal changes of similar timing were observed for paired epididymal weight and sperm content. Although changes in total testicular spermatid content were largely the result of change in testicular weight (R2 = 0.72, P < 0.001), the elongated spermatid content of testicular parenchyma (mean, 127 x 10(6) g-1) exhibited significant seasonal variation with elevated values between February and June, suggestive of an increase in the efficiency of spermatogenesis. Daily sperm production, calculated by means of a spermatogenic time divisor for sheep, ranged from 2.76 x 10(9) in September to 7.23 x 10(9) in February. Scrotal circumference, scrotal volume and testicular length x diameter2 were identified as accurate predictors of testicular weight (R2 > or = 0.87) and sperm content (R2 > or = 0.70). The results demonstrate that: (a) cashmere bucks exhibit considerable seasonal variation in spermatogenesis associated primarily with changes in testicular mass but also with changes in the efficiency of spermatogenesis; and (b) indirect measures of testicular size are good predictors of testicular elongated sperm content. When the correct spermatogenic time divisor for goats is determined, such indirect measures may be used to predict daily sperm production.

Testicular and epididymal sperm reserves of Brazilian hairy rams.

SummaryTesticular and epididymal sperm reserves were estimated by the haemocytometric method in six adult Brazilian hairy rams, with normal spermatogenesis and kept at sexual rest. Mean values for testicular sperm reserve were 111.4 ± 44.6 × 106 sperm cells/gram of testis parenchyma and 11.2 ± 6.6 × 10′ sperm cells/testis. Epididymal sperm reserve amounted 27.7 ± 16.6 × 109 spermatozoa/organ, distributed as follows: 13.4% in the head, 6.4% in the body and 80.2 % in the tail. Sperm reserves were highly correlated with testis weight, epididymal weight and scrotal circumference, but not with body weight.ZusammenfassungSpermareserven im Hoden und Nebenhoden brasilianischer Haar‐Schafböcke: Die Spermareserven im Hoden und Nebenhoden wurden mittels der hämozytometrischen Methode bei sechs adulten brasilianischen Haar‐Schafböcken bestimmt. Die Tiere wiesen eine normale Spermatogenese auf und wurden sexuell nicht beansprucht. Die Mittelwerte für die Spermareserven des Hodens lagen bei 111,4 ± 44,6 × 106 Spermien/g Hodenparenchym und 11,2 ± 6,6 × 109 Spermien pro Hoden. Die Spermareserve des Nebenhodens betrug 27,7 ± 16,6 × 109 Spermien pro Organ, wobei sich 13,4% der Spermien im Kopf, 6,4% im Körper und 80,2% im Schwanz des Nebenhodens befanden. Die Spermareserven waren mit dem Hodengewicht, dem Nebenhodengewicht und der Circumferenz des Scrotums ausgeprägt korreliert, nicht dagegen mit dem Körpergewicht.

Effects of scrotal insulation and unilateral vasoligation on ejaculate characteristics and sperm reserves in the bull

Ten mature Bos indicus cross bulls were unilaterally vasoligated and the scrotum was insulated for 48 hours in six of the animals (treated). Semen was collected at 2-day intervals by electroejaculation, until the reproductive tract was recovered at slaughter either 14, 20 or 26 days after treatment. Decapitate spermatozoa and spermatozoa with proto-plasmic droplets increased significantly ( P < 0.01) over pre-treatment values at 12 to 16 and 16 to 20 days, respectively, after insulation. Vasoligation and scrotal insulation had no effect on testicular sperm reserves, but epididymal sperm reserves on the ligated side were significantly ( P < 0.05) reduced in the caput and increased in corpus and cauda. Total numbers of spermatozoa recovered from the patent side (epididymal sperm reserves and ejaculatory sperm output) exceeded sperm reserves recovered from the ligated side at 20 (28.2 vs. 23.2 × 10 9) and 26 days (47.1 vs. 18.7 × 10 9) after treatment in the insulated bulls. The percentage of decapitate spermatozoa was higher and the proportion of spermatozoa with protoplasmic droplets was consistently lower in the ligated cauda epididymidis. These findings are discussed in relation to likely alterations in epididymal function following scrotal insulation.

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 × 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 × 10 9. Scrotal circumference was positively correlated to testicular weight (r = 0.86), testicular spermatids (r = 0.77), and caudas spermatozoa (r = 0.83).

Postpubertal changes in gonadal and extragonadal sperm reserves in [formula omitted][formula omitted] strain bulls

Testes and epididymides were collected from 136 young (1.5 to 3.5 years of age) and 33 mature Bos indicus strain bulls, reared under extensive range conditions in the tropics. Testicular and epididymal sperm reserves and weights increased at different rates in the young bulls. Daily sperm production per gram of testis (DSPG) increased significantly before and epididymal sperm reserves after 2.5 years of age. Testicular and epididymal weights increased linearly with bodyweight. Sahiwal cross bulls had higher testicular and epididymal weights, and greater sperm reserves than did Brahman cross bulls at the same age. Testicular and epididymal weights, daily sperm production and epididymal sperm reserves for mature Brahman bulls were 670g, 61g, 4.9 billion and 25.5 billion respectively. Testis weight was highly correlated with total daily sperm production (DSP) and epididymal weight.

Testicular and epididymal sperm reserves of crossbred European boars raised and maintained in the humid tropics.

The testicular and epididymal sperm reserves of 32 adult crossbred European boars (mean age 17.4 months, range 15--21 months) raised and maintained in Ibadan, Nigeria were 43.77 x 10(9) and 207.20 x 10(9) cells respectively, and were correlated (P less than 0.01) with age and organ weight. The distribution of spermatozoa in the epididymis was 16, 6 and 78% in the caput, corpus and cauda epididymidis respectively. The testicular and epididymal sperm reserves were correlated (P less than 0.05), suggesting that sperm production and storage are associated. All the values studied were comparable with those reported for boars kept in temperate climates.

Effects of selection for postweaning gain on testicular function in mice.

Changes in testicular and epididymal function and selected endocrine organ size were examined in a line of mice selected for rapid postweaning gain (M16) and in reciprocal crosses with an unselected pedigree control line (ICR). The larger body weight of the M16 line was accompanied by larger testes, epididymides, seminal vesicle, pituitary, thyroid and adrenal weights (P smaller than .01) although the testes, epididymides, seminal vesicle and adrenal weights of M16 mice, expressed per gram body weight, actually decreased (P smaller than .01) relative to the ICR line. Testicular and epididymal sperm reserves were higher in M16 mice but the difference was not significant. However, when adjusted for gland size, testicular and epididymal sperm reserves were lower in the M16 line (P smaller than .01). Absolute and relative weights of testes, epididymides and pituitary were larger (P smaller than .01) in M16 male times ICR female crosses than in ICR male times M16 female crosses. Although testicular and epididymal sperm reserves were higher in M16 male times ICR female males the reciprocal difference was significant only for testicular sperm (P smaller than .05). Heterotic effects were significant for both absolute and relative weights of testes, epididymides (P smaller than.01), pituitary (P smaller than .05) and relative weight of siminal vesicles (P smaller than .05). Although percent heterosis was 8.5 for testicular and epididymal sperm reserves, significant heterotic effects were found only for epididymal sperm (P smaller than .05).