Effects of sublethal doses of chlorfluazuron on insemination and number of inseminated sperm in the common cutworm, Spodoptera litura (F.) (Lepidoptera: Noctuidae)

Sublethal doses (LD₁₀: 1.00 ng larva^?1; or LD₃₀: 3.75 ng larva^?1) of chlorfluazuron were applied topically to the cuticles of newly moulted fifth instars of the common cutworm, Spodoptera litura (F.) (Lepidoptera, Noctuidae). During mating, the treated males transferred spermatophores of a significantly lower weight into females. The weight of spermatophores transferred by LD₃₀‐treated males was significantly lower than the weight of spermatophores transferred by LD₁₀‐treated males, which was in turn significantly lower than the weight of spermatophores transferred by untreated males. The transfer of spermatophores was delayed by 5–15 min in LD₁₀‐ and LD₃₀‐treated males. However, mating duration was not affected by chlorfluazuron treatment. The transfer of spermatozoa was also delayed by 5–10 min in LD₁₀‐ and LD₃₀‐treated females. Polygynous male adults mated an average of ten times during their lifespan of 11–13 days when paired every day with a new virgin female of the same age. The number of matings per polygynous male was not affected by chlorfluazuron treatment, but the first mating was delayed by 1 day. The number of inseminated sperm found in the spermatophore averaged 10.3 (± 2.1) × 10⁵ over the lifespan of a male, in which the number of eupyrene sperm was 5.4 (± 1.1) × 10⁵. The number of inseminated eupyrene sperm decreased by 66% and 88%, respectively, in LD₁₀‐ and LD₃₀‐treated males. No significant reduction in the number of inseminated eupyrene sperm was observed when females were treated with LD₁₀ or LD₃₀ doses, nor was there a significant reduction when both sexes were treated with the LD₁₀ or LD₃₀ doses relative to treatment of males with the same doses. The ratio of inseminated eupyrene to apyrene sperm was not affected by chlorfluazuron treatment.     

Movement of spermatozoa in the reproductive tract of adult male Spodoptera litura: daily rhythm of sperm descent and the effect of light regime on male reproduction

Sperm production and movement from the fused testes into the male reproductive tract of the common cutworm Spodoptera litura were studied in insects maintained in a 12 h:12 h light dark (LD) regime. Two types of sperm bundles, eupyrene (nucleated) and apyrene (anucleate) were present in the adult testes. Eupyrene bundles constituted about 25% of the total. Descent of spermatozoa from the testes into the upper vas deferens (UVD) first occurred about 24-30 h before adult eclosion. On entering the reproductive tract, eupyrene spermatozoa remained in bundles while apyrene bundles became dissociated before they reached the UVD. Downward movement of both eupyrene and apyrene spermatozoa within the male tract occurred in a daily rhythm. Sperm descent from the testes into the UVD occurred during the early scotophase, followed by their further descent into the seminal vesicle (SV) during the photophase. Spermatozoa remained in the SV for only a short duration, whence sperm quickly passed through the lower vas deferens into the duplex, which acted as the main sperm storage organ until mating was initiated. During mating 80% of sperm left the duplex, but mating did not influence the number of sperm bundles that subsequently descended into the duplex or the rate of their descent. There was no evidence of sperm reflux. Rearing in constant light (LL) and in constant dark (DD) reduced the number of eupyrene sperm present in the testes of adults that emerged in LL and DD compared to controls (LD), although there was no significant effect on the number of apyrene sperm in the testes. The rhythmic pattern of sperm descent was suppressed in both LL and DD regimes, and the number of sperm in the duplex was adversely affected, with a marked impact in LL reared insects. Male longevity, mating behaviour, oviposition and fertility were found to be more severely affected in LL than in DD.     

Morphological changes in eupyrene and apyrene spermatozoa in the reproductive tract of the male butterfly Atrophaneura alcinous Klug

Summary

Eupyrene and apyrene spermatozoa are contained in separate cysts in the testis of the butterfly Atrophaneura alcinous. Spermatozoa of both types from various parts of the male reproductive tract were examined with particular reference to their morphological characteristics. All spermatozoa collected from the vas deferens and the vesicula seminalis were found to be immotile under a dissecting microscope. No spermatozoa of either type were recognized in any part of the ejaculatory duct. Within the testis, eupyrene spermatozoa are present in bundles and each spermatozoon has a slender nucleus with an acrosome and a long flagellum containing mitochondrial derivatives. Two kinds of appendages, lacinate and reticular, are present on the surface of the sperm membrane. They are replaced with an extracellular sheath during passage through the vas deferens. In contrast, apyrene spermatozoa have neither nucleus nor acrosome, whereas a cup-shaped structure was found at the sperm tip instead of the acrosome. Unlike eupyrene spermatozoa, they are surrounded by a concentric sheath outside the sperm membrane in the vas deferens. Individual apyrene spermatozoa and coiled bundles of eupyrene spermatozoa were both found to accumulate in the vesicula seminalis before mating. These morphological changes during passage through the male reproductive tract suggests the occurrence of a kind of maturation and capacitation process reminiscent of mammalian spermatozoa.     

Daily rhythm in myogenic contractions of vas deferens associated with sperm release cycle in a moth

In the gypsy moth, Lymantria dispar, release of sperm bundles from the testis into the upper vas deferens (UVD) and subsequent transfer of sperm bundles into the seminal vesicles (SV) occurs in a daily rhythm. The UVD undergoes different types of contractions despite the fact that its musculature appears to receive no innervation. Patterns of the UVD movements were recorded throughout the daily sperm release and transfer cycle. In males kept in light-dark cycles, transfer of sperm from the UVD to the SV was accompanied by a characteristic pattern of UVD contractions of high frequency and amplitude. In males kept in constant light, which fail to transfer sperm, this contraction pattern was absent. It is concluded that the vas deferens muscles undergo daily changes in contraction pattern in phase with the light-dark cycle. The increased muscular contractions appear to be a causal factor in the gated sperm transfer from the UVD to the SV.Abbreviations LD light-dark - LL constant light - SV seminal vesicle - UVD upper vas deferens     

东方扁虾雄性生殖系统的解剖学和组织学研究

东方扁虾雄性生殖系统由精巢、输精管及雄性生殖孔三部分组成,输精管可分为前、中、后三段。精巢由卷绕的前、后收集管及持靠其上的许多生精腺囊所组成。同一腺囊内的精细胞发生基本同步,而不同腺囊内则可以不同步。收集管的主要功能是将精细胞团输送至输精管。精荚在输粗管内运行时一直进行着精子的形成过程,直至精子成熟。位于输精管末段不肌层外的索带状细胞团被认为是造雄腺。     

Circadian rhythm of sperm release in the gypsy moth,Lymantria dispar: ultrastructural study of transepithelial penetration of sperm bundles

Release of mature bundles of spermatozoa from the testis into the vas deferens is a critical but poorly understood step in male insect reproduction. In moths, the release of sperm bundles is controlled by a circadian clock which imposes a temporal gate on the daily exit of bundles through the terminal epithelium-a layer of specialized epithelial cells separating testis follicles from the vas deferens. The sequence of cellular events associated with the daily cycle of sperm release was investigated by scanning and transmission electron microscopy. In the hours preceding sperm release, there is a solid barrier between the testis and the vas deferens formed by the interdigitation of cytoplasmic processes of adjacent terminal epithelial cells. At the beginning of the sperm release cycle, sperm bundles protrude through this barrier while the terminal epithelial cells change their shape and position relative to the bundles. Subsequently, the cyst cells enveloping the sperm bundles break down and spermatozoa move out of the testis through the exit channels formed between the epithelial cells. Afterwards, cyst cell remnants and other cellular debris are released into the vas deferens lumen, and the epithelial barrier is reconstructed due to phagocytic activity of its cells. These data provide a foundation on which to build an understanding of the cellular mechanisms of clock-controlled sperm release in insects.     

Sperm morphology and arrangement along the male reproductive tract of the butterfly Euptoieta hegesia (Insecta: Lepidoptera)

Summary

The present study was undertaken to describe the morphological and organizational modifications that occur in apyrene and eupyrene spermatozoa along the male adult reproductive tract of the butterfly, Euptoieta hegesia. Testis, vas deferens, vesicula seminalis and ductus ejaculatorius were studied by transmission electron microscopy. In the testis, both sperm types are organized into cysts; apyrene sperm are devoid of extracellular structures while eupyrene ones have lacinate and reticular appendages. In the testis basal region, both sperm pass through an epithelial barrier and lose their cystic envelope. The eupyrene morphological and organizational modifications are more drastic than the apyrene ones. From the vas deferens to the ductus ejaculatorius, apyrene sperm are dispersed in the lumen and acquire several concentric layers that are formed by the folding of their abundant cell membrane. The apyrene distribution observed here suggests that their functions include eupyrene transportation. Eupyrene sperm, however, remain aggregated along the tract. In the vas deferens, they are covered by a filamentous material that develops into a homogeneous matrix surrounding the spermatozoa coat in the vesicula seminalis and the ductus ejaculatorius. Eupyrene sperm undergo complex morphological changes that include the loss of lacinate appendages and the formation of a dense and heterogeneous extracellular coat. The formation of the matrix and the coat in eupyrene extratesticular sperm is related to the loss of lacinate appendages. These changes are in general extracellular and are probably important for sperm maturation.     

BmPMFBP1 regulates the development of eupyrene sperm in the silkworm,Bombyx mori

Sperm deliver the male complement of DNA to the ovum, and thus play a key role in sexual reproduction. Accordingly, spermatogenesis has outstanding significance in fields as disparate as infertility treatments and pest-control, making it a broadly interesting and important focus for molecular genetics research in a wide range of species. Here we investigate spermatogenesis in the model lepidopteran insect Bombyx mori (silkworm moth), with particular focus on the gene PMFBP1 (polyamine modulated factor 1 binding protein 1). In humans and mouse, PMFBP1 is essential for spermatogenesis, and mutations of this gene are associated with acephalic spermatozoa, which cause infertility. We identified a B. mori gene labeled as “PMFBP1” in GenBank’s RefSeq database and sought to assess its role in spermatogenesis. Like in mammals, the silkworm version of this gene (BmPMFBP1) is specifically expressed in testes. We subsequently generated BmPMFBP1 mutants using a transgenic CRISPR/Cas9 system. Mutant males were sterile while the fertility of mutant females was comparable to wildtype females. In B. mori, spermatogenesis yields two types of sperm, the nucleated fertile eupyrene sperm, and anucleated unfertile apyrene sperm. Mutant males produced abnormal eupyrene sperm bundles but normal apyrene sperm bundles. For eupyrene sperm, nuclei were mislocated and disordered inside the bundles. We also found the BmPMFBP1 deficiency blocked the release of eupyrene sperm bundles from testes to ejaculatory seminalis. We found no obvious abnormalities in the production of apyrene sperm in mutant males, and double-matings with apyrene-deficient sex-lethal mutants rescued the ΔBmPMFBP1 infertility phenotype. These results indicate BmPMFBP1 functions only in eupyrene spermatogenesis, and highlight that distinct genes underlie the development of the two sperm morphs commonly found in Lepidoptera. Bioinformatic analyses suggest PMFBP1 may have evolved independently in lepidoptera and mammals, and that despite the shared name, are likely not homologous genes.     

Effect of constant light on male sterility in the cotton leafworm Spodoptera littoralis

Females of the cotton leafworm (Spodoptera littoralis) reared in long day conditions (LD 16:8 h) and mated to males kept throughout the whole period of development in continuous light (LL) oviposit very small numbers of mostly sterile eggs. It was found that in control males reared from the first larval instar in long day conditions there was a large accumulation of euperene sperm bundles in their testes on day 1 after imaginal moult. On day 10 of adult life the number of the sperm bundles was very small. In males kept from the first instar in continuous light there was also high number of sperm bundles on day 1 after imaginal moult but it did not decrease significantly on day 10 as was observed in controls. Transfer of different developmental stages of S. littoralis from long day conditions to continuous light resulted in a big difference in the density of eupyrene sperm bundles in their testes. In control insects reared through the whole of their development in long day conditions there was a significant decrease in the density of eupyrene sperm bundles on day 10 of adult life. By contrast, in males in continuous light, regardless of their developmental stage when transferred, there was either no change in density of sperm bundles in day 10 adults or there was a significant increase in comparison with day 1 adults. The highest density of eupyrene sperm bundles was observed in day 10 adults when they were transferred to continuous light shortly before moulting to the last instar (as day 4 larvae in the last stadium or day 1 pupae). Generally, the density of eupyrene sperm bundles on day 10 of adult development was about 2–2.5 times higher in males in continuous light then those under long day conditions. The results presented here indicate that the last larval instar and the pupa are the stages most sensitive to constant light treatment, which greatly reduces the amount of eupyrene sperm bundles released from the testes.     

Difference of fertilizing capacity between testicular sperm and vas deferens sperm in Cynops pyrrhogaster

The fertilizing capacity was compared between testicular and vas deferens sperm in Cynops pyrrhogaster. The testicular sperm was not capable of fertilizing jelly eggs. In contrast, the vas deferens sperm was already capable of fertilizing the newt jelly eggs. There was no inhibitory factor for fertilizing jelly eggs in the testis. These results suggest that the testicular sperm is immature as to the fertilizing capacity. The testicular sperm gained the fertilizing capacity for the jelly eggs by treatment with Holtfreter's solution or 1/20 strength Holtfreter's solution. The treatment may promote the step of maturation to achieve the fertilizing capacity. The treated testicular sperm did not fertilize dejellied eggs, although vas deferens sperm fertilized dejellied eggs. Therefore, the maturation state of the treated testicular sperm is different from that of vas deferens sperm. Newt sperm may be matured within the vas deferens, as the newt does not have an organ like the mammalian epididymis.     

In vitro cultivation of spermatocysts to matured sperm in the silkworm Bombyx mori

Bombyx spermatogonia are bipotential, producing nucleate eupyrene sperm and anucleate apyrene sperm. An in vitro cultivation of spermatocysts of Bombyx mori from spermatocytes to matured sperm was established. The present experiment made clear that: (i) spermatocysts must be isolated; (ii) constant shaking at 45 r.p.m. was necessary; and (iii) the addition of Bombyx hemolymph (BH) was indispensable for successful cultivation. In the absence of BH, spermatogenesis proceeded normally for 2 or 3 days and, thereafter, spermatocytes and sperm bundles began to degenerate. The best results for normal eupyrene spermatogenesis were obtained when culture medium containing BH of the corresponding stage was used in every exchange of the medium at 72 h intervals. None or only a small number of apyrene sperm bundles was produced by this culture system when spermatocysts from larval testes were used, although eupyrene spermatogenesis proceeded normally to form matured, or squeezed, sperm bundles.     

Effects of 20-hydroxyecdysone on sperm release from the testes of the Mediterranean flour moth,Anagasta kuehniella (Zeller)

Abdominal injection of 1 μg aqueous 20-hydroxyecdysone into Anagasta kuehniella, anytime prior to the initiation of sperm release from the testes, prevents the impending release of eupyrene sperm bundles. Apyrene sperm release is not prevented and there is complete recovery of eupyrene release by the following cycle 24 hr later. If 20-hydroxyecdysone is administered on consecutive days, no eupyrene bundles are released and although apryene sperm release continues, it diminishes with time. The effect of 20-hydroxyecdysone in preventing eupyrene release is dose dependent. Administration of decreasing 20-hydroxyecdysone dosages results in increasing numbers of eupyrene bundles released. When a single injection of 20-hydroxyecdysone is administered to isolated abdomens, recovery time of eupyrene sperm release is slower than in whole moths and total recovery is not seen even by 5 days after administration. Apyrene sperm release is also affected to a greater extent than in whole moths, and in some cases, no apyrene release was detected at all. Treatment with 20-hydroxyecdysone prevents cupyrene bundles from passing through the testicular basilar membrane into the vasa efferentia, thus causing a build up of bundles near the basilar membrane but no disintegration of these eupyrene sperm bundles.     

Effects of larval exposure to sublethal concentrations of the ecdysteroid agonists RH-5849 and tebufenozide (RH-5992) on male reproductive physiology in Spodoptera litura

Sublethal concentrations of the bisacylhydrazine moulting hormone agonists, RH-5849, and tebufenozide (RH-5992) were fed to sixth (final) instar larvae of Spodoptera litura. Both RH-5849 and tebufenozide adversely affected the mating success of S. litura when the surviving treated males were crossed with normal females. The ecdysone agonists decreased the longevity of treated males and of untreated females when crossed with treated males. The number of eggs laid by untreated females mated to treated males was decreased, and the fertility (percentage of hatching success) of the resulting eggs was reduced. These effects on male reproductive success were at least in part explained by a reduction in the number of sperm transferred during mating. The adverse effects of tebufenozide on male reproductive function were qualitatively the same as those of RH-5849, but tebufenozide was active at lower concentrations. To understand the reason for these adverse effects on male reproduction, we investigated the effects of the insecticides on male reproductive physiology. Male reproductive tract development and testicular volume of resulting adult moths were adversely affected by sublethal larval exposure to the ecdysone agonists. Dose-dependent reductions occurred in the production of eupyrene and apyrene spermatozoa in the adult testes, and in the number of spermatozoa released from the testes into the male reproductive tract. The descent into the male tract of both eupyrene and apyrene sperm was found to start at the normal stage of development in both normal and treated insects, but the daily rhythm of sperm descent was subsequently disturbed in the insecticide-treated moths. This affected the numbers of sperm in the upper vas deferens (UVD), seminal vesicle (SV), and duplex (duplex). Injections of RH-5849 given to pharate adult or newly emerged adult S. litura also caused drastic reduction in the number of sperm in the upper regions of the male tract, when measured 24 h after injection. The possible importance of pest population reduction through the sublethal anti-reproductive effects of insecticides is discussed.     

Effects of a single ethanol injection into the vas deferens on the testicular function of rats.

1. A new approach to rapid male sterilization has been studied by giving a single injection of 95% ethanol directly into the vas deferens. It produced an effective block in the lumen. The mating exposure test showed that the males were sterile. The sperm granulomas at the site of vas injection were confirmed. 2. Ethanol injection in the vas deferens caused an atrophy of the testes. Extensive necrosis and exfoliation of the seminiferous elements were conspicuous. 3. Decrease in testicular weight, seminiferous tubule diameter and RNA and sialic acid levels after 4 weeks of vas injection were associated with the histological evidence for severe degeneration of spermatogenic elements. The protein contents of testis, epididymides and seminal vesicles did not change. 4. Testicular cholesterol, total lipids and alkaline phosphatase activity was increased. 5. Low sialic acid levels in the testis, epididymides and seminal vesicles of vas-injected rats indicated an inhibition of androgen production, which was further reflected in reduced nuclear diameters of leydig cells.     

Peristaltic squeezing of sperm bundles at the late stage of spermatogenesis in the silkworm, Bombyx mori

Silkworm (Lepidoptera) males produce dimorphic sperm, nucleate eupyrene sperm, and anucleate apyrene sperm. The eupyrene sperm is the ordinary sperm fertilizing eggs, while the function of the apyrene sperm, which are about four times as numerous as the eupyrene sperm, is still uncertain. We found the peristaltic phenomenon at the very late stage of spermatogenesis. Peristalsis occurs in both eupyrene and apyrene sperm bundles. Through peristaltic action, cytoplasm of the eupyrene sperm and both cytoplasm and nuclei of the apyrene sperm are discarded from the posterior end of the sperm bundles. Peristaltic squeezing seems to be a process to eliminate the irregular nuclei of apyrene sperm while preserving the nuclei of eupyrene sperm.     

The circadian rhythm of sperm release in the codling moth, Cydia pomonella

The release of sperm bundles from testes to the vas deferens is controlled by a circadian clock in several moth species. We investigated the pattern of sperm release in the codling moth, Cydia pomonnella L. (Lepidoptera: Tortricidae). Sperm release in the codling moth follows a two-step rhythm in light-dark cycles: sperm is released from the testis before lights-off, remains in the vas deferens during the dark phase and is transferred to the seminal vesicles after lights-on. This rhythm continues in constant darkness indicating that it has a circadian nature. The release of sperm is asynchronous in moths held in constant light. In contrast to previously investigated moths, constant light has no adverse effects on the male reproductive capacity in the codling moth.     

THE EUPYRENE-APYRENE DICHOTOMOUS SPERMATOGENESIS OF LEPIDOPTERA. ORGAN CULTURE STUDY ON THE TIMING OF APYRENE COMMITMENT IN THE CODLING MOTH

Lepidopteran spermatogenesis is dichotomous, producing eupyrene (nucleated) and apyrene (anucleated) spermatozoa. The eupyrene precedes the apyrene spermatogenesis. The timing of the switchover from eupyrene to apyrene spermatogenesis was determined by cultivating testes of accurately aged codling moth larvae in a medium containing mammalian serum but neither hemolymph nor insect hormones. In cultures, eupyrene spermatogenesis occurred in testes dissected from either 4th or 5th instar larvae, probably due to macromolecular factor-like activity of the serum of the medium. But apyrene spermatogenesis occurred only in testes explanted during or after the fourth day of the 5th instar larva. It is concluded that: (1) An apyrene spermatogenesis inducing factor (ASIF) becomes active on the fourth day of the 5th instar larva in addition to the already existing macromolecular factor. (2) Primary spermatocytes can develop into either eupyrene or apyrene spermatozoa. (3) The apyrene spermatogenesis commitment and pupal commitment of other tissues coincide about the fourth day of the 5th instar larva.     

Effects of residual chlorfluazuron on haemolymph-borne oviposition-stimulating factors in Spodoptera litura

Acylurea insecticides can have various effects on insect reproduction and may even interfere with haemolymph‐borne oviposition‐stimulating factors (OSFs). This study describes the effects of injecting haemolymph into females of the common cutworm, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), the effects of chlorfluazuron on the activities of OSFs, when sublethal doses (LD₁₀: 1.00 ng larva^?1 or LD₃₀: 3.75 ng larva^?1) were applied topically to newly ecdysed fifth instars under laboratory conditions. The haemolymph of moths of varying age, sex, and mating status resulted in the following increases in oviposition rates within the first 24 h, listed in decreasing order: the haemolymph of mated females injected into mated females (56%), mated females into newly emerged virgin females (53%), virgin males into virgin females (49%), and virgin females into mated females (29%), compared with uninjected mated or virgin females. Two factors are involved in the activation of ovipositon: OSF‐I is found in virgin females, whereas OSF‐II may be formed or received by males during mating. By contrast, the haemolymph taken from chlorfluazuron‐treated adults (treated as fifth instars with sublethal doses) injected into females resulted in the following percentage decreases in oviposition rates within the first 24 h, listed in decreasing order: the haemolymph of LD₁₀‐ and LD₃₀‐treated virgin males injected into untreated virgin females (77 and 84%, respectively), LD₁₀ and LD₃₀‐treated virgin females into untreated mated females (70 and 80%, respectively), LD₁₀ and LD₃₀‐treated mated females into untreated mated females (61 and 69%, respectively), LD₁₀ and LD₃₀‐treated mated females into untreated virgin females (59 or 68%, respectively), compared with untreated ones. Hence, residual chlorfluazuron decreases the activities of OSFs by significantly decreasing the oviposition rates. Moreover, virgin females’ or males’ OSFs are more sensitive to chlorfluazuron than those of mated cutworms. Both OSFs are most likely proteins.     

Circadian rhythm of glycoprotein secretion in the vas deferens of the moth, Spodoptera littoralis

Background  

Reproductive systems of male moths contain circadian clocks, which time the release of sperm bundles from the testis to the upper vas deferens (UVD) and their subsequent transfer from the UVD to the seminal vesicles. Sperm bundles are released from the testis in the evening and are retained in the vas deferens lumen overnight before being transferred to the seminal vesicles. The biological significance of periodic sperm retention in the UVD lumen is not understood. In this study we asked whether there are circadian rhythms in the UVD that are correlated with sperm retention.     

Clinical, ultrasonographic and pathological features following unilateral vasectomy in rams

The effects of vasectomy on testes and related structures of animal species and men are largely disputable. These possible effects were studied in the ram, an established experimental animal model used to investigate genitalia pathophysiology. In each of five rams, vasectomy in the left spermatic cord was carried out; subsequently, the clinical and ultrasonographic features were monitored up to 12 months post-operatively. The rams were sequentially euthanatized 1, 3, 6, 9 and 12 months post-operatively; gross- and histo-pathological examination of their testes and related structures were carried out. Four of the five rams developed sperm granulomas at the proximal to the testis end of vas deferens or/and at the tail of the epididymis; these were palpable from the first and the third month after vasectomy, respectively. Ultrasonographic findings on the vasectomy side were increased size and echogenicity of the epididymal tail, as well as anechoic areas, representing sperm granulomas, visible in the epididymal tail 1 week after vasectomy and in the proximal to the testis end of vas deferens 4 weeks after vasectomy. Gross pathological findings were limited on the vasectomy side and included adhesions between the parietal and the visceral vaginal tunic, enlarged and firm epididymal tail and presence of sperm granulomas at the epididymal tail or/and at the proximal to the testis end of vas deferens; the granulomas contained creamy material. Histopathological changes were observed mainly in the epididymal tails, consisting of a central mass of spermatozoa, surrounded by a layer of macrophages, surrounded in turn by loose vascular connective tissue rich in lymphocytes and plasma cells. With the exception of signs of mild hypospermatogenesis observed in one ram euthanatized 9 months after surgery, and of a slight increase in seminiferous tubule diameter and in seminiferous epithelium height in the rams euthanatized 6 and 9 months after surgery, which are both findings of no clinical importance, no clinical, ultrasonographic, gross- or other histo-pathological changes were observed in the testicular parenchyma during a 12-month post-operative period. These results demonstrate that vasectomy has little if any detrimental effect on the morphologic characteristics of the spermatogenesis in rams.