Key aspects of domestic cat spermatogenesis.

In mammals, spermatogenesis is a complex and cyclic process in which a spermatogonia turns into a highly differentiated cell: the spermatozoa. Spermatogenesis comprises proliferation of spermatogonia (spermatocytogenesis), meiosis of spermatocytes and finally differentiation of spermatids into spermatozoa (spermiogenesis). This review summarizes the current knowledge on domestic cat spermatogenesis including its physiology, development, efficiency and pathologies as well as their novel non-invasive diagnostic methods. This information will provide a resource for further studies to achieve precise fundamental knowledge of key aspects that will facilitate breeding, management and contraception in this popular species.

Cellular development of the germinal epithelium during the female and male gametogenesis of Chaetodon striatus (Perciformes: Chaetodontidae).

Butterflyfish Chaetodon striatus is highly sought after in the marine ornamental aquarium, although studies about its reproductive biology are scarce. Therefore, to contribute to a better understanding of the reproductive aspects of C. striatus, we describe in detail with the use of high resolution histology the cellular dynamics of the germinal epithelium during the reproductive life history of this species. Based on the activity of the germinal epithelium, this study describes different stages of the gonadal development, similar to the reproductive phases found in other fish, to determine the reproductive period of C. striatus. In characterization of gonadal development, the following germ cells are described for males: spermatogonia, spermatocytes, spermatids and spermatozoa. Oogonia, early, primary, secondary, full-grown and maturing oocytes are described for females. Female germinal epithelium of C. striatus showed substantial changes over the study period, indicating that there was an active spawning period. Male germinal epithelium also presented relevant alterations, indicating reproductive activity in the testicular lobules. Morphological data confirm how informative was the cellular dynamics of the germinal epithelium for understanding gonadal development during adult reproductive life of fish in general. Although Chaetodon are a popular species, previous studies have only produced superficial and rough histological analyses. Therefore, this study demonstrates important information on germinal epithelium of Chaetodon. This knowledge could be a fundamental tool for development of new strategies for breeding of several species in captivity, especially butterflyfishes.

Revealing stage-specific expression patterns of long noncoding RNAs along mouse spermatogenesis.

The discovery of a large number of long noncoding RNAs (lncRNAs), and the finding that they may play key roles in different biological processes, have started to provide a new perspective in the understanding of gene regulation. It has been shown that the testes express the highest amount of lncRNAs among different vertebrate tissues. However, although some studies have addressed the characterization of lncRNAs along spermatogenesis, an exhaustive analysis of the differential expression of lncRNAs at its different stages is still lacking. Here, we present the results for lncRNA transcriptome profiling along mouse spermatogenesis, employing highly pure flow sorted spermatogenic stage-specific cell populations, strand-specific RNAseq, and a combination of up-to-date bioinformatic pipelines for analysis. We found that the vast majority of testicular lncRNA genes are expressed at post-meiotic stages (i.e. spermiogenesis), which are characterized by extensive post-transcriptional regulation. LncRNAs at different spermatogenic stages shared common traits in terms of transcript length, exon number, and biotypes. Most lncRNAs were lincRNAs, followed by a high representation of antisense (AS) lncRNAs. Co-expression analyses showed a high correlation along the different spermatogenic stage transitions between the expression patterns of AS lncRNAs and their overlapping protein-coding genes, raising possible clues about lncRNA-related regulatory mechanisms. Interestingly, we observed the co-localization of an AS lncRNA and its host sense mRNA in the chromatoid body, a round spermatids-specific organelle that has been proposed as a reservoir of RNA-related regulatory machinery. An additional, intriguing observation is the almost complete lack of detectable expression for Y-linked testicular lncRNAs, despite that a high number of lncRNA genes are annotated for this chromosome.

Stereological and morphological analysis of the effects of aging on spermatogenesis in rat testis 1.

PURPOSE: To quantify, through stereological and morphometric analysis, spermatogenesis in rats undergoing the natural aging process. METHODS: Seventy-two male Wistar rats were divided into 6 equal groups according to age at the time of killing: 3, 6, 9, 12, 18, and 24 months. All the rats were subjected orchiectomy and collection of testicular parenchymal fragments for histological and morphometric analysis. The numerical density of spermatids was calculated using a stereological study, and morphometric analysis was conducted to measure the height of the germinal epithelium and the area of the seminiferous tubules. RESULTS: We found that the 18 and 24 months groups showed a significant reduction in the number of round spermatids. However, the height of the germinal epithelium was not significantly different between the groups. The area of seminiferous tubules was also significantly reduced in the elderly rats compared to that in the young ones. CONCLUSION: Aging of rats showed a significant reduction in the number of round spermatids and the area of the seminiferous tubules, more pronounced in the rats at 18 and 24 months of life.

Stereological and morphological analysis of the effects of aging on spermatogenesis in rat testis

Abstract Purpose: To quantify, through stereological and morphometric analysis, spermatogenesis in rats undergoing the natural aging process. Methods: Seventy-two male Wistar rats were divided into 6 equal groups according to age at the time of killing: 3, 6, 9, 12, 18, and 24 months. All the rats were subjected orchiectomy and collection of testicular parenchymal fragments for histological and morphometric analysis. The numerical density of spermatids was calculated using a stereological study, and morphometric analysis was conducted to measure the height of the germinal epithelium and the area of the seminiferous tubules. Results: We found that the 18 and 24 months groups showed a significant reduction in the number of round spermatids. However, the height of the germinal epithelium was not significantly different between the groups. The area of seminiferous tubules was also significantly reduced in the elderly rats compared to that in the young ones. Conclusion: Aging of rats showed a significant reduction in the number of round spermatids and the area of the seminiferous tubules, more pronounced in the rats at 18 and 24 months of life.

Morphofunctional evaluation of the testis, duration of spermatogenesis and spermatogenic efficiency in the Japanese fancy mouse (Mus musculus molossinus).

Japanese fancy mouse, mini mouse or pet mouse are common names used to refer to strains of mice that present with different colour varieties and coat types. Although many genetic studies that involve spotting phenotype based on the coat have been performed in these mice, there are no reports of quantitative data in the literature regarding testis structure and spermatogenic efficiency. Hence, in this study we researched testis function and spermatogenesis in the adult Japanese fancy mouse. The following values of 68 ± 6 mg and 0.94 ± 0.1% were obtained as mean testis weight and gonadosomatic index, respectively. In comparison with other investigated mice strains, the fancy mouse Leydig cell individual size was much smaller, resulting in higher numbers of these cells per gram of testis. As found for laboratory mice strains, as a result of the development of the acrosomic system, 12 stages of the seminiferous epithelium cycle have been described in this study. The combined frequencies of pre-meiotic and post-meiotic stages were respectively 24% and 64% and very similar to the laboratory mice. The more differentiated germ cell types marked at 1 h or 9 days after tritiated thymidine administration were preleptotene/leptotene and pachytene spermatocytes at the same stage (VIII). The mean duration of one spermatogenic cycle was 8.8 ± 0.01 days and the total length of spermatogenesis lasted 37.8 ± 0.01 days (4.5 cycles). A high number of germ cell apoptosis was evident during meiosis, resulting in lower Sertoli cell and spermatogenic efficiencies, when compared with laboratory mice strains.

Testicular parameters and spermatogenesis in different birthweight boars.

The present study investigated the effect of birthweight on testicular development and spermatogenesis in boars. Twenty-four pairs of littermate boars were selected: one piglet with the highest birthweight (HW) and the other with the lowest birthweight (LW) within the litter. Two subsets of 12 pairs of male littermates from each birthweight group were obtained after selection: one subset was orchiectomised at 8 days and the other at 8 months of age. HW boars had higher body and testicular weights at both ages (P<0.05). Testosterone concentrations and the relative expression of 17α-hydroxylase in the testis were similar between birthweight groups. Birthweight affected somatic and germ cell numbers in the neonatal testis, which were higher in HW boars (P<0.05). Moreover, a significant reduction in the number of pachytene spermatocytes and round spermatids was observed in LW boars (P<0.05) at 8 months of age, which caused a decrease in the total number of elongated spermatids and daily sperm production (P<0.05). Hence, HW boars have the potential to produce more spermatozoa and consequently more semen doses per ejaculate, and would be very valuable to an industry that relies on AI.

Spermatogenesis in Leptodactylus chaquensis. Histological study.

The organization and the histological characteristics of Leptodactylus chaquensis testis throughout the reproductive cycle were analyzed in the presented study. Gonads of adult males, processed with routine techniques for optical microscopy, revealed that during the reproductive period the seminiferous tubules were characterized by presentation of a large number of cysts, germ cells at the same maturation stage supported by Sertoli cells. All the germ line cells were also present in the postreproductive period and maintained their morphological characteristics. Primary spermatogonia were large-sized cells found isolated or in small groups. The rest of the cells of the germ line formed cysts. Secondary spermatogonia showed morphological characteristics similar to their predecessors, although they were smaller. Primary and secondary spermatocytes showed images of the different stages of the first and second meiotic division respectively. One finding was the presence of intercytoplasmic bridges between the secondary spermatocytes. Primary spermatids were rounded cells with an acrosomal vesicle associated with the nucleus and had cysts that were characterized by large intercellular spaces. Secondary spermatids were elongated cells with a well defined acrosome, which in the spermatozoa had the shape of an arrowhead. Another peculiar characteristic of this species was the fusion of the walls of the seminiferous tubule with the efferent duct that formed a path for spermatozoa during spermiation. The presence in the seminiferous tubules of all stages of the spermatogenic line during the two periods of the cycle studied indicated that Leptodactylus chaquensis had a potentially continuous reproductive cycle.

Analysis of spermiogenesis like a tool in the study of the triatomines of the Brasiliensis subcomplex.

The specific identification and systematic of triatomines have been based fundamentally on morphological observations. These organisms are classified into complexes and specific subcomplexes, principally for morphological parameters and geographical disposition. The use of cytogenetic analyzes has been represented as a tool in systematic and taxonomy of triatomines. Thus, the present work, through the analysis of spermiogenesis, aims to characterize this stage of spermatogenesis in triatomines little studied, and especially to compare it among the species Triatoma lenti and T. sherlocki, to assist in the diagnosis of differentiation of these insects. The presence of the heteropyknotic corpuscle is shown as a diagnostic tool to differentiate T. sherlocki and T. lenti, since it is absent in T. lenti. The analysis of the spermiogenesis in T. sherlocki also allowed us to address morphological differences between elongating cells, which were relatively smaller and more filamentous when compared to T lenti. Furthermore, the flagellum was observed in all stages of cell differentiation and elongation. This structure, which helps in the locomotion of the sperm, is hardly observed in cytogenetic analysis, especially throughout spermiogenesis. Thus, although other comparative approaches should be taken, this paper allowed emphasizing the analysis of spermiogenesis as an important cytotaxonomic tool that assists in the differentiation of morphologically related species, such as T. lenti and T. sherlocki.

Intracytoplasmic spermatid injection and in vitro maturation: fact or fiction?

Intracytoplasmic injection with testicular spermatozoa has become a routine treatment in fertility clinics. Spermatozoa can be recovered in half of patients with nonobstructive azoospermia. The use of immature germ cells for intracytoplasmic injection has been proposed for cases in which no spermatozoa can be retrieved. However, there are low pregnancy rates following intracytoplasmic injection using round spermatids from men with no elongated spermatids or spermatozoa in their testes. The in vitro culture of immature germ cells to more mature stages has been proposed as a means to improve this poor outcome. Several years after the introduction of intracytoplasmic injection with elongating and round spermatids, uncertainty remains as to whether this approach can be considered a safe treatment option. This review outlines the clinical and scientific data regarding intracytoplasmic injection using immature germ cells and in vitro matured germ cells.

Differential effects of temperature on reactive oxygen/nitrogen species production in rat pachytene spermatocytes and round spermatids.

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) like superoxide and nitric oxide are produced by testis and spermatogenic cells in response to heat stress. However, the magnitude and mechanisms of this production in spermatogenic cells have not been described. In this work, we evaluated ROS/RNS production, its pharmacology, mitochondrial oxidative metabolism, membrane potential and antioxidant capacity at different temperatures in isolated rat pachytene spermatocytes and round spermatids. Our results showed an increment in ROS/RNS production by pachytene spermatocytes when increasing the temperature to 40 °C. Instead, ROS/RNS production by round spermatids did not change at temperatures higher than 33 °C. ROS/RNS production was sensitive to NADPH oxidase inhibitor diphenylene iodonium or the mitochondrial complex I inhibitor rotenone. No additive effects were observed for these two compounds. Our results suggest an important mitochondrial ROS/RNS production in spermatogenic cells. Oligomycin-insensitive oxygen consumption (uncoupled oxygen consumption) increased with temperature and was significantly larger in round spermatids than pachytene spermatocytes, indicating a likely round spermatid mitochondrial uncoupling at high temperatures. A similar conclusion can be reached by measuring the mitochondrial membrane potential using rhodamine 123 fluorescence in permeabilized cells or JC-1 fluorescence in intact cells. The antioxidant capacity was higher in round spermatids than pachytene spermatocytes at 40 °C. Our results strongly suggest that at high temperatures (40 °C) pachytene spermatocytes are more susceptible to oxidative stress, but round spermatids are more protected because of a temperature-induced mitochondrial uncoupling together with a larger antioxidant capacity.

Intracytoplasmic spermatid injection and in vitro maturation: fact or fiction?

Intracytoplasmic injection with testicular spermatozoa has become a routine treatment in fertility clinics. Spermatozoa can be recovered in half of patients with nonobstructive azoospermia. The use of immature germ cells for intracytoplasmic injection has been proposed for cases in which no spermatozoa can be retrieved. However, there are low pregnancy rates following intracytoplasmic injection using round spermatids from men with no elongated spermatids or spermatozoa in their testes. The in vitro culture of immature germ cells to more mature stages has been proposed as a means to improve this poor outcome. Several years after the introduction of intracytoplasmic injection with elongating and round spermatids, uncertainty remains as to whether this approach can be considered a safe treatment option. This review outlines the clinical and scientific data regarding intracytoplasmic injection using immature germ cells and in vitro matured germ cells.

Multinucleation of spermatozoa and spermatids in infertile men chronically exposed to carbofuran.

OBJECTIVE: To report the findings encountered in semen samples coming from two infertile men chronically exposed to carbofuran. METHODS: Semen samples were collected and analyzed as recommended by the World Health Organization. A morphological analysis was carried out by light microscopy. RESULTS: Seminal analysis revealed in the first case a total concentration of 42 million spermatozoa/mL with 17% motility and 20% normal shape. The second patient presented a total concentration of 5 million spermatozoa/mL with 6% motility and 2% normal shape. The patients presented a similar percentage of binucleated spermatozoa (28 and 26%) and of multinucleated spermatids (10 and 6%). CONCLUSION: To our knowledge, this is the first time that alterations in semen samples of men exposed to carbofuran are reported. More research in this area is needed to make conclusions on the subject.

Nucleolar cycle and its correlation with chromatoid bodies in the Tilapia rendalli (Teleostei, Cichlidae) spermatogenesis.

The aim of this study was: (1) to monitor the nucleolar material distribution using cytological and cytochemical techniques and ultrastructural analysis; and (2) to compare the nucleolar material distribution with the formation of the chromatoid body (CB) in the germ epithelium of Tilapia rendalli. Nucleolar fragmentation occurred during the leptotene of prophase I and nucleolus reorganization occurred in the early spermatid nucleus. The area of the early spermatid nucleolus was significantly smaller than that of the spermatogonia nucleolus. Ultrastructural analysis showed an accumulation of nuages, which form the CB, before nucleolar fragmentation in the spermatogonia cytoplasm. The CB was observed in association with mitochondrial clusters in the cytoplasm of primary spermatocytes, as well as in those of initial and later spermatids. In conclusion, the nucleolus seems to be related to CB formation during spermatogenesis of T. rendalli, because at the moment of nucleolus fragmentation in the primary spermatocytes, the CB reaches its largest area and it is able to complete important functions during spermatogenesis. The reorganized nucleolus of the initial spermatids has a lower area due several factors, one of which is the probable migration of nucleolar fragments from the nucleus to the cytoplasm, therefore playing a role in CB formation.

Spermatogenic efficiency in the spiny rat, Trinomys moojeni (Rodentia: Echimyidae).

The spiny rat (Trinomys moojeni) is a rodent found in the Atlantic Forest, which is considered one of the most diverse and threatened biomes in the world. Knowledge on reproductive biology and physiology is critical to conservation and species management, allowing the prevention of extinction and the use of males in natural and artificial reproduction programs. The main objectives of the present study were to investigate the testis structure as well as spermatogenic and Sertoli cell efficiency in the spiny rat captured in the Caraça Natural Reserve, a fragment of the Atlantic Forest located in the State of Minas Gerais, Brazil. Ten sexually mature spiny rats were analyzed. Intraperitoneal injections of tritiated thymidine were administered to estimate duration of spermatogenesis. The testes were perfused-fixed in buffered glutaraldehyde and routinely processed for histological and morphometric analyses as well as the characterization of the stages of seminiferous epithelium cycle. Volume density (%) of seminiferous tubules and Leydig cells were 97 +/- 0.3 and 0.3 +/- 0.02, respectively. The duration of one spermatogenic cycle and total duration of spermatogenesis were 8.6 +/- 0.1 and 38.5 +/- 0.5 days, respectively. Due to the very great volume density of the seminiferous tubules, short duration of spermatogenesis, tubule length per gram of testis (approximately 40 m), great Sertoli cell efficiency (approximately 15 spermatids per Sertoli cell) and large number of Sertoli cells per testis gram (53 million), spermatogenic efficiency in the spiny rat (82 million) is by far the greatest of the mammalian species investigated thus far.

Short-term antiandrogen flutamide treatment causes structural alterations in somatic cells associated with premature detachment of spermatids in the testis of pubertal and adult guinea pigs.

In spite of widespread application of flutamide in the endocrine therapies of young and adult patients, the side effects of this antiandrogen on spermatogenesis and germ-cell morphology remain unclear. This study evaluates the short-term androgen blockage effect induced by the administration of flutamide to the testes of pubertal (30-day old) and adult (65- and 135-day old) guinea pigs, with an emphasis on ultrastructural alterations of main cell types. The testes removed after 10 days of treatment with either a non-steroidal antiandrogen, flutamide (10 mg/kg of body weight) or a pharmacological vehicle alone were processed for histological, quantitative and ultrastructural analysis. In pubertal animals, flutamide androgenic blockage induces spermatogonial differentiation and accelerates testes maturation, causing degeneration and detachment of primary spermatocytes and round spermatids, which are subsequently found in great quantities in the epididymis caput. In post-pubertal and adult guinea pigs, in addition to causing germ-cell degeneration, especially in primary spermatocytes, and leading to the premature detachment of spherical spermatids, the antiandrogen treatment increased the relative volume of Leydig cells. In addition, ultrastructural evaluation indicated that irrespective of age antiandrogen treatment causes an increase in frequency of organelles involved with steroid hormone synthesis in the Leydig cells and a dramatic accumulation of myelin figures in their cytoplasm and, to a larger degree, in Sertoli cells. In conclusion, the transient exposition of the guinea pigs to flutamide, at all postnatal ages causes some degenerative lesions including severe premature detachment of spermatids and accumulation of myelin bodies in Leydig and Sertoli cells, compromising, at least temporarily, the spermatogenesis.

Exposure of young rats to high estrogen doses leads to degeneration of elongated spermatids.

Single high doses of estrogen (35 mg/kg body weight) were administered to young rats aiming to exacerbate its effects on germ cell populations. The short-term (1 week) and medium-term (7 weeks) consequences of this estrogenic treatment (ET) on the testis were evaluated using light and electron microscopies, quantitative methods and TUNEL reaction. Short-term ET led to 50% atrophy of the testis, however, in the medium term the gonado-somatic index was recovered. No histopathological alterations were found at seminiferous epithelium except for short-term severe degeneration of elongated spermatids (EL) and low frequency of these cells in both time intervals. Two morphologically distinct patterns of degeneration were observed: (1) clusters of EL which were TUNEL-negative and exhibited bizarre appearance and nuclear fragmentation, (2) isolated apoptotic EL within the cytoplasm of Sertoli cells (SC). Both degenerative phenomena were more frequent in stages III-VIII of seminiferous cycle, whereas at stages I and II only coiling of flagellum was observed. One week after ET, small amounts of EL were detected in stages IX-XII, suggesting spermiation failure. Signs of functional SC damage such as an accumulation of myelin-like inclusions in their cytoplasm were observed in the short but not medium-term. However, the apoptotic rates still remained five times higher and the number of elongated spermatids was three-fold lower. Our data indicate that exposure to a high dose of estrogen around puberty has stage-specific effects on the testis and causes massive degeneration of elongated spermatids.

Comparative analysis of spermiogenesis and sperm ultrastructure in Callichthyidae (Teleostei: Ostariophysi: Siluriformes)

In Corydoradinae, the presence of spermatids in the lumen of the testicular tubules together with spermatozoa suggests that spermatogenesis is of the semicystic type, whereas in Callichthyinae, sperm production occurs entirely within spermatocysts in the germinal epithelium, characterizing cystic spermatogenesis. Spermiogenesis in Callichthyinae is characterized by an initial lateral development of the flagellum, the presence of nuclear rotation to different degrees, an eccentric or medial formation of a nuclear fossa, formation of a cytoplasmic channel, and presence of centriolar migration, being more similar to type I spermiogenesis. In Corydoradinae, spermiogenesis is characterized by eccentric development of the flagellum, the absence of nuclear rotation, an eccentric nuclear fossa formation, formation of a cytoplasmic channel, and absence of centriolar migration, differing from the types previously described. The process of spermatogenesis and spermiogenesis in Corydoradinae and Callichthyinae revealed unique characters for each of these subfamilies, corroborating the hypotheses that they constitute monophyletic groups. In relation to sperm ultrastructure, the comparative analysis of the callichthyid species shows that the general characteristics found in the spermatozoa were similar, thus, reinforcing the hypothesis that the family is monophyletic

Em Corydoradinae, a presença de espermátides junto com espermatozóides no lúmen dos túbulos testiculares sugere uma espermatogênese do tipo semicística, enquanto que em Callichthyinae a produção do esperma ocorre inteiramente dentro dos espermatocistos no epitélio germinativo, caracterizando a espermatogênese cística. A espermiogênese em Callichthyinae é caracterizada por um desenvolvimento inicial lateral do flagelo, pela presença de rotação nuclear em diferentes graus, formação de uma fossa nuclear excêntrica ou medial, formação de um canal citoplasmático, e presença de migração centriolar, sendo mais similar à espermiogênese do tipo I. Em Corydoradinae, a espermiogênese é caracterizada pelo desenvolvimento excêntrico do flagelo, ausência de rotação nuclear, fossa nuclear excêntrica, formação de um canal citoplasmático, e ausência de migração centriolar, diferindo dos tipos descritos previamente. O processo de espermatogênese e espermiogênese em Corydoradinae e Callichthyinae revelaram caracteres únicos para cada subfamília, corroborando a hipótese de que as mesmas constituem grupos monofiléticos. Em relação à ultraestrutura do esperma, a análise comparativa das espécies de Callichthyidae mostra que as características gerais encontradas nos espermatozóides foram similares, reforçando a hipótese de monofilia da família

Comparative analysis of spermiogenesis and sperm ultrastructure in Callichthyidae (Teleostei: Ostariophysi: Siluriformes)

In Corydoradinae, the presence of spermatids in the lumen of the testicular tubules together with spermatozoa suggests that spermatogenesis is of the semicystic type, whereas in Callichthyinae, sperm production occurs entirely within spermatocysts in the germinal epithelium, characterizing cystic spermatogenesis. Spermiogenesis in Callichthyinae is characterized by an initial lateral development of the flagellum, the presence of nuclear rotation to different degrees, an eccentric or medial formation of a nuclear fossa, formation of a cytoplasmic channel, and presence of centriolar migration, being more similar to type I spermiogenesis. In Corydoradinae, spermiogenesis is characterized by eccentric development of the flagellum, the absence of nuclear rotation, an eccentric nuclear fossa formation, formation of a cytoplasmic channel, and absence of centriolar migration, differing from the types previously described. The process of spermatogenesis and spermiogenesis in Corydoradinae and Callichthyinae revealed unique characters for each of these subfamilies, corroborating the hypotheses that they constitute monophyletic groups. In relation to sperm ultrastructure, the comparative analysis of the callichthyid species shows that the general characteristics found in the spermatozoa were similar, thus, reinforcing the hypothesis that the family is monophyletic(AU)

Em Corydoradinae, a presença de espermátides junto com espermatozóides no lúmen dos túbulos testiculares sugere uma espermatogênese do tipo semicística, enquanto que em Callichthyinae a produção do esperma ocorre inteiramente dentro dos espermatocistos no epitélio germinativo, caracterizando a espermatogênese cística. A espermiogênese em Callichthyinae é caracterizada por um desenvolvimento inicial lateral do flagelo, pela presença de rotação nuclear em diferentes graus, formação de uma fossa nuclear excêntrica ou medial, formação de um canal citoplasmático, e presença de migração centriolar, sendo mais similar à espermiogênese do tipo I. Em Corydoradinae, a espermiogênese é caracterizada pelo desenvolvimento excêntrico do flagelo, ausência de rotação nuclear, fossa nuclear excêntrica, formação de um canal citoplasmático, e ausência de migração centriolar, diferindo dos tipos descritos previamente. O processo de espermatogênese e espermiogênese em Corydoradinae e Callichthyinae revelaram caracteres únicos para cada subfamília, corroborando a hipótese de que as mesmas constituem grupos monofiléticos. Em relação à ultraestrutura do esperma, a análise comparativa das espécies de Callichthyidae mostra que as características gerais encontradas nos espermatozóides foram similares, reforçando a hipótese de monofilia da família(AU)

Ultrastructure of a spermatid transport system in the mature proglottids of experimental Taenia crassiceps (WFU strain).

In classical textbooks of parasitology, the mature proglottids of taeniids are depicted as structures in which the individual testis are connected to the vas deferens through the vas efferens system, usually depicted as a network of channels. From our morphological analyses of proglottids in the cestode Taenia crassiceps, we have been unable to identify this channel network. It is unclear how the spermatids are transported from the testes to the vas deferens, as is unresolved the location of the cells responsible for the production of testosterone (Leydig cells) or the possible equivalent of Sertoli cells, necessary for the differentiation process of these cells. In this experimental work, we have examined the ultrastructure of tissues in the vicinity of the vas deferens in mature proglottids obtained from the intestines of hamsters infected with cysticerci from the peritoneum of infected mice. Worm tissues were fixed, processed, and sectioned for transmission electron microscopy. Significant areas of the testis epithelia emitted cytoplasmic projections surrounded by extracellular matrix, where they appear as septated pockets enclosing free axonemes and spermatids. Vas efferens walls are made up of nucleated cells with cytoplasm annealing to each other through cell membrane junctions. Lodged between the junctions are membrane-bound pouches with dense granules found as aggregates or aligned in a semicircular array. The efferens wall exhibits numerous spermatids emerging into the lumen, an observation that suggests the epithelial wall may have the maturing functions of Sertoli cells of vertebrates. Large cells adjacent to the vas efferens contained prominent rough endoplasmic reticulum and large mitochondria, characteristics described for Leydig cells of vertebrates. Our observations suggest that taeniid spermatids are either transported from the testes to the vas system by epithelial pockets or that the epithelial pockets may be cross-sections of a highly coiled vas efferens system.