Abstract Letrozole comprises a non-steroid aromatase inhibitor that has been applied as a preventive for many uses, such as breast cancer prevention, treatment of hormonal dysfunction, and male infertility. Precisely in Northeast Brazil, ovine consist of the leading livestock produced, and their reproduction in captivity has been demonstrated difficult. Thus, we hypothesized whether the application of letrozole will improve male sheep reproduction. One group of 6 animals received a daily dosage of 0.5mg/Kg of letrozole for 60 days, while the other six animals were used as control. Samples were collected from control and treated animals after 30 and 60 days of the experiment. Blood samples were collected to measure the steroid hormone levels. Semen was collected from control and treated groups using an artificial vagina and cryopreserved for spermatozoa morphology and CASA analysis. The testicles were collected for histological analysis, gene expression, and immunohistochemistry of P450aromatase protein. Hormone levels demonstrate no differences in the estradiol/testosterone levels among the control and both treated groups. Immunohistochemistry analysis revealed the presence of P450aromatase protein in spermatogonia cells and Leydig cells in the control and treated groups in both periods analyzed. Moreover, there were no differences in the P450aromase gene expression in the control and treated group. Morphological analysis of the spermatozoa revealed that letrozole treatment did not affect mitochondrial activity or cause any deformities. In addition, motility parameters in the sperm from the treated group were not affected by letrozole treatment compared to the control group. Morphological analysis of the testis demonstrated that letrozole treatment increase the seminiferous tubule area but no signs of germ cell damage. Our results show that letrozole has a morphological effect on the testicles in the ovine model but no pathological or severe effect caused by hormone level imbalance. Overall, letrozole comprises a non-steroid aromatase inhibitor, which can be applied to ovine reproduction.

Abstract Sex steroid hormones are critical in gonadal differentiation in turtles. The gonads are not the only organs responsible for producing these hormones during this phase. Mesonephros play an important role in steroidogenesis. The present study aimed to investigate the presence of steroidogenic cells in mesonephros of Podocnemis expansa during gonadal differentiation and to evaluate their morphology and ultrastructure. Ten embryos of P. expansa were collected from 5 nests on day 36 of incubation, during spawning period on an artificial beach. Embryos were extracted from eggs by slicing the shell and euthanized. They were dissected under a stereoscopic microscope to collect the gonad-mesonephro complex, in which were fixed and subsequently processed for light microscopy, immunohistochemistry and transmission electron microscopy analysis. During histological analysis was observed mesonephros has typical morphological structure. Immunohistochemistry showed immunoreaction to aromatase in cells of intertubular space. Confirming these findings, it was possible to observe a type of intertubular cell in several regions of mesonephro, being more predominant in region close to blood vessels, distal and proximal tubules. In ultrastructural analysis these cells were characterized by having a clear, large, and rounded nucleus with evident nucleolus and cytoplasm rich in electron-dense droplets. This study demonstrated for the first time the presence of cells with morphological, immunohistochemical and ultrastructural characteristics similar to steroid-producing cells in P. expansa mesonephrons, suggesting that this organ may contribute to gonadal differentiation in this species.

Abstract Estrogens and progestogens are hormones produced by maternal organs and it is required for recognition and maintenance of pregnancy. In addition, the embryo may also be a source. For this, the aim was to identify steroidogenic expression on Galea spixii embryos early in the embryonic period. Embryos were collected on Days 10 and 15 of gestation; some were fixed in 4% paraformaldehyde for morphological and immunohistochemical analysis (P450arom), whereas others had RNA extracted to determine presence of CYP19a1 gene. In addition, for immunochemistry, maternal ovaries were collected as positive control tissues. Maternal tissues had positive staining for aromatase, whereas none of the embryos stained for P450 aromatase. Based on qPCR reactions, CYP19a1 gene were expressed in all embryos. Galea spixii embryos expressed steroidogenic genes during the post-implantation period, indicating they have the potential to produce steroid hormones.

SUMMARY: This study aimed to construct three-dimensional (3D) anatomical models of the tongue of domestic mammals of veterinary interest. The tongues were obtained from the didactic collection of the Laboratory of Veterinary Macroscopic Anatomy in the Surgery Department of the School of Veterinary Medicine and Animal Science, University of Sao Paulo. Tongues from a cow, dog, horse, and pig were selected for scanning and creation of the 3D-printed models. The printer used a filamentous thermoplastic material, acrylonitrile-butadiene-styrene (ABS), which was deposited together with a support resin. In addition to the printing of models, an interactive 3D PDF was generated, creating a didactic collection for students. The anatomical characteristics and peculiarity of the tongues were easily identified in the scanned and printed images. The 3D scanning and printing offered an innovative method of visualizing different anatomical structures and, together with the existing methods, can optimize anatomy teaching in an educational context.

RESUMEN: Este estudio tuvo como objetivo construir modelos anatómicos tridimensionales (3D) de la lengua de mamíferos domésticos de interés veterinario. Las lenguas se obtuvieron de la colección didáctica del Laboratorio de Anatomía Macroscópica Veterinaria del Departamento de Cirugía de la Facultad de Medicina Veterinaria y Zootecnia de la Universidad de São Paulo. Se seleccionaron lenguas de vaca, perro, caballo y cerdo para escanear y crear los modelos impresos en 3D. La impresora utilizó un material termoplástico filamentoso, acrilonitrilo-butadieno-estireno (ABS), que se depositó junto con una resina de soporte. Además de la impresión de modelos, se generó un PDF 3D interactivo, creando una colección didáctica para los estudiantes. Las características anatómicas y la peculiaridad de las lenguas se identificaron fácilmente en las imágenes escaneadas e impresas. El escaneo e impresión 3D ofrecieron un método innovador para visualizar diferentes estructuras anatómicas y, junto con los métodos existentes, puede optimizar la enseñanza de la anatomía en un contexto educativo.

Abstract Letrozole is used as a therapeutic agent in reproductive disorders caused by high estrogen levels. Letrozole inhibits cytochrome P450 aromatase and reduces estrogen levels. However, the effects of long-term use on reproductive traits are unknown. The aim of this study was to evaluate the prolonged use of letrozole in the gonads of rodents (Spix's yellow-toothed cavy; Galea spixii). Forty-eight rodents (24 males and 24 females) were randomly divided into the treated and control groups. Letrozole administration started at 15 days of age and continued weekly until 30, 45, 90, and 120 days of age. The body, testis, and ovary weights were analyzed, as well as the morphological progression of spermatogenesis and folliculogenesis. Macroscopically, body weight gain and gonads weight were increased in the letrozole group. Microscopically, the ovaries of treated females showed stratified epithelium and a cellular disorder of the tunica albuginea. In the testes of treated males, the development of seminiferous tubules was delayed and sperm was absent. The collective findings indicate that the prolonged use of letrozole alters secondary sexual characteristics, and causes weight gain, reproductive changes, and male infertility.

SUMMARY: To contribute knowledge of an important experimental model for studies on skin embryology, a study was carried out to describe the morphological events of the skin during the intrauterine life of Cavia porcellus from the 10th to the 60th day of gestation. Embryos and fetuses were dissected, and the skin of the nasal, cranial, lumbar and anal regions was processed byoptical microscopy. At 30 days the first hairs, called lanugos, were observed in the cranial region. The morphological description showed that a few days can make a great difference in development.

RESUMEN: Con el objetivo de contribuir al conocimiento de un importante modelo experimental para estudios sobre embriología de la piel, se llevó a cabo un estudio para describir los eventos morfológicos de la piel durante la vida intrauterina de Cavia porcellus desde el día 10 hasta el día 60 de gestación. Los embriones y los fetos se disecaron y se procesó la piel de las regiones nasal, craneal, lumbar y anal, mediante microscopía óptica. A los 30 días se observaron los primeros vellos, llamados lanugos, en la región craneal. La descripción morfológica mostró que unos pocos días pueden marcar una gran diferencia en el desarrollo.

Este estudo teve como objetivo caracterizar a morfologia dos ductos deferentes deKinosteron scorpioides por meio de análise macroscópica e microscópica. Foram utilizados 20 machos adultos, coletados em intervalos regulares durante o ano, os quais foram divididos em quatro grupos experimentais nas estações chuvosa e seca. Os ductos deferentes foram processados para análise por microscopia de luz, microscopia eletrônica de varredura e microscopia eletrônica de transmissão. Morfometria para diâmetros tubular e luminal e altura epitelial também foram realizadas. Na época das chuvas, o ducto deferente apresentou epitélio pseudoestratificado com células cilíndricas, espermatozoides e líquido leitoso no lúmen, além de com organelas citoplasmáticas e vesículas lipídicas. Na estação seca, o epitélio do ducto deferente foi do tipo pseudoestratificado com células cuboides e debris celulares, sendo que nenhum espermatozoide foi encontrado nesta estação. Houve variação significativa (p <0,05) para a morfometria dos ductos deferentes, com menores valores de diâmetros tubular e luminal na estação chuvosa, e maior altura do epitélio na estação seca.

This study aimed to characterize the morphology of the vas deferens ofKinosteron scorpioides by macroscopic and microscopic analysis. Were used 20 adult male jurarás collected at regular intervals during the year and divided into four experimental groups in the rainy and dry seasons, being processed for light microscopy, scanning electron microscopy and transmission electron microscopy. Morphometry for tubular and luminal diameters and epithelial height were also performed. On rainy season, vas deferens presented pseudostratified epithelium with cylindrical cells, spermatozoids and milky fluid in the lumen, with cytoplasmic organelles and lipid vesicles. On dry season, epithelium was pseudostratified with cuboid cells, with cellular debris and no spermatozoids. There was significant variation (p<0,05) for morphometry of vas deferens, with lower values of tubular and luminal diameters on rainy season, and higher epithelial height on dry season.

Realizou-se um estudo para analisar morfologicamente os dentes do saguis-de-tufo-branco (C. jacchus), saguis-de-tufo-preto (C. penicillata) e saguis-de-cara-branca (C. geoffroyi), para compara-los entre si e com outras espécies já descritas na literatura. Utilizou-se dentes das três espécies para analises macroscópicas, microscópicas e ultraestrutural e os resultados correlacionados com os obtidos com outras espécies citadas na literatura. Chegou-se a conclusão de que: as três espécies apresentaram uma fórmula dentária idêntica, chegando a um total de 32 dentes, expressa na fórmula 2x: incisivos 2/2; caninos 1/1; pré-molares 3/3 e molares 2/2, estes são classificados como diplodontes, anelodontes, bunodontes, e braquiodontes.

A study was conducted to analyze the morphology of the teeth of white-tufted-ear-marmoset (C. jacchus) black-tufted-ear-marmoset (C. penicillata) and marmosets-white-faced (C. geoffroyi), to compare them among themselves and with other species described in the literature. Teeth of the three species were submitted to macroscopic, microscopic and ultrastructural analyzes. The results were correlated with those of other species. We concluded that: the three species have a similar dental formula, reaching a total of 32 teeth, expressed in the formula 2x: incisors 2/2; canines 1/1, pre-molars 3/3 and molars 2/2, ich are classified as diplodont, anelodont, bunodont and brachyodont.

O objetivo deste trabalho foi analisar a distribuição dos vasos arteriais nos testículos em caprinos com diferentes graus de divisão escrotal. A configuração escrotal foi classificada da seguinte forma: Grupo I: constituído por caprinos com escroto único, Grupo II: com escroto separado até a metade do testículo e Grupo III: com separação escrotal estendendo-se além da metade do testículos. As artérias foram injetadas e coradas com solução de acetado de vinil, sendo os orgãos (30 pares) submetidos à corrossão para obtenção dos moldes vasculares. As artérias testiculares emergem da aorta abdominal, com trajeto retilíneo, atravessam o canal inguinal, apresentam-se espiraladas e envolvidas parcialmente pelo plexo pampiniforme. Próximo à extremidade caudada do testículo, dividem-se mais freqüentemente nos ramos cranial e caudal, os quais emitem vasos colaterais, de onde emergem ramos penetrantes. Os testículos dos animais com nível intermediário de divisão escrotal (Grupo II) apresentam menor quantidade destes ramos, sendo os quadrantes mais povoados o ventrolateral e o dorsolateral. Conclui-se que a origem, o trajeto e a distribuição das artérias testiculares não apresentam variações relacionadas ao grau de divisão escrotal em caprinos.

The objective of this study was to describe the distribution of testicular arterial vessels in caprines with different degrees of scrotal division. Scrotal configurations were classified as follows; Group I: scrotum without bipartition; Group II: scrotum showing a ventral division until the middle of the testis; and, Group III: scrotal separation extended beyond the middle of the testis. A colored vinyl acetate solution was injected into 60 testicular arteries (30 pairs). After, the samples were submitted to corrosion cast method to obtain tubular vascular models for macroscopic analysis. We observed that the testicular arteries emerge from the abdominal aorta, cross the inguinal canal to become coiled and involved by the pampiniform plexus. Close to the caudal extremity of the testis, the arteries become divided in cranial and caudal branches that emit collateral vessels to originate emerging branches. Testicles with intermediate level of scrotal division (group II) showed a smaller amount of those branches than the others, being the most populated the ventrolateral and the dorsolateral quadrants. The origin, distribution and localization of the testicular arteries did not show any differences related to the degree of scrotal division in caprines.

Aspectos macroscópicos e morfométricos dos testículos em catetos e queixadas. Este trabalho objetiva fornecer dados macroscópicos e morfométricos dos testículos dos catetos e queixadas. O material utilizado consistiu de catetos e queixadas oriundos da Fazenda Devaneio Pró-Fauna, Iguape, SP (Reg.1/3593/08480). Em 33 queixadas e 20 catetos, após o abate, os testículos foram colhidos e tomados dados morfométricos como: comprimento, largura e espessura (com o auxílio de um paquímetro). Os testículos são ovalados, localizados na região pélvica, inclinados dorso-caudalmente e possuem posição intermediária. O mediastino testicular esta no centro do testículo, ligeiramente desviado para a margem epididimária deste, e termina na extremidade capitata. Os queixadas adultos possuem em média 30,92 ± 3,82 kg de peso corporal e 78,89 ± 4,77 cm de comprimento corporal, enquanto os jovens apresentam 22,93 ± 2,07 kg e 71,57 ± 3,95 cm de comprimento. Os resultados demonstram que no grupo de queixadas adultos estudado o testículo direito teve comprimento, largura e espessura médios de 5,36 ± 0,64cm; 3,64 ± 0,64cm e 3,30 ± 0,52cm respectivamente, enquanto que o esquerdo teve 5,45 ± 0,77cm; 3,68 ± 0,59cm e 3,32 ± 0,54cm. Nos queixadas jovens os valores encontrados foram de 3,20 ± 0,44cm, 2,12 ± 0,26cm e 2,11 ± 0,40cm, e de 3,23 ± 0,47cm; 2,21 ± 0,39cm e 1,99 ± 0,36cm, para a largura, comprimento e espessura dos testículos direito e esquerdo respectivamente. Já para os catetos o testículo direito teve comprimento, largura e espessura de 4,36 ± 0,38cm; 2,74 ± 0,27cm e 2,33 0,46cm respectivamente, enquanto que o esquerdo teve 4,19 ± 0,36cm; 2,68 ± 0,31cm e 2,34 ± 0,28cm. Os dados analisados não tiveram diferenças significativas (p<0,05) entre os valores encontrados para os testículos direito e esquerdo pelo testes de Qui-dradado.

Macroscopic and morphometric features of testicles in collared peccary and white-lipped peccary. This work aims to describe the morphometrical aspects on the testicles of the collared peccary and white-lipped peccary. The material derived from the Devaneio Pro-Fauna Farm, Iguape, SP (Reg.1/3593/08480). From 33 white-lipped peccary and 20 collared peccary after the slaughter, the testicles were removed and morphometric information was taken like: length, width and thickness (with the help of a pachymeter). Testicles are oval shaped, located into the pelvic region, laying dorsocaudally and they have intermediary position. The mediastinun testis is in the center of the testis and ends on the capitata extremity. The adult white-lipped peccary has 30.92 ± 3.82 kg in average and 78.89 ± 4.77 cm of length and the young has 22.93 ± 2.07 kg and 71.57 ± 3.95 cm of length. Results obtained show that in the adult white-lipped peccary group, the right testicle measured, in average, length, width and thickness of 5.36 ± 0.64cm, 3.64 ± 0.64cm and 3.30 ± 0.52cm respectively while the left testicles measured, in average, 5.45 ± 0.77cm, 3.68 ± 0.59cm and 3.32 ± 0.54cm. In the young group the testis measured in average 3.20 ± 0.44cm, 2.12 ± 0.26cm and 2.11 ± 0.40cm, to right testis and 3.23 ± 0.47cm, 2.21 ± 0.39cm and 1.99 ± 0.36cm, to left testis, to length, width and thickness, respectively. As per the collared peccary, the right testicles measured, in average, 4.36 ± 0.38cm; 2.74 ± 0.27cm and 2.33 ± 0.46cm respectively for length, width and thickness, when for the left ones measures were 4.19 ± 0.36cm, 2.68 ± 0.31cm and 2.34 ± 0.28cm. The data does not have significative difference (p<0.05) between right and left testicular measurements using the Qui-square test.

Foi estudado, por meio da histometria, o desenvolvimento testicular em 31 cutias da espécie Dasyprocta aguti desde o nascimento até 14 meses de idade. O diâmetro e a área, médios, foram obtidos a partir de 30 secções transversais de cordões e/ou túbulos seminíferos, em cada testículo, utilizando-se sistema de computadorizado de analises de imagem e uma ocular micrométrica Zeiss CPL 10X, acoplada a uma objetiva de 40X. As proporções volumétricas do testículo foram obtidas com o método estereométrico, segundo Elias, Henning e Schwartz¹. O diâmetro tubular médio apresentou crescimento lento desde o nascimento até os oito meses de idade, nas duas metodologias empregadas. Quando foi usada a ocular micrométrica observou-se que, a partir de nove meses, o diâmetro tubular teve um crescimento acelerado, chegando a duplicar o seu valor, se comparado com grupo etário que o antecedia. A proporção volumétrica dos cordões testiculares e túbulos seminíferos cresceu gradualmente, atingindo, aos nove meses, seu valor máximo (86,50%). As células de Leydig apresentaram proporção volumétrica decrescente, e seus maiores valores foram expressivos do nascimento até quatro meses de idade (7,00 ± 1,77% a 9,55 ± 0,64%) e mínimos a partir de nove meses, tendendo ainda a uma estabilização. O estroma diminuiu com a evolução da idade caindo bruscamente a partir da puberdade. Conclui-se que o diâmetro dos cordões testiculares e túbulos seminíferos apresentou maior crescimento, coincidindo com o início da puberdade e a proporção volumétrica das células de Leydig encontrou-se, respectivamente, mais alta e mais baixa no mesmo período.

The testicular development in 31 Agoutis, of the Dasyprocta aguti species, from the birth up to 14 months of age was studied through the histometric analysis. Mid diameter and the mean area, in each testicle, were obtained through 30 crosscuts of the funiculus and/or the seminiferous tubule, by means of a computerized system for image analysis and a Zeiss CPL 10X ocular micrometric device, coupled to an objective lens of 40X. Testicles volume proportions were obtained through the stereometric method, according to Elias, Henning and Schwartz¹. Tubule medium diameter presented a slow growth from the birth to the eight months of age, for both used methodologies. When the ocular micrometric device was used it was observed that, beginning in the ninth month, the tubule diameter had an accelerated growth getting to duplicate its value if compared with the preceded age group. The volume proportion of the testicle cord and the seminiferous tubule grew gradually, reaching its maximum value (86,50%) on the ninth month. The Leydig cells presented a decreasing volume proportion, and their largest values were expressive from the birth up to four months of age (7,00 ± 1,77% to 9,55 ± 0,64%) and a minimum value, starting from nine months, still tending to stabilize. The stroma decreased with the development of age and fall abruptly when the puberty starts. It is concluded that the diameter of the testicles cords and seminiferous tubule presented a larger growth coinciding with the start of puberty and the volume proportion of the Leydig cells was lower in the same period.

A determinação do estabelecimento da puberdade é bastante estudada em animais domésticos e roedores, no entanto, são escassas as pesquisas com a finalidade de estabelecer parâmetros para a biologia reprodutiva em cutias. Foram utilizadas 31 cutias machos da espécie Dasyprocta agouti, oriundas da Universidade Federal do Piauí, Estado do Piauí, e da Escola Superior de Agricultura de Mossoró, Estado do Rio Grande do Norte. Imediatamente após a orquiectomia foram retirados fragmentos e estes foram processados histologicamente, os tecidos foram corados com hematoxilina-eosina e analisou-se os parâmetros seguintes: aspectos de luminação dos túbulos seminíferos; presença de espermatócitos primários; presença de espermátides e formação dos primeiros estágios do ciclo do epitélio seminífero (CES) segundo o método da morfologia tubular. O período desde o nascimento até os cinco meses de idade correspondeu à fase impúbere; dos seis aos oito meses de idade a fase de transição da pré-puberdade à puberdade; dos nove aos dez meses de idade à fase da puberdade; e dos doze aos quartoze meses de idade à fase da pós-puberdade. A puberdade da cutia (Dasyprocta aguti), ocorreu em animais a partir dos sete meses de idade, e o estabelecimento da puberdade foi constatado em todos os animais estudados aos nove meses de idade.

The determination of the puberty beginning is widely studied in domestic animals and rodents. However, there are scarce researches with the purpose to establish parameters for the reproductive biology in Agoutis. Thirty-one male Agoutis, Dasyprocta agouti species had been used, originated from the Universidade Federal do Piauí - PI, and from the Mossoró Superior Scholl of Agriculture - RN. Immediately after the orchiectomy, histological sections were made, the tissues were stained with hematoxylin-eosine and analyzed for the following parameters: aspects of the seminiferous tubule lumen; presence of primary spermatocytes; presence of spermatid cells and formation of the first stages of the seminiferous epithelium cycle (SEC), in accordance with the tubular morphology method. The period from the birth up to five months of age corresponded to the impuberal phase; from six to eight months, to the transition from the prepuberal phase to puberty; from nine to ten months, to the puberty; and, from twelve to fourteen months of age to the after-puberty phase. The puberty of the Agouti (Dasyprocta aguti), occurred since seven months of age, being the establishment puberty beginning evidenced at nine months of age.

Analisou-se os dados biométricos do desenvolvimento testicular e peso corporal de 31 cutias (Dasyprocta aguti) desde o nascimento até os 14 meses de idade. As correlações entre o peso corporal, idade e parâmetros testiculares apresentaram-se altamente significativas. O peso testicular, o volume testicular, assim como os demais parâmetros biométricos testiculares (comprimento, diâmetro e perímetro), evoluíram lenta e gradualmente até os 8 meses de idade. A partir dos 9 meses, o crescimento foi mais rápido. O desenvolvimento biométrico do testículo pode ser dividido em duas fases, de 0 - 8 meses e de 9 - 14 meses de idade, sendo 9 meses considerado ponto de corte em se tratando de desenvolvimento testicular de cutias criadas em cativeiro.

Biometric data of the testicular and corporal weight development of 31 Agoutis (Dasyprocta aguti), from the birth up to 14 months of age, were analyzed. The correlations between corporal weight, age and testicular parameters were highly significant. Testicular weight, testicular volume, as well other testicular biometric parameters (length, diameter and perimeter), evolved slow and gradually until eight months of age. Beginning on 9 months of age, the growth was faster, and in this period. the seminiferous epithelium was already formed. Biometric development of the testes can be shared in two phases: 0 - 8 months and 9 - 14 months of age, however the 9 months age are the maximum point of the testicular development in Agoutis (Dasyprocta aguti) rised in captivity.

A cutia (Dasyprocta aguti) é um roedor silvestre encontrado amplamente na região Nordeste do Brasil. É uma espécie muito utilizada pela população humana de baixa renda como fonte alternativa de proteína na alimentação. Foram utilizadas 31 cutias, machos, provenientes da Universidade Federal do Piauí, Estado do Piauí e da Escola Superior de Agricultura de Mossoró Estado do Rio Grande do Norte. Os animais foram divididos em grupos etários desde o nascimento até os 14 meses de idade. O diâmetro nuclear médio foi obtido pela medida de 10 núcleos do tipo celular estudado em cada testículo, no estágio 1 do ciclo do epitélio seminífero. Nos animais que não apresentaram o epitélio organizado em estágios bem definidos em virtude da idade, foram feitas medidas em secções transversais escolhidas somente pelo contorno circular. O início da assincronia do processo espermatogênico foi observado a partir dos seis meses de idade. A puberdade, na cutia Dasyprocta aguti, foi definitivamente estabelecida a partir dos nove meses de idade, pois estavam presentes todos os tipos celulares e espermatozóides liberados no lume tubular em grande parte do parênquima testicular.

The Agouti (Dasyprocta aguti) is a wild rodent that, in the Northeast region of Brazil, is a species that is very used by the low-income population as an alternative protein source for human feeding. Thirty-one male Agouti were used, coming from the Universidade Federal do Piauí (UFPI) - Piauí State, and from Escola Superior de Agricultura de Mossoró (ESAM) - Rio Grande do Norte State - Brazil. The animals were divided in to age groups, from the birth to fourteen months old. The average diameter average of the nucleus was obtained by measuring 10 nuclei of the studied cellular type, in each testicle that was in the stage I of the seminiferous epithelium cycle. This was performed in animals that did not present an organized epithelium in well-defined periods due to the age, and measurements were made in transversal sections chosen only for the circular contour. The beginning of the asynchronism of the spermatogenic process was observed since the six months of age. The puberty of the Agouti Dasyprocta aguti was definitely established at nine months of age, because all the cellular types and free spermatozoa in the tubular lumen were present in a large extent of the testicular parenchyma.