Caracterização do ciclo reprodutivo de machos e fêmeas de Eptesicus furinalis (Vespertilionidae, Chiroptera): morfologia e variação hormonal
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Data
2018-02-23
Autores
Bueno, Larissa Mayumi
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Universidade Estadual Paulista (Unesp)
Resumo
Os morcegos apresentam ampla diversidade nos aspectos reprodutivos, entretanto, são poucos os estudos detalhados sobre a morfologia reprodutiva de Chiroptera, principalmente nas espécies de clima tropical. O estudo dos aspectos reprodutivos de uma espécie é de grande importância para, por exemplo, o entendimento de estratégias para sua conservação. Portanto, o presente estudo teve como objetivos analisar a morfologia dos órgãos reprodutivos de machos e fêmeas de Eptesicus furinalis (Vespertilionidae), uma espécie de grande distribuição pela América do Sul, além de comparar a foliculogênese e a morfologia geral dos ovários dessa espécie com a espécie simpátrica Artibeus planirostris (Phyllostomidae). Nos machos de E. furinalis, durante o processo de regressão testicular, no qual o testículo apresenta quatro fases reprodutivas distintas morfologicamente (fase ativa, em regressão, regredida e recrudescência), as células testiculares apresentaram variação na imunomarcação de receptores hormonais androgênicos (AR) e luteinizantes (LHR). Essa variação na imunomarcação desses receptores indica a participação hormonal no controle do processo da regressão testicular, por meio da ativação do AR nas células de Sertoli, e LHR nas células de Leydig. Na fase de regressão testicular, a imunomarcação de LHR e AR tende a diminuir, causando a desativação da espermatogênese, e na fase de recrudescência testicular ocorre um aumento na imunomarcação de LHR e AR, os quais reativam a espermatogênese. A morfologia do epidídimo, que é dividido em cabeça, corpo e cauda, e tem o epitélio composto por células principais, apicais, basais, estreitas, claras e halo, também sofre influencia do processo de regressão testicular, evidenciadas principalmente pela altura do epitélio e porcentagem relativa do lúmen e do estroma. Com relação às fêmeas, a morfologia geral dos ovários diferiu entres as espécies: enquanto E. furinalis apresentou uma abundância de glândulas intersticiais e folículos primordiais distribuídos por todo o ovário, os ovários de A. planirostris apresentaram poucas glândulas intersticias e os folículos primordiais estão localizados em uma área específica, constituindo um ovário polarizado. No processo da foliculogênese de A. planirostris e E. furinalis foram reconhecidos cinco tipos de folículos ovarianos: primordiais, primários, secundários, terciários e antrais. Em E. furinalis a ovulação ocorre em ambos os ovários, podendo ser liberados mais de um oócito por ovário (poliovular), enquanto em A. planirostris as fêmeas liberam um único oócito predominantemente pelo ovário esquerdo (monovular). No período de Janeiro a Julho, as fêmeas de E. furinalis estavam em condição não reprodutiva, ou seja, não estavam em período de gravidez ou lactação, sendo que de Maio a Julho foram observados espermatozoides no útero, indicando portanto, ocorrência de cópula. No período de Agosto a Dezembro, as fêmeas apresentaram condições de gravidez e/ou lactação, podendo exibir até quatro embriões no útero bicórneo no estágio inicial da gravidez (Agosto e Setembro), que se reduziu para dois embriões em estágio mais avançado (Outubro). As variações na concentração sérica de estradiol, a presença de folículos antrais nos períodos de gravidez e lactação, e a presença de fêmeas lactantes e grávidas concomitantemente sugerem a ocorrência de estro pós-parto na espécie. Portanto, os resultados obtidos nesse trabalho demonstram a variação morfológica dos órgãos reprodutivos entre espécies de morcegos simpátricas, em especial, as espécies A. planirostris e E. furinalis, bem como a complexidade da morfologia e do controle hormonal da reprodução em E. furinalis
Bats show the greatest reproductive diversity within all mammals, however, there are few studies about the detailed reproductive morphology in Chiroptera, principally about tropical species. The study of the reproductive aspects of a species is of great importance to understand, for example, the strategies for its conservation. Therefore, our aims were to analyze the morphology of male and female reproductive organs of Eptesicus furinalis (Vespertilionidae), a species of great distribution in South America, and to compare the folliculogenesis and general morphology of the ovaries of this species with the sympatric species Artibeus planirostris (Phyllostomidae). In males of E. furinalis, during the process of testicular regression, in which testes show four reproductive phases morphologically distinct (active phase, regression, regressed and recrudescence), the testicular cells showed variation in the immunostaining of androgen and luteinizing hormone receptors. These immunostaining indicate the involvement of these hormones in the control of the process of testicular regression, and this control occurs through the activation of androgen receptors in Sertoli cells and luteinizing hormone receptors in Leydig cells. In the testicular regression phase, the immunostaining of LHR and AR tends to decrease, which causes the deactivation of spermatogenesis, and in the testicular recrudescence phase occurs an increase in the immunostaining of LHR and AR, which reactivates spermatogenesis. The morphology of the epididymis, which is divided into caput, corpus and cauda, and has the epithelium composed of main, apical, basal, narrow, clear and halo cells, is also influenced by the process of testicular regression, evidenced mainly by the height of the epithelium and percentage of lumen and stroma. In regard of the females, the general morphology of the ovaries differed between species, in which E. furinalis presented an abundance of interstitial glands cells and the primordial follicles are distributed throughout the ovary, and the ovaries of A. planirostris showed few interstitial glands cells and the primordial follicles are located in a specific area of the ovary, composing a polarized ovary. In the folliculogenesis process of A. planirostris and E. furinalis, five types of follicles were recognized: primordial, primary, secondary, tertiary and antral follicles. In E. furinalis, ovulation occurs in both ovaries, and more than one oocyte can be released per ovary (poliovular), whereas in A. planirostris, females release a single oocyte predominantly from the left ovary (monovular). In the period from January to July, the females of E. furinalis were in a non-reproductive condition, i.e., they were not in the period of pregnancy or lactation, and from May to July we observed spermatozoa in the uterus, indicating the occurrence of copulation in these months. In the period from August to December, females were in pregnancy and / or lactation conditions, and presented four embryos in the bicornous uterus at the initial stage of pregnancy (August and September), which was reduced to two embryos in late pregnancy (October). Variations in the concentration of serum estradiol, the presence of antral follicles during pregnancy and lactation, and the presence of lactating and pregnant females at the same time suggest the occurrence of postpartum estrus in the species. Therefore, our results demonstrate the variation of the morphology of the reproductive organs among sympatric species of bats, in particular, the species A. planirostris and E. furinalis, and the complexity of the morphology and the hormonal control of the reproduction in E. furinalis.
Bats show the greatest reproductive diversity within all mammals, however, there are few studies about the detailed reproductive morphology in Chiroptera, principally about tropical species. The study of the reproductive aspects of a species is of great importance to understand, for example, the strategies for its conservation. Therefore, our aims were to analyze the morphology of male and female reproductive organs of Eptesicus furinalis (Vespertilionidae), a species of great distribution in South America, and to compare the folliculogenesis and general morphology of the ovaries of this species with the sympatric species Artibeus planirostris (Phyllostomidae). In males of E. furinalis, during the process of testicular regression, in which testes show four reproductive phases morphologically distinct (active phase, regression, regressed and recrudescence), the testicular cells showed variation in the immunostaining of androgen and luteinizing hormone receptors. These immunostaining indicate the involvement of these hormones in the control of the process of testicular regression, and this control occurs through the activation of androgen receptors in Sertoli cells and luteinizing hormone receptors in Leydig cells. In the testicular regression phase, the immunostaining of LHR and AR tends to decrease, which causes the deactivation of spermatogenesis, and in the testicular recrudescence phase occurs an increase in the immunostaining of LHR and AR, which reactivates spermatogenesis. The morphology of the epididymis, which is divided into caput, corpus and cauda, and has the epithelium composed of main, apical, basal, narrow, clear and halo cells, is also influenced by the process of testicular regression, evidenced mainly by the height of the epithelium and percentage of lumen and stroma. In regard of the females, the general morphology of the ovaries differed between species, in which E. furinalis presented an abundance of interstitial glands cells and the primordial follicles are distributed throughout the ovary, and the ovaries of A. planirostris showed few interstitial glands cells and the primordial follicles are located in a specific area of the ovary, composing a polarized ovary. In the folliculogenesis process of A. planirostris and E. furinalis, five types of follicles were recognized: primordial, primary, secondary, tertiary and antral follicles. In E. furinalis, ovulation occurs in both ovaries, and more than one oocyte can be released per ovary (poliovular), whereas in A. planirostris, females release a single oocyte predominantly from the left ovary (monovular). In the period from January to July, the females of E. furinalis were in a non-reproductive condition, i.e., they were not in the period of pregnancy or lactation, and from May to July we observed spermatozoa in the uterus, indicating the occurrence of copulation in these months. In the period from August to December, females were in pregnancy and / or lactation conditions, and presented four embryos in the bicornous uterus at the initial stage of pregnancy (August and September), which was reduced to two embryos in late pregnancy (October). Variations in the concentration of serum estradiol, the presence of antral follicles during pregnancy and lactation, and the presence of lactating and pregnant females at the same time suggest the occurrence of postpartum estrus in the species. Therefore, our results demonstrate the variation of the morphology of the reproductive organs among sympatric species of bats, in particular, the species A. planirostris and E. furinalis, and the complexity of the morphology and the hormonal control of the reproduction in E. furinalis.
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Palavras-chave
AR, LH, Morfologia reprodutiva, Ovários, Úteros, Regressão testicular, Epidídimos, Estradiol, Reproductive morphology, Ovaries, Uterus, Testicular regression, Epididymis