Spermatogenesis of Amphisbaena silvestrii (Boulenger, 1902): First Report for Amphisbaenidae
Gametogenesis studies are important to understand ecological and evolutionary processes. We report the first detailed description of spermatogenesis in amphisbaenians and describe the morphology of the male germ cells of Amphisbaena silvestrii and the organization of the germinal epithelium. We sampled the testes of 25 specimens and cut 3-μm thick sections. We then stained these sections by using 1% toluidine blue and photo-documented them. Testes are covered by the tunica albuginea that sends septa between the seminiferous tubules. The interstitial tissue is highly vascularized and consists of loose connective tissue with Leydig cells. Seminiferous tubules are coiled and coated with juxtaposed myoid cells. Sertoli cells and sperm series present a digitiform or pyramidal organization. We observed eight stages of development of the spermatids and the final maturation of spermatozoa during spermiogenesis. Further, we noted significant variation in the nuclear diameters of germ cells. This trait could be used to characterize germ cell types. Estudos da gametogênese são muito importantes no entendimento dos processos ecológicos e evolutivos. Nós apresentamos a primeira descrição detalhada da espermatogênese em anfisbenídeos e descrevemos a morfologia das células germinativas masculinas de Amphisbaena silvestrii e a organização no epitélio germinativo. Nós amostramos os testículos de 25 espécimes, cortados a 3 μm de espessura. Nós, então, coramos estes cortes com azul de toluidina 1% e os fotodocumentamos. Os testículos são revestidos pela túnica albugínea, a qual emite septos por entre os túbulos seminíferos. O tecido intersticial é altamente vascularizado e constituído por tecido conjuntivo frouxo juntamente com as células de Leydig. Os túbulos seminíferos apresentam-se enovelados e revestidos com células mióides justapostas. As células de Sertoli e a série espermática apresentam organização digitiforme ou piramidal. Nós observamos oito estágios de desenvolvimento das espermátides e a maturação final do espermatozoide, durante a espermiogênese. Além disso, nós constatamos uma variação significativa nos diâmetros nucleares das células germinativas. Esta característica pode ser útil para diferenciar os tipos de células germinativas.Abstract
Resumo
Histological features of the testes of Amphisbaena silvestrii. (A) Testes are covered with the tunica albuginea (TA) that sends septa between the seminiferous tubules (double arrow), with evidence of the presence of several fibroblasts (fb), fibrocytes (fc), and larger vessels (V). (B) Smaller vessels (sv) are present below the tunica albuginea and in the interstitial space (int). (C) Interstitial tissue is composed of loose connective tissue with various Leydig cells (circle), which exhibit lipid vesicles (lv) and a large nucleus (n) with dense chromatin. (D) Seminiferous tubules are coiled, evidenced by the different tubular sizes in one section (dotted line). (E) Tubules are lined on the surface by juxtaposed myoid cells (M), and the Sertoli cells (S) can be seen in the periphery of the internal compartment that are responsible for maintaining the germinal epithelium (GE).
Morphology of the germinal chalices in seminiferous tubules of Amphisbaena silvestrii. (A) Sertoli cells and spermatic series with pyramidal organization (dotted line). (B) Morphology of germ cells according to their development in the seminiferous tubule: type A spermatogonia (SgA), type B spermatogonia (SgB), preleptotene primary spermatocyte (Sc1 − pL), leptotene primary spermatocyte (Sc1 − L), zygotene primary spermatocyte (Sc1 − Z), pachytene primary spermatocyte (Sc1 − P), diplotene primary spermatocyte (Sc1-D), primary spermatocyte metaphase 1 (Sc1 − M1), interphase secondary spermatocyte (Sc2 − In), secondary spermatocyte metaphase 2 (Sc2 − M2), spermatid stage 1 (S1), spermatid stage 2 (S2), spermatid stage 3 (S3), spermatid stage 4 (S4), spermatid stage 5 (S5), spermatid stage 6 (S6), spermatid stage 7 (S7), spermatid stage 8 (S8), and spermatozoa (Sz) in the lumen of the seminiferous tubule; (C) variation of nuclear diameter of germ cell types (F = 215.452; P < 0.001), and when compared in subsequent cell classes, the difference between the variances remained in most of the cell types (tSgA−SgB = 5.253; tSgB−Sc1−pL = 8.437; tSc2−In−Sc2−M2 = 10.577; tS1−S2 = 7.875; tS2−S3 = −4.574; tS3−S4 = 9.428; tS4−S5 = −3.600; tS5−S6 = −15.638; tS6−S7 = −11.218; tS7−S8 = −15.656; tS8-Sz = −3.297; P < 0.01).
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