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Descriptive morphometry and stereology of the tubular compartment in the wild rodent Hylaeamys megacephalus (Rodentia: Cricetidae) from Central Brazil

Abstract:

Information on reproductive characteristics of wild rodents is scarce in the literature. This study aimed to assess the testis morphometry and stereology of Hylaeamys megacephalus. We used five animals in the study, captured in forest fragments in southwestern Goias State, between April and August 2009. The testes were fixed in Karnovsky solution, dehydrated, and embedded in methacrylate. Two-micrometer-thick sections from each sample were stained with toluidine blue/sodium borate 1%. Images of the testicular parenchyma were obtained from photomicroscope and morphometric and stereological analyses were carried out using the Image Pro-Plus software. The average body weight observed in the specimens of H. megacephalus in the study was 47.84g, of which, 0.40% is allocated to the gonads (GSI) and 0.36% to the seminiferous tubules (TSI). These parameters suggest promiscuous reproductive behavior, of the polyandrous type, favoring males with higher sperm production and consequently, larger testes. The volume density of the seminiferous tubules was 94.46%, which represented a volume of 0.18mL. The volume density and volume of the interstitium were 5.54% and 0.011mL, respectively. The diameter of the seminiferous tubules was 206.5μm and the height of seminiferous epithelium was 71.27μm. H. megacephalus presents 5.06m of seminiferous tubules and an average of 27.96m of seminiferous tubules per gram of testis. The mitotic and meiotic indexes showed losses of 85 and 42%, respectively and an overall loss of 90% over the full spermatogenic process. The number of Sertoli cells per testis and per gram of testis was 7.8×106 and 95.28×106, respectively. Most of the morphometric parameters evaluated in H. megacephalus in this study are within the range of values described for most mammals. © 2013 Elsevier B.V.