Caracterização histológica e biologia reprodutiva de Leptodactylus macrosternum (Anura, Leptodactylidae), Nordeste do Brasil

Abstract

Aspects of animal breeding are highly diverse and complex. The existence of a number of reproductive strategies may have evolved in order to maximize the fitness avoid predation, competitors or are simply related to environmental conditions. In environments with semi-arid characteristics, the air temperature and relative humidity related to pluviometric index determine the reproductive pattern of amphibians. In this perspective anatomical and morphological characteristics of the reproductive system of Leptodactylus macrosternum correlated to climatic factors, enable the assessment of reproductive behavior of this species expanding the knowledge of the reproductive biology of neotropical frogs. Thus, this study aims to describe the annual reproductive cycle of the species L. macrosternum based on these parameters: morphology of the gonads and fatty bodies, histology and morphometry of the gonads and production of sex hormones and its relation to environmental conditions in the studded area. This work was carried out in the area of Horto Florestal Olho d'água da Bica (HFODB), caatinga area fragment in the municipality of Cuité, state of Paraiba. The animals were captured fortnightly through active collecting, between the months of January to December 2013. For the determination of the reproductive and dynamic energy of the species based on morphology of the gonads and fatty bodies, body weight values (WT), the weight of the gonad (WG), liver weight (WF) and weight of fatty bodies (WFB) were used for the calculation of gonadosomatic relation [RGS = WG (100) / WT],hepatosomatic [RWF = WH (100) / WT] and liposomal [RFB = WFB (100) / WT] and condition factor [K1 = W / lb]. The gonads were fixed in Bouin solution for 24 hours and then dehydrated in ascending series of alcohol proceeded embedded in paraffin and 5 μm cross-sections were obtained and subsequently stained with hematoxylin and eosin. The identification of oocyte cell types and quantification of oocyte and testicular cell types was preceded in conventional bench microscope, trinocular and coupled to a digital system of image acquisition. To assess possible changes in the histology of the ovaries, it was proceeded the quantification of the types of oocytes performed by the density method in a test area of 88mm2. The evaluation of possible changes in histology and morphometric of the testes was performed by stereological analysis for determining the density of primary spermatids, secondary and sperm volume calculated from the density of these cell types. To quantify the density profiles (QA, primary spermatids, secondary and sperm) were counted respectively 14, 5 and 6 fields in a test area (AT) with 0.044 mm2 for each animal in each study group. The final result (mm2) was acquired after the utilization of the mean value for each profile and applying the following formula: QA = Σprofile / AT. Hormone analysis was performed by quantifying the dosages of progesterone and estrogen levels in females by ELIZA method. The weather temperature monthly data (° C) and rainfall (mm) were acquired through the database of Center's of Agency Executives of State of Paraiba Water Management (EFSA). The results for RGS variables, RGH, RFB and K1 over the months of collection were subjected to seasonal comparison, by the application of non-parametric Kruskal-Wallis test (Zar, 1999).The correlation between these variables was also tested by applying the Spearman correlation coefficient. The values of the density of cells in the reproductive lineage, RGS, progesterone and estrogen levels were analyzed for the months by Kruskal-Wallis test. The dependence between climate variables (rainfall and temperature), density of oocytes III and IVwas verified by the simple linear regression test. The values of the density of primary spermatids, secondary and sperm and testosterone levels were analyzed between the months by Kruskal-Wallis test. The dependence between climate variables (rainfall and temperature), the population density of spermatids primary, secondary and sperm were assessed using the simple linear regression test. Only in the months from May to August and November to December records and therefore catches were made. The variation in values of the gonadosomatic (RGS), hepatosomatic (RWF), liposomal (WFB) ratioand Condition Factor (K1) over the months of collection. The population density of the types of oocytes and the demonstrated dependence values to the variation in rainfall and temperature of the region, also determining for the species a short breeding season, concentrated between the months of May and June 2013.The monthly values of the densities of the primary spermatids, secondary spermatids and sperm showed significant variations over the months of collection demonstrating also dependence on the variation in rainfall and temperature of the region. By observing the gamete maturation process as well as the observation of changes in K1 values, RGS, RWL, RFB and the average values of estrogen and progesterone in animals collected, as well as their relationship with climatic variables area demonstrate to L. macrosternum a short reproductive activity, probably concentrated in the months of June, July and December 2013, being consistent to contend that the species has a typical reproductive cycle of seasonal tropical environments such as "potentially continuous".