Dinâmica populacional e reprodução de poecilla reticulata peters, 1859 (cyprinodontiformes: poecillidae) em sistemas abertos de coleta residual no campus UFPA (Belém-Pa)

Abstract

The population structure of a given species is the result of several abiotic and biotic factors that have acted both in the past and in the present. Through the large amount of eggs/ovocytes and ova found in the belly of a mature female it is possible to determine its population fecundity. Poecilia reticulata Peters, 1859 commonly known as i1guppy", is a viviparous species that presents a marked sexual dimorphism, and has a worldwide distribution. The present work aimed to describe aspects of the population structure (sex ratio, size structure and weight-length relationship) and reproductive of Poecilia reticulata Peters, 1859 on the campus of the Federal University of Pará, Belém-PA. Monthly collections were made from June 2006 to March 2007. The material used in the collection consisted of a 1mm mesh hook with dimensions of 32.5 x 23.5 cm. The specimens captured were sexed and had their total length and total weight measured. Under thisoromicroscope, the gonads of the specimens were classified as mature and immature, where the females had the number of oocyte-eggs and embryos counted and classified according to their development. From the data obtained in the 10 months of collection, the total number of individuals captured was 1,962, of which 1,002 were females and 962 males. The sex ratio of Poecilía reticula in each month remained the same as expected (1:1), with the exception of July (2:1).The maximum total length found for females and males was 35.08 mm and 25.56 mm, respectively, and the maximum total weight found for females and males was 0.464 g and 0.122 g, respectively. The fecundity found for the species ranged from 1 to 20 oocytes/egg and 1 to 22 embryos per female throughout the collection period, with the presence of mature females observed in all months. A reproductive peak was verified in July, where the highest values of embryos and oocytes/egg were found, demonstrating that in this month there was a more intense reproductive period for the species. The significant differences in the growth equations between the sexes of P.reticulata, indicated a high degree of dimorphism of the species (superior growth of females compared to males). It was also found that females were sexually mature in all months of collection since oocytes, eggs and embryos were found simultaneously in the incubator chamber, thus indicating an overfetation of the species.