Reproductive Biology, Population Dynamics and Risk of Extinction of Aegla strinatii Türkay, 1972 (Crustacea, Decapoda, Aeglidae) / Biologia reprodutiva, estrutura e dinâmica populacional e avaliação do grau de risco de extinção de Aegla strinatii Türkay, 1972 (Crustacea, Decapoda, Aeglidae)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

This study aims to contribute for preservation of the only known population of Aegla strinatii and to reinforce the necessity to preserve the areas where this species occur. Therefore, monthly collections were realized during a two year period at Jacupiranga State Park which is considered to be the second largest conservation unit of São Paulo State. The specimens were sampled with the aid of sieves and traps, in the Ostras stream (S 24°3816.2"; W 48°2405.2"), Eldorado County. The objectives of this study were: to determine the sex ratio, recruitment period and growth in length and weight of the species; to check heterochelous condition; to verify the reproductive period and fecundity; to check the possibility of egg size variation during embryonic development and the occurrence of successive spawning; to evaluate macroscopic and microscopically the gonads of females; to calculate the size at onset maturity in males and females; to determine the geographical distribution of Aegla strinatii with the finding of new populations; to establish the risk of extinction of the species based on criteria established by the IUCN Species Survival Commission. This PhD Thesis is divided into four chapters, each one focused in a subject of the biology of A. strinatii, so that the readers can have a much more dynamic reading. In Chapter 1 there are information about population structure and reproductive biology of A. strinatii. To achieve the results, 867 individuals, being 401 males and 466 females (sexual reason 1:1.16) were sampled with mean carapace length of 19.08 mm (males) and 18.01 mm (females). The reproduction of the species occurred from May to September and the mean fecundity was 186 eggs. The eggs showed variation in both size and color during the embryonic development. The macroscopic analysis of the gonads allowed distinguishing four maturation stages. Histological sections showed a synchronism between those macroscopic stages and the development of ovarian cells. Spermatozoids completely formed were observed in males with carapace length superior to 14.49 mm. In Chapter 2 there is information on the preferential handedness and the relative growth of the first pair of pereopods, carapace length with and without the rostrum, weight and abdomen width of males and females of Aegla strinatii. All comparisons revealed significant differences and demonstrated that claws of A. strinatii are markedly asymmetrical in terms of both length and width in both sexes. The prevalence of a more developed chela was significantly higher in the left chela than in the right one. Positive allometric growth was predominant in all biometric relations of males and females of A. strinatii. In males, all biometric relationship showed significant difference between adult and young specimens. In females only the relative growth of major claw width, abdomen width and weight showed statistical difference between young and adults. The size at the onset of morphometric maturity for males and females was established for each biometric relation studied. Chapter 3 presents the study on the growth in length of Aegla strinatii. The data on the carapace length of males and females were distributed in size classes for animals captured with sieve and trap. Cohorts were recognized using the method of Bhattacharya and the software FISAT II (version 1.2.2). The von Bertalanffy growth function was adjusted on modal CC vs. time plots with the aid of CAJUS software. Estimation of maturation age was based on the maturation size obtained by relative growth analysis (males) (Cap. 2) and on the size which 50% of all females are considered to be mature (Cap. 1). Longevity was based on the CC below which 95% of the sampled individuals were represented. Males and females presented similar growth patterns (L = 27.51, K = 0.73 for males; L = 26.96, K = 0.73 for females). Males and females attained maturation size in 16.5 and 16.8 months respectively. Longevity was estimated as 33.52 months for males and 34.04 for females. The information obtained on the reproductive biology, population dynamics, geographical distribution and possible threats to the population were used to calculate the risk of extinction of A. strinatii, which is the scope of Chapter 4. Through the analysis of all data the species was classified as "Threatened". Its geographical distribution is restricted (only three localities), the area of occupation in less than 500 km², the estimated size of adult population was less than 2.500 individuals and a constant decline on the quality of the habitat was detected. This study is a continuation of BIOTA / FAPESP Program that took place from 1998 and 2003. With the end of this program there was an increment of the knowledge of the decapod crustacean fauna from Ribeira do Iguape River Basin. However, the studies on biology and ecology of these crustaceans, particularly eglids, were still scarce. The present contributes to the knowledge increment on the biology and ecology of a aeglid species.

ASSUNTO(S)

growth aeglidae biologia reprodutiva reproduction crescimento jacupiranga aeglidae dinâmica populacional jacupiranga extinction extinção

ACESSO AO ARTIGO

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