Morfologia do apêndice masculino e maturidade sexual dos machos de Macrobrachium jelskii (Miers, 1877) (Crustacea: Decapoda: Palaemonidae)

Abstract

Caridean prawns males have a structure with an important reproductive role called appendix masculina, which is located in the second pair of pleopods. In addition, its morphology is also an important taxonomic character. Thus, the present study investigated the morphology of the appendix masculine and the size at the onset of sexual maturity of males of Macrobrachium jelskii. Specimens were collected in the artificial reservoir of Engenho São João farm, municipality of Cruz das Almas, Bahia. The appendix masculina of each specimen captured was analyzed and photographed under an optical microscope. In addition, measurements of carapace length (CC), appendix masculina length (CAM) and appendix interna length (CAI) were taken, using an image manipulation software. Relative growth analyzes were carried out, considering the biometric relationships CAMvs.CC and CAMvs.CAI. In both cases, CAM was considered as dependent variable. All linear equations were compared and had their allometry pattern determined. The average size at the onset of maturity (L50%) was estimated from relative growth analysis considering the biometric relationships mentioned above. In total, 195 males were analyzed, with CC ranging from 3.42mm to 7.41mm. The analysis of the appendix masculina under optical microscopy allowed the description of four stages of development (undeveloped; development 1; development 2 and; fully developed), and the observation of morphological changes during the development. The comparison of the slopes and elevations of the linear regressions showed significant difference between the four stages of development of the appendix masculina. Considering individuals at “undeveloped” stage, both biometric relationships were not statistically significant. CAMvs.CC and CAMvs.CAI relationships showed the same allometric patterns, with positive allometric in the "development 1" and "fully developed" stages and isometric in the "development 2" stage. The L50% for CAMvs.CC and CAMvs.CAI relationships were respectively 4.82 mm and 4.81 mm. The morphology and development of the appendix mascilina of M. jelskii were similar to that observed in other caridean prawns. Finally, there was a decrease in the growth rate with advancing development of the male appendix.