Characterization of a protandrous hermaphroditic reproductive system in transitional and female phases of Norileca indica — morphological, histological and ultrastructural approach

Abstract

Abstract The present study explores the reproductive system of Norileca indica during its transitional and female phase at morphological, histological, ultrastructural and histochemical levels. The paired and symmetrical hermaphroditic reproductive system of N. indica in the transitional and female phases lies dorsally in the thorax on either side of the gut, each consisting of a three-lobed testis (with lobes t1, t2 and t3) followed by an ovary and then a vas deferens, which opens into the paired penes located at sternite 7; the oviduct, arising laterally from the ovarian lobe, opens into the gonopore located on the 6th pereonite. In the transitional phase, the gonads show a presence of germ cells at different maturation stages: spermiogenesis in the testes has already halted, while the ovary undergoes active vitellogenesis. Spermatophores are frequently seen in the vas deferens but seldom in the testes; the size of the oocytes then is 250-1200 μm. The gonadosomatic index (GSI) and nucleocytoplasmic index (NCI) range over 0.090-0.198 and 0.46-0.11, respectively. In the female, oocyte size increases to 1500 μm; the GSI ranges 0.019-0.235 and the NCI from 2.40 to 0.09; testes and vas deferens are not prominent. This paper discusses the possible role of protandrous hermaphroditism in the reproductive life of N. indica.