This paper reports the protandric hermaphroditic changes in the reproductive system of the male-phased Norileca indica, a cymothoid that parasitizes the scombrid fish Rastrelliger kanagurta. Each part of N. indica's paired reproductive system lies on either side of the gut. This study considers the three successive size classes of the male phase - designated as M1, M2 and M3 - using light microscopy and ultrastructural methods. The testis comprises of three bulged sac-like lobes labelled t1, t2 and t3, all of which open into the ovary of their respective side. The vas deferens, which emerges as a posterior extension of the ovary, opens into the penis and the distal end of each oviduct leads to a sealed gonopore on their respective sides. Each testis lobe (t1/t2/t3) displays clusters of germ cells undergoing stage-specific differentiation. Spermatids undergoing sequential changes associated with spermiogenesis keep close proximity to somatic accessory cells. The characteristic histological changes associated with protandric hermaphroditism are visible in the ovaries of sequential size classes (M1, M2 and M3). In early M1, besides spermatophores, the ovary has abundant polymorphic nuclei; in the mid/late M1, the posterior ovary has abundant spermatophores, anterior displayed oogonia, previtellogenic oocytes and two distinct forms of follicle cells. In M2, the anterior ovary shows compactly arranged oocytes while the posterior region accommodates spermatophores - fewer, however, than during M1. The entire ovary during M3 is crowded with previtellogenic oocytes, which marginalize the spermatophore passage. The vas deferens of the smallest M1 lack spermatophores. As the size class progresses through late M1 into M2 and M3, the posterior vas deferens is filled with spermatophores, which closely associate with the glandular epithelial lining.
Keywords: Male reproductive system; Norelica indica; Ovary; Protandric hermaphroditism; Spermatogenesis; Spermiogenesis; Testis.
The reproductive system of Derocheilocaris typica (Crustacea, Mystacocarida).Arthropod Struct Dev. 2012 May;41(3):281-91. doi: 10.1016/j.asd.2012.02.003. Epub 2012 Mar 8. Arthropod Struct Dev. 2012. PMID: 22406764
Male internal reproductive structures of European pea crabs (Crustacea, Decapoda, Brachyura, Pinnotheridae): vas deferens morphology and spermatozoal ultrastructure.J Morphol. 2013 Nov;274(11):1312-22. doi: 10.1002/jmor.20184. Epub 2013 Sep 11. J Morphol. 2013. PMID: 24027013
Histological and ultrastructural investigation of the female reproductive system of Argulus bengalensis Ramakrishna, 1951 (Crustacea: Branchiura).J Morphol. 2016 Jun;277(6):707-16. doi: 10.1002/jmor.20528. Epub 2016 Mar 15. J Morphol. 2016. PMID: 26991011
Testicular structure and germ cells morphology in salamanders.Spermatogenesis. 2015 Mar 12;4(3):e988090. doi: 10.4161/21565562.2014.988090. eCollection 2014 Sep-Dec. Spermatogenesis. 2015. PMID: 26413406 Free PMC article. Review.
Fasciola hepatica: Histology of the Reproductive Organs and Differential Effects of Triclabendazole on Drug-Sensitive and Drug-Resistant Fluke Isolates and on Flukes from Selected Field Cases.Pathogens. 2015 Jun 26;4(3):431-56. doi: 10.3390/pathogens4030431. Pathogens. 2015. PMID: 26131614 Free PMC article. Review.