Reproductive System in the Male Phase of a Parasitic Isopod (Crustacea) - Morphological, Histological and Ultrastructural Evidence for Sequential Protandrous Hermaphroditic Changes.

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.

Norileca indica (Crustacea: Isopoda, Cymothoidae) Infects Rastrelliger kanagurta Along the Malabar Coast of India - Seasonal Variation in the Prevalence and Aspects of Host-parasite Interactions.

This paper reports seasonal variations in the prevalence of host-parasite associations between Norileca indica, a cymothoid, and the Indian mackerel Rastrelliger kanagurta along the Malabar Coast of India. Eighty-eight marine fish species belonging to diverse families were examined, and only R. kanagurta was shown to be parasitized by N. indica, indicating a narrow host specificity. The prevalence, mean intensity, and abundance were 30.70, 1.71, and 0.52%, respectively. Different life cycle of this parasite, from larva to adult, infect the host fish. In most instances, a pair of N. indica infected the host, and in these instances a male-female combination was the most common (89.17%). The monthly occurrence of N. indica was charted for a period of 38 months (July 2012 to July 2014; March 2017 to March 2018), and statistical comparison of the data showed a significant difference (p < 0.001) among seasons. A positive correlation (r = 0.40) was observed between the size of female parasites and that of their respective host fish. There was a positive correlation (r = 0.78) between the size of female parasites and their fecundity. In all instances, adult N. indica individuals were found to specifically attach to the mucus membrane of branchial operculum, causing visible physical damage, including atrophy (reduced length) of the gill filaments and overall loss of gill normalcy. Furthermore, permanent occupancy by female N. indica resulted in the formation of a deep pit in the gill chamber floor and also caused atrophy of gill filaments. Overall, our findings yielded a greater understanding of the occurrence, season-wise prevalence, and potential host- parasite associations of N. indica.

Agarna malayi Tiwari 1952 (Crustacea: Isopoda: Cymothoidae) Parasitising the Marine Fish, Tenualosa toli (Clupeidae) from India: Re-description/description of Parasite Life Cycle and Patterns of Occurrence.

Panakkool Thamban Aneesh, Kappalli Sudha, Ameri Kottarathil Helna, and Gopinathan Anilkumar (2018) This paper re-describes the female stage of Agarna malayi Tiwari 1952, a protandrically hermaphroditic parasitic cymothoid, and describes the remaining life cycle stages for the first time. The re-description (female phase) of A. malayi was made based on the type specimens deposited by Tiwari (1952) in the National Zoological Collections of the Zoological Survey of India (NZC-ZSI) and data obtained from several live specimens collected from Ayyikkara Fish Landing Centre (11°51'N, 75°22'E, of Malabar Coast, India) and Marina Beach (13.0500°N, 80.2824°E, Bay of Bengal, India). General morphology, mouthparts and appendages of the species' life cycle stages such as larvae, juveniles, male and transitional stages are also reported for the first time. We closely observed 80 marine fish species belonging to 35 different families to identify the potential host of A. malayi, and only recovered the parasite from one fish, Tenualosa toli, signifying A. malayi's oligoxenous host specificity; the prevalence and intensity of parasitisation is 17.3 and 1.86%, respectively. The present paper also discusses sequential life cycle stages of the species.

Mothocya renardi (Bleeker, 1857) (Crustacea: Isopoda: Cymothoidae) parasitising Strongylura leiura (Bleeker) (Belonidae) off the Malabar coast of India: Redescription, occurrence and life-cycle.

Mothocya renardi (Bleeker, 1857), a protandrically hermaphroditic cymothoid, parasitising the banded needle fish Strongylura leiura (Bleeker) from the Malabar Coast, India is redescribed and morphological data for different life-cycle stages [male, transitional and ovigerous female, larvae (pre-manca and manca) and juvenile] are provided. Mothocya renardi exhibited strict oligoxenous host specificity by infesting only S. leiura and showed high prevalence levels (reaching up to 92%). The life-cycle of M. renardi comprises three major phases (marsupial phase, free living phase and infestive phase). The marsupial phase comprised one zygotic, three embryonic and two larval stages, all of which remained in the marsupium until the final staged manca is released into the surrounding water. After having led a short free- swimming life, the manca infested the branchial cavity of the host fish, S. leiura. Subsequently it was transformed successively into juvenile, male, transitional and finally functional female through biphasic moult which occurs in between each stage. Based on the presence (or absence) of a brood pouch and/or marsupiumites, six successive stages of the female population were also identified. These data will help precise identification of the female M. renardi irrespective of their stage. The present paper also discusses the host-parasite interactions between S. leiura and M. renardi.

Cymothoa frontalis, a cymothoid isopod parasitizing the belonid fish Strongylura strongylura from the Malabar Coast (Kerala, India): redescription, description, prevalence and life cycle.

BACKGROUND: Cymothoa frontalis Milne Edward, 1840 is a very poorly described cymothoid, notwithstanding the previous redescription of the female. Pertinently, to date, the host of C. frontalis has not been identified with adequate precision. Most of the descriptions of cymothoids carried out hitherto were based primarily on females, but practically ignoring other life cycle stages. The present paper redescribes the female and describes other life cycle stages of the species C.frontalis toget better precision in their identification. RESULTS: The female phase of C. frontalis is redescribed according to type specimens extant in the NMNH, Paris, and also by the data obtained from live specimens collected during the present study. The general morphology and appendages of various life cycle stages of the species are described. Among 80 fish species from 35 families examined, C.frontalis wasrecovered only from Strongylurastrongylura signifyingits oligoxenous host specificity, the prevalence and intensity being 68.65% and 1.9, respectively. Each host fish in more than 85% of the population was infested with a pair of C. frontalis, in three combinations, predominantly with male-female pair (70.9%). C. frontalis exhibitedstrict site specificity attaching to the buccal cavity of the host fish. The study has also identified three major phases (marsupial, free living and infective) in the life cycle of C. frontalis. The zygotic-staged marsupiumites were developed through five sequential ontogenetic stages. The manca released from the marsupium become infective aftera brief period of free swimming life. During the infective phase, C.frontalis completesremaining life cycle stages with successive moulting. Further, six successive stages of the ovigerous females have also been identified. CONCLUSIONS: Thepresent redescription of the female and the description of transitional, male, juvenile and larvae of C. frontalis facilitate precise identification of the species at any stage of the life cycle. Further, the strict host and site specificitiesof the parasite, as borne out from the present study, and its high degree of prevalence in the host make C. frontalis as an ideal model organism to study the strategies to be adopted for the management of parasites infesting edible fishes.