New record of Norileca indica from the west coast of India

Seasonal variation of the prevalence of cymothoid isopod Norileca indica (Crustacea, Isopoda), parasitizing on the host fish Rastrelliger kanagurta collected from the Southwest coast of India

Parasitological investigations on the occurrence of isopod parasites in fishes collected from off Cochin coast along Southwest India was carried out for a period of 1 year from January 2018 to December 2018. Altogether 20 species of fishes were analysed from 12 families including Scombridae, Carangidae, Clupeidae, Nemipteridae, Hemiramphidae, Belonidae, Menidae, Priacanthidae, Sphyraenidae, Stromateidae, Coryphaenidae. Infestation of Norileca indica was noticed only in the host fish Rastelliger kanagurta. Totally 619 specimens of R. kanagurta were examined for the presence of isopod parasite, N. indica. Among those, one hundred and seventy five specimens were found to be infested by N. indica. Overall prevalence, mean intensity and abundance were found to be 28.27%, 1.21, and 0.342 respectively. Highest prevalence of infestation, mean intensity and abundance were recorded in the month of August 2018.

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.

Distribution of isopod parasites in commercially important marine fishes of the Miri coast, East Malaysia

Isopods occur very commonly as parasites in food fishes. Parasitic isopods are typically marine and usually inhabit the warmer seas. They are blood-feeding; several species settle in the buccal cavity of fish, others live in the gill chamber or on the body surface including the fins. Isopods can cause morbidity and mortality in captive fish populations. The infestation usually pressure atrophy often accompanies the presence of larger parasites. The present study was aimed at collecting information on the neglected group of isopod parasites of the marine fishes from the Miri coastal environment, East Malaysia. A very little information available regarding the distribution of isopod parasites of Malaysian coastal environment. In the present study, nine isopod parasites were  oberved from ten marine fish species. The maximum number of parasites were observed in the months of June and October, 2013. Maximum prevalence was observed in October (50 %) and the minimum was observed in June (7.14 %). The parasitic infestation may lead to an economic loss in commercial fish species.