Low diversity, high dominance, and high host prevalence of parasitic isopods of the family Cymothoidae in Chilika lagoon, India: a comparative study between a semi-enclosed ecosystem and its adjoining open region.

Patterns in parasite diversity are shaped by their environmental and ecological settings, and to better understand their interactions with hosts and the corresponding biology, it is crucial to understand these context-dependent patterns. To achieve this, we use cymothoid isopods, an important group of fish parasites, to test a long-standing hypothesis about parasite diversity and prevalence pattern: whether semi-enclosed water bodies allow low diversity and high prevalence of parasitic isopods. Specifically, we compare these patterns between Chilika lagoon (Odisha, India), a semi-enclosed water body, and the adjoining Odisha coast (India). Our finding reveals that the semi-enclosed Chilika lagoon has a considerably lower diversity of parasitic isopods than its adjoining open sea along the Odisha coast. Additionally, the parasitic isopod infection levels in Chilika lagoon are noticeably higher, and isopod assemblage is less even than those in coastal waters along the Odisha coast. Our results support the hypothesised association between enclosed water bodies, parasite diversity, and host prevalence and contribute to an enhanced comprehension of the ecology of parasitic isopods in distinct marine environments.

Description of the Life Cycle Stages of the Parasitic Cymothoid, Cymothoa indica Schioedte and Meinert, 1884, and Its Prevalence in Commercial Fishes from Chilika Lagoon, India.

PURPOSE: To study the morphology of all the life stages and the life cycle of the parasitic isopod Cymothoa indica Schioedte and Meinert, 1884, and its prevalence in different commercial fishes in the Chilika Lagoon, India. METHODS: From April 2021 to December 2022, different life stages of the said parasites were collected from five different fish species from four localities of the Chilika Lagoon. The parasites were carefully removed from the host with a pair of forceps and then identified following standard literature and description. The morphology of all life stages, life cycle, and prevalence of the isopod C. indica were carried out as per the standard protocol. RESULTS: A total of 1252 host fishes were analysed. The total prevalence was 44.5%. The host with the highest prevalence of C. indica was Glossogobius giuris, with 58.79% of the hosts parasitized by at least one parasite individual. Followed by the host Datnoides polota (50.98%), Johnius dussumieri (46.25%), Etroplus suratensis (28.45%) and the least prevalence was in Lates calcarifer (14.70%). The description of the life stages is based on the observation of 523 females, 116 males, 46 Juveniles, and 50 embryonic stages of the said parasites. CONCLUSION: The description of all the life stages and life cycles certainly helps to identify this species with clarity and ease in understanding the species' biology. In future, this study may be helpful in the effective management towards the improvement of aquaculture productivity.

Overlapping and partitioning of niche among different life stages of the parasitic isopod Cymothoa indica in the host Glossoglobius guiris collected from the Chilika lagoon, India.

The present paper reports the site of attachment preference, overlapping and partitioning of niche among different life stages of parasitic isopod Cymothoa indica Schiöedte and Meinert, 1884 in the Gobiidae fish Glossogobius giuris (Hamilton 1822) collected from the Chilika lagoon, India. Out of 2113 host fishes, 176 were found to be infected by the parasites. Out of the 233 different life stages of the parasites examined, 89 were female, 104 were male, and the rests were juveniles. 100% of the females, 84.6% of the male and 72.5% of the juveniles were found to be attached to the buccal cavity, while the rest of the males and juveniles were attached to the branchial cavity. In most cases, there was niche overlapping, leading to competition for the resources. Females preferred more specialized niches as compared to males and juveniles. In a few instances, there is niche partitioning, as shown by the male and juveniles. There is a negative correlation between the number of parasites found in the body of the fishes and the weight of the host fishes. This manuscript also provides a brief description of the different life stages of this parasite in the above-mentioned host collected from the same lagoon.

First report of parasitic isopod Nerocila orbignyi (Cymothoidae) from India with its molecular characterization.

The present report provides the first material evidence of Nerocila orbignyi (Guérin-Méneville, 1832) collected from two different landing centres of the Chilika lagoon, thus claiming the first report of this parasite from India. One of the specimens was recorded from the host fish species Plotosus canius Hamilton 1822, constituting the first host record for this isopod. A key for the identification of N. orbignyi among its congeners is also provided. Molecular characterization of Cytochrome C Oxidase I (COI) gene of N. orbignyi was based on one specimen submitted for the first time to the NCBI database. This parasite is differentiated from the other available sequences of its related congeners retrieved from the NCBI and BOLD database by 26-34% in the Kimura 2 Parameter (K2P) distance and belongs to a separate cluster in Maximum likelihood (ML) tree analysis.

Confirmation on the occurrence of Cymothoa indica, and first record of Norileca indica, with a note on new host records of Nerocila arres, and Nerocila depressa (Isopoda: Cymothoidae) from Odisha coast, India.

The parasitic isopod Cymothoa indica Schiöedte and Meinert, 1884 was recorded from the buccal cavity of the host Glossogobius giuris (Hamilton, 1822) collected from Chilka Lake, Odisha in 1924, but its identification was doubtful as mentioned by the author in his book on "Fauna of Chilika Lake: Tanaidacea and Isopoda". The present report of parasitic isopod C. indica from the buccal cavity of the host Sphyraena obtusata Cuvier, 1833 collected from the water of Bay of Bengal, Gopalpur-on-Sea confirms its occurrence along the Odisha coast. The record of the isopod parasite Norileca indica (H. Milne Edwards, 1840) from the branchial cavity of the host Atule mate (Cuvier, 1833) collected from the water of Bay of Bengal, Gopalpur-on-Sea is the first record of this parasite from the coastal water of Odisha, India. The record of Nerocila arres Bowman and Tareen, 1983 from the caudal peduncle of the host fish species Terapon puta Cuvier, 1829, and the isopod N. depressa Milne Edwards, 1840 from the host fish species Megalaspis cordyla (Linnaeus, 1758) are the new host records for these respective parasites.

First record of Mothocya renardi and Mothocya collettei (Isopoda: Cymothoidae) from northern part of East Coast of India and new host record of Mothocya collettei.

The present record of different developmental stages of the parasite Mothocya renardi (Bleeker, 1857) and gravid female of Mothocya collettei Bruce, 1986 from different individuals of same host Strongylura leiura (Bleeker, 1850) collected from Bay of Bengal, Gopalpur-on-Sea, Odisha, India are the first record of these parasites from the northern part of east coast of India. The record of Mothocya collettei from the host Strongylura leiura is the first host record for this parasite.