ABSTRACT
Marine parasitology is especially important in marine science, especially in the fishing industry. The present study was conducted to investigate and identify the ecology of protozoan parasites in the digestive system of Tenualosa ilisha fish in the waters of Khuzestan province. The results showed that the parasites isolated from this fish belonged to trematodes, acanthopods, and crustaceans. In this research, in general, 9 types of parasites, from the class of trematodes, including adult parasites Opecoelina persicus, Faustula karounensis, Faustula clupii, Faustula brevichrus, Faustula gangeticus, and Opecoelus parasite larvae, from acanthocephals Neoechinorhynchus pennahia and Neoechinorhynchus sp. from the digestive tract and epidermis The parasite Chondracanthus persicus was isolated from the gills of the host Tenualosa illisha in the investigated stations. During this research, Opecoelina persicus, Faustula karounensis, Chondracanthus persicus species were identified, named and registered for the first time.
It should be noted that the genus Chondracanthus of parasitic crustaceans, the genera Opecoelina and Faustula of trematodes, and the species Neoechinorhynchus pennahia of acanthocephalans were reported for the first time from the Persian Gulf waters. Faustula genus was isolated from 120 Tenualosa ilisha samples in the studied stations and this shows the host specialization of this parasite genus. The highest number of total species was related to Mousa Cove station. The highest species diversity index was found in the Karun River station, and the biological balance index was found in the Arvand estuary station. According to the observations made in this research, it seems that Genus species from Faustula and Neoechinorhynchus have the potential to be used as biological indicators. Still, more research is needed to prove this theory.

INTRODUCTION

The Tenualosa ilisha belongs to the shag fish family (Clupeidae). This species is one of the migratory fish of tropical and subtropical waters, which is distributed from the north of the Persian Gulf to Pakistan, India, Burma and the Far East, including China and South Vietnam (Mostafa et al., 2019). Parasitology is one of the important parts of marine ecology, which in this part (parasitic ecology) does not end only with the knowledge of parasitic species, but also pays attention to species relationships and the relationship of parasites with the surrounding environment. Therefore, knowing the factors affecting parasites and interspecies relationships, in general, the ecology of parasites is a necessary thing to fight against parasites and control them (Palm and Caira, 2008).


MATERIALS AND METHODS

The location of the stations was recorded using a Garmin MAP 62S GPS device (global positioning). Sampling was done in the season of migration and reproduction of sabour fish (winter 2011 and spring 2012) from three areas on the coast of Khuzestan province, which have different salinity in terms of stations, and the gill net method was used for sampling. The environmental factors of salinity were measured using a Hech Sension5 digital device. Then, to measure the species diversity in the study period, the Margalef population richness index, Shannon diversity index, Simpson dominance index, biological balance, and similarity index (Bray-Curtis) were calculated and compared in the population of parasites in each station.


RESULTS

Based on the results shown, a species of trematodes that was in the larval stage was identified at the genus level. From the Khor Musa station, 4 species of trematode parasites including F. Brevichrus, F. gangeticus, F. Clupii, Opecoelus, and two species of acanthocephalus including Neoechinorhynchus sp., N. pennahia and one species of coupe poda C.persicus was isolated and identified from the intestine and stomach of fish. The highest percentage of prevalence in Mousa Cove was related to Opecoelus trematode (97.5%) and the lowest was related to C. persicus (5%). From the Arvand estuary station, 4 trematode species including F. brevichrus, F. gangeticus, F. Clupii, O. persicus was isolated and identified from the intestine and stomach of fish. In this station, the highest percentage of prevalence was related to the trematode F. Brevichrus (80%), and the lowest percentage of prevalence was related to the parasite O. persicus (17.5%). From the Karoon River station, 5 species of trematodes including O. persicus, F. Brevichrus, F. gangeticus, F. Clupii and F. caroonasis were isolated and identified from the intestine and stomach of fish. The highest prevalence percentage was related to the trematode F. Brevichrus (90%) and the lowest prevalence percentage was the parasite O. persicus (20%).


DISCUSSION AND CONCLUSION

In this research, in general, 9 types of parasites, from the category of trematodes, including adult parasites (O. persicus, F. karounensis, F. clupii, F. brevichrus, F. gangeticus), parasite larvae (Opecoelus); Acanthocephalic parasites include N. pennahia and Neoechinorhynchus sp. The parasite Chondracanthus persicus was isolated and identified from the gills of the target host from the digestive system and cuticle. During this research, the species O. persicus, O. karounensis, and C. persicus were identified and named for the first time. It should be noted that the genus Chondracanthus of parasitic crustaceans, the genera Opecoelina and Faustula of trematodes, and the species N. pennahia of acanthopods were reported for the first time from the waters of the Persian Gulf.

REFERENCES

Mostafa A. R., Isha Das, H., Genevierc, L., Hazra, S., Rahman, M. and Palm, H. W., 2004. The Trypanorhyncha Diesing, PKSPL-IPB, Bogor.
Palm, H.W. and Caira, J.N., 2008. Host specificity of adult versus larval cestodes of the elasmobranch tapeworm order Trypanorhyncha. International Journal for Parasitology, 38(3-4), pp.381-388. https://doi.org/10.1016/j.ijpara.2007.08.011