Biodiversity of Parasites of the Ichthyofauna of Continental Freshwaters in the Northern Sahara (Algeria)

Chabira, Djouhina (2025) Biodiversity of Parasites of the Ichthyofauna of Continental Freshwaters in the Northern Sahara (Algeria). Doctoral thesis, Faculty of Exact Sciences, Nature and Life Sciences.University Mohamed Khider, Biskra.

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Abstract

Freshwater ecosystems harbor a rich diversity of life, yet the parasites of their fish inhabitants remain poorly understood, particularly in the Northern Sahara region of Algeria. This study investigated the parasite fauna of five fish species – Oreochromis sp. (14.53%), Cyprinus carpio (34.19%), Barbus sp. (17.09%), Luciobarbus biscarensis (16.67%) and Carassius gibelio (17.52%) – across three study regions of the northern Sahara (Biskra, Djelfa and Laghouat) over a seasonal period from October 2022 to June 2024. Parasites were identified using standard techniques, including the preparation of direct wet mounts for fresh examination, staining, and morphological examination. Stomach content analysis was performed on C. carpio to assess the dietary habits of this species. The analysis further investigated the relationship between host body shape/size and sex with overall host weight, documented the abundance, prevalence, and intensity of identified parasite species and assessed the impact of season, host size, and sex on their infection values, including those in the endemic L. biscarensis. Our findings revealed a diverse parasite community, with six parasite species and genera identified: Ergasilus sp., Myxobolus sp., Trichodina sp., Dactylogyrus extensus, Dactylogyrus fimbriphallus and Bothriocephalus acheilognathi. The C. carpio samples exhibited a consistent preference for zooplankton (Copepoda: %IRI = 38.92, Cladocera: %IRI = 33.59). Furthermore, a clear link was observed between the consumption of copepods and infection with B. acheilognathi (prevalence: 25.93%, mean intensity: 1.71 ± 1.01, abundance: 0.44 ± 0.91). The infection values for the identified parasite species varied significantly according to season, host size, and sex for several parasites. This research provides novel insights into the parasite ecology of freshwater fish in an understudied Saharan ecosystem, contributing valuable data on host-parasite interactions. Future research should prioritize molecular confirmation of parasite identities, implementing long-term monitoring against threats like climate change, and detailed study of B. acheilognathi prevalence in copepod intermediate hosts.

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