The parasitic fauna of Sardinella aurita Valenciennes, 1847 from the Gulf of Bejaia (eastern coast of Algeria) was studied. The parasites collected from 400 host fish specimens, comprised 10 taxa including 6 species of Digenea, 1 species of Copepoda, 1 species of Nematoda, 1 larva of Cestoda and an unidentified Microsporidian species. The Nematoda Hysterothylacium sp. and the Copepoda Clavellisa emarginata (Krøyer, 1873) are newly reported for S. aurita. The Digenean parasites were numerous, diverse and constituted the most dominant group (P = 33.63%). The checklist of all known parasite species collected from S. aurita in the Mediterranean Sea includes 13 species, among which eight are Digeneans.

Five specimens of Xiphias gladius Linnaeus, 1758 were sampled from the eastern coast of Algeria and examined for their metazoan parasites. Pathological effects of the collected parasites were examined for the whole body of X. gladius. Four metazoan parasites species were collected: two monogeneans (Tristoma coccineum Cuvier, 1817; T. integrum Diesing, 1850), one copepod (Pennella instructa (Wilson, 1917)) and one parasitic nematode (Hysterothylacium aduncum (Rudolphi, 1802)). We report here for the first time a symbiotic species, Conchoderma virgatum Spengler, 1789 (Cirripedia) fixed on P. instructa. Collected monogenean and the copepod species are newly recorded for Algerian coast. Xiphias gladius is a new host for H. aduncum in the studied region. All examined specimens were infected (P = 100 %). The collected copepod parasite, P. instructa (P = 60 %) induces serious pathological effects to its host (necrosis and hemorrhage particularly). Histological sections showed that this copepod causes skin lesions, deteriorations on the dermal and muscle tissue.

Numerous marine fishes from the Algerian coast were examined for nematode parasites. Our study revealed five species of nematodes that were identified according to morphological characteristics: Anisakis simplex, Hysterothylacium aduncum, Hysterothylacium reliquens, Hysterothylacium fabri, Dichelyne pleuronectidis. D. pleuronectidis was newly collected from the study region. Four new host species were recorded for A. simplex, six for H. aduncum, and three for H. fabri. The infection rates observed were higher for Hysterothylacium and Dichelyne than Anisakis. The highest infection rate by Nematoda parasites were recorded for Trachinus draco L., Pagellus acarne (Risso) and Mullus barbatus L. (P = 100%, P = 53.33%, P = 42.5%), respectively. Nematoda larvae were found in body cavity and musculature. Histological changes associated with nematode musculature infestation revealed myodegeneration of fibers with a loss of striated texture and skin damage.

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