Light and scanning electron microscopy on Serrasentis sagittifer Linton, 1889 (Acanthocephala): Palaeacanthocephala: Rhadinorhynchidae) infecting the common sea bream in Egypt.

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Serrasentis sagittifer is one of the most important acanthocephalan parasites parasitizing fish. This species attach to the intestinal wall via their armed proboscis which is anchored by rows of recurved spines. In the present study, Twenty two out of 50 fish specimens (44.0%) were found to be naturally infected by adult worms of Serrasentis Sagittifer Linton, 1889 (Acanthocephala: Rhadinorhynchidae) which were collected from the stomach and intestine of the common sea bream Pagrus pagrus (family: Sparidae) from locations along the Red Sea at Hurghada City, Egypt. The light and scanning microscopic study revealed that the adult worm possessed a proboscis which was long, cylindrical with a uniform width measured 0.81 ± 0.020 (0.77-0.84) mm in length and 0.48 ± 0.020 (0.33-0.69) mm in width. Claviform, armed with 25 (23-28) longitudinal rows of hooks which show a distinct dorsoventral asymmetry, with ventral hooks stouter, larger. Proboscis receptacle was 2.12 ± 0.30 (2.10-2.14) long, double-walled, with ganglion at mid-level; two unequal, long and thin lemnisci 2.9 ± 0.30(2.41-3.33) length, arised from the base of the neck, and extend up to the med-level of the trunk. The present species is compared morphologically and morphometrically with some of the previously recorded species isolated from different host species, which revealed that the present species should be classified as Serrasentis sagittifer with a new host record in Egypt.