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The microscaphidiid Hexangium sigani Goto & Ozaki, 1929 was found in the intestine of Siganus rivulatus, a siganid fish permanently resident in a lagoon within the mangrove swamps on the Egyptian coast of the Gulf of Aqaba. Intra-molluscan stages of this trematode (mother sporocysts, rediae and cercariae) were found in the gonads and digestive gland of Nassarius pullus (Gastropoda: Nassariidae), a common snail in the same lagoon. Consequently, the life cycle of H. sigani was elucidated under natural conditions: eggs are directly ingested by the snail; mother sporocysts and rediae reach maturity 5-7 and 16-17 weeks post-infection; rediae contain 18-26 developing cercariae; fully developed cercariae are monostome, without penetration glands, emerge from the snail during the night 18-19 weeks post-infection and rapidly encyst on aquatic vegetation (there is no second intermediate host); encysted metacercariae are not progenetic; 2-day-old metacercariae encysted on filamentous algae fed to S. rivulatus developed into fully mature worms 5-6 weeks post-infection. The cycle was completed in about 24 weeks. The intra-molluscan stages are very similar to those of Dictyangium chelydrae Stunkard, 1943, the only described intra-molluscan stages of any microscaphidiid. However, they are also similar to those of the family Mesometridae. The present study of H. sigani describes the first complete microscaphidiid life cycle, and implicitly supports the phylogenetic relationship of this family with the Mesometridae inferred from molecular phylogenetic studies.

In this study 200 marine fish samples, Morone labrax were collected from Suez Canal area and investigated for presence of Caligid parasites, in the period from January 2014 to December 2014. The study revealed that 80 out of 200 (40%) were infested with a different Caligus species (C. minimus,C.longipedis and C. lagocephali). In respect to its incidence, it showed that Caligus species present all over the year, spring represent season of high prevalence while winter is the season of low prevalence. Morone labrax represent new host record for Caligus lagocephali with a percent of 1% infestion from total examined fish (2 out of 200), C.lagocephali females only were obtained .It characterized by its creamy color, wide angle between frontal plates, well developed processes located proximally on the inner margin of the female maxilliped, sternal furca with tapering tines and the genital complex nearly 1.50 time longer than abdomen and has no distinct postero-lateral lobes. Genital complex and abdomen combined about two times longer than cephalothorax. Outer margin of the second endopodal segment of second leg densely ornamented with fine spinules.

The present study was carried out on 360 of two species of freshwater fishes (200 Oreochromis niloticus and 160 Clarias gariepinus, which were collected randomly and seasonally from different localities in Ismailia governorate from December 2017 to November 2018. Naturally infested fishes revealed no phathognomonic clinical signs except dark coloration and ulcers on skin in O. niloticus and Cl. gariepinus. Postmortem examination showed hemorrhages, abrasions in the skin, presence of yellow cysts embedded in musculature and enlargement of liver with yellowish discoloration in both O. niloticus and Cl. gariepinus. The total infestation rate was 70%; in O. niloticus (62%) and in Cl. gariepinus (80%). The isolated monogenetic trematode was Cichlidogyrus tilapiae from gills of O. niloticus. The isolated digenetic trematodes were Orientocradium batrachoides, Astiorema reniferum and Afromacroderoides lazera from the intestine of Cl. gariepinus. Eumesenia aegypticus was isolated from the intestinal lumen of O. niloticus, while encysted metacercariae (EMC) were isolated from different organs of infested O. niloticus. Confirmation of trematode infestation was done by using molecular diagnosis (PCR). Seasonal distribution and histopathological examinations were also recorded and discussed.

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