Ovarian balls (Floating ovaries) of Rhadinorhynchus niloticus Mohamadain, 1989 from the Nile perch Lates niloticus Linnaeus, 1758; an electron microscope study.

In Acanthocephala, the ovarian balls (floating ovaries) are distinctive structures found suspended in the fluid-filled metasoma of females and are responsible for egg production and maturation. Those structures have not been studied in Rhadinorhynchus niloticus. We aimed to investigate their ultra-structure by means of scanning and transmission electron microscopy. A total of 30 Lates niloticus fish individuals were collected by fishermen from the River Nile, Egypt, and the isolated adult female specimens were processed for electron microscopy studies. The ovarian balls are elongated and lobulated structures freely scattered in the metasoma. They exhibited three distinct primary structural zones, a central oogonial syncytium, a peripheral cellular zone and a surrounding somatic supporting syncytium. The oogonia, within the central syncytium, give rise to developing oocytes that transform into mature oocytes. The latter enclose some inclusions such as large yolk granules and smaller egg-shell granules. We also describe the process of fertilization within the ovarian ball. The structure of the ovarian ball and the steps of fertilization in R. niloticus are described, for the first time, in the present study.

Surface Ultrastructure of the Adult and Juvenile Stages of the Trematode Astiotrema Impletum (Looss, 1899) Looss 1900 (incertae Sedis) from the Nile puffer, Tetraodon Lineatus Linnaeus, 1758.

A scanning electron microscope study was performed on the surface of the trematode Astiotrema impletum (Looss, 1899) Looss 1900 from the Nile puffer, Tetraodon lineatus Linnaeus, 1758 (Syn. Tetraodon fahaka) for the first time. Adult A. impletum have a markedly large, sub-terminal oral sucker and a small ventral sucker. As with most trematodes, tegumental spines are concentrated anteriorly and are absent just anterior the ventral sucker. Spines have serrated tips on a short, tongue-shaped body. At the level of the ventral sucker the base of each spine exhibits a three bulbous-like structure that can be partially or completely withdrawn into the tegument. Sensory papillae are concentrated around the oral and ventral suckers and genital pores. Papillae are conical or knob-like, either ciliated or non-ciliated; some are protruded and others are embedded inside the tegument. In the juvenile stage, spines are smaller, less well-developed and tightly packed. The cytoplasmic processes of the posterior quarter of body show brain-like velvety appearance on the adult and small cobblestone-like on the juvenile.