First record of an intermediate thiarid snail host; Tarebia granifera (Lamarck, 1822) of the lung trematod (Paragonomus westermani Kerbert) in Qena Province, Upper Egypt

Abstract

In a one-year study, a new record of the freshwater thiarid snail, Tarebia granifera, was collected in huge amounts from the River Nile in Qena province, Upper Egypt. Tarebia granifera is a highly invasive species that has spread throughout the tropical world and can displace native gastropods as well as cause damage to water systems by clogging pipes and machinery. The shell is extremely variable in size, shape, and sculpture: obtusely to elongate conical, elevated spire up to 8 – 13 whorls, the ultimate whorl large; coarsely sculptured by elevated ridges in a vertical and spiral direction, causing a pattern of strong and blunt nodules. It was noticed that the apex is always eroded and the umbilicus is closed. Aperture is almost vertical, oval, pointed above, and rounded below. The operculum is corneous, opaque, dark reddish-brown. The type of operculum of the investigated snail is paucispiral with the nucleus placed in the far bottom right corner. Growth lines are coarse and irregular. The soft parts show the typical parts of the gastropod body, which are; the head, foot, and visceral mass. The head and foot of the active snail can be seen protruding out of the shell. The pallial organs are typically like thiarid in both form and position. The mantle is the most important and specialized organ of the Gastropoda, for it not only bears the glands that secrete the shell but it also serves as a base to which the ctenidium, ospharadium, and several excretory and reproductive outlets are attached. The mantle of the present species is a thin, fleshy, cone-shaped cap and hangs over the body. It is appressed closely to the interior of the last half of the last whorl and thus creates an open cavity into which water may enter freely to bathe the gills. The anterior border bears a series of 4– 5 large, projecting, fleshy papillae; the farthest to the left being the largest. The four papillae, the farthest to the left, are bulbous at their basal attachment to the mantle and are pointed at their distal ends, which may be seen projecting well beyond the edge of the shell. While, to the right, there are 6 to 8 progressively smaller papillae that are not bulbous at their base and act as the accessory respiratory systems and as chemoreceptors.