Ultrastructure of musculature of the marginal hooklets of Macrogyrodactylus congolensis, a monogenean skin parasite from the catfish Clarias gariepinus

Abstract

The musculature of the marginal hooklets of adult Macrogyrodactylus congolensis (Prudhoe, 1957) Yamaguti, 1963 has been studied. Each marginal hooklet of M. congolensis is associated with three pairs of muscles. The possible role of these muscles in the operation of the marginal hooklet is discussed. Transmission electron microscopy has been used for the first time to study the marginal hooklets of M. congolensis. The handle articulates with the blade in the region of the guard. Internally, the handle, the proximal region of the blade in the articulation region and the distal pointed region of the blade consist of three layers. Distal to the articulation region, the blade consists of four layers with differing electron densities. A cavity is associated with the distal region of the blade and the handle. A cyton containing secretory bodies of different sizes and shapes was found in association with each marginal hooklet. The possible function of these secretions is discussed.

Ultrastructure of the digestive system and experimental study of feeding in the monogenean skin and fin parasite Macrogyrodactylus congolensis

“…The latter was recorded for the first time in Egypt by El-Naggar et al (1999). Since then, there have been several studies of M. congolensis (see, for example, El-Naggar et al 2001a,b;Arafa et al 2003;El-Naggar et al 2007;Arafa 2011). None of these studies has focussed on food, feeding and digestion in M. congolensis.…”

“…Whole living fishes were not suitable for feeding experiments because the movements of the fish created difficulties during the observation period. Specimens which were observed to feed successfully were preserved for TEM as described by Arafa (2011) at the following intervals: just after feeding, 30 min after feeding, 1 h 30 min after feeding and 2 h after feeding. Specimens were processed for TEM, sectioned at different levels through the intestine and observed with the transmission electron microscope as described by Arafa (2011).…”

“…Specimens which were observed to feed successfully were preserved for TEM as described by Arafa (2011) at the following intervals: just after feeding, 30 min after feeding, 1 h 30 min after feeding and 2 h after feeding. Specimens were processed for TEM, sectioned at different levels through the intestine and observed with the transmission electron microscope as described by Arafa (2011). Part of the pelvic fin of a freshly killed fish was processed for TEM and sectioned and observed in a similar way.…”

“…To study the ultrastructure of the digestive system of M. congolensis, some specimens were processed for TEM according to Arafa (2011) and sections through different regions of the digestive system were examined. To induce parasites to feed, they were isolated from the host for 30 min -2 h at about 25°C in dishes containing river water.…”

On some ultrastructural features of the reproductive system of the monogenean parasite Macrogyrodactylus congolensis from Clarias gariepinus inhabiting the River Nile in Egypt

“…Some previous accounts of M. congolensis were limited in scope (Prudhoe 1957, Yamaguti 1963, Thurston 1970, Douël-lou and Chishawa 1995. Other detailed anatomical studies (Arafa 2000;El-Naggar et al 2001a,b;Arafa et al 2003;El-Naggar et al 2007;Arafa 2011;Arafa et al 2013) did not focus on the ultrastructure of the reproductive system.…”