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1

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

100%
Arafa S. Z.
Acta Parasitologica
|
2011
|
tom 56
|
nr 2
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.
2

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

51%
Arafa S. Z., El-Naggar M. M., Kearn G. C.
Acta Parasitologica
|
2014
|
tom 59
|
nr 2
Some organs of the reproductive system of the protogynous monogenean skin parasite Macrogyrodactylus congolensis (Prudhoe, 1957) Yamaguti, 1963 have been studied using transmission electron microscopy. The vesicula seminalis is enclosed by a prominent layer of circular muscle fibres and has inner syncytial protrusions. The penis bulb is a highly muscular organ with prominent radial and circular muscle fibres, a gutter-shaped large spine and 16 small spines. Two syncytial male accessory glands, and a single reservoir for male accessory secretion were identified. The secretory bodies in the male accessory glands and male accessory reservoir have a unique structure. A large oocyte is situated in a chamber, previously referred to as the “ootype” or “egg-cell-forming region” (ECFR), which also contains one or two small undifferentiated cells and vacuolated tissue. Mature spermatozoa were abundant in the receptaculum seminis and dispersed in the vacuolated tissue in the ECFR and appeared to be attached to the membrane of the large oocyte. Mature spermatozoa were also seen in the parenchymal tissue near the chamber containing embryos and even in the tissues of the embryo.
3

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

51%
Arafa S. Z., El-Naggar M. M., Kearn G. C.
Acta Parasitologica
|
2013
|
tom 58
|
nr 4
In the present study, transmission electron microscopy (TEM) has been used to study the ultrastructure of the digestive system, namely the pharynx, oesophageal glands and intestine, of the monogenean skin and fin parasite Macrogyrodactylus congolensis. The pharynx consists of an anterior highly muscular region and a posterior mainly glandular syncytial region. The anterior region is provided with six pharyngeal papillae, the centre of each of which is occupied by electron dense secretory bodies, identical with those in the posterior region of the pharynx. The intestine has an uninterrupted syncytial gastrodermis and the luminal surface is provided with many unbranched lamellae. The intestine of living specimens contains large and small granules which give it a reddish brown colour. Large particles, presumed to be lipid droplets, and small granules, presumed to be melanin granules, were found in the gastrodermis and in the intestinal lumen. Parasites were induced to feed and then preserved for TEM at the following intervals: just after feeding, 30 min after feeding, 1 h 30 min after feeding and 2 h after feeding. The specimens were then processed for TEM and sections cut through the intestine of each specimen were examined with the transmission electron microscope. Three types of vacuoles (V1, V2, V3) were detected in the gastrodermis. Vacuoles V1 have thick walls and are likely to be endocytotic, enclosing luminal contents at the surface of the gastrodermis. V2 vacuoles may be lysosomes that fuse with V1 vacuoles. V3 vacuoles may serve to dispose of residual digestive material into the lumen.
4

Mode of attachment and histopathological effects of Macrogyrodactylus clarii, a monogenean gill parasite of the catfish Clarias gariepinus, with a report on host response

51%
Arafa S. Z., El-Naggar M. M., El-Abbassy S. A.
Acta Parasitologica
|
2009
|
tom 54
|
nr 2
103-112
A detailed account is given about the mode of attachment and histopathological effects of Macrogyrodactylus clarii Gussev, 1961, a viviparous monogenean from the gills of the catfish Clarias gariepinus. Most parasites attach their haptors to the proximal region of the gill filament (primary gill lamellae), while few specimens were seen attached to the distal region. Attachment of the haptor was achieved mainly by the blade of the hamuli, but no evidence was found indicating the participation of marginal hooklets in the attachment. The hamuli of M. clarii penetrate into the interlamellar epithelium of the gill tissue. Some evidences were found to indicate that M. clarii may also utilize suction force during haptoral attachment. The pathological effects of M. clarii are manifested by breakdown of the coating epithelium, necrosis of the epithelial cells, vacuolations inside and outside the host cells, fusion of the gill lamellae, rupture of blood capillaries, infiltration of erythrocytes and degeneration and fibrosis of the interlamellar epithelium. The host response includes the appearance of lymphocytes, mucoid secretions and hyperplasia of the tissue at the site of attachment.
5

Egg variability, hatching and anatomy of the oncomiracidia of three Quadriacanthus species [Monogenea] from the Nile Delta catfish, Clarias gariepinus

51%
Reda E. S., El-Naggar M. M., Arafa S. Z.
Acta Parasitologica
|
2003
|
tom 48
|
nr 4
An account has been given of the egg variability, egg development, egg hatching and behaviour and anatomy of the oncomiracidia of three species of the genus Quadriacanthus, monogeneans parasitizing the gills of the catfish Clarias gariepinus inhabiting Nile Delta waters in Egypt. Each of the three species of the genus Quadriacanthus produces eggs of different shapes and sizes. Quadriacanthus clariadis clariadis and Q. allobychowskiella produce four types of eggs while Q. aegypticus produces nine types of eggs. All types of eggs differ from each other in the presence or absence, size and shape of the appendages. It is suggested that eggs of different types are not genetically determined or functionally different. There is no significant increase in the egg size during incubation. Fluid-filled sacs are found only in the fully developed eggs of Q. c. clariadis and Q. aegypticus; they are absent from eggs of Q. allobychowskiella. It is suggested that opening of the operculum and emergence of the oncomiracidium are brought about by a mechanical, chemical and/or osmotic hatching mechanism. The glandular system of the oncomiracidia of the genus Quadriacanthus includes two anterior median head glands, at least six lateral head glands constituting the anterior adhesive apparatus and four posterior body glands. Two crescent-shaped sclerites, representing the precursors of the ventral hamuli, are present in the haptor of the oncomiracidium of Q. allobychowskiella but these sclerites were not observed in the oncomiracidia of Q. c. clariadis and Q. aegypticus.
6

Cholinergic components of the nervous system of the digenean parasites, Haplorchoides cahirinus and Acanthostomum absconditum from the catfish Bagrus bayad in Egypt

51%
Arafa S. Z., Reda E. S., El-Naggar M. M.
Acta Parasitologica
|
2002
|
tom 47
|
nr 4
A comparison has been made for the first time between the cholinergic components of the nervous system of the intestinal digeneans, Acanthostomum absconditum and Haplorchoides cahirinus from catfish, Bagrus bayad caught in Egypt. Some important differences in the central and the peripheral nervous systems are recorded between the two digeneans. The number of transverse connectives in A. absconditum is greater than in H. cahirinus, while the number of ring commissures in H. cahirinus (10) is greater in A. absconditum (3). Innervation of the subtegumental muscles, anal opening, excretory pores and ootype are revealed only in A. absconditum. Many cholinergic bipolar and multipolar nerve cell bodies (somata) are evident in A. absconditum. These cells lie close to the dorsal surface and are associated with the dorsal nerve cords and nerves supplying the subtegumental muscles. Possible functions of some nervous components are discussed.
7

Scanning electron microscope observations on the monogenean skin parasite Macrogyrodactylus congolensis [Prudhoe, 1957] Yamaguti, 1963

51%
Arafa S. Z., El-Naggar M. M., Kearn G. C.
Acta Parasitologica
|
2003
|
tom 48
|
nr 3
The anterior adhesive areas and haptor of the viviparous monogenean skin parasite Macrogyrodactylus congolensis were studied using scanning electron microscopy (SEM). The worm has two head lobes, each provided with a single, ventrally located adhesive area. This adhesive area has few adhesive papillae. The tegument covering the adhesive papillae is microvillous and penetrated by many small and a few large gland duct openings. There is a single spike-like and a dome-shaped sense organ associated with each adhesive area. The possible functions of the microvilli and sensory structures and the role they might play in the temporary attachment of the adhesive areas are discussed. The haptor is cup-shaped and possesses an anterior and two lateral rows of papillae, the possible function of which was also discussed. There is good evidence to suggest a suctorial mechanism for the haptor during its attachment to the host skin and fins. The hamuli may insert into the host tissue while the marginal hooklets were found to play a relatively small part in attachment.
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