Topography and ultrastructure of the tegument of Lecithochirium musculus (digenea: Hemiuridae), a parasite of the European eel Anguilla anguilla (osteichthyes: Anguillidae)

Abstract

The tegumental ultrastructure of the stomach fluke Lecithochirium musculus was studied using scanning and transmission electron microscopy. The surface of the tegument was smooth and covered by transverse cytoplasmic ridges. Cobblestone-like units of the tegument were observed on the ventral surface. Invagination and evagination of the ecsoma induced variations in the tegumental surface. The ultrastructural study revealed that the tegument of L. musculus had a typical syncytial organization with a distal cytoplasm lying over a basal matrix and cytons. Two types of intra-tegumental sensory structures were observed. Type 1 sensory receptor was a domed-like fusiform structure consisting of a smooth elevation of the tegument. Four receptors of this type were observed on the anterior dorsal surface of the fluke. Three nerve bulbs filled with electron-lucent material and mitochondria composed this receptor. Hemispherical electron-dense collars were observed at the top of the nerve bulbs. Striated rootlets laid just beneath the hemispherical electron-dense collars. Type 2 sensory receptor presented two morphological variations, i.e., a bulb-like monolobed structure, and a bulb-like bilobed structure observed at two different degrees of evagination. For both variations, the nerve bulb enclosed mitochondria, electron-lucent material, and a conical electron-dense collar from which extended a striated rootlet. Numerous sensory receptors of this type were observed around the ventral sucker.

An ultrastructural study of the surface and attachment structures of Paradiplozoon homoion (Bychowsky & Nagibina, 1959) (Monogenea: Diplozoidae)

“…Comparison with previous studies concerning platyhelminth surface structures [38–40] confirms that P. homoion share analogous morphological characteristics with other Platyhelminthes. While there have been numerous previous studies focused on the morphology and ultrastructure of monogenean surface and attachment structures using TEM [10, 11, 23, 24, 26, 27, 41], none have included species from the family Diplozoidae.…”

A transmission electron microscopical study of the tegument of Maritrema feliui (Digenea: Microphallidae)

“…The general topography and ultrastructural organisation of the tegument in Maritrema feliui is essentially similar to that previously described for other digeneans by, inter alia, Threadgold (1963Threadgold ( , 1968Threadgold ( , 1984, Lee (1966), Burton (1966), Świderski (1966), Bogitsh (1968), Hockley (1973), Lumsden (1975), McLaren (1980), Choi and Yoo (1985), Brennan et al (1991), Cohen et al (1996), Ferrer et al (1996) and, more recently, by Filippi et al (2010Filippi et al ( , 2012Filippi et al ( , 2013. The nature of the tegumental surface of M. feliui, with infolding, pits and spines, inevitably increases the total surface area, which is probably important for the inward and outward transmission of nutrients and waste products, respectively.…”

“…An extracellular matrix, composed of a basal matrix and an interstitial matrix, as seen in other digenean species (Filippi et al 2010(Filippi et al , 2012(Filippi et al , 2013 and in other parasitic platyhelminths (Conn 1993), occurs between the perikayra and the distal cytoplasm.…”

“…Differences in spine structure and their distribution may be related to differences in the host-parasite relationship (Filippi et al 2010(Filippi et al , 2012(Filippi et al , 2013. For example, Køie (1977) has suggested that large, pointed spines may be involved in feeding, with these spines being used for abrading host tissues, although Lumsden (1975) was of the opinion that the main function of spines is to assure and help maintain the parasite's attachment to the host.…”

Histochemical Study of the Progenetic TrematodeAlloglossidium renale

“…The tegument of trematodes is typically covered with spines and contains secretory vesicles and granules [18, 19], and, in A. renale , the tegument aids in the destruction of host antennal gland tubules as the host tissue is compressed and abraded [8]. Carbohydrate staining of the tegument demonstrated that it is positive for acidic sulfated mucosubstances (AB1), acidic carboxylated mucosubstances (AB2.5), and neutral sugars (PAS), likely attributable to secretory vesicles.…”