The ecsoma in Hemiuridae (Digenea: Hemiuroidea): tegumental structure and function in the mesocercaria and the metacercaria of Lecithochirium furcolabiatum (Jones, 1933) Dawes, 1947

Abstract

Ultrastructural, histochemical and autoradiographical techniques have been used to investigate the development and function of the tegument of both somal and ecsomal body regions in the hemiurid Lecithochirum furcolabiatum. The terms mesocercaria and metacercaria are here adopted for those stages in the copepod second and fish third intermediate hosts respectively on the basis of morphology and on analogy with the Strigeidae. Mesocercariae were obtained by experimental infection of the harpacticoid copepod Tigriopus brevicornis with the cystophorous cercariae (syn. Cercaria vaullegeardi), whilst metacercariae were removed from the body cavities of naturally-infected rockpool teleosts including Gobius paganellus and Blennius pholis. Observations on the mesocercaria show the origin of the ecsoma from the distal half of the excretory vesicle, which at 21 days post-infection is capable of eversion through the terminal pore. The nucleated microrugous surface layer of the ecsoma at this stage is modified or replaced in the metacercaria by anucleate syncytial tegument similar to that of the adult organ. The metacercarial stage is also associated with the more advanced development of the somal tegument. The two stages differ in metabolic activity, the somal tegument of only the metacercaria resembling that of the adult in acid phosphatase distribution. In the mesocercaria the ecsomal tegument showed the strongest uptake of 3H-tyrosine; absorption of the latter was not detected in the metacercaria. 3H-glucose uptake was restricted to the intestinal caeca of both stages.

A New Nested Polymerase Chain Reaction Method Very Efficient in Detecting Plasmodium and Haemoproteus Infections From Avian Blood

“…Species of Lecithochirium have a life cycle that involves 3 or 4 hosts depending on the presence or absence of small fish that act as paratenic hosts (Gibson and Bray, 1986;Matthews and Matthews, 1988;Koie, 1990). Sexual reproduction takes place in the definitive host, which, in the case of Lecithochirium fusiforme, is usually the eel Conger conger.…”

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

“…Among Digenea, studies on tegumental sensory structures have mainly focused on cercaria or metacercaria stages (Fujino et al,1979b; Matthews and Matthews,1988a; Žd'árská,1992; Bogea and Caira,2001; Abdul‐Salam and Sreelatha,2004; Poddubnaya et al,2010) as they require orientation to stimuli such as light and gravity more than adults do, a condition related to the necessity of finding a host quickly (Roberts and Janovy,2000). However, some authors have emphasized the description of tegumental structures of adult digeneans (Žd'árská,1993; Ferrer et al,1996; Ibraheem,2000; Filippi et al,2010).…”

“…Metacercarial and adult stages of Brachyphallus crenatus (Køie,1992) such as adults of Erilepturus hamati (Abdou,2001) have been studied using scanning electron microscopy (SEM). Mesocercarial or metacercarial stages of L. furcolabiatum (Matthews and Matthews,1988a) and cercaria of Vaullegeardi pelseneer (Popiel,1978) have been studied using transmission electron microscopy (TEM). Only three adult hemiurids have been studied using TEM, that is, Hemiurus communis (Kryvi,1972; Matthews and Matthews,1988b), Lecithochirium rufoviride , and Lecithochirium fusiforme (Matthews and Matthews,1988b).…”

Redescription of the Cercaria ofLecithochirium rufoviride(Rudolphi, 1819) Lühe, 1901 (Digenea, Hemiuridae) (=Cercaria vaullegeardiPelseneer, 1906)

“…The excretory appendage of infective cercariae of L. rufoviride is vestigial and without function even though in early stages it is capable of some restricted movements. Unlike the free-swimming cystophorous cercariae of D. varicus and H. luehei, which use pelagic copepods as second intermediate hosts, the immotile cercariae of L. rufoviride and L. furcolabiatum (Matthews 1981b, Matthews & Matthews 1988) use benthic harpacticoid copepods as the main second intermediate host. The caudal filaments of the cercaria of L. rufoviride may coil around or entangle in fine algae or stick to hard structures and thus prevent the cercariae from drifting away to the open sea where they have no access to benthic crustaceans.…”

“…Four-host life-cycles have been proposed for L. fusiforme and L. furcolabiatum (Chabaud & Campana-Rouget 1959, Matthews & Matthews 1988) and for L.…”