Ultrastructure of Interlamellar Henneguya exilis in the Channel Catfish

Abstract

Ultrastructural aspects of interlamellar Henneguya exilis infections in channel catfish are reported. The plasmodium wall of this form differs from that of other species in that it is composed of two outer unit membranes which give rise to a zone of numerous pinocytic canals. Single-membraned canals appeared to be a stable feature of the wall while double-membraned canals are interpreted as those actively carrying out pinocytosis. Evidence suggests that host cellular cytoplasm as well as interstitial material is taken in by plasmodia. Plasmodium wall integrity, aggregation of parasite ectoplasmic components, numbers of pinocytic canals, and number of mitochondria proximal to the wall vary among different plasmodium profiles and may be related to plasmodium maturity. The parasite causes extensive hyperplasia of basal cells, which in turn replaces most other cell types found in noninfected gill filaments. Cytoarchitectural differences between basal cells of noninfected filaments and basal cells adjacent to plasmodia include significantly shorter microfilament bundles in the latter.

Histology, ultrastructure and prevalence of Henneguya piaractus (Myxosporea) infecting the gills of Piaractus mesopotamicus (Characidae) cultivated in Brazil

“…A similar organization of the plasmodial surface has been described in Henneguya listerine (Hallett & Diamant 2001) and for the interlamellar plasmodia of Henneguya exilis (Current & Janovy 1976). In H. exilis, regions of the plasmodial surface are in direct contact with the host cells, with the cytoplasm of the host cell appearing to pass into pinocytic canals of the plasmodial wall (Current & Janovy 1976).…”

“…The plasmodial wall of Henneguya piaractus consisted of a single membrane, as in other myxosporean species (Current & Janovy 1978, Current 1979, Hallett & Diamant 2001, Dohole et al 2002, and contained pinocytic canals that extended into the plasmodial ectoplasm, as also seen in several other Henneguya species (Current & Janovy 1976, Current 1979, Rocha et al 1992, Hallett & Diamant 2001, Azevedo & Matos 2002, El-Mansy & Bashtar 2002. However, there was no coat, nor was the wall surrounded by a capsule of collagen fibres.…”

“…In H. exilis, regions of the plasmodial surface are in direct contact with the host cells, with the cytoplasm of the host cell appearing to pass into pinocytic canals of the plasmodial wall (Current & Janovy 1976). In H. listerine, the pinocytic canals of the plasmodial wall function as a nutrient transport system (Hallett & Diamant 2001), and in Henneguya suprabranchiae these canals supply various developing stages with the nutrients necessary for growth (ElMansy & Bashtar 2002).…”

“…Various species of Henneguya that parasitise gills are reported to be important pathogens, including H. exilis in the channel catfish (Current & Janovy 1976), H. psorospermica in Perca fluviatis (Dyková & Lom 1978), H. waltairensis in Channa punctatus (Kalavati & Narasimhamurti 1985), H. creplini in Stizostedion lucioperca (Molnár 1998), H. curvata in Serrasalmus spilopleura (Barassa et al 2003a) and H. chydadea in Astyanax altiparanae (Barassa et al 2003b).…”

Light and electron microscopic studies on Myxobolus egyptica sp. nov. (Myxozoa, Myxosporea), infecting the hornlip mullet Oedalechilus labiosus from the Red Sea

“…The plasmodial wall of the present species consisted of two membranes with pinocytotic channels, which was similar to that of Henneguya exilis (Current and Janovy 1977) and Myxobolus sp. (Desser and Paterson 1978).…”