Microscopic anatomy and histochemistry of the crayfish parasite Psorospermium haeckeli

Abstract

Psorospemum haeckeli, a common parasite of the European noble crayfish Astacus astacus, occurs as an egg-shaped spore of ca 100 X 60 X 60 pm, particularly within the collagenous layer of the thoracic arteries and the surrounding subepidermal connective tissue. Smaller numbers are also found within the connective tissues of virtually all organs. The morphology and histology of these spores was investigated by microscopic techniques and the composition of their major structural components was identified by histochemistry. Each spore is enveloped by a layer of connective tissue which is assumed to derive from the host. It varies in thickness and composition among the infected organs. The spore proper consists of a 3-layered shell enclosing many globules. The outer shell layer is composed of solid, collagen-and elastin-negative, proteinaceous plates separated by sutures. The medial shell layer appears less compact and includes glycoprotelns or neutral mucopolysaccharides. The inner layer is composed of 2 membranous structures including glycoproteins, glycolipids, and collagen-and elastin-like proteins. The interior of the spore contains lipid globules of variable size, intensely staining nonlipid globules with crystalline and vacuolar inclusions, and 2 closely associated nuclei. In most of the crayfish investigated some of the spores were encapsulated by haemocytes and melanized.

The Class Mesomycetozoea: A Heterogeneous Group of Microorganisms at the Animal-Fungal Boundary

“…This finding indicated that the infecting units of this pathogen could be its amoeba-like form. The ability to develop motile amoeba-like forms was also found in some other members of the order Ichthyophonida (89,91,92,97), but so far not in members of the order Dermocystida. (29).…”

“…In addition, little is known about their feeding habits. It has been found, however, that during their parasitic stages D. salmonis (65), I. hoeferi (45), P. haeckeli (89,91), and R. seeberi (59) absorb nutrients from the hosts through the mesomycetozoean's cell walls, a finding that might suggest a similar behavior during their environmental stages. However, more studies are necessary to validate this assumption.…”

Diseases of crayfish: A review

“…Two European morphotypes are differentiated by size. Psorospermium haeckeli is elongate, slightly spindle shaped with roundish or lance-like ends and measures 120-180 Â 50 Â 50 lm, the other type being egg-shaped and measuring $100 Â 60 Â 60 lm (Vogt and Rug, 1995). Both types cooccur in several crayfish species (Henttonen et al, 1997;Vogt et al, 1996;Rug, 1995, 1999).…”

Synopsis of freshwater crayfish diseases and commensal organisms

“…Psorospermium haeckeli in astacid crayfish is found in highest concentration in connective and epidermal tissues under the carapace (Henttonen et al, 1994;Rug and Vogt, 1995;Vogt and Rug, 1995). In cambarid crayfish, on the other hand, very few of these parasites are detected in connective and epidermal tissues, the highest concentration being found in abdominal muscles (Henttonen et al, 1994).…”