title: Characterisation of two novel types of hexactinomyxon spores (Myxozoa) with subsidiary protrusions on their caudal processes.
abstract: Two types of hexactinomyxon spores, Hexactinomyxon type 1 nov. and Hexactinomyxon type 2 nov., are reported from freshwater tubificid oligochaetes, Limnodrilus hoffmeisteri and L. udekemianus. Spores are triradially symmetrical and comprise a spore body, style and 6 caudal processes. The caudal processes arise from the division of each of the 3 valve cells into an equal pair of projections at the base of the style. One of each pair is fused conspicuously to its nearest neighbour for the initial 1/5 to 1/4 of their total length. Distally, each process possesses subsidiary protrusions which are irregularly distributed and irregularly shaped extensions of the valve cell. Scanning electron microscopy of Hexactinomyxon type 2 nov. revealed that these protrusions are a seamless extension of the valve cell wall which branch distally, occasionally laterally, and terminate in a distinct bulbous structure; they also form the terminus of each process. The small subunit ribosomal DNA gene (18S) of both hexactinomyxon types was amplified through a nested PCR, then digested with the restriction enzymes Dde I and Hha I. The resultant cleavage patterns suggested the presence of 2 forms. Subsequent partial sequencing of 18S rDNA confirmed the identification of 2 novel types.
authors.affiliation: Institute of Zoology, Fish Biology and Fish Diseases, University of Munich, Kaulbachstrasse 37, 80539 Munich, Germany.
authors.forename: Sascha L
authors.initials: SL
authors.lastname: Hallett
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Atkinson
authors.forename: Heidron
authors.initials: H
authors.lastname: Schöl
authors.forename: Mansour
authors.initials: M
authors.lastname: El-Matbouli
mesh_terms: D000818:Animals; D001483:Base Sequence; D016054:DNA, Protozoan / Q000737:chemistry; D004275:DNA, Ribosomal / Q000737:chemistry; D056890:Eukaryota / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000648:ultrastructure; D005784:Gene Amplification; D005838:Genotype; D008855:Microscopy, Electron, Scanning / Q000662:veterinary; D009835:Oligochaeta / Q000469:parasitology*; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000662:veterinary; D011529:Protozoan Infections, Animal; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D015183:Restriction Mapping / Q000662:veterinary; D033761:Spores, Protozoan / Q000235:genetics / Q000648:ultrastructure
chemical_list: D016054:DNA, Protozoan; D004275:DNA, Ribosomal; D012337:RNA, Ribosomal, 18S