Revision of Myxobolus heterosporus Baker, 1963 (syn. Myxosoma heterospora) (Myxozoa: Myxosporea) in African records

Abstract

There is uncertainty regarding the validity of Myxobolus heterosporus Baker, 1963. The present study revises the taxonomy, using specimens isolated from plasmodia situated in the infected cornea of Oreochromis aureus, O. niloticus or Tilapia zillii inhabiting the River Nile, Egypt. In addition, histological effects of the parasite on the infected tissue were examined. The spores of M. heterosporus had a variety of shapes expressing remarkable heteromorphism. Five main Myxobolus-like spore types and tailed-spores were found. All forms were photographed, measured, sketched and described. Light and electron microscopy supported that spores of a Myxobolus-like morphology co-existed with so-called tailed-spores in one plasmodium. Some transitional stages from Myxobolus-like spore types to tailed-spores were observed. Therefore, some tailed-spores may be simply heteromorphs of Myxobolus. KEY WORDS: Myxosporea · Revision · Myxobolus heterosporus · Heteromorphism · Plasmodium · Cornea · Oreochromis aureus · O. niloticus · Tilapia zillii · River NileResale or republication not permitted without written consent of the publisher Dis Aquat Org 63: 205-214, 2005 (2) Baker described Myxobolus heterosporus from what he called trophozoites and spores adjacent to blood capillaries and sinusoids of liver, spleen and from the kidney. In addition, Baker (1963) and Landsberg (1985) reported an absence of cysts in spleen and kidney where melano-macrophage centers were accumulation sites for spores. The variation between the 3 spore types of M. heterosporus and the inadequate description of the trophozoites led Landsberg (1985) to assume that Baker probably confused melano-macrophage centers and trophozoites. In addition, Landsberg (1985) reported that the spore formation occurs elsewhere and that spleen and kidney might act as concentrating areas for scattered spores, thus possibly providing useful knowledge of myxosporean infections. Dyková (1982) suggested that melano-macrophages are able to transport mature spores to the melano-macrophage centers where they are destroyed. Therefore, the myxosporean parasite should be described from its original plasmodium (Lom & Arthur 1989, Molnár 1994. This was discussed by Landsberg (1985), Hegazy (1999) and El-Mansy & Abdel-Ghaffar (2003), who reported that various spores may come from their original plasmodia to the kidney via blood. In this case, the kidney infection may be used as diagnostic evidence for the presence of myxosporeans but could not be used as taxonomic evidence, and further studies to detect their exact original sites is necessary.(3) Unclear drawings and the lack of some important characters such as the number of polar filament coils led to an incomplete description. Therefore, the species described by Baker should be considered as of uncertain taxonomic status. Lom (1969) considered the number of polar filament coils an important taxonomic character.(4) In addition, all descriptions and dimensions of spores were based on fixed material which led to atypical for...

Molecular Phylogeny of the Myxobolus and Henneguya Genera with Several New South American Species

“…A piece of evidence that provides support for this theory is the occurrence of some Myxobolus spp. that develop spores both with and without a Henneguya -like caudal prolongation within a single plasmodium, as reported for Myxobolus turpisrotundus Liu et al, 2010 [19], Myxobolus bizerti Bahri and Marques, 1996, Myxobolus mulleri Bahri, 1997 and Myxobolus heterosporus Baker, 1963 [55].…”

Myxobolus turpisrotundus (Myxosporea: Bivalvulida) spores with caudal appendages: investigating the validity of the genus Henneguya with morphological and molecular evidence

“…Bahri (2008) reported on this in Myxobolus bizerti and Myxobolus mülleri spores with caudal appendages. El-Mansy (2005) also observed the same phenomena in Myxobolus heterosporus and demonstrated that tailed-spores might be heteromorphs of this species. Shulman (1966) dedicated significant discussion to atypical spores of Myxobolus kawabatae and Myxobolus gigi that also possess these variable appendages.…”

“…2). Given these findings and earlier observations on Myxobolus species with Henneguya-like tails (Shulman 1966;El-Mansy 2005;Bahri 2008), the caudal projections are clearly a trait that many of these species have the genetic capacity to express. Alternatively, this is a convergent trait having arisen multiple times in the evolution of the myxobolids.…”

Myxobolus pseudowulii sp. n. (Myxozoa: Myxosporea), a new skin parasite of yellow catfish Tachysurus fulvidraco (Richardson) and redescription of Myxobolus voremkhai (Akhmerov, 1960)

“…Myxobolus spores with caudal appendages have been reported in several previous studies (Shulman 1966, Bahri 2008, El-Mansy 2005, Liu et al 2010a, 2014a, indicating that species of Myxobolus have the genetic capacity to develop Henneguya-like caudal appendages, and the caudal appendages may not be a valid character to distinguish Myxobolus with Henneguya. Tissue tropism was found to be an important feature for general clustering of myxozoans (Fiala 2006, Carriero et al 2013, Shin et al 2014, but this trend was not observed for clustering of species within the Myxobolus clade in the present study.…”