Small subunit ribosomal DNA characterization of an unidentified aurantiactinomyxon form and its oligochaete host Tubifex ignotus

Abstract

In this study, the small subunit (18S) ribosomal DNA gene from an aurantiactinomyxon form of unknown taxonomic position (A1) and from its aquatic oligochaete host (Tubifex ignotus) were characterized. Molecular sequence information on A1 was obtained to allow comparisons of this gene with known sequences from known myxosporean forms, and therefore to investigate possible relationships between this organism and its alternate myxosporean stage. Sequence data for the oligochaete host, together with morphological features, will allow reliable identification of this species in the future. Sequence data derived from the 18S DNA gene and data from other related or non-related organisms were analyzed and used to construct a phylogenetic tree. Phylogenetic studies provided an insight into the taxonomic position of A1. Sequence similarities within the 18S rDNA A1 gene and compared organisms indicated that A1 was most closely related to members of the suborder Variisporina (Myxidium lieberkuehni [Ml] and Sphaerospora oncorhynchi [So]). Clustering of the 3 organisms in the same branch was well supported by high bootstrap values (81%). A1 showed higher similarities with sequences of Ml (approximately 80%) than with So (approximately 79%). Myxosporean sequence analysis indicated that phylogenetic arrangements do not support traditional classification based on morphological criteria of the spores, but rather support arrangement by tissue location. Marine actinosporeans Triactinomyxon sp. and Tetraspora discoidea were found to be associated with Platysporinid myxosporeans, supporting previous findings. In this study, 18S rDNA sequence data are generated for first time for the aquatic oligochaete T. ignotus. Phylogenetic 18S rDNA gene analyses performed with T. ignotus support and confirm existing morphological and molecular phylogenetic studies. Paraphyly of the Tubificidae family was noticed. KEY WORDS: Aurantiactinomyxon · Tubifex ignotus · 18S rDNA sequences · Phylogenetic analysisResale or republication not permitted without written consent of the publisher

The life cycle of Myxobolus lentisuturalis (Myxozoa: Myxobolidae), from goldfish (Carassius auratus auratus), involves a Raabeia-type actinospore

“…The identifi cation of the actinospores should not be based only on morphology, as already suggested by several authors , Hallett et al 1999, Kent et al 2001, Negredo et al 2003, Eszterbauer et al 2006, for the possibility of multiple infections in oligochaetes and the similarity of the actinospores of different myxosporeans (as pointed out in the differential diagnosis above). In our survey, the morphology and morphometry of the Raabeia-type spore detected and measured were referable to a single type, identifi ed as the actinosporean stage of M. lentisuturalis and morphologically different from the Raabeia-type spore described by Yokoyama et al (1995) as the actinosporean stage of M. cultus.…”

“…cultus Raabeia Yokoyama et al 1995M. dispar Raabeia Molnár et al 1999, Holzer et al 2004, Hallett et al 1999, Negredo et al 2003, and SSU rRNA sequences have been used successfully for the confi rmation of heteroxenous life cycles in several studies (Andree et al 1997, Bartholomew et al 1997, Anderson et al 1999, Lin et al 1999, Køie et al 2004, 2008, Atkinson et al 2007. In Italy, goldfi sh Carassius auratus auratus (L.) farming has been a traditional activity since the end of the 1800's, with a current production of more than 25 million fi sh per year.…”

Occurrence of actinosporean stages (Myxozoa) in the Nera River system (Umbria, central Italy)

“…The majority of these researches described the actinospores by morphological analyses while, as suggested by several authors (El-Mansy et al 1998b;Hallett et al 1999;Negredo et al 2003), the inclusion of the molecular analysis is the right way to avoid misidentifications as actinospores can exhibit significant intraspecific morphometric variation (Hallett et al , 2004Özer et al 2002a). For these and other reasons, the molecular methods are being increased to assist in species differentiation (Eszterbauer et al 2001(Eszterbauer et al , 2006.…”

Molecular data infers the involvement of a marine aurantiactinomyxon in the life cycle of the myxosporean parasite Paramyxidium giardi (Cnidaria, Myxozoa)

“…Consequently, the morphological characterization of actinospores is important but not enough for the description of new types, making the acquisition of molecular data indispensable for the identification of actinosporean stages. Our study strengthens this contention, given that without the use of molecular data, the Aurantiactinomyxon type described here could easily have been misidentified with the Aurantiactinomyxon type 1 of Negredo and Mulcahy (2001), as these types share a strong morphological resemblance (Negredo and Mulcahy, 2001; Negredo et al ., 2003). Despite morphological comparison to types without molecular data having revealed significant similarity to the Aurantiactinomyxon type of McGeorge et al .…”