Intraspecific morphometric variation in myxosporeans

Abstract

Abstract:Morphometric data from spores of ten myxosporean species were statistically analysed to explore myxosporean intraspecific variation in measurements when obtained from a sample from: (1) the same plasmodium, (2) different plasmodia from the same host and (3) different host individuals and localities. In some cases, significant differences in spore dimensions were found between samples from the same plasmodium, highlighting the difficulty of obtaining representative measurements of myxosporean spore. In addition, significant differences in spore dimensions were found when plasmodia from the same site of infection were compared, suggesting that measurements of spores should come from several different plasmodia of the sampling to increase the reliability of the morphology data. Moreover, significant differences in spore dimensions were observed for most spore dimensions when data were compared between localities. In all cases, there was clear overlap in ranges of dimensions even when means differed significantly. The present statistical analysis shows that intraspecific morphometric variation of myxosporean species commonly occurs, highlighting the importance of reporting ranges of measurements for a species, not just the mean dimensions, and taking into account all evidence when assigning or describing myxosporean species.Keywords: intraspe cific variation, Myxozoa, morphology, species differentiation, Myxobolidae Traditionally, myxosporean species have been identified principally on the basis of spore morphology, but DNA sequencing data have become important for resolving relationships and determining taxonomic affinities (Atkinson et al. 2015). Given that molecular data on most species are absent, comparison of spore morphology, especially detecting differences in morphometry, is crucial and necessary. However, criteria for what might represent intraspecific and interspecific morphometrics is undefined, making the species identification based on morphometric comparison somewhat subjective.Often, when a species is collected, the range and mean spore dimensions (usually including spore length, spore width and polar capsule dimensions) can be compared to known species and where overlap occurs there is a candidate species match. Host, geography and tissue infected are other characters that must be considered. When spore dimensions overlap, but other information suggesting distinct species is present, more sophisticated statistical analyses can be performed to determine if statistical differences occur between spore dimensions. For example, Easy et al. (2005) found evidence of two species of Myxobolus Bütschli, 1882 species in the musculature of Percopsis omiscomaycus (Walbaum) based on histology and molecular data. These species had overlapping but significantly different spore lengths, with the intermuscular Myxobolus procerus Kudo, 1934 Gilchrist, 1924 and Kudoa histolytica Pérard, 1928, Whipps and Kent (2006 found geographically distinct genetic lineages of the parasite and some statistical differen...

Morphological and molecular studies on two myxosporean infections of cyprinid fishes: Thelohanellus pyriformis from tench and Thelohanellus cf. fuhrmanni from nase

“…fuhrmanni found together in a cyst caused well observable tumors in the nostrils of the nase. Similar nodules with pathogenic characters were found in the skin of Cyprinus carpio infected by T. kitauei ( Egusa and Nakajima, 1981 ; Zhai et al, 2016 ; Liu et al, 2019 ) and in Cyprinella venusta infected by T. magnacysta ( Ksepka et al, 2020 ).…”

Molecular diagnostic based on 18S rDNA and supplemental taxonomic data of the cnidarian coelozoic Ceratomyxa (Cnidaria, Myxosporea) and comments on the intraspecific morphological variation

“…Morphological plasticity in myxospores are acknowledged to be one of the main factors responsible for the difficulties encountered in myxosporean taxonomy and species identification, resulting in taxonomic dilemmas (Zhai et al 2016, Guo et al 2018, Xi et al 2019. It is widely recognised that Ceratomyxa spp.…”

Morphological plasticity in Myxobolus Bütschli, 1882: a taxonomic dilemma case and renaming of a parasite species of the common carp

“…Molecular analysis revealed that the two myxozoan samples share almost identical SSU rDNA sequences (99.6–99.8%). Considering the fact that intraspecific morphometric variation [ 11 ] and morphotypes [ 10 , 32 ] are common in myxozoans, the two samples from the gills of common carp were considered to be conspecific with each representing a morphotype of the same species, i.e. wide type (spores collected in 2013) and narrow type (spores collected in 2015).…”

“…However, there are exceptional cases that involve extensive intraspecific polymorphism, interspecific morphological similarity, identical interspecific biological traits, and blurred SSU rDNA-based species boundaries [ 8 – 11 ]. In these situations, if more than two of above exceptional cases are encountered at the same time, a systematist might again run into what we call a “taxonomic dilemma”.…”