Morphological, Physiological, and Molecular Evidences Suggest that Euplotes parawoodruffi is a Junior Synonym of Euplotes woodruffi (Ciliophora, Euplotida)

Abstract

Euplotes woodruffi Gaw 1939 is a striking ciliate species commonly used in many fields of protistology. Euplotes parawoodruffi Song and Bradbury 1997 is separated from E. woodruffi by several morphological differences (e.g. the absence of pre-oral pouch) and in particular the brackish habitat (vs. freshwater). However, recent molecular data dispute the separation of E. woodruffi into two species. Based on a brackish isolate from the southeast of China, we investigated the morphology, molecular phylogeny, and adaptation of E. woodruffi using living observation, protargol impregnation, gene sequencing, and cultivation experiments. The morphological variability present in our isolate encompasses the previous descriptions of E. woodruffi and E. parawoodruffi. The pre-oral pouch, which occurs in living cells of freshwater isolates, is also recognizable in the brackish specimens. Laboratory experiments suggested that the brackish isolate could acclimatize and reproduce in both brackish and fresh water. The molecular analyses using 13 available small subunit (SSU) rRNA gene sequences showed that the minimum pairwise sequence similarity is as high as 99.2% and nine sequences from both brackish and freshwater isolates are even 100% matched. Therefore, we conclude that E. parawoodruffi is a junior synonym of E. woodruffi.

Species delimitation for the molecular taxonomy and ecology of the widely distributed microbial eukaryote genus Euplotes (Alveolata, Ciliophora)

“…Additionally, most species are found in freshwater habitats, although E. woodruffi and E. harpa live in brackish waters and E. encysticus inhabits fresh and brackish waters [26]. It has been demonstrated, however, that E. woodruffi is capable of salinity adaptation [57], which may have resulted in its separation from its ancestral lineage. The distinctly characteristic T-shaped macronucleus also supports the validity of E. woodruffi.…”

A new obligate bacterial symbiont colonizing the ciliate Euplotes in brackish and freshwater: ‘Candidatus Protistobacter heckmanni’

“…Although their adaptation to brackish-water environment and the different lengths of the 2 arms of the T-shaped macronucleus suggest they could belong to the species E. parawoodruffi (Song & Bradbury 1997), this last species has been recently recognized as a junior synonym of E. woodruffi (Dai et al 2013). …”

“…Scale bars: 10 µm gene sequence was obtained (1832 bp, accession number HF548208). This sequence gave as the best hit on NCBI BLAST the E. woodruffi sequence JQ801447 (Dai et al 2013) with a similarity value of 100%. This result was confirmed by the similarity analysis performed on ARB: the sequence showed a range of similarity values between 99.7 and 100% with respect to 18S rRNA gene sequences of previously characterized E. woodruffi and E. parawoodruffi.…”

Application of DNA barcoding for identifying potential biotechnological candidate organisms from the River Nile, Egypt.

“…However, since short time, referred to molecular data for E. woodruffi and E. parawoodruffi that cast doubt on the separation of the two species from each other. Dai, et al, (2013) isolated E. parawoodruffi and E. woodruffi from brackish waters and referred to E. parawoodruffi as a junior synonym for E. woodruffi. The 99 % sequence identity between the Mansoura's Nile species and both E. woodruffi and E. parawoodruffi indicated that our species is then E. woodruffi.…”