A redescription of morphologically similar species from the genus Euglena:E. laciniata, E. sanguinea, E. sociabilis, and E. splendens¹

Abstract

Euglena sanguinea (Ehrenberg 1831) was one of the first green euglenoid species described in the literature. At first, the species aroused the interest of researchers mainly due to the blood-red color of its cells, which, as it later turned out, is not a constant feature. Complicated chloroplast morphology, labeled by Pringsheim as the "peculiar chromatophore system", made the correct identification of the species difficult, which is the reason why, throughout the 20th century, new species resembling E. sanguinea were continually being named due to a lack of suitable diagnostic features to distinguish E. sanguinea. Interest in E. sanguinea has returned in recent years, following findings that the species can produce ichthyotoxins. This was followed by the need to classify E. sanguinea correctly, which was achieved through the verification of morphological and molecular data for all species similar to E. sanguinea. As the result of the analysis, the number of species sharing some morphological similarities with E. sanguinea could be reduced from 12, as described in the literature, to four, with established epitypes and updated diagnostic descriptions. The most important diagnostic features included: the presence of mucocysts (i.e., whether they were visible before and/or after staining), the number of chloroplasts, the size of the double-sheathed pyrenoids, and the presence of the large paramylon grain in the vicinity of the stigma. Moreover, sequence analysis revealed the presence of unusually long SSU rDNA sequences in E. sanguinea. Previously, SSU rDNA sequences of such length were known to be present in primary osmotrophic euglenoids.

A new photosynthetic euglenoid isolated in Poland: Euglenaria clepsydroides sp. nov. (Euglenea)

“…The last 10 years have seen much taxonomic reclassification of these organisms, based on morphological and molecular data. As a result, the number of previously recognized species has been greatly reduced (Zakryś, 1997;Zakryś et al, 1997Zakryś et al, , 2002Zakryś et al, , 2004Shin & Triemer, 2004;Kosmala et al, 2005Kosmala et al, , 2007aKosmala et al, , 2007bKosmala et al, , 2009Karnkowska-Ishikawa et al, 2010, 2011, 2013 and some new species have been described based solely on molecular data (Kosmala et al, 2007a(Kosmala et al, , 2009. Among the green euglenoids, as is the case with many other groups of organisms, it has become increasingly difficult to find a new species that is clearly distinct morphologically.…”

DNA barcoding in autotrophic euglenids: evaluation of COI and 18s rDNA

“…The whole sequence of 18S rDNA is too large to be easily sequenced (usually ~2,000 bp, but in the case of Euglena sanguinea up to 6,000 bp; Karnkowska‐Ishikawa et al. ), thus we focused on fragments of 18S rDNA. No pair of previously proposed universal eukaryotic primers (Hadziavdic et al.…”

“…, Karnkowska‐Ishikawa et al. , , ). Sequences from Stromobomonas and Trachelomonas were assigned to the clades described by (Ciugulea et al.…”

Trachelomonas bituricensis var. lotharingia M.L. Poucques 1952, a morphologically interesting, rare euglenoid new to the algal flora of the Czech Republic

“…Many reports about euglenoid taxonomy based on morphological and molecular data (e.g., Karnkowska-Ishikawa et al 2010, 2011, 2012, 2013 and Kosmala et al 2005, 2007a, 2007b, 2009) show that several species or other intraspecific taxa may instead only represent eco-morphs or ontogenetic stages of individual species, as discussed in a report about Monomorphina genus taxonomy (Kosmala et al 2007b). Unfortunately, similar studies about the taxonomy of the genus Trachelomonas remain to be performed.…”