Present status of the molecular ecology of kathablepharids.

In the last few years, environmental sequence surveys have identified several putative novel lineages within the eukaryotes. This interpretation is however limited by the absence of taxon sampling for several well known and abundant eukaryotes (Cavalier-Smith 2004; Simpson and Roger 2004). It is therefore important to complement classical morphological studies with molecular sequencing, as well as with data available from the growing database of environmental phylotype sequences. One of those neglected but abundant protist groups are the kathablepharids (Kathablepharida — ICZN, Katablepharidophyta — ICBN); predatory heterotrophic flagellates that have escaped molecular sequencing until very recently. Kathablepharid flagellates are a significant component of freshwater and coastal food webs (Arndt et al. 2000), but their relationship to other eukaryotic groups remained uncertain, although most authors suggested their affinity with the cryptophytes (for review see Okamoto and Inouye 2005). In a previous publication we reported the environmental SSU rDNA survey of a freshwater pond, where we identified an unknown phylotype distantly related to the cryptophytes (Šlapeta et al. 2005). We hypothesised that this phylotype could belong to the kathablepharids, a group not represented in sequence databases at that time. The proposed identity remained unsettled until a recent study by Okamoto and Inouye (2005) provided the first SSU rDNA sequences from two well-characterised marine kathablepharid species, Kathablepharis japonica and Leucocryptos marina. Phylogenetic analyses based on the SSU rDNAs of these two species as well as btubulin sequences indicated their sister relationship to cryptophytes (Okamoto and Inouye 2005). Using the published SSU rDNA sequences of K. japonica and L. marina (Okamoto and Inouye 2005) as queries for BLAST searches, we identified 11 phylotypes very similar to these kathablepharid sequences (see Table 1). Maximum