NEW EVIDENCE FOR MORPHOLOGICAL AND GENETIC VARIATION IN THE COSMOPOLITAN COCCOLITHOPHORE EMILIANIA HUXLEYI (PRYMNESIOPHYCEAE) FROM THE COX1b‐ATP4 GENES¹

Abstract

Emiliania huxleyi (Lohmann) W. W. Hay et H. Mohler is a cosmopolitan coccolithophore occurring from tropical to subpolar waters and exhibiting variations in morphology of coccoliths possibly related to environmental conditions. We examined morphological characters of coccoliths and partial mitochondrial sequences of the cytochrome oxidase 1b (cox1b) through adenosine triphosphate synthase 4 (atp4) genes of 39 clonal E. huxleyi strains from the Atlantic and Pacific Oceans, Mediterranean Sea, and their adjacent seas. Based on the morphological study of culture strains by SEM, Type O, a new morphotype characterized by coccoliths with an open central area, was separated from existing morphotypes A, B, B/C, C, R, and var. corona, characterized by coccoliths with central area elements. Molecular phylogenetic studies revealed that E. huxleyi consists of at least two mitochondrial sequence groups with different temperature preferences/tolerances: a cool-water group occurring in subarctic North Atlantic and Pacific and a warm-water group occurring in the subtropical Atlantic and Pacific and in the Mediterranean Sea.

Morphology of <i>Emiliania huxleyi</i> coccoliths on the northwestern European shelf – is there an influence of carbonate chemistry?

“…Intriguingly, recent molecular genetic work on E. huxleyi using rapidly evolving mitochondrial genes has highlighted a major subdivision of type A E. huxleyi into groups, termed clades I and clade II (Hagino et al, 2011;Bendif et al, 2014). These have been characterised as broadly warm water and cool water groups; although, strains of both genotypes occurred in the current study area (Hagino et al, 2011) with the boundary between them approximating the shelf break.…”

“…These have been characterised as broadly warm water and cool water groups; although, strains of both genotypes occurred in the current study area (Hagino et al, 2011) with the boundary between them approximating the shelf break. Hence it is possible that the coastal and oceanic populations characterised here may correspond to the clades I and II of Hagino et al (2011).…”

“…Third, genotypic variation occurs within each group as evidenced by both morphological work (e.g. Young, et al, 2003) and molecular genetic work (Hagino et al, 2011;Bendif et al, 2014). Notably both Hagino et al (2011) and Bendif et al (2014) distinguish warm and cool water clades within the global E. huxleyi population with overlapping occurrence in the NW European shelf area.…”

“…Young, et al, 2003) and molecular genetic work (Hagino et al, 2011;Bendif et al, 2014). Notably both Hagino et al (2011) and Bendif et al (2014) distinguish warm and cool water clades within the global E. huxleyi population with overlapping occurrence in the NW European shelf area. So, a scanning electron microscope (SEM) based technique was adopted to allow consistent identification of taxa, accurate size measurement, and study of degree of calcification independent of size.…”

Influence of changing carbonate chemistry on morphology and weight of coccoliths formed by <i>Emiliania huxleyi</i>

“…Furthermore, visual evaluations are easy to adapt to all coccolithophore species, whereas quantification of malformations by direct measurements of morphological structures can thus far only be applied to complete coccoliths from E. huxleyi morphotype A (including var. corona), B, C, and O; but it cannot be applied to morphotype R since there are usually no slits between two adjacent distal shield elements in these morphotypes (for morphotype taxonomy see Young et al, 2003;Hagino et al, 2011). Although adaption of Eq.…”