MORPHOLOGY, PLOIDY, PIGMENT COMPOSITION, AND GENOME SIZE OF CULTURED STRAINS OFPHAEOCYSTIS(PRYMNESIOPHYCEAE)¹

Abstract

We examined cell morphology, ploidy level, cell size, pigment composition, and genome size in 16 cultured strains of Phaeocystis Lagerheim. Two strains originated from the Antarctic, 3 from the tropical Western Atlantic, and 11 from temperate regions (Eastern Atlantic, English Channel, North Sea, and Mediterranean Sea). Thirteen strains made colonies morphologically similar to P. glo‐bosa Scherffel, whereas three never formed colonies under any circumstances. Five‐rayed star‐like structures with filaments were observed in 11 strains. In several strains, two ploidy levels were observed, one (haploid) linked to flagellates and one (diploid) linked to colonies. Cell size did not appear to be a very good criterion for distinguishing strains since size distributions overlapped. Pigment analysis by reversed‐phase‐high‐performance liquid chroma‐tography allowed the strains to be grouped into three clusters that differed from each other mainly by the relative proportions of three carotenoids: fucoxanthin, 19′‐hex‐anoyloxyfucoxanthin, and diadinoxanthin. All strains contained low levels of 19′‐butanoyloxyfucoxanthin. Differences in genome size measured by flow cytometry delimited at least five groups. On the basis of both pigment composition and genome size, six clusters were defined, one corresponding to an Antarctic species (possibly P. antarc‐tica), one to P. globosa, and the rest probably to several yet‐undescribed species or subspecies. Two main conclusions emerge from this study. First, the taxonomy of the genus Phaeocystis needs to be clarified through a combination of morphological, biochemical, and molecular studies. Second, sexuality is a prevalent phenomenon in Phaeocystis, but controls of the sexual cycle are most likely strain‐dependent.

Photosynthetic pigments in 37 species (65 strains) of Haptophyta: implications for oceanography and chemotaxonomy

“…Vaulot et al (1994) observed 3 pigment clusters in 16 strains of Phaeocystis isolated mainly from temperate oceanic areas, supporting some of the present observations. In their Phaeocystis strains, both fucoxanthin and 19'-hexanoyloxyfucoxanthin were dominant or codominant, but 19'-butanoyloxyfucoxanthin in their study was never present except in minor or trace quantities.…”

Phytoplankton composition and selective feeding of the pearl oyster Pinctada margaritifera in the Takapoto lagoon (Tuamotu Archipelago, French Polynesia):in situ study using optical microscopy and HPLC pigment analysis

“…Literature ranges of chl a to marker pigment ratios used to determine the different amounts of the algal classes contributing to total chl a. See Table 1 Vaulot et al (1994), (k) Kana et al (1988), (1) Letelier et al (1993), (m) Hooks et al (1988), (n) Simon et al (1994), (0) BustillosGuzman et al (1995) and (p) Tester et al (1995) solved with the use of a least-square algorithm in order to minimise differences between chl a values observed and calculated (linear regression with constraints). This method was applied to the 72 data of chl a obtained at the 3 sampling sites.…”

A taxonomic review of the genus Phaeocystis

“…The molecular data published to date are derived only from colonial stages or from Xagellate stages that were originally colonial. There is only a single type of ITS sequence pres- Scott and Marchant (2005), (e, h, i) from Zingone et al (1999), (b) and (g) from Vaulot et al (1994). Scale bar = 1 m on (a, b, g) Scale bar = 10 m on (c, d) Scale bar = 2 m on (e-j) Scale bar = 0.3 m on (i) ent in each strain in contrast to the multiple ITS variants in P. pouchetii and P. globosa, which strongly suggests that colonial Phaeocystis from the Antarctic are not a species complex.…”

“…The colonies resembled those of P. globosa (Larsen and Moestrup 1989), whereas temperature tolerance was similar to that of P. pouchetii. Notably, strains from the Antarctic had diVerent pigment spectra (Buma et al 1991;Vaulot et al 1994) and DNA content . First indications that further undescribed species could exist were provided by Pienaar (1991Pienaar ( , 1996 who illustrated a Phaeocystis Xagellate with cup-shaped scales from South African waters suggesting it was a new species but not publishing a formal description.…”