M. Geisen, I. Probert & J. Young: Coccolithophores for exhibition, p. 3-7

Journal of Nannoplankton Research, 24, 1, 2002

COCCOLITHOPHORES FOR EXHIBITION: A NOTE
Markus Geisen*, Ian Probert† & Jeremy R. Young**Palaeontology Dept., The Natural History Museum, London, SW7 5BD, UK; †Lab. de Biologie & Biotechnologies
Marine, Univ. de Caen Basse Normandie, Caen, France; M.Geisen@nhm.ac.uk

Introduction
When we work with coccolithophores, we sometimes overlook
their beauty, strangeness and visual impact. However, recently
their visual qualities were amply confirmed, after one of us (MG)spent an afternoon false-colouring an SEM image for a sciencephotography competition: the resultant image won First Prizein the ‘Science Close Up’ category of the Novartis/Daily
Telegraph Visions of Science competition. Further information
about the competition, and this winning image, can be viewed
at www.visions-of-science.co.uk. Through this medium, nonscientists got their first vision of the beauty of these minuteworks of art.
By a happy coincidence, The Natural History Museum hasrecently devoted space to temporary exhibitions of artwork
related to natural history. Consequently, we were asked toprepare a temporary exhibition of coccolithophore images forit. In collaboration with an editor and exhibition designer, weselected 14 images of coccospheres. Selection was partly basedon image quality and attractiveness but, also, an attempt to show

reproduced from Journal of Nannoplankton Research, 24, 1, 2002

a wide range of morphologies and some of the more interesting
structures was made. A TEM section was included to provide agraphic illustration of the relationship between the coccosphereand the cell, and also a coccolithophore bloom image (courtesyof S. Groom, PML) to highlight the potential ecological impactof coccolithophores.
The images were false-coloured both to increase the visual
impact and to highlight specific features for text-reference. The
images have been enlarged to 1m across for the exhibition andmake a very attractive display, which the visitors seem to like.
The plate captions presented here are essentially the same as
those in the exhibition and reflect how we have tried toencourage public understanding of our science, although there
are limits to what you can do in the number of words allowed.
The exhibition will be displayed in the public galleries until
March/April and after that will probably move to our commonroom. If any other INA members would like an opportunity touse the exhibition for public display we would be pleased tohear from you.

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M. Geisen, I. Probert & J. Young: Coccolithophores for exhibition, p. 3-7

Plate 1
Fig.1: Calcidiscus leptoporus
Coccolithophores mostly reproduce asexually by simple binary cell-division. But sexual reproduction does occasionally occur andis marked by production of haploid daughter-cells covered by holococcoliths. Following fusion of two daughter-cells, a diploid cellis produced and the coccolith type reverts to heterococcolith. This award-winning image provides rare documentation of this process,as the diploid cell with its cover of heterococcoliths (in pink) emerges from within the cover of the fused daughter-cells (in green).
For a detailed figure explaining the life-cycle refer to Plate 2, Figure 7. This specimen is from the Alboran Sea, western Mediterranean(R/V Hesperides cruise Mater II, station 69).
Fig.2: Syracosphaera pulchra
Coccolithophores can produce different scales to cover their surface. This cell has an inner, endothecal layer (in pink), with coccoliths
bearing spine-like protrusions around the flagellar pole (top right), and an outer, exothecal cover (in green). This specimen is fromthe Canary Islands, North Atlantic (R/V Poseidon cruise P233b, station 3). Image courtesy of Claudia Sprengel, Alfred Wegener
Institute, Bremerhaven, Germany.
Fig.3: Syracosphaera nodosa
In this specimen, the wheel-like exothecal coccoliths (in green) have fallen off and are lying on the filter. Again, the inner coccoliths(in pink) show spine-like protrusions around the flagellar pole. This specimen is from the Alboran Sea, western Mediterranean (R/V Hesperides cruise Mater II, station 61).
Fig.4: Syracosphaera anthosThis is a rare example of Syracosphaera anthos with the exothecal cover of coccoliths (in green) almost completely in place.
Species with exothecal coccoliths are very fragile and often disintegrate during the filtration process. This specimen is from theNorth Atlantic (station FB16).
Fig.5: Algirosphaera robusta
This species is of interest since it lives in the deep photic zone, more than 50m below the surface, and is therefore poorly known. A
single cell was recently isolated from Mediterranean sea-water and successfully maintained in culture, which has allowed detailed
study of its morphology and behaviour. This specimen is from the Alboran Sea, western Mediterranean (R/V Hesperides cruise
Mater II, station 69).
Fig.6: Algirosphaera robusta
This very different image was taken with a TEM, and shows the internal structure of a coccolithophore. Two types of heterococcolithcover the cell – some are hood-like (in pink) and others elongated (in green) around the flagellar pole. The interior is dominated bya large chloroplast (in dark green), the light-collecting motor of the cell. Above this sits the nucleus (in pink), which contains theorganism’s genetic material. In addition, a coccolith in production can be seen inside the cell. This specimen is from the Alboran
Sea, western Mediterranean (R/V Hesperides cruise Mater II, station 69). Image courtesy of Ian Probert, Université de Caen BasseNormandie, Caen, France.
Fig.7: Emiliania huxleyi
This is perhaps the best known and most intensively researched coccolithophore. With the exception of the Southern Ocean around
Antarctica, this species can be found in all oceans. This single species can form massive blooms (see Plate 2, Figure 6), the lateralextent of which can be very broad and, with the ability to calcify and fix biomass, this species, and coccolithophores in general,
contributes significantly to the carbon cycle. This specimen is from the Canary Islands, North Atlantic (R/V Poseidon cruise P233b,station 2).
Fig.8: Reticulofenestra sessilis
This species (in green) forms unique symbiotic associations with the diatom Thalassiosira (in pink). This specimen is from the Gulfof Mexico (R/V Gyre cruise 90-G-15, station 9).

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M. Geisen, I. Probert & J. Young: Coccolithophores for exhibition, p. 3-7

Journal of Nannoplankton Research, 24, 1, 2002

12

Calcidiscus leptoporus

Syracosphaera pulchra

34

Syracosphaera nodosa

Syracosphaera anthos

56

Algirosphaera robustaAlgirosphaera robusta

78Emiliania huxleyi

Reticulofenestra sessilis

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Journal of Nannoplankton Research, 24, 1, 2002

M. Geisen, I. Probert & J. Young: Coccolithophores for exhibition, p. 3-7

Plate 2
Fig.1: Discosphaera tubifera
The coccoliths produced here are trumpet-shaped. The actual cell is very small in comparison to the coccoliths. The cell diameter isless than the length of the coccolith, thus the coccolith is produced inside the cell with its base folded, which causes considerablestretching for the cell. This specimen is from the Alboran Sea, western Mediterranean (R/V Hesperides cruise Mater II, station 69).
Fig.2: Rhabdosphaera clavigera
Rhabdosphaera (in green) forms long protrusions from the centre of the coccolith, and the precise architecture of these spines can beseen. A coccosphere of Emiliania huxleyi (in pink) can be seen in the background. These specimens are from the Alboran Sea,
western Mediterranean (R/V Hesperides cruise Mater II, station 69).
Fig.3: Gephyrocapsa ornata
This species reflects the ornamentation, with an elevated bridge spanning the central area (in pink). Whilst a number of Gephyrocapsa
species have been described, and Gephyrocapsa oceanica is distributed globally, Gephyrocapsa ornata is very rare. This specimen
is from the Alboran Sea, western Mediterranean (R/V Hesperides cruise Mater II, station 44).
Fig.4: Michaelsarsia elegans
Michaelsarsia belongs to a group of coccolithophores the most striking feature of which is the presence of long appendages (in pink)around the flagellar pole. These are highly modified coccoliths, the function of which, however, is unknown. This specimen is fromthe Alboran Sea, western Mediterranean (R/V Hesperides cruise Mater II, station 69).
Fig.5: Periphyllophora mirabilis
This species represents another example of a holococcolith. The hole surrounded by the coccoliths (in green) is the flagellar opening.
Creating a good micrograph of holococcoliths is difficult, as they are rare in the plankton and tend to disintegrate rapidly. This
specimen is from the Alboran Sea, western Mediterranean (R/V Hesperides cruise Mater II, station 15).
Fig.6: Emiliania huxleyi bloom off Cornwall
Under certain conditions, Emiliany huxleyi can form massive blooms which can be detected by satellite remote sensing. What looks
like white clouds in the water, is in fact the reflected light from billions of coccoliths floating in the water-column. Image courtesyof Steve Groom, Plymouth Marine Laboratories.
Fig.7: Coccolithophorid life-cycles
Schematic representation of coccolithophorid life-cycles. The diploid stage of Calcidiscus leptoporus is covered with heterococcoliths(left, in pink) which are produced inside the cell, whereas the motile stage is covered with holococcoliths (right, in green) which areproduced outside of the cell membrane.

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M. Geisen, I. Probert & J. Young: Coccolithophores for exhibition, p. 3-7

Journal of Nannoplankton Research, 24, 1, 2002

12Discosphaera tubifera

Rhabdosphaera clavigera

34Gephyrocapsa ornata

Michaelsarsia elegans

56

Periphyllophora mirabilis

Emiliania huxleyi bloom

7

Coccolithophorid life-cycles
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