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Markus Geisen, Lluisa Cros, Ian Probert, Jeremy R. Young:
Life-cycle associations involving pairs of holococcolithophorid species - complex life cycles or cryptic speciation?
(Talk)

Cros et al. (in press) documented remarkable new examples of combination coccospheres, involving heterococcoliths and holococcoliths, and argued that these most probably were formed as part of a haplo-diplontic life-cycle. Subsequent observations have strongly supported this hypothesis (see separate abstract). Cros et al. (in press) also, however, recorded some anomalous examples of holococcolith-holococcolith combination coccospheres. They suggested that these might be caused by intraspecific variation. We have now found further cases where two holococcoliths appear to be associated with one heterococcolithophorid. This is getting slightly complex! To summarise, the combinations are:

Coccolithus pelagicus with Crystallolithus hyalinus and C. braarudii (Rowson et al., 1986). The two holococcoliths show a structural and a slight morphological variation and do not co-occur on a single cell. Intermediate forms have not been observed.

Helicosphaera carteri with Syracolithus catilliferus and S. confusus (Cros et al., in press). With the structure being similar, S. confusus appears to be a morphological variation of S. catilliferus. Both holococcoliths can co-occur on the same sphere, and intermediate forms have been observed.

Syracosphaera sp. with Zygosphaera bannockii and Corisphaera sp.A (Cros et al., in press). The two holococcoliths show only morphological variation and can co-occur on one cell. Intermediate forms have been observed.

Syracosphaera pulchra with Calyptrosphaera oblonga and Daktylethra pirus (Cros et al., in press; new obs.). The two holococcoliths are morphologically and structurally significantly different and do not co-occur on the same cell.

Calcidiscus leptoporus with C. leptoporus f. rigidus and Syracolithus quadriperforatus (Kleijne, 1991; Cortes, in press; new obs.). The two holococcoliths are morphologically and structurally significantly different and do not co-occur on the same cell.

Various possible causes are open for these associations and it is possible that they have multiple causes. However, we suggest that at least some of them provide strong evidence for cryptic speciation, i.e. speciation which was not clearly recognisable from heterococcolithophorid morphology.

Figure 1: Combination coccospheres of Calcidiscus leptoporus with Syracolithus quadriperforatus (left) and Syracosphaera pulchra with Daktylethra pirus (right). Both from the Alboran Sea (W Mediterranean)

References

Cortes, M.Y. In press. Further evidence for the heterococcolith-holococcolith combination Calcidiscus leptoporus - Crystallolithus rigidus. Marine Micropaleontology. INA7 Proceedings Special Issue, 39.

Cros, L., Kleijne, A., Zeltner, A., Billard, C., Young, J.R. In press. New examples of holococcolith-heterococcolith combination coccospheres and their implications for coccolithophorid biology. Marine Micropaleontology. INA7 Proceedings Special Issue, 39.

Kleijne, A. 1991. Holococcolithophorids from the Indian Ocean, Red Sea, Mediterranean Sea and North Atlantic Ocean. Marine Micropaleontology, 17: 1-76.

Rowson, J.D., Leadbeater, B.S.C. & Green, J.C. 1986. Calcium carbonate deposition in the motile (Crystallolithus) phase of Coccolithus pelagicus (Prymnesiophyceae). British Phycological Journal, 21: 359-370.

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