Lluïsa Cros

Life-cycle associations involving pairs of holococcolithophorid species: intraspecific variation or cryptic speciation?

New holococcolith-heterococcolith life-cycle associations are documented based on observations of combination coccospheres. Daktylethra pirus is shown to be a life-cycle phase of Syracosphaera pulchra and Syracolithus quadriperforatus a life-cycle phase of Calcidiscus leptoporus. In addition, new observations from cultures confirm the life-cycle associations of Crystallolithus braarudii with Coccolithus pelagicus and of Zygosphaera hellenica with Coronosphaera mediterranea. In all four cases previous work has shown that the heterococcolithophorid species is associated with another holococcolithophorid. Two other examples of a heterococcolithophorid being associated with two holococcolithophorids have previously been identified, so this seems to be a common phenomenon. The six examples are reviewed to determine whether a single underlying mechanism is likely to be responsible for all cases. It is concluded that there is no single mechanism but rather that the six examples fall into three categories: (a) in two cases the holococcolith types are probably simply ecophenotypic morphotypes; (b) in two other cases the holococcolith types are discrete and are paralleled by morphometric differences in the heterococcolith types; (c) in the final two cases the holococcolith types are discrete but are not paralleled by any obvious morphological variation in the heterococcolith morphology. We infer that cryptic speciation may be widespread in heterococcolithophorid phases and that study of holococcolithophorid phases can provide key data to elucidate this phenomenon.

New examples of holococcolith¯heterococcolith combination coccospheres and their implications for coccolithophorid biology.

Abstract Recently discovered coccospheres with combinations of coccoliths normally considered to belong to different taxa are presented here. By analogy with other coccolithophorids especially Coccolithus pelagicus we can hypothesize that these associations probably represent moments of phase change in a complex, possibly haplo-diplontic, life-cycle. Seven of these associations are composed of heterococcoliths with holococcoliths; five of them are presented here for the first time: Helicosphaera carteri with Syracolithus catilliferus, Syracosphaera pulchra with Calyptrosphaera oblonga, Syracosphaera anthos with Periphyllophora mirabilis, Acanthoica quattrospina with holococcolithophorid sp. and Syracosphaera sp. with Corisphaera sp. type A (see Kleijne, A., 1991. Holococcolithophorids from the Indian Ocean, Red Sea, Mediterranean Sea and North Atlantic Ocean. Mar. Micropaleontol. 17, 1–76); the other two are Coronosphaera mediterranea with Calyptrolithina wettsteinii, found previously by Kamptner (Kamptner, E., 1941. Die Coccolithineen der Sudwestkuste von Istrien. Naturhistorischen Museum in Wien. Annalen 51, 54–149), and Syracosphaera nana with undescribed holococcoliths, figured previously by Kleijne (1991) as Syracosphaera sp. type A. In addition the association of Neosphaera coccolithomorpha and Ceratolithus cristatus, recently presented by Alcober and Jordan (Alcober, J., Jordan, R.W., 1997. An interesting association between Neosphaera coccolithomorpha and Ceratolithus cristatus (Haptophyta). Eur. J. Phycol. 32, 91–93) is verified by discovery of a further example. A further five combinations of heterococcoliths and holococcoliths are shown, these probably mostly represent life-cycle combinations but the evidence in each case is insufficient to consider these as definite associations although in these collapsed coccospheres the association of different species is less certain. Two examples of holococcolith–holococcolith associations are presented: S. catilliferus with Syracolithus confusus, and Zygosphaera bannockii with Corisphaera sp. type A. These are probably examples of intra-specific variation. A new species, Syracosphaera delicata sp. nov., is described.

Species level variation in coccolithophores

Coccolithophores are an ideal test group for investigating fine-scale differentiation within the phytoplankton since their taxonomy is rather well-documented and their biomineralised periplasts – the coccoliths – provide a rich suite of qualitative and quantitative morphological characters and a uniquely extensive fossil record. In addition, extant coccolithophore species can be grown in culture and hence are available for studies of morphological variability under controlled conditions, molecular genetic studies and cytological research.

Ventimolina stellata gen. et sp. nov. (Haptophyta, Papposphaeraceae) from warm water regions

It has been known for some time that the distinctive polar weakly calcified coccolithophores are also present in samples from lower latitudes. While polar species may actually have a geographic range that vastly extends beyond the polar realms, it is often the case that the warm water regions contribute species that can be allocated to genera previously described based on polar material. We are currently in the process of formally dealing with the warm water species diversity affiliated with the family Papposphaeraceae. In this paper we describe a new genus and species Ventimolina stellata based on material from the Andaman Sea (type locality) and the NW Mediterranean.

Formonsella pyramidosa (Haptophyta, Papposphaeraceae): a new weakly calcified coccolithophore genus from warm-water regions

A new species Formonsella pyramidosa gen. et sp. nov. is described to accommodate a widely distributed warm-water coccolithophore species that has previously been referred to as Pappomonas sp. 2. Formonsella differs from Pappomonas with respect to, in particular, the detailed structure of the rim on both calicate and non-calicate coccoliths. In Formonsella the rim comprises two cycles of rod-shaped elements. Although elements in the distal layer are higher at one end, giving this cycle a serrate outline, the overall appearance is very different from the Pappomonas rim which encompasses a distal cycle of pentagonal elements, giving the rim a very distinct toothed appearance. Inverted rectangular pyramidal structures terminate the calicate F. pyramidosa coccoliths. In non-calicate coccoliths the central area calcification comprises differently sized tile-shaped elements, mostly arranged along the longitudinal axis in a rather irregular way.