[coccoliths] Discoaster coccosphere

Thu Apr 20 08:20:21 -03 2023

Hi Everyone

No, I have not seen any discoaster coccospheres, but you might want to 
check out the following references (both downloadable from the internet) 
...

Malte Elbrächter, Marc Gottschling, Tania Hildebrand-Habel, Helmut Keupp,
Rolf Kohring, Jane Lewis, K.J. Sebastian Meier, Marina Montresor, 
Michael Streng,
Gerard J.M. Versteegh, Helmut Willems and Karin Zonneveld (2008).
Establishing an Agenda for Calcareous Dinoflagellate Research (
Thoracosphaeraceae,
Dinophyceae) including a Nomenclatural Synopsis of Generic Names.
Taxon , Vol. 57, No. 4 (Nov., 2008), pp. 1289-1303.

Horner, R, Carstens, M, Gradinger, R, Ikavalko, J. & Spindler, M. 1998. 
Discoasters are recent taxa [Abstract]. Rapport/Botanisk serie/
Vitenskapsmuseet, Universitet i Trondheim: 70.
Abstracts from the Sixth International Conference on Modern and Fossil 
Dinoflagellates, Dino 6, Trondheim, June 1998.

In the first reference it states ...

Dinoflagellates with calcareous endoskeletons.

Discoasters have been highly diverse throughout the
Cenozoic and are traditionally considered as an extinct
group of calcareous nannofossils with potential affinity
to calcifying haptophytes, especially to the coccolitho
phorids (Tappan, 1980). Discoasters are believed to have
become extinct at the latest Pliocene (~2 Ma), but Horner
& al. (1998) discovered similar calcareous intracellular
skeletal elements in living, unequivocally gymnodinoid
cells, thus providing evidence for extant discoaster equiv
alents among the dinoflagellates. They have been found
in ice samples from Alaska, Greenland and the Antarctic
(Elbr?chter, unpub. data; Horner, pers. comm. to M.E.),
but it was not possible to grow cultures for subsequent
morphological and molecular investigations. In addition,
Bursa (1964, 1971) described, without validly published
names, various taxa producing calcareous structures
similar to Discoaster S.H. Tan. We do not include such
organisms in the calcareous dinoflagellates yet, since
their precise phylogenetic relationships require further
investigation.

In the second reference it states ...

The first real evidence that discoasters may
be living today was provided by Bursa (1965,
1971), based primarily on sea ice samples
from the Canadian Arctic. He described a
new genus, new species, and transferred
discoasters to a new family in the dinoflagellates.
Live discoasters have also been
grown in rough cultures started with pieces
of sea ice from northern Alaska (R. Horner)
and seen in first-year ice samples from the
Weddell and Greenland seas (M. Elbrachter,
M. Spindler, M. Carstens, R. Gradinger & J.
Ikavalko). Scanning electron microscopy and
elementa1 analysis show that the stars are
composed of calcium carbonate (J. Juhanoja).
Thus, there is evidence that discoasters are
still living today in polar sea ice, albeit in
relatively small numbers.

References:
Bursa, A.S. 1965. Discoasteromonas calciferus
n. sp., an Arctic relict secreting Discoaster
Tak [sic] Sin Hok 1927. - Grana
Palynol. 6: 148- 165.

Bursa, A.S. 197 1. Morphogenesis and taxonomy
of fossil and contemporary Dinophyta
secreting discoasters, pp. 129-143. -
In Farinacci, A. (ed.) Proceedings of the II
Planktonic Conf. Roma 1970. 1. Edizioni
Technoscienza, Rome.

So, perhaps we should keep an open mind about the origin of discoasters.
Although clearly, more investigations are needed to clarify this 
relationship.

Best wishes

Ric Jordan

----- Original Message -----
> Ciao!
> 
> I've never seen a Discoaster coccosphere, in 46 years spent in  
> analyzing nannofossil assemblages from Mediterranean and open  
> ocean...is it an utopia? 😱
> Best,
> Isabella
> 
> 
> "Self-Trail, Jean M" <jstrail at usgs.gov> ha scritto:
> 
> > Hey all,
> >
> > Has anyone ever seen (or published) a Discoaster coccosphere??  If  
> > so, do you have a reference?
> >
> > Cheers,
> > Jean
> >
> > Jean M. Self-Trail, Ph.D.
> > U.S. Geological Survey
> > 926A National Center
> > 12201 Sunrise Valley Dr.
> > Reston, VA 20192
> > 703-648-6013
> >
> > "You are not entitled to your opinion.
> > You are entitled to your informed opinion.
> > No one is entitled to be ignorant."  --Harlan Ellison
> 
> 
> 
> -- 
> Isabella Raffi, PhD h c
> già Professore ordinario di Paleontologia e Paleoecologia
> Senior Scientist at International Research School of Planetary 
Sciences-IRSPS
> Dipartimento di Ingegneria e Geologia (InGeo)
> Universita' degli Studi "G. d'Annunzio" di Chieti-Pescara
> Campus Universitario, via dei Vestini 31
> 66013 Chieti Scalo (Italy)
> phone: (+39)08713556421
> 
> Independent Fellow member - Institute for Climate Change Solutions  
> (ICCS - www.i4ccs.com)
> 
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