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TitleThe Peridiniacean lineage and its transition to freshwater environments: the strange case of Peridinium limbatum
AuthorMcCarthy, F M G; Krueger, A M; Gurdebeke, P R; Mertens, K N; Fensome, R A; Lucas-Clark, J
Source52nd Annual Meeting, AASP-The Palynological Society, program book; 2019 p. 51 Open Access logo Open Access
LinksOnline - En ligne (complete volume - volume complet, PDF, 4.35 MB)
Alt SeriesNatural Resources Canada, Contribution Series 20190269
PublisherAASP - The Palynological Society
Meeting52nd Annual Meeting of AASP-The Palynological Society; Ghent; BE; June 30-July 5, 2019
Mediaon-line; digital
File formatpdf
AreaPlastic Lake
Lat/Long WENS -79.0000 -78.5000 45.2500 45.0000
Subjectspaleontology; Nature and Environment; Science and Technology; micropaleontology; microfossils; paleoenvironment; systematic paleontology; taxonomy; lake sediments; Holocene; Dinoflagellates; Peridiniacean; Peridinium limbatum; Peridinium cinctum; Protoperidinium; Palaeocystodinium golzowense; Fusiperidinium wisconsinense; Phytoplankton; lacustrine sediments; Phanerozoic; Cenozoic; Mesozoic; Cretaceous
ProgramScience laboratory network
Released2019 06 01
AbstractThe large thecate cells of Peridinium limbatum have one distinctive left-laterally inclined apical horn and two short antapical horns. The species was reassigned to Peridinium from the marine genus Protoperidinium because its tabulation is identical to that of Peridinium cinctum. Its proximocavate cyst has a morphology that echoes that of the theca, and may be the last of a long lineage of bipesioid cysts that diverged from the ovoidinioid lineage during the Cretaceous. This lineage adapted to freshwater environments through the Cenozoic, and peridiniacean dinoflagellates with organic-walled cysts have been exclusively freshwater taxa since the extinction of Palaeocystodinium golzowense in the middle upper Miocene. The distinctive cysts of Peridinium limbatum have been commonly reported in Holocene lake sediments, but they are generally rare (<2% of cyst assemblage). Sediment trap studies from Plastic Lake, Ontario, where this taxon is a dominant constituent of the phytoplankton from spring through fall, indicate that the vast majority of cysts of Peridinium limbatum decompose in the water column, whereas cysts of Fusiperidinium wisconsinense have a much better fossilization potential, despite blooming for only a relatively short interval in the summer. Micro-FTIR analysis identified many similarities in the cyst wall composition with those measured on the two cyst types from Plastic Lake, consistent with complex carbohydrate-based biopolymers in cyst walls of photoautotrophic dinoflagellates. While some of the absorption bands were present in spectra from both cysts (i.e. 1120, 1040, 985 cm-1), a strong sharp absorption at 722 cm-1 was unique to Peridinium limbatum and characteristic of long carbon chains (>C22). This chemical difference may explain the lower fossilization potential of Peridinium limbatum in Plastic Lake, but it does not explain occasional abundant occurrences in Holocene sediments, nor does it explain the long fossil record of this lineage. It is possible that cyrptic species of Peridinium limbatum currently exist, of which only a typically rare form has a high fossilzation potential.
Summary(Plain Language Summary, not published)
Dinoflagellates are generally single-celled organisms that live today in marine and freshwater environments, and as fossil have been found mainly as preservable cysts in marine environments. Cysts may have a resistant organic-wall or a calcareous wall. The modern freshwater species Peridinium limbatum produces organic-walled cysts that resemble organic-walled fossils that are restricted to the Cretaceous marine realm during the Cretaceous, but also resembles younger calcareous cysts. An investigation into the biology, biochemistry and ecology of Peridinium limbatum may reveal important information about dinoflagellate evolution, how some species transitioned from marine to non-marine environments, and the relationship between forms that produce organic-walled cysts and those that produce calcareous cysts.

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