Chromista Thomas Cavalier-Smith (1981)
substantial modification of existing system of 5 kingdoms
Chromista
common ancestor – origin by a secondary endosymbiosis of Rhodophyte plastids
main autotrophic lineages: Cryptophyta, Haptophyta, Stramenopiles
analýza plastidových genů
Chromista chloroplasts – 4 membranes (2 of plastid origin + 2
derived from ER), girdle lamella
chlorophyl a, c; diato/diadinoxanthophyl cycle
storage product - chrysolaminaran (β-1,3-1,6-glucan)
pleuronematic flagella
interplastidial stigma in flagellates
Chromista
common ancestor – origin by a secondary endosymbiosis of Rhodophyte plastids
secondary loss of plastids in several groups of organisms
Chromista
common ancestor – origin by a secondary endosymbiosis of Rhodophyte plastids
secondary loss of plastids in several groups of organisms
67 Taxa
159 protein
genes
Brown et al. 2012
150 Taxa
250 protein genes
Burki et al. 2016
Haptophyta
predominantly marine flagellates
two flagella without mastigonemata
haptonema – 6-7 MT in a cross-section
plastids with lamellae comprised of 3 thylakoids, no stigma, no girdle lamella
production of inorganic cellulosic or calcareous scales (coccoliths).
Satellite image of a bloom in the English Channel off the coast of Cornwall, 24 July 1999.
significantly affecting the global clima on the Earth (biogeochemical cycle of carbon and sulphur)
Haptophyta
de Vargas et al. 2007
Dimethylsulphide (DMS) –
formation of clauds in the
atmosphere.
White tide – extensive bloom of
a haptophyte Emiliania huxleyi
White tide + clouds –
increasing of albedo (i.e.
increasing of total light
reflection from the Earth surface
– cooling down the Earth
Haptophyta
coiled haptonema Haptonema
Haptophyta
thin organelle resembling the flagellum
variable length
6-7 microtubules arran-ged in a circle or a cross, surrounded by the ER cisterna
Chrysochromulina. Bacterial particles stick on the haptonema. They are
transported to the aggregation center. The clump of bacteria is then
transported to the end of haptonema, and delivered to the posterior cell
end, where it is engulfed.
Haptophyta
Haptonema
ingestion of bacteria and smaller eukaryotes (phygotrophy)
cellulosic scales
(Chrysochromulina)
calcareous coccoliths
(Cyrtosphaera)
silica scales
(Hyalolithus)
Scales
Prymnesium
Haptophyta - polysaccharide scales (cellulose)
Chrysochromulina sp. Ch. vexillifera
Tiny cellulosic scales formed in many
Haptophyte species
Chrysochromulina – only cellulosic
scales
Pleurochrysis carterae
Haptophyta - scales
In Coccolithophorids, calcified scales (called coccoliths) are usually formed in
addition to underlying organic scales.
(a) two calcit layers surround the polysaccharide scale.
Hymenomonas lacuna
Biosynthesis in Golgi
aparatus, each scale in it
own cisterna
Haptophyta - polysaccharide scales (cellulose)
Calcareous coccoliths surrounds the cell in one or several layers
(coccosphaere)
Haptophyta - coccoliths
Holococcoliths
calcification occurs extra-
cellularly, individual crystals
have simple morphologies, no
distinction between the rim
and central area
Heterococcoliths
calcification occurs intra-
cellularly, complex
morphologies, a rim of radial
crytal units surrounding
thecentral area
Haptophyta - coccoliths
Syracosphaera
n 2n
n 2n
n 2n
Alisphaera
Emiliania
holococcoliths and heterococcoliths occur on alternate phases of the life-cycle of single species
it reflects a haplodiplontic life-cycle, with holococcoliths consistently occurring in the haploid phase
Syracosphaera
Biosynthesis – (1) Golgi vescicles fuse to form one big vesicle attached to the nuclear
membrane, (2) thin organic lamella is formed inside the vesicle, reticular body
(microtubular net) is attached outside, (3) calcification, (4) disappearing of reticular
body, (5) complete coccolith is transferred to the cell surface and released outside
Haptophyta - coccoliths
Emiliania huxleyi – biosynthesis of the heterococcolith
Haptophyta - coccoliths
Scyphosphaera
Biosynthesis (E. huxleyi)
Haptophyta - coccoliths
Calcification: production of CO2 utilised during the photosynthesis
2HCO3− + Ca2+ → CaCO3 + CO2 + H2O
Higher intensity of photoynthesis =
higher intensity of calcification.
There is a very fast, effective
transport of calcium ionts over the
plasmatic membrane. In Emiliania
huxleyi, one coccolith is formed ca
1 hour.
Haptophyta - calcification
Haptophyta – value of coccoliths
utilisation of CO2 for the photosynthesis
defence against the predators (higher cell volume) and pathogens (bacteria, viruses)
regulation of floating (production of heavy coccoliths)
diffraction of sunlight into the cell center (photosynthesis in deap-sea species)
Chrysochromulina
Haptophyta – plastids
1 - 2 plastids with pyrenoids
4 plastid membranes
chlorophyl a + c (yellow-brown colour)
Calyptrosphaera
sphaeroidea - pyrenoid
Haptophyta – plastids
Chrysochromulina polylepis ichtyotoxins
Haptophyta – production of toxins
White Cliffs of Dover
Haptophyta – fossil records
first appear in the fossil of the Late Triassic, approximately 220 million years ago
the higher abundance during the Late Cretaceous (95 mya)
80 % of all coccolithophorids went extinct during the Cretaceous-Tertiary (K-T) event at the end of the Cretaceous
Evardsen et
al. 2000
18S rDNA
Pavlovaphyceae
Phaeocystales
Prymnesiales
Isochrysidales
(coccoliths)
Haptophyta – evolution and phylogeny
Pry
mnes
iop
hy
ceae
Haptophyta, Pavlovaphyceae
without coccoliths or organic scales
two unequal flagella covered by a tiny hairs
short, non-contractile haptonema
nákres Pavlova
named according to the famous
russian ballerina
Exanthemachrysis noctivaga
Haptophyta, Pavlovaphyceae
originally described by Tomáš Kalina from peat bogs in Krkonoše Mts.
Haptophyta, Prymnesiophyceae, Phaeocystales
primitive evolutionary lineage among haptophytes
Phaeocystis pouchetii – flagellates in large mucilaginous colonies
major emitter of DMS
Phaeocystis bloom
foam accumulated on beaches
Chrysochromulina
Prymnesium
Haptophyta, Prymnesiophyceae, Prymnesiales
unicellular flagellates with two flagella of equal length
haptonema variable in its length, often contractile
predominantly marine species
non-calcified scales
Pleurochrysis carterae
Haptophyta, Prymnesiophyceae, Isochrysidales
calcareous coccoliths
two smooth flagella
Pleurochrysis
simple coccoliths
Hymenomonas roseola
freshwater
in metaphyton of clear, oligotrophic waters
Emiliania huxleyi
most abundant coccolithophore found in the Earth’s oceans, forming extensive blooms (white tides)
significant impact on global climate
Emiliania huxleyi
Emiliania huxleyi
http://ina.tmsoc.org/Nannotax3/index.ph
p?dir=Coccolithophores&top=34&base=
300
Algirosphaera robusta
Thorosphaera
flabellata
Pontosphaera
syracusana
Isochrysidales - coccoliths
Florisphaera profunda
Braarudosphaera
bigelowi
Rhabdosphaera
clavigera
Isochrysidales - coccoliths F. profunda
Freshwater Haptophyta
Schalchian-Tabrizi et al. 2011
Cryptophyta predominantly flagellates, flagella of unequal length
coccoids (Tetragoniella), capsal, trichal (Bjornbergiella, soil in Havaii)
1 Cryptomonas curvata, 2 Rhodomonas pusilla, 3 Chroomonas
nordstedtii, 4 Chilomonas paramaecium
Cryptophyta – plastids
1-2 plastids (4 membranes)
chlorophyls a+c2
phycobiliproteins: (crypto)-
phycocyanin, (crypto)-
phycoerytrin in thylakoid
lumen
starch (α-1-4-glucan) in
periplastidial space (between
ER and plastid membranes),
lipid granule, chrysolaminaran is
not produced!
pyrenoid, stigma
no girdle lamella
Rhodomonas
plastids with lamellae comprised of 3 thylakoids
Cryptophyta – plastids
Cryptophyta - flagella
organic scale on the
flagellar surface
Cryptophyta – cell morphology
Cryptophyta - ejectosomes
explosive structures surrounding the furrow, and under the plasmatic membrane
two connected ribbons of different sizes, that are rolled up and under tension
discharged upon mechanical or chemical stress irritating the cells
Cryptophyta – nucleomorph
often attached to pyrenoids
two membranes
Chroomonas coeruela – wavy periplast, inner and outer plates
Cryptophyta - periplast
Cryptomonas ovata – periplast beneath the plasmatic membrane
PM
protein plates
Cryptomonas sp. – arrangement of plates
Cryptophyta - periplast
angular arrangement
of plates
plates
E = trichocysts (ejectosomes) EP = ejectosome
openings
hexagonal arrangement
of plates
Cryptophyta - periplast
Cryptophyta - reproduction
asexual – schizotomy of flagellates
sexual – isogamy, formation of planozygote (4 flagella)
Cryptophyta - ecology
autotrophs, heterotrophs
freshwater, marine, brackish
endosymbionts in dinoflagellates, in a ciliate Mesodinium rubrum (red tides)
Amphidinium Mesodinium
Cryptophyta - systematics
ca 20 genera, half of them in freshwater
molecular data still unknown for many genera = traditional
systematics
Cryptomonadales – free-living flagellates, genera delimited
by the colour of plastids
olive-brown: Cryptomonas, Campylomonas
blue-green: Chroomonas
red-green: Rhodomonas
colourless (loss of plastids): Chilomonas
Cryptomonas Cryptomonas reflexa Cryptomonas rostratiformis
Cryptomonas sp.
Cryptomonas acuta
Cryptomonas, Campylomonas Campylomonas
Cryptomonas, Campylomonas
Hoef-Emden (2003): cell dimorphism during the
haplo/diplontic cell cycle
Chroomonas coeruela
Chroomonas
nordstedtii
Chroomonas diplococca
Chroomonas
Rhodomonas Rhodomonas baltica
Rhodomonas duplex
Rhodomonas cf. marina (Balt)
Chilomonas – heterotrophic
Chilomonas paramecium
Hemiselmis – marine
Cryptophyta - molecular data
phylogenetic data do not correspond with the traditional
morfological features - needed revision of the genus
Cryptomonas
Hoef-Emden et al., 2002
Proteomonas
Chroomonas
Rhodomonas
Cryptomonas
Chilomonas
Cryptophyta - molecular data phylogenetic data do correspond with pigment composition
C. paramecium
Cryptophyta - molecular data
3 independent losses of plastids (photosynthesis)
increased mutation rate in colourless lineages (change of
life style)