Dinophyta Flashcards
_____% of dinoflagellates are planktonic
90
Dinoflagellates are included in the group ________
Why?
Alveolates
Presence of alveoli (membrane bound vehicle)
Cell covering a of dinoflagellates
Continuous outermost membrane + single membranes bound thecal vesicles (alveoli)
Thecal vesicles contain little or no cellulose or thick cellulose plates (thecal plates)
Amphiesma
Array of membranes and vesicles
Dinoflagellate cell types distinguished by position of flagella:
Desmokont: flagella emerge apex
-both flagella inserted anteriorly
Dinokont: flagella emerge from mid point (ventrally inserted)
-both flagella are inserted centrally and lie in surficial grooves (whiplash and tinsel flagella)
Typical dinokont cell types
Upper half: Epicone
Lower half: Hypocone
Transverse groove-encircles the cell: girdle
Sulcus: extends posteriorly in the hypocone from the cingulum
Part of cell directed forward during swimming is considered to be ______
Anterior
Region from which flagella emerge is considered _____
Ventral side
Dinophyta vary in the number and arrangement of ______
Thecal plates
Controversy of thecal plate arrangement
Was many thecal plates original to ancestor or was few???
Dinoflagellates originated from ______ ancestors
Why is this supported
Heterotrophic (800mya)
Many dinoflagellates are heterotrophic today
In the fossil record, _____% of dinoflagellates produce an organic layer of _______ beneath thecal plates
40
Dinosporin
____% of dinoflagellates are __________
But most are _______
Photosynthetic (50%)
Mixitrophic
Most photosynthetic dinoflagellates originated from _____ symbiosis with a ______ and therefore contain ______
Secondary
Red algae
Chlorophyll a and c as well as peridinin (carotenoid) and pyrenoids
Plastid membranes of dinoflagellates
Two membranes of chloroplast envelope
One membrane of chloroplast e.r from primary host ebdosymbiont
Tertiary endosymbiosis in dinoflagellates
- Begins with a loss of a Plastid (originally deceived from a secondary endosymbiosis of red algae)
- Followed by endosymbiosis of a diatom
- Instead of peridinin pigment it has fucoxanthin pigments from diatom
In Dinophyta, photosynthates are stored as _____
Cytoplasmic starch grains, lipids droplets, unsaturated fatty acids and sterols
Some dinoflagellate sterols are linked to fossil _______
Oil deposits
Blooms contributed to oil deposits in areas with incomplete degradation of organic lipids
In a dinoflagellate, where can you find lipid bodies and starch grains
Lipid-anterior end of cell
Starch-posterior end of cell
Chromatic adaption
Dinophyta are able to capture and harvest more light by using water soluble peridinin-chlorophyll-protein light harvesting complex (PerCP) found in the lumen of plastids and membrane bound light harvesting complexes
Peridin absorbs in the blue-green range (450-550) which is beyond chlorophyll-A’s capability
More peridinin to chlorophyll is chromatic adaptation
Dinophyta motility
-longitudinal flagellum (whiplash) projects out->speed and steeering
-transverse flagellum (tinsel) coiled and closest appressed and used for rotating
Great swimmers (200-500mm/sec)
How are the flagellum arranged in dinophyta
9+2 array of microtubules
What percent of dinoflagellates have an eyespot?
What does the eyespot do?
<5%
They are simple: lipid droplets packaged within membranes
Or
They are complex: rows of lipid globules
Contain carotenoids for phototaxis
-reposition longitudinal flagellum and swim towards light
Do dinophyta have a flavin based light detector at the base of the flagella?
No
Dinophyta Trichocysts
-defensive trichocysts: rod shaped crystalline, protein filaments
-triggered by changes in temperature, turbulence, and other disturbance
-discharged upon rapid hydration
-discharge causes a jet-propulsive response to predators
Or can be used to catch prey (nematocysts)
Dinophyta reproduction
Asexual division of haploid, motile cells
Sexual reproduction due to changes in nutrients, irradiance, photoperiod, temp
-gametes resemble vegetative cells, syngamy is slow and difficult to distinguish from cell division, and often occurs at night. Making it hard to observe!!!!
-early stages of zygote development have >2 flagella
-formation of cysts often follow sexual reproduction and are viable for 100 years
Photosynthetic _______ are second to diatoms as primary producers in costal waters
Dinoflagellates
Zooxanthellae
Unarmoured marine dinoflagellates are marine symbionts of most reef bulking coral polyps
“Bleaching”
When coral polyps expel their zooxanthellae and therefore their colour
Zooxanthellae and coral exchange of nutrients
Coral gets plenty of carbon from zooxanthellae
Zooxanthellae get carbon dioxide from coral
Dinoflagellates were once called what?
Why?
Pyrrhophyta (fire plants)
Some species are bioluminescent
Adaptation to bioluminescence
Reduce attack by predators by shocking predators
How does bioluminescence work
Scintillons: spherical intracellular structures derived from invaginations of vacuole membranes that contain luceiferin (chlorophyll-derived molecule)
Luciferase oxidizes luciferin, causing a flash of blue light
Circadian rhythm in synthesis and destruction of scintillons: night phase (540 scintillons per cell) vs day phase (46/cell)
Red tides
Surface upwellings of nutrients trigger blooms of photosynthetic dinoflagellates
-some species in blooms produce neurotoxins-> paralytic shellfish poisoning
Saxitoxins
Block Na+ movement through voltage-dependent channels in nerve and muscle cell membranes=prevent action potentials
-dinoflagellates that produce toxins contain chloroplasts: ability to produce toxins drives from endosymbiotic Cyanobacteria
Pfiesteria sp
Predatory dinoflagellate common in estuaries
-kill fish by feeding on their skin (large lesions)
-dinoflagellate zoospores feed on the fish by phagocytizing fish tissue through peduncle.
- the peduncle is swollen with haustoria/like penetrating extensions when feeding on the fish
