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I.  Diagnostic characters for common phytoplankton - Diatoms (dinoflagellates below).

How many are there? about 265 genera with about 100,000 (morphological) to 10 million (genetic) species
How old are they? probably not before the Cretaceous (centric diatoms ~120 mya; pennates ~ 70 mya)
Where are diatoms found?
50 % of species in freshwater habitats.
50 % are marine species.
Off the Hawaiian islands, our diatom flora has over 90 species.
How are their cells organized? Uninucleate organization throughout all cells.
What pigments do they possess? Chlorophyll a, Chlorophyll c and Fucoxanthin.
How is the chloroplast constructed?
Thylakoids in stacks of 3 to 6 forming grana.
Chloroplast is enclosed by double unit membrane.
Chloroplast enclosed by an additional two layer membrane system (Chloroplastic Endoplasmic Reticulum or CER).
This additional membrane system in continuous w/ ER of cell.
What storage product is made? Typically oils.
Cell wall features?  Siliceous cell wall (made of SiO2) in the shape of a petri dish and called a frustule.
Cell  complexity?
Unicells exist as free living adults or chains of cells.
These cells typically have motile males and sessile eggs as gametes.
Check out this diversity!

II. Simple cell construction.

Centric diatoms have a radial symmetry in cell form:

Cyclotella top (valve) and side (girdle) view via Light Microscopy (LM)
Thalassiosira valve view via LM
Planktoniella valve view via Scanning Electron Microscopy (SEM)
Biddulphia girdle view via SEM
Chaetoceros girdle view of chain of cells via LM
Triceratium valve view via LM

All of these genera reproduce via the  Gametic Meiosis Life History.

Life histories among Centric diatoms demonstrates very advanced life history features with nuclei disintegration in egg formation.

III. Developmental lineages and comparative life history strategies.

        Pennate diatoms have a bilateral symmetry in cell form and typically a raphe (slit along long axis of frustule) in at least one frustule:

Diatoma valve and girdle views showing raphe and girdle bands via LM
Mastogloia valve view shows raphe via SEM
Eunotia girdle view via SEM
Asterionella chain of cells via LM
Navicula valve view shows raphe and chloroplast volume via LM

All of these genera reproduce via the Gametic Meiosis Life History.

Life histories among Pennate diatoms demonstrate very advanced features with nuclei disintegration and morphologically isogamous gametes that exhibit ameboid movement.

IV. Recap major themes for Diatoms.

Complexity shown in adult morphology and subtlies of life history strategies.

Gamete type is extremely conservative character but demonstrates wide ranging differences among diatom types.

V.  Diagnostic characters for common phytoplankton - Dinoflagellates.

How many are there? about 130 genera with about 2,000 species.
How old are they? probably not before the late Precambrian (600 mya).
Where are dinoflagellates found?
10 % of species in freshwater habitats.
90 % are marine species and especially in coral reefs as coral symbiont - "zooxanthellae".
Off the Hawaiian islands, our tropical dinoflagellate flora has over 40 spp.
How are their cells organized? Uninucleate organization throughout all cells but mesokaryotes.
What pigments do they possess? Chlorophyll a, Chlorophyll c and Peridinin.
How is the chloroplast constructed?
Thylakoids in stacks of 3 forming grana.
Chloroplast is enclosed by double unit membrane.
Chloroplast enclosed by an additional one layer membrane system (Chloroplastic Endoplasmic Reticulum or CER).
This additional membrane system in continuous w/ ER of cell.
What storage product is made? starch.
Cell wall features?  naked cells with cellulosic plates underlying the plasmalemma; 2 flagella present.
Cell complexity?
Unicells exist as free living adults or chains of cells.
These cells typically have swimming gametes.
Check out this diversity!

VI. Simple dinoflagellate cell construction.

      Dinoflagellate cell exterior shows the pattern created by internal cellulosic plates.

             Examples of dinoflagellates

Peridinium
Ceratium
Dinophysis and Ceratium
Tropical dinoflagellates show spectacular shapes!

All of these genera reproduce via the Zygotic Meiosis Life History.

Coral bleaching in Porites is tied to the loss of  dinoflagellate symbiont from animal cells.
Coral bleaching and African dust - Scientific American video

VII.  hotlinks.gif (5957 bytes)

Diatoms, UC Berkeley Phytoplankton overview
The Diatom homepage (University of Indiana) Pictures of temperate diatoms
Experiments in phytoplankton growth: in the field and in the lab Phytoplankton ecology in Florida
Domoic acid as a toxin Red tides in Texas
What are red tides? Manatees linked to red tides
Dinoflagellates, UC Berkeley Global change and your health
Tropical dinoflagellates (University of Tsukuba) Coral bleaching;    Belizean reefs bleach

This page is maintained by Celia Smith and intended for use by undergraduates and graduates, Botany Dept, Univ Hawai'i at Manoa.