The Phytoplankton! Phytoplankton - Euglenophytes!

Transcription

1 9/29/14 The Phytoplankton Phytoplankton - Euglenophytes - abundant, nutrient-rich fw, some marine = DOM facilitates abundance - auxotrophic = require vitamin B1/B12 (unable to synthesize these vitamins) - chl a and b, b-carotene, diadinoxanthin - color of most green though some produce red water blooms 1

2 9/29/14 Evolution/Range first continuous record during Eocene however, considered to be the some of the oldest of the eukaryotic algae Taxonomic Relationships 2

3 9/29/14 - positively phototactic Characteristics - metaboly: flexible movement of pellicle (cell wall) = cell shape, allows movement between sandgrains - may produce polysaccharides/glycoproteins = mucilage - asexual reproduction = longitudinal cell division, sexual unknown - cyst formation during unfavorable conditions, rounded, eyespots may be present 3

4 9/29/14 - thallus : unicellular - cell covering: pellicle, inner surface composed of protein strips - nucleus one, condensed chromosomes - chloroplast many, small, thylakoids in triplets, chlorophylls a and b, paramylon = plastids may be absent, dependent on lifestyle - eyespots present Morphology Flagellation - one/two (visible) flagellae - emerge from anterior (reservoir, ampullae), sometimes one extends outside pocket - ampulla with adjacent contractile vacuole - flagellar root, bands of microtubules from flagellar basis to cytoplasm 4

5 9/29/14 Variations on a Theme Phacus - one of the few marine sp. Euglena - typical, fw Entosiphon - transparent Trachelomonas - loricate Distigma - two flagellae Dinoflagellates and Stramenopiles 5

6 9/29/14 Dinoflagellates Division Dinophyta (Gr. dinos: whirling; L. flagellum: whip) (= Pyrrophyta) (Gr. pyros: fire, and phyton: plant) refers to bioluminescence of many forms, i.e. Pyrocystis, Lingulodinium - most are biflagellated, unicellular - may be unarmored (naked) or armored (thecate, cellulose) Amphidinium Ceratium Evolution/Range most primitive eukaryotes earliest record from Silurian earliest continuous record from Triassic (deposits in fossils from Australia) peak during Cretaceous, followed by decline (today = levels at 1/3 of Cretaceous) 6

7 9/29/14 - marine, brackish, and fw, none terrestrial, about 4,500 species (2,000 living) - usually ~2-200µm, but may be up to 2 mm in size - interesting ecologically: some forms do not have chloroplasts = completely heterotrophic Protoperidinium Characteristics Gyrodinium - these may prey on diatoms, protozoans, other dinoflagellates or even copepod nauplii ~ 60 species have been identified to secrete powerful neurotoxins Alexandrium - chl a&c, peridinin, b-carotene Gambierdiscus toxicus - pyrenoids of varied shapes - many different eyespots 7

8 9/29/14 - very important as endosymbionts in coral reef spp. (e.g. Symbiodinium General Morphological Characteristics light-harvesting carotenoid complex cell covering in thecal dinos golgi body metabolic Non-contractile vacuole mitochondrion nucleus flagella 8

9 9/29/14 The Dinokaryon nucleus is very different from eukaryotic nuclei lack nucleosomes = repeating subunit of chromatin, DNA chain coiled around histones ratio proteins:dna lower than in other eukaryotes (i.e. much more DNA thousand MBP) => humans: 2,900 Mbp/cell chromosomes remain condensed Two main taxonomic groups based on where flagella insert desmokonts: 2 flagella arise from anterior part of cell dinokonts: one flagellum in transverse groove (cingulum): whirls cell around, 2nd simpler flagellum in longitudinal groove (sulcus) helps pull cell thru water 9

10 9/29/14 Dinokonts amphiesma = single layer of vesicles, beneath cell membrane, structural => athecate and thecate (cellulose plates) 2 dissimilar flagellae 1. wavy ribbon = transverse (undulating) 2. more conventional longitudinal flagellum Dinoflagellate Lifecycle (n) (n) (n) (n) (n) (2n) (2n) (2n) (2n) 1. cyst on ocean floor, stable, germination under favorable conditions 2. cyst germination ( C, light, O 2 ), hatching, cell reproduces by mitosis 3. optimal conditions, exponential cell reproduction creating vegetative cells, 4. nutrient gone, growth halts, gamete formation 5. gametes join, zygote, encystment 10

11 9/29/14 Diatoms Kingdom Protista Phylum Heterokontophyta Class Bacillariophyceae Heterokont Relationships ranging from diatoms (unicellular) to giant kelp (multicellular) = motile lifecyclce stage three classes: Bacillariophyceae, Chrysophycea, Phaephyceae 11

12 9/29/14 Diatom Characteristics Diatoms (Gr. dia: across, temnein: to cut) = Petri dish, most diverse and abundant - unicellular (may form chains), or sometimes filamentous - hard mineral shell (= frustule) composed of hydrated, polymerized silicic acid Si(OH 4 ) - same as opal golden-brown (yellow-brown) when healthy; greenish when not - marine, brackish, fw; planktonic and benthic; also in air, ice - poles to tropics; most abundant polar to temperate - usually 5-200µm, but may be up to 4 mm Evolution/Range first records from Jurassic earliest well preserved diatoms from early Cretaceous = centric pennate diatoms appear first during late Cretaceous = all marine fw diatoms first appear during Palaeocene 12

13 9/29/14 Heterokonts Bacillariophyceae, Chrysophycea, Phaephyceae - overall non-flagellated cells = sperm exhibits flagellum - pigments: 13

14 9/29/14 Two Forms of Diatoms Centric - Pennate - Overall Morphological Structure frustule - made out of two valves (epitheca and hypotheca), connected through epi and hypocingulum (= girdle), raphe for gliding movements, pores (areolea) penetrate valves and cingula (gas/nutrient exchange) 14

15 9/29/14 Cell Division with a Hard Shell 1 max # girdle bands 2 new silica deposition in each sibling cell 3 valve expansion and silica deposition 4 sibling cell with fully developed valves 5 cleavage furrow, valve deposition 6 separation of sibling cells 7/8 expansion & synthesis of girdle 9 completed division Diatom Lifecycle 15

16 9/29/14 Harmful Algal Blooms (HAB) Blooms of marine algae which produce: toxic effects to organisms (and humans) physical impairment of fish/shellfish nuisance conditions from odor, discoloration severe oxygen depletion or benthic overgrowth Major HAB-related events in the United States 16

17 9/29/14 The other side of blooms Eutrophic and Hypoxic Areas Eutrophic Hypoxic In recovery 17

18 9/29/14 No Oxygen = No Life Chrysophyceae chrysos = Greek for Dinobryon gold, named for Phaeoplaca their golden-brown pigmentation = large amount of fucoxanthin, also chl a and c, in addition a blue light receptor = aureochrome Unicellular or colonial, a few forms are multicellular Many form silica cysts typically fw, but also marine and brackish species, moderately diverse (about 1,000 species) not truly autotrophic but facultative heterotrophs => in absence of light/plentiful presence of bacterial or diatomaceous food source the algae may turn predatorial one Ochromonas or two flagellae = Strameopile characteristic 18

19 9/29/14 Evolution/Range fairly complete record due to presence of resting cysts first occurrence in Cretaceous in Palaeoncene deposits chrysophyceae outnumber diatoms greatest diversity during Miocene Chrysophycean Morphology ES = Eye spot, apical, located close to the flagellae G = golgi, anterior flagellar apparatus with banded rhizoplast (striated contractile structure, beat) N = nucleus is large and central V = large vacuole P = plastids, lateral as well as centrally located 19

20 9/29/14 Stomatocyst = statospore or siliceous cyst - walls heavily silicified, resist silica dissolution - different species = structurally distinct stomatocyst - spherical, 2-30µm - single pore often with a collar (elevated) Forms Ochromonas - solitary, mobile Dinobryon - arbusculate colony, mobile, loricate Synura - globular colony, flagella outwards Cyclonexis - ring shaped mobile colony Chrysamoeba -globoid, cytoplasmic extensions 20

21 9/29/14 Forms Chrysocapsa - elyptical cells, enclosed in mucilage Hydrurus - multicellular, arbuscular Chrysonephele - either unicellular building filamentous colony 21