lecture 12: cryptophytes and euglenoids

This is part of chapter 8 and 9 from the graham et al book

Euglenoids / Eugelnophyceae

• found in the pelagic and the upper layer of the ocean

• More abundant in…

• no supergroup

• in the group discoba

• orphan lineages

discoba (orphan lineages)

• discoba consists of four main lineages: jakobida, euglenozoa, heterolobosea, and tsukubamonadida.

• named for disk-shaped mitochondrial cristae (stalked cristae)

euglenozoa diversity

• 1500 described species

• sinle celled flagellates

• ubiquitous

• symbionts are anaerboci deep sea microbial eukaryotes with sulfur-oxidising epsilon proteobacteria epibionts

euglenoids

• ddiverse modes of nutrition (phagotrophy, photoautotrophy, etc)

• characterised by:

  • flagella emerge form a cellular depression known as a pocket

  • longitudinal mitotic division (close mitosis)

  • nuclear chromosomes are condensed

  • they have a flexible pellicle (cell surface)

pellicle

• “small skin” - parallel ribbon like strips

• also present in peranemids and anisonemids

• rigid cover

• eneath the cell membrane, series of regularly spaced parallel protein strips (pellicular strips) supported by microtubules

• allows a specific motion called Metaboly

euglenophyceae chloroplasts

• chloroplasts with 3 membranes

  • chlorophylla a + b (green algae chloroplast origin fro pyramimonas)

• the number and morphology of euglenoid plastids are very diverse (e.g. shiled shaped, disc shaped, and star shaped)

• most euglenoids plastids contain pyrenoids

• eyespot outside chloroplast (stigma)

• paramylon (solid beta 1.3 glucan) - outside the chloroplast

  • pyrenoid shiled or grains in cytoplasma

flagella

• one row of loong fine hairs

• paraaxial rod (striated strand)

• 2, 4, 8 or more flagella

• ligth senisitve flagellar swimming

light migration in euglenophytes

• forms green patches in sandy bottoms of marine, estuarine, and freshwater habitats

• diurnal patterns of vertical migration

  • cell on the surface during the day

  • below the surface during the daytime hightides and at night

• can avoid excessive ligth by downward migration

ligth sensing system in euglenoids

• stigam (eyespot) - 50 to 60 globules in single of …

• paraflagellar body

  • contains blue, light sensitive flavoproteins

main genera in marine and brackish waters

• eutrepia

• eutretiella

• eugelna

main genera in freshwater systems

• phacus

• trachelomonas

habitats and ecology

• only a few planktonic genera/species

  • not detected in metabarcoding studies - long gene marker because of introns

• on surfaces; air-water, sediment-water (sandy shores, mud flats), sea ice

• reducing environments (low oxygen) - ponds, marshes, mudflats

• resting cysts, non motile with thick wall

• eugelna sanguinea can form brigh tred blooms

summary - euglenophycea

• hetero- and autotrophic flagellates

• pellicle and metaboly

• paramylon - storage metabolite

• flagella form pocket

• chloroplasts with 3 membranes

• chlorophylls a + b

• mitochondria with stalked cristae

cryptomonads or cryptophyta

• in the group cryptista

phylum cryptophyta

• ubiquitous in marien, brackish, and freshwater habitats

  • benthic - goniomonas, aplastidic genus

• most species are motile, palmelloid forms are also known

• ca 200 species (21 accepted genera)

• most species are photosynthetic (some, if not all, are phago-mixotorphic)

• additional nucleus form an ancient symbiosis (nucleomorph)

general morphology

• cell size less than 5 µm up to 50 µm.

• easily recognized, flattened asymmetric cells (distinctive swimming motion)

  • left side - two unequal flagella insert subapically or laterally

  • right side - teh vestibulum of an invagination, the furrow-gullet system

  • the furrow gullet defines teh ventral side of the cell

  • vestibulumn - contactile vacoule

  • ejectosomes (explosive organelles)

furroe-gullet system

• suggested funtion - digestion of smaller cells (phago-mixotrophy)

  • gullet - tubular system

  • forrow - cell indentation

ejectosomes

• cytoplasmi strucutres consisting of two coiled ribbons

• violently discharged upon irritation (probably as a defensive repsonse to herbivore)

• they are lining in rows lining furrow / gullet

• when discharged, both ribbons unfurl, forming a narrow

flagella

• two flagella inserted subapically

  • two rows of hairs on the longer flagellum

  • one row of hairs on teh shorter flagellum

• the axoneme has a typical 9 + 2 arrangement

• transtion zone - between teh emergent portion of the flagellum and the intracellular basal body

• TEM - two or more platelike partitions just below the point where teh two central axonemal microtubules appear

flagellar apparatus

• rhizostyle - microtubules originated near the basal bodies

• it extends posteriorly deep into the cell, passing near teh nucleus in some species (no physical connections with th enuclear envelope)

• in some species, each of the rhizostyle microtubules bears a winglike lamellar projection

• the compound rootlet consists of microtubules associated with a striated fibrous band (present in some genera)

periplast

• cryptophytes plasma membrane is sandwiched between protein layers that together are known as the periplast

• inner periplast component (IPC) may consists of hexagonal, polygonal, rectangluar, or elongate plates or may be continuous and sheetlike

• surface periplast component (SPC) is covered by congruent plates, rosulate scales, and/or a fibrous coat

chloroplast

• four membranes enclose the plastid

• the outermost plastid membrane is coated with ribosomes

• periplastidal endoplasmic reticulum (PER) - the two outermost membranes are connceted to the cellular endplasmic

• periplastidal compartment - teh space betweenthe outer and inner memebrane plastid membranes

• starch granules are formed not within the chloroplast but rather, within teh periplastidal compartment

chloroplast pigments

• chlorophyll a + c

• different carotens

  • alloxanthin, licopene, zeaxanthin, crocoxanthin, monadoxanthin

• phycocyanin or phycoerythrin

  • in the thylakoids, not inphycobilisomes

• two thylakoid in lamella

cryptophytes symbiont → mesodinium rubrum