Introduction to Kingdom Stramenopila

Introduction to
Kingdom Stramenopila
4032604 Lecture 19
Kingdom Stramenopila
Alternate spelling Straminipila
Colloquial name ‘stramenopiles’
Includes diatoms, chrysophytes, brown
algae and some protozoa
Phyla of fungal-like organisms:
Hyphochytriomycota
Labyrinthulomycota
Oomycota
Stramenopiles
Name was introduced by D. J. Patterson
in 1989 based on tinsel-type flagellum
Tinsel flagellum with two rows of tubular
tripartite hairs
Pulls zoospore through water
Presence of filamentous thallus in some
stramenopiles and Fungi is evidence of
convergent evolution
Convergent Evolution
Evolution of similar features
independently in different evolutionary
lineages, usually by different
developmental pathways
Eukaryotes--From Tree of Life Project
http://tolweb.org/tree?group=Eukaryotes&contgroup=Life
Stramenopiles
Mitchell L Sogin and David J. Patterson
Phylum Hyphochytriomycota
Occur in soil, fresh water and marine
habitats
Saprotrophs or parasites on algae and
fungi
Hyperparasites of Oomycete oospores and
spores of AM fungi
Closely related to Oomycota
Characters
Cell walls contain chitin and cellulose
Thallus types similar to chytrids
Holocarpic or eucarpic (mono- or
polycentric)
Zoospores with one anteriorly inserted
tinsel flagellum
Sexual reproduction poorly known
2 families, 6 genera, 23 species
Thallus types in hyphochytrids
holocarpic
Eucarpic/
monocentric
zoospore
encystment
germination
Eucarpic/polycentric
Hyphochytrium catenoides
Eucarpic, polycentric thallus
photo by D. J. S. Barr
Phylum Labyrinthulomycota
Called marine slime molds
Parasitic or saprotrophic
On marine organisms such as mollusks,
aquatic plants or on organic debris
Labyrinthula zosterae responsible for wasting
disease of eelgrass (Zostera marina)
Characteristics
Ectoplasmic net produced by
bothrosomes (sagenogens)
Thallus covered with thin, golgi-derived
scales
Biflagellate zoospores with long, tinsel
flagellum and shorter whiplash
flagellum
Classification
Two families:
Labyrinthulaceae (labyrinthulids)
• Spindle-shaped trophic cells glide through
ectoplasmic net
• Zoospores have eyespots
Thraustochytriaceae (thraustochytrids)
• Thallus covered with scales, anchored by
ectoplasmic net and converted into
zoosporangium
• Zoospores lack eyespots, covered with layer of
scales
Trophic cells
surrounded by
ectoplasmic net
Ectoplasmic net
formed from
bothrosomes;
trophic cells
have a single
layer of golgiderived scales
Labyrinthula
zoospores contain
a dark eyespot, but
lack surface scales
Thraustochytrium
thallus wall
composed of
layered scales
formed by golgi
apparatus
Thraustochytrium
Zoospores lack
an eyespot and
are surrounded
by a single
layer of scales
Labyrinthula
Ectoplasmic net
http://www.botany.uga.edu/zoosporicfungi/labyrint.htm
Labyrinthula trophic cells
bothrosome
http://www.arches.uga.edu/~charla/labies.html
Eelgrass (Zostera marina)
Eelgrass beds are an
important
component of
coastal areas:
provide habitat to a
diversity of animals
Provide food for
overwintering
waterfowl
Provide erosion
protection
Wasting Disease of Eelgrass
Eelgrass populations on both sides of
the Atlantic underwent major decline in
1930s
Recovery occurred slowly over 40 year
period
Second decline occurred in 1980s
Causal agent identified as Labyrinthula
zosterae
Rapid Blight Disease in Turf
Labyrinthula sp. was isolated from cool
season turfgrasses including Poa trivialis
(rough bluegrass) and Lolium perenne
(perennial ryegrass) in 11 states
First observed in southern CA in 1995
In Arizona, it is associated with high
salinity irrigation water
Thraustochytrids
Ectoplasmic net of Schizochytrium can
grow into mollusk shells
Schizochytrium and Thraustochytrium are
used for commercial production of
omega-3-fatty acids