GELIDIALES

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GELIDIALES
Wilson Freshwater University of North Carolina at
Wilmington
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GELIDIALES
The Gelidiales are a relatively small red algal
order that includes species of economic
importance as sources of high quality agars.
Lamouroux chose the name Gelidium when originally
describing the type genus because most of the
species composing it can be reduced to a
gelatinous substance by boiling and maceration
(Lamouroux 181340). Kylin (1923) erected the
order Gelidiales based on the presence of a
diplobiontic life cycle and absence of typical
auxiliary cells. Papenfuss (1966) further
characterized the order by the presence of
nutritive cells formed during carpogonial
development, apical growth by transverse division
of a single apical cell, and Gelidium-type
spore germination (Chihara Kamura 1963).
Hommersand Fredericq (1988) conducted detailed
morphological studies of vegetative and
reproductive development and redefined the
order. Despite the economic importance of some
Gelidiales species, solid vegetative characters
for recognizing genera and species are generally
lacking (e.g. Rodriguez Santelices 1988,
Satelices 1990), and reproductive structures are
often not available on specimens collected in
nature. Consequently the classification of genera
and species in the order has been difficult, and
its taxonomy historically confused. Molecular
analyses have proven very useful for resolving
the relationships of Gelidiales species (e.g.
Freshwater et al. 1995, Shimada et al. 1999) and
integrated molecular and morphological analyses
are refining the intra-ordinal classification of
the Gelidiales (e.g. Tronchin et al. 2002,
Tronchin Freshwater 2007). Wynne (1998) lists
23 Gelidiales species in the Caribbean. Six of
these reports are questionable and probably do
not represent Caribbean species. Many are
inconspicuous and part of the algal turf
community. These turf species may be
exceptionally difficult to identify. Chihara M
Kamura S (1963) Phycologia 369-74. Freshwater DW
et al. (1995) J. Phycol. 31616-632. Hommersand
MH Fredericq S (1988) Phycologia
27254-272. Lamouroux JVF (1813) Ann. Mus. Natl.
Hist. Nat. 2021-47. Papenfuss GF (1966)
Phycologia 5247-255. Rodriguez D Santelices B
(1988) Taxonomy of Economic Seaweeds...Vol. II.
Pp. 115-125. Santelices B (1990) Hydrobiologia
204/205125-135. Shimada S et al. (1999)
Phycologia 38528-540. Tronchin EM et al. (2002)
Bot. Mar. 45548-558. Tronchin EM Freshwater DW
(2007) Phycologia 46325-348.
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What to look for when identifying Gelidiales
species
-Is there a single apical cell? (will separate
small gelids from other wirey turfs like
Gelidiopsis and Wurdmania) -Size of
thallus? -What does it look like in transverse
section? Are there rhizines? (cells with thick
walls tiny lumens) What is x.s. shape?
(terete, compressed, flattened) Is the
arrangement of medullary cells distinct near
apical tips? -What do cystocarps look
like? Bilocular or unilocular? How are
nutritive filaments, gonimoblast, carpospores
arranged? -What do tetrasporangial branches look
like? Is there a sterile margin? How are
tetrasporangia arranged (number per segment,
pattern)? -How are rhizoidal holdfast arranged?
(Perrone et al. 2006. Botanica Marina
4923-33) Are they scattered, clumped as brushes
or cylindrical or tapered pegs? -What does
branching look like? Are branch bases
constricted, tapered, or not? Are reproductive
branchlets clustered in lower parts of
thallus? Is there a bilateral series of small
branchlets along the main axis?
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Apical Cell
single apical cell
Millar Freshwater 2005
Gelidiales will have a single apical cell
Millar Freshwater 2005
Millar Freshwater 2005
multiple apical cells
Gelidiopsis, Wurdmania will have multiple apical
cells
Littler Littler 2000
Littler Littler 2000
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Transverse Section Characters
Are there rhizines?
Rico et al. 2002
NO Gelidiella Parviphycus
no rhizines
Millar Freshwater 2005
rhizine pattern may not be consistent
Thomas Freshwater 2001
Thomas Freshwater 2001
rhizines scattered in medulla
rhizines concentrated in central medulla
YES Gelidium Pterocladiella
Thomas Freshwater 2001
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Transverse Section Characters
What is shape?
Millar Freshwater 2005
compressed
Millar Freshwater 2005
terete
sub-terete
flattened
Millar Freshwater 2005
Millar Freshwater 2005
Is medullary cell arrangement distinct near
apical tips?
central axial cell
3rd order branch cell
NO Gelidiella YES Parviphycus
2nd order branch cells
Millar Freshwater 2005
Millar Freshwater 2005
2nd order branch cells
central axial cells
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Cystocarps characters
Millar Freshwater 2005
Millar Freshwater 2005
Millar Freshwater 2005
Gelidium Bilocular cystocarp Central bisecting
placental tissue Two ostioles Carpogonia develop
on both sides of blade Nutritive filaments
develop around 2nd order branch cells
Millar Freshwater 2005
Pterocladiella Unilocular cystocarp Placental
tissue surrounds central axis One ostiole
(usually) Carpogonia develop only as part of cell
filaments immediately adjacent to the central
axis Nutritive filaments develop around central
axis
Thomas Freshwater 2001
Tronchin Freshwater 2007
Tronchin Freshwater 2007
Pterocladia Unilocular cystocarp Placental tissue
on floor of cystocarp cavity One
ostiole Carpogonia develop on one sides of
blade If you see anything like this youll be
famous
Millar Freshwater 2005
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Rhizoids-holdfasts
Refined and expanded by Perrone et al. (2006)
Botanica Marina 4923-33.
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Rhizoids-holdfasts
Gelidiella Parviphycus (Gelidiellaceae) Indepen
dent unicellular rhizoidal filaments originating
from surface cortical and that remain in open
connection with their mother cells
Rico et al. 2002
independent
Millar Freshwater 2005
Gelidium Ptilophora? (Gelidiaceae) Complex
brush-like haptera consisting of both internal
rhizoidal filaments growing independently and
between surface cortical cells, and pigmented
multicellular uniseriate filaments originating
from surface cortical cells. Rhizoidal filaments
independently attaching to or penetrating the
substrate
peg
Tronchin in Millar Freshwater 2005
Millar Freshwater 2005
Pterocladia Pterocladiella (Pterocladiaceae) Com
plex peg-like haptera consisting of both internal
rhizoidal filaments coalescing in a thick sheath
and protruding between surface cortical cells,
and pigmented multicellular uniseriate filaments
originating from surface cortical cells around
the hapteron base and forming a basal
cortication. Coalesced rhizoidal filaments
attaching to or penetrating the substrate
tapered
Tronchin Freshwater 2007
Tronchin Freshwater 2007
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Tetrasporangial branch characters
Is there a sterile margin?
Millar Freshwater 2005
sterile margin
Thomas Freshwater 2001
How are tetrasporangia arranged?
Millar Freshwater 2005
no sterile margin
Millar Freshwater 2005
Millar Freshwater 2005
chevrons
Millar Freshwater 2005
specific or non-specific number per segment
Millar Freshwater 2005
Less organized
Millar Freshwater 2005
Abbott 1999
Santelices 2002
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Some Caribbean Species of the Bocas Region
Gelidium microdonticum Small turfy species with
flattened blades that have serrated margins.
Thomas Freshwater 2001
Pterocladiella bartlettii Small slender species
often with a bi-lateral series of small
branchlets along the main branch.
Thomas Freshwater 2001
Gelidium floridanum Small to medium species with
reproductive branches often clustered towards the
base of thallus apex of main axes sometimes
elongated, and tetrasporangial branchlets with a
wide sterile margin.
Thomas Freshwater 2001
Pterocladiella caerulescens (including P.
beachiae) Small flattened species constricted
branch bases, monoecious
Millar Freshwater 2005
Thomas Freshwater 2001
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This presentation is a contribution of the
Pan-American Advanced Studies Institute