Rhodophyta Flashcards
Rhodophyta: Schizoseris sp.
Prevalence of phycoerythrin
Rhodophyta: Chroodactylon ornatum
prevalence of phycocyanin
Chloroplast
Big arrow: pyrenoid in centre of Chloroplast
Small arrow: Floridean starch
Florideophyceae (Rhodophyta) present 2 different types of construction
A: Uniaxial: main axis consisting of a main central filament, derived from an apical initial which has divided by transverse divisions. The short lateral shoots (branches) develop from the central axis.
B: Multiaxial: main axes consisting of multiple filaments, derived from the division of a group of apical initials.
Another example of the 2 construction types in
Filaments with open branching (Rhodophyta)
Branched filaments have several layers of small cortical cells (blue arrow) that can be arranged only in the nodal regions or completely cover the axial cells (red arrow)
Cortical cells are pigmented while axial cells contain large vacuoles and can be depigmented
Filaments with open branching (Rhodophyta)
Ceramium sp
foliose and fleshy erect thalli, Nemalion (Rhodophyta)
They are attached with a discoid holdfast. From the center of holdfast the erect thallus develops with a basic scheme consisting of:
one or more central axial filaments (red arrow)
lateral branches (blue arrow) with defined growth, whose terminal parts form a layer forming the external surface of the thallus
the shape of the resulting thallus can be:
Pseudolaminar thallus
system of cylindrical branches
hollow tubes
Nemalion helmintoides
Foliose and fleshy erect thalli (Rhodophyta)
Gigartina pistillata (Rhodophyta)
Foliose and fleshy erect thalli,
Hypoglossum sp. (Rhodophyta)
Foliose and fleshy erect thalli
Halymenia floresia (Rhodophyta)
Foliose and fleshy erect thalli
Encrusting thalli (Rhodophyta)
Thalli are composed of basal filaments, adhering to the substrate, and of erect branches that arise from the substrate forming a compact mass
some thalli are so thin, they look like coloured rocks
Encrusting thalli
Rhodophyta species belonging to the order Corallinales can be encrusted with calcium carbonate, reaching up to 70% of their dry weight
Calcification gives the alga a pink colour and a stone consistency
Erect calcareous thalli
Order Corallinales (Rhodophyta) includes also species with erect thalli
Erect calcareous thalli
Order Corallinales (Rhodophyta) includes also species with erect thalli
Erect calcareous thalli
We observe calcified segments (blue arrow) alternating with flexible non-calcified junctions (red arrow)
they have a multiaxial construction like that of fleshy erect thalli
Junctions consist only of axial cells
Porphyridium (Rhodophyta)
This genus includes unicellular coccoid species
Cell wall is lacking, but a mucilaginous sheath is present
Unicellular Bangiales
Bangiales have a greater variety of types of thalli than Florideophyceae. The simplest are unicellular
Bangia (Rhodophyta)
Complex filaments
This genus includes both freshwater and marine forms
It often forms a felt on splash-wet rocks
Thallus is unbranched filamentous, which in the older basal parts becomes multiseriate
Erythrotrichia sp (Bangiales, Rhodophyta)
Multicellular, simple filaments
Porphyra sp.
Parenchymatic thallus with
a foliose blade composed of single or double layers
Thallus colour is variable (yellow, olive-green, pink or red)
Macrothalli generally
do not have pit-connections or if there are, they lack the “cap membrane”.
They exhibit diffuse growth
These thalli show stellate chloroplasts arranged in the centre of the cell
Trottoirs, characteristic structures of the Mediterranean with a thickness of up to 1m, consisting of
- Lithophyllum tortuosum accompanied and reinforced at the base by other calcareous algae
- Rhodophycean: Peyssonnelia species
- sciaphilous chlorophytes: Halimeda, Udotea species
associated with many other algae
Peyssonnelia sp.
Important component of trottoirs
Lithophyllum tortuosum
Important component of trottoirs
Polysiphonia morrowii
Rhodophyta of the Venice lagoon and North Adriatic Sea
Grateloupia turuturu
Rhodophyta of the Venice lagoon and North Adriatic Sea
Hypnea flexicaulis (syn. H. cervicornis)
Rhodophyta of the Venice lagoon and North Adriatic Sea
Gracilaria bursa-pastoris
Rhodophyta of the Venice lagoon and North Adriatic Sea
