Ochrophyta Flashcards
Ectocarpus sp.
Ectocarpales are considered to be the most primitive order of the Phaeophyceae
Uniseriate branched filaments
e.g. Ectocarpus sp.
Filamentous, with one of the simplest thalli among brown algae
It is very common, living on rocks or on larger algae, as an epiphyte
Dictyota dichotoma
Order: DICTYOTALES
Thalli with regular dichotomous branching pattern:
Growth occurs by division of an apical cell, at the end of each branch, which at almost regular intervals undergoes a longitudinal division giving rise to two equivalent initials, from which two identical branches are formed.
Padina pavonica also called pavonia or peacock tail
It shows a typical fan-shaped thallus with a peduncle anchored to the substrate by rhizoids.
The thallus has a hard texture. It is one of the few brown algae with thallus encrusted with calcium carbonate, in the form of aragonite crystals.
Padina pavonica also called pavonia or peacock tail
It shows a typical fan-shaped thallus with a peduncle anchored to the substrate by rhizoids.
The thallus has a hard texture. It is one of the few brown algae with thallus encrusted with calcium carbonate, in the form of aragonite crystals.
Desmarestia sp. (Flattened Acid Kelps)
Order: DESMARESTIALES
Specialized genus, widespread in cold temperate waters (North Pacific from the Aleutian Islands to Kodiak Alaska)
Desmarestia cells are able to produce and accumulate sulfuric acid in intracellular vacuoles. The sulfuric acid protects the alga from attack of herbivores.
Desmarestia ligulata alga able to change its colour
Vacuoles with pH 0.8-1.8
Under different environmental stress (air exposure or temperature) it releases sulfuric acid, which causes damage not only to its own tissues but also to those of other nearby algae.
Himantothallus grandifolius
Among Desmarestiales there is the species Desmarestia antarctica and two endemic genera of Antarctica: Himantothallus and Phaeurus. These two genera, moreover, are monospecific.
Saccharina latissima (syn. Laminaria saccharina)
It shows the basic structure typical of the order:
thallus 3 m or more long
blade: of various shapes
stipe: cylindrical, can vary considerably in length
holdfast: consisting of digitations, called haptera, growing in the cracks of the substrate (it is not the typical discoid holdfast of brown algae)
Organization sporophytes
MER: meristoderm
COR: cortex
MED: medulla
Trumpet hyphae in medulla
The transverse walls in the filaments are perforated by areas of plasmodesmata, so that they look like sieve plates and for this reason they are called sieve cells.
Trumpet hyphae in medulla
The transverse walls in the filaments are perforated by areas of plasmodesmata, so that they look like sieve plates and for this reason they are called sieve cells.
Alaria sp.
shows a long primary blade which secondarily forms small spatula-shaped sporophylls at the base
Laminaria digitata
It has a finger-like blade for the action of the waves that split the thallus along predetermined areas
Alaria sp.
shows a long primary blade which secondarily forms small spatula-shaped sporophylls at the base
Dictyoneurum sp.
Stipe dichotomously branching as a result of longitudinal splitting which extends through the blades
Corda sp.
shows the most primitive condition
the thallus is constituted by a long unbranched cylinder not differentiated into lamina and stipe
The holdfast is discoidal and without haptera
Agarum sp.
Single blade with distinct perforations
Nereocystis luetkeana
In this species, below the blade stipe has swellings with gas vesicles form
Nereocystis luetkeana
In this species, below the blade stipe has swellings with gas vesicles form
Juvenile thalli of Undaria pinnatifida
Adult thalli of Undaria pinnatifida
Temporal development dynamics of Undaria pinnatifida
Fucus sp.
It is a widespread genus.
It has a flattened thallus less than 1 m long and with a dichotomous branching pattern
The tip of each branch is invaginated and at the bottom of the notch is present an apical cell. This cuts off cells laterally which become two new branches.
Internally, the thallus is differentiated into cortex and medulla
The branches have a thick midrib.
Fucus vesiculosus
At regular intervals the thallus bears pairs of vesicles, called bladders.
As the bladders are full of gas, the thalli stand erect when submerged.
The development of the vesicles depends on the environmental conditions. They are much more abundant in the populations that live in calm waters
Fucus virsoides
Ascophyllum sp
The seaweeds belonging to this genus are common in intertidal areas, especially in the North Atlantic, but also in the Mediterranean.
It can reach 3 m in length and has a variable appearance depending on the wave motion.
Gas vesicles form annually at regular intervals along the thallus.
This allows us to calculate the age of the alga which normally reaches 8-10 years.
Sargassum sp
This genus is widespread with a high number of species.
It has thin and long stipe that support blades with the appearance of pointed leaves
They have gas vesicles that look like berries
Sargassum thalli
Among the photosynthetic epiphytes on Sargassum thalli there are some rhodophytes and numerous benthic diatoms.
In these large tangles of thalli live a unique community of fish and invertebrates that often camouflages itself resembling the thalli of Sargassum
Sargassum muticum
Accidentally introduced to Europe probably with Japanese oysters.
The first report dates back to 1973
since then it has spread quickly along the coasts of France and Great Britain
In 1992 it also settled in the Venice Lagoon.
In many areas during the favorable period it reaches such densities as to appear as continuous belts around banks and shallow waters. The thalli reach the surface even on bottoms higher than 1.5 m, thanks to the buoyancy ensured by the characteristic spherical vesicles.
The first report dates back to 1973
since then it has spread quickly along the coasts of France and Great Britain
In 1992 it also settled in the Venice Lagoon.
In many areas during the favorable period it reaches such densities as to appear as continuous belts around banks and shallow waters. The thalli reach the surface even on bottoms higher than 1.5 m, thanks to the buoyancy ensured by the characteristic spherical vesicles.
Temporal development dynamics of Sargassum muticum
