ROCKY INTERTIDAL FAUNA
Armintza: a case study for Echinoderms, Bryozoans
and Cnidarians
CNIDARIANS
• The phylum Cnidaria is divided
in 3 classes, Hydrozoa,
Scyphozoa and Anthozoa.
• In the intertidal zone we find
mainly Anthozoans (anemones)
and some Hydrozoa with polyp
form attached on algae.
• Some small scyphozoa(medusas)
may be present in some rock
pools but detecting them would
require special sampling and
identification techniques.
Anthozoans
• Subclass Hexacoralia (or Zoantharia) are found in the
intertidal zone with two species present: Actinia equina
and Anemonia sulcata . Octacorallia contain calcified
species that form many coral reefs and are not present in
the intertidal area.
• Actinia equina has the ability of gathering its “tentacles”
inside its body when it is not covered by water and
expanding them when water covers it. It was found on rock
pools in the lower intertidal area either covered or
uncovered by water.
Actinia equina when
uncovered by water
Actinia equina when
covered by water
Anemonia sulcata is also found
in two forms depending on
the existence of symbiotic
zooxantheles in its
“tentacles”.If zooxantheles
that are a form of unicellular
algae, are present in the
Anemonia, its tentacles have
a green colour. Zooxantheles
provide oxygen, giving an
advantage to the animal that
bares them, and are of great
importance in coral reefs.
HYDROZOANS
• The Hydrozoan
Bouganvillia ramosa
was found on some red
algae mainly Chondrus
crispus, in the lower
intertidal zone.
BRYOZOANS
• Bryozoans are animals
living in polymorphic
colonies where each
individual may have a
different role. May live
attached on rocks and
mollusc shells but in the
intertidal area were found
most on large algae.
• Crytosula pallasiana was
found living on rocks
forming extended colonies
• Electra pilosa was found
on some red algae, such
as Chondrus crispus and
Gigartina elongata
forming abundant yet
small colonies. Present in
lower intertidal zone can
also encrust stones or
boulders. It is an
important feeding source
for Opisthobranchia or
Prosthobranchia
gastropoda that graze on
the algae.
ECHINODERMS
• The phylum Echinodermata is
divided into 5 classes,
Crinoidea, Ophiuroidea,
Asteroidea, Echinoidea and
Holothuroidea. All show
pentasymmetry and have a
skeleton of calcareous plates.
• In Armintza we found
Asteroidea, Echinoidea and
Holothuroidea in small rock
pools, under boulders in hte
lower to mid-intertidal zone.
Asteroidea
• Asterina gibbosa was
found intertidally in rock
pools and under stones.
This small, abundant
starfish feeds on dead
plants and animals. They
have the ability to change
sex at will.
• Marthasterias glacialis,
the common sea star
was found under some
boulders but is more
abundant in the
sublittoral zone.It feeds
on small fish,
bivalvians, crustacenas
and echinoderms. In the
small rock pools can be
considered to be the top
predator but in its
aquatic larval stage
bares more dangers.
Echinoidea
• Paracentrotus lividus, was
abundant in lower intertidal
zone in small rock pools.
These pools had a small
diversity in other species
with Paracentrotus being
the dominant one. Forms
his own substrate, small
holes where the urchin fits
exactly. As all regular
echinoideans is a grazer so
feeds on algae. Uses
substrate piece or algae as
camouflage-.
Holothuroidea
• Holothuria tubulosa was
found in rock pools,
under boulders, together
with Marthasterias
glacialis,gastropods and
anomourans. Ejects its
stomach when
threatened, (regenerates
it) which with its sticky
substance can trap its
possible predators.
• Abundant in numbers but not in species as
Mollusca or Crustacea
• More species found in rock pools.
• Probably can not withstand high levels of
wave exposure
• Need to be covered by water for the
maximum of time, mostly because of
their feeding habits.