ROCKY INTERTIDAL FAUNAArmintza: 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.