SOME THECATE HYDROIDS ASSOCIATED WITH POSIDONIA OCEANICA (L.) DELILE MEADOWS IN THE EGYPTIAN MEDITERRANEAN WATERS

SOME THECATE HYDROIDS ASSOCIATED WITH POSIDONIA

OCEANICA (L.) DELILE MEADOWS IN THE EGYPTIAN

MEDITERRANEAN WATERS

BY
M. EL BESHBEESHY*
*National Institute of Oceanography and Fisheries, Alexandria-Egypt.
Key Words: Coelenterates, Hydroids, Mediterranean.
ABSTRACT
Seven thecate hydroids were registered as epiphytes on Posidonia
leaves in the Egyptian Mediterranean waters. These comprise: Clytia
hemisphaerica (Linnaeus), Obelia geniculata (Linnaeus), Dynamena
disticha (Bosc), Sertularia distans Lamoroux, Aglaophenaia
lophocarpa Allman, Kirchenpaaueria pinnata (Linnaeus) and
Antennella secundaria (Gmelin).
For depth distribution, two zones shallow and deep were
distinguised. Each zone was characterized by its own species. In the
mean time a few species showed wide depth distribution. The
colonization of the thecate hydroids takes place on the edges of
Posidonia leaves. The widespread adoption ofasexual reproduction by
stolonization and the usual topographical separation between Posidonia
and hard substrata have favoured the isolation ofhydroidpopulations
inhabiting Posidonia leaves.