Preprint volume - SIBM

Pre-print Volume - Posters
BENTHOS COMMITEE
M.C. MANGANO, A. COSENTINO, F. DE DOMENICO, N. SPANÒ
Dip.to di Biologia Animale ed Ecologia Marina, Università di Messina, Salita Sperone, 31 - 98166 Messina, Italia.
mmangano@unime.com
ANTEDON MEDITERRANEA (ECHINODERMATA: CRINOIDEA) AS
HOST OF COMMENSAL SUBADYTE PELLUCIDA (ANELLIDA:
POLYCHAETA)
ANTEDON MEDITERRANEA (ECHINODERMATA: CRINOIDEA) OSPITE
DEL COMMENSALE SUBADYTE PELLUCIDA (ANELLIDA: POLYCHAETA)
Abstract – The Mediterranean endemic comatulid Antedon mediterranea (Echinodermata: Crinoidea) is
herein reported as host for symbiotic Subadyte pellucida (Annelida, Polychaeta: Polynoidae). Three adult
specimens were found on two crinoids, positioned on the oral surface or on the brachial pinnules. A mating
couple was confirmed by presence of cohesive egg masses in the mid parapodial region of the smaller
specimen; some potential implications of reproductive strategy for this ectosymbiotic scaleworm are
discussed.
Key-words: Polynoidae, Comatulidae, symbiosis, Mediterranean Sea.
Introduction – Symbiotic relationships involving echinoderms are well known and
supported by a wide litterature. Physical protection, exploitation of new substrates and
alternative trophic pathways related to the different habitats of the hosts may favour the
establishment of these associations (Coppard and Campbell, 2004). Although
Asterophylia, Hololepidella, Paradyte and Subadyte, are known to be associated to
crinoids (Barel and Kramer, 1977; Martin and Britayev, 1998), the knowledge of these
associations in the Mediterranean Sea is scanty. In this paper some information on
Antedon mediterranea (Lamarck, 1816) and Subadyte pellucida (Ehlers, 1864)
association, from Southern Tyrrhenian Sea, were reported.
Materials and methods – Four A. mediterranea were collected in Capo d’Orlando
(Sicilian coasts, Southern Tyrrhenian Sea) by trammel net at 59 meters of depth in
autumn 2008 and two of them were found hosted by S. pellucida. The crinoids were
fixed with ethanol 70°. The life position of scaleworm specimens on the crinoid host
and their main morphological characters were subsequently assessed by means of light
microscope equipped with micrometric ocular.
Results – Three adults of S. pellucida were found on two A. mediterranea. Two
incomplete polynoids (18 and 11 segments respectively) were found on the same host
at the level of pinnules. The larger specimen showed a marked colouration pattern (Fig.
1A); the smaller was an ovigerous female, with compact sub-spherical egg masses
attached on the dorsal parapodial surface, beneath the elytrae (Fig. 1B and 1C) at least
on some parapodia. The two individuals probably constituted a mating couple. The
third smaller specimen was recorded alone on its host, positioned on its oral surface; it
was also incomplete (30 segments) and almost colourless. The occurrence of a mature
couple is a not common feature in polychaetes, and in polynoids particularly (Martin
and Britayev, 1998). Some polynoids are known to bring embrios beneath elitrae
(Daly, 1972). The peculiar external position of egg mass let to suppose that fertilized
eggs may be preciously brooded by females, but this hypothesis needs more accurate
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