Dear Paul, about the paper:
“Mercurio M., Corriero G., Scalera Liaci L. - Free-living specimens of
Geodia cydonium Jameson from a shallow environment” Biol
Mar Medit (1997), 4 (1): 407-409” the summary is the following:
“In Marsala Lagoon (Sicily ? southern Italy), the sessile specimens of
Geodia cydonium are irregularly globose, and settle primarily on
the rhizomes of Posidonia oceanica, at depth ranging between 0.5 and 2
m; their density is about 2.5 samples/m2. The non-sessile
specimens are subspherical and occur on the soft bottom of the lagoon in
wide 'storing' areas about 2 m deep; their density is about 0.8
samples/m2. Most of them are uniformely covered by a thick layer of the
red alga Rytyphlöea tinctoria, whose thallus penetrates for some
millimeters into the sponge cortex. The sponge-alga complex grows into a
ball shape and rolls on the soft bottom of the lagoon due to the
movement of slow circular currents.”
If you are interested in the paper (but it is in italian!) I could send
you by e-mail.

Moreover, we are studiyng (unpublished data) the free-living habitus in
Geodia cydonium from another Mediterranean sheltered
environment (Porto Cesareo Basin ? SW Apulia ? southern Italy): in the
study site the non-sessile specimens of G. cydonium assume
different shape from that of Marsala Lagoon, in relation to the
different environmental conditions. Indeed, while the wide storing areas
on
the bottom of Marsala Lagoon allow the occurrence of spherical specimens
which roll on the soft bottom due to the movement of slow
circular currents, on the contrary, in Porto Cesareo Basin, with higher
water circulation and moderate wave turbulence, the non-sessile
specimens of G. cydonium assume a flattened shape capable to reduce the
risk of stranding (the flattened shape of G. cydonium is very
similar to the shape of Hudsonospongia!!!)
The presence of non-sessile sponges cannot be considered an occasional
event, since it is a recurrent phenomenon, also described for
other demosponges in Marsala Lagoon (Tethya aurantium, Pellina
semitubulosa, Tedania anhelans, Ircinia variabilis) and Porto Cesareo
Basin, (Sarcotragus spinosulus, Aplysina aerophoba, Cacospongia
scalaris) (Corriero 1989; 1990); this habitus is clearly related to the
low water movement conditions and could play an important role in the
colonization process of soft bottom environments.

References
Corriero G (1989) The Sponge fauna from the Stagnone di Marsala
(Sicily): taxonomic and ecological observations. Boll Mus Ist Biol
Univ Genova, 53: 101-113.
Corriero G (1990) Distribuzione ed ecologia dei Poriferi in ambienti
“confinati mediterranei”. Ph.D. thesis, University of Genova, Italy.

Hope this helps
Best wishes

Dr Mercurio Maria
Zoology Department of Bari University (Italy)
Via Orabona, 4 - 70124 Bari - Italy
e-mail: [log in to unmask]