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422 DANILO SCUDERI ET ALII

The right valve shows a not very marked in outline (Fig. 25), almost entirely red-brownish
rounded byssal ridge. with darker radial strips, sculpture of dense and
The hinge bears a well-defined and duplicated pointed process, organized in numerous rows, soft
posterior tooth and a not very well defined but thick parts mainly orange (see Table 1).
anterior tooth with two often marked sockets. The second is here named P. fucata, on account
The left valve shows a very marked rounded of comparisons with Indo-Pacific materials (Figs.
byssal ridge and bears straight and not duplicated 23, 24), and is characterized by a smaller shell in
anterior tooth; posteriorly an almost deep socket full grown specimens, oval in outline (Fig. 26), al-
with two not market teeth is present. most greenish in colour (75–80% of the specimens
Straight hinge line, which do not or only slightly observed) with paler radial strips, sculpture essen-
become curved near the umbo. Seen from inner tial, tending to vanish (valves often almost
side, the umbo is prominent in the left valve, almost smooth), process sparse, blunt and wider, organ-
invisible in the right one. ized in low number of rows, soft parts mainly
Anatomy of soft parts: digestive gland, kidney greenish. The former species, seen from umbo, is
and gonad pale orange to green, ctenidium greenish quite flattened (Fig. 31), while the latter appears
with white stains (Fig. 37); foot whitish with nu- markedly convex.
merous black spots; margin of mantle deep green Besides the morphological differences above
to pale orange, with white stains and black radial mentioned, P. fucata differs in habitat preferences.
bands corresponding to the marginal tips, anal fun- While P. radiata is present, nowadays with dense
nel graysh and speare-shaped (Fig. 38). Byssus populations in Southern regions of East and Cen-
green with almost thick filaments (Fig. 42). tral Mediterranean, on hard substrata with algal
DISTRIBuTION AND BIOLOGY. Sporadically re- covering (Cystoseira spp.), P. fucata was instead
ported in Eastern basin, in these last few years it is found near river’s estuary on other shells, but the
very abundant in Eastern Sicily and quite common most abundant material is represented by vegetal
in other Southern regions in Italy. The Adriatic residuals of the river cane Phragmites australis
record is reported fide the statements of the maricul- (Cav.) Trin. ex Steud., accumulated by winter
ture operators in Faro lake, Messina and should be storms. Less commonly it was found on the ascid-
confirmed. Sandy bottoms near estuarine areas, at- ians of the genus Microcosmus Heller, 1877 (As-
tached with byssus each other (Fig. 43) or on other cidiacea Pyuridae).
shell, like mussels, Cardiidae (Fig. 44), Pinnidae Considering the complicated taxonomy and the
(Fig. 46) and dead gastropods (Fig. 45), on ascidians high polymorphism of the species of Pinctada, all
(Fig. 50), on Annelid tubes (Fig. 47), to the stolons these morphological differences are, according to
of the sea-grass Cymodocea nodosa (ucria) Asch- us, enough to consider the two different morphs
erson, 1870 (Fig. 48) or the algae Caulerpa taxifolia here studied as different species. We therefore refer
var. distichophylla (Sonder) Verlaque, Huisman et to the conclusions chapter the full reasons of our
Procaccini in Jongma et al., 2013 (Fig. 49), but on personal interpretation of the taxonomical problem
plastic objects too, in low (-1/8 m) depths. concerning these two taxa.
Moreover, in E-Sicily P. fucata was sporadically
collected or never recorded before, in the same lo-
DISCUSSION cality where thousands of specimens have been
found in very recent times.
After a critical evaluation of the morphological This population shows preferences for more
characters observed in very abundant amount of brackish waters and sandy bottoms, where is more
specimens of the two different forms of Pinctada, likely arrived with human mediated transportation,
despite a high variability in both and the genetic as its population dynamics seem to suggest.
studies of mainly Eastern Mediterranean specimens The current status of the above reported popu-
(Barbieri et al., 2015), we concluded that two dif- lations of P. fucata in E-Sicily seems to attest their
ferent species are involved progressive expansion, after a first period of accli-
The first, attributable to P. radiata, on account mation in the more suitable geographical zones
of a bigger shell in full grown specimens, rounded where they arrived.