Psolidium complanatum is mentioned for the first time from the Mediterranean Sea. It is also the first record of a Psolidae in this sea

Massin, C.

Open Marine Archive

BULLETIN DE L'INSTITUT ROYAL DES SCIENCES NATURELLES DE BELGIQUE, BIOLOGIE, 67: 101 - 106, 1997 
BIOLOGIE, 67: 101 - 106, 1997 BULLET! VAN I-lET KONINKLIJK BELGISCI-I INSTITUUT VOOR NATU URWETENSCHAPPEN, 
First record of a Psolidae (Holothuroidea, Echinodermata) 
in the Mediterranean Sea (Sicilian Channel) 
by Claude MASSIN 
Abstract 
Psolidium complanalum is mentioned for the first time from the 
Mediterranean Sea. It is also the first rec r,d of a Psolidae in 
this sea. 
Key-words: Echinodermata, Holothuroidea, Psolidae, first record, 
Mediterranean Sea. 
Resume 
Psolidium comp/anatum est mentionne comme espece nouvelle 
pour la faune de Mediterranee. C'est aussi la premiere foi s 
qu ' un Psolidae est s ignale dans cette mer. 
Mots-cles: Echinodermata, Holothuroidea, Psolidae, premiere 
mention, Mediterranee. 
Introduction 
The holothurian fauna of the Mediterranean Sea is fairly 
well known and many faunistical lists have already been 
published (CHERBONNIER, 1956; TORTONESE, 1965, 1980; 
PEREZ-RUZAFA & LOPEZ-lBOR, 1988). Recent dredgings 
on the continental slope (200-2000 m) have brought new 
species for the Mediterranean fauna or new bathymet-
rical distributions of known species (ALVA, 1991 ; MASS IN, 
in press). Dendrochirote holothurians are represented by 
many species. However, not a single Psolidae has been 
mentioned up to now. 
During the expedition CS96 of R/V Urania (chief scientist 
M. TAVIANI) in the Sicilian Channel (27-1 2-96 to 09-01-97) 
within the frame of the I.G.M.-C.N.R. project on deep-
sea carbonate sedimentation, four small Psolidae have 
been collected between 274 and 786 m depth from hard 
substrate, such as fossil lithif ied sponges and fossil oyster 
shells. H. ZIBROWIUS sorted the material on board and 
sent it to me for identif ication. It is the object of the 
present note. 
Results 
0 . Dendrochirotida GRUBE, 1840 
F. Psolidae R. PE~RIER, 1902 
G. Psolidium LUDWIG, 1886 
Psolidium complauatum CHERBONNIER, 1969 
Fig. l A-B, Fig. 2A-F, Fig. 3A-D 
Pso/idium comp/anatum CHERBONNIER, 1969: 355, fig. 4A-R; 
CHERBONNIER, 1970: 1268- 127 1. 
MATERIAL EXAMl'NED 
CS96-St.l43 (30-12-96, 36°50' 28"N-l3° l0 ' ll "E, 786-
274, dredge) one specimen; CS96-St.l58 (3 1- 12-96, 
36°29'48"N- l2°57'4 l"E, 397-375, dredge) two specimens; 
CS96-Sta.229 (04-01-97, 36°51 '50"N-l3°08 '24"E, 768-
403 , dredge) one specimen. The specimens from station 
158 are held in the Museum National d'Histoire Naturelle 
(MNHN), Paris (France), the specimen of station 143 is 
held in the Zoologica l Museum of the University of 
Bologna (ZMB), Bologna (Italy) and the specimen of 
station 229 is held in the Royal Belgian Institute of 
Natural Sciences (IRSNB), Brussels (Belgium). 
5 mm 
Fig. l . - Psolidium complanatum. Genera l view. A : dorsa l; 
B: ventral. a : anus; m: mouth. 
I I 
l 02 C. MASS IN 
Type material: Holotype (MNHN, EcHh. 3447); Paratypes 
(MNHN, EcHh . 3431) 
DESCRlPTION 
Small holothurians (see table l ), very flat , with a distinct 
ventral so le, whitish in alcohol. The dorsal side is covered 
by large, overlapping scales (Fig. lA), 500-950 ~un in 
diameter. These scales are smaller near the edge of the 
body and on the buccal and anal cones. Between the two 
cones, there are four to five scales. The 20 to 44 dorsal 
podia are small and scattered. The number of dorsal podia 
is not re lated to the size of the specimens. The ventra l 
face is translucent and the internal organs are partly 
visible. The midventral ambulacrum is free of podia. Both 
lateral ambu lacra have a double row of podia (Fig. l B). 
The ones of the internal row ... are large whereas those of 
the external row are small and twice as numerous as the 
large ones (see table I). The number of podia increases 
with body length (see table 1). In between the podia of 
the internal row and posteriorly along the midventral 
ambulacrum there are brown spots of pigment (Fig. I B). 
Their number and size vary greatly from one specimen 
to another. Tentacles are digitiform. 
The calcareous ring is made of ten pieces without posterior" ' 
projections (Fig. 2A). Radial and interradial pieces are 
of the same width and height. The anterior tooth of the 
radial pieces is bifurcated at the apex and is larger than 
the one of the interradial pieces (Fig. 2A). The gonad is 
made of several large wh ite tubes. 
The ossicles of the ventral sole are numerous but well 
separated from each other. They are perforated plates with 
4 to 8 holes , exceptionnally 12 (Fig. 2B), 55-100 J..lm in 
diameter. Most of the plates have blunt spines. The ventral 
podia end by a terminal plate (Fig . 2C), 150 J..lm in 
diameter. The wall of the podia is sustained by elongated 
perforated plates (Fig. 2D), 75-210 J..lm long, sometime 
knobbed. 
Dorsally, there are sca les with their edge made of one 
layer perforated by small ho les (Fig. 2E). Towards the 
center, the number of layers increases and the center of 
the scale looks like knobbed (Fig. 2E). Together with 
II 
the large scales small nodular buttons can be observed 
(Fig. 2F). They are very rare and can be easi ly overlooked. 
The dorsa l podia have on ly small arched perforated plates 
(Fig. 3A) and nodular cups (Fig. 3B). In the introvert, 
there are large knobbed perforated plates (Fig. 3C), I 00-
180 ~tm long. In the tentacles, there are curved rods , 
perforated at the extremities and with twu, sometimes 
three, central perforated a!Jophyses (Fig. 3D). 
BATHYMETRICAL RANGE: 274-1045 m. 
DISTRIBUTION: Coast of Spain (Galicia) and Sici lian 
Channel . 
ECOLOGY: Psolidium complanatum is always associated 
with rocky bottom or soft bottom containing large amount 
of pebbles and stones on which it is adhering by the 
ventral sole. 
REMARKS: This is the first record of a Psolidae in the 
Mediterranean Sea. Psolidae are not very abundant in the 
temperate part of the East Atlantic Ocean. Only three 
species are know from the north coast of Spain, the Bay 
of Biscaye, Madeira Islands, Canary Islands and the coast 
of Morocco, viz. Psolus nummularis R. PERRI ER, 1902, 
Psolidium arcuatum HEROUARD, 1912 and Psolidium 
compfanatum CH ERBO NN IER, 1969. 
The Mediterranean specimens of P complanatum are 
similar to the Atlantic ones with minor variations. The 
Mediterranean specimens are characterized by the presence 
of small knobbed plates dorsally, by the presence of perfo-
rations at the apex of the apophyses of the tentacular 
rods , by the cups of the dorsal podia being knobbed 
instead of smooth and by the ventral pigment in between 
the podia. Those variations are less important than the 
variations which occur between the holotype and paratypes 
(at the level of the tentacular rods for example). 
No intermediary populations are known, up to now, 
between the Atlantic coast of Spain and the Straits of 
Sicilia. A direct gene flow between both populations is 
unlikely because of the brief planktonic stage of most 
Table I. Measures and observation on Psolidium complanatum. Diam: diameter; DP: dorsal podia; OS: dorsa l scale; OS M-A: 
number of scales between mouth and anus cones; H: height; L: left ventral row; LP: large podia; Lt: lenght; Nbr: number; Pig: 
pigmentation; R: right ventral row; SP: small podia; Sta: station; W: width. 
Lt w H Nbr.LP Nbr.SP Nbr. DS Diam . DS Pig. Sta. 
mm mm mm R-L R-L DP M-A J..ll11 
------ ----
6.8 4.8 1. 1 12-12 24-25 24 4 550-850 ++ 158 
7.1 4.2 1.2 16-16 32-30 34 5 500-800 ± 229 
7.5 5.6 1.2 17-16 33-31 44 5 650-900 + 143 
8.9 6.1 1.7 19-19 40-38 20 5 600-950 ++ 15 8 
First record of a Psolidae in the Mediterranean Sea I 03 
Psolidae (numerous species are brooding) and of the slow 
current ( 15-20 cm/s, BECKERS et al., 1997) entering the 
Mediterranean Sea through the Straits of Gibraltar and 
heading towards Sicily along the northern coast of Africa. 
This means that intermediate populations most probably 
occur between Spain and the Straits of Sicily but these 
are still to be discovered . 
The presence of an East Atlantic (coasts of Spain, Portugal, 
Morocco, Canary Islands and Madeira) Psolidae in the 
Mediterranean Sea is not surprising regarding the well 
known affinities between East Atlantic and Mediterranean 
echinoderm fauna (PEREZ-RUZAFA & LOPEZ-lBOR, 1988), and 
considering that individuals living on the continental slope 
experience homogeneous water temperatures in both regions. 
1.00 mm A~---~ 
500 Jlm E ___..:..___ _ 
100 Jlffi C,D~---
100 Jlffi B,F----------
Fig. 2. - Psolidium comp/anatum . Ca lcareous ring and ossicles. A: ca lca reous rin g (R: radial piece ; IR: interradial piece) ; B: perfo-
rated plates of the ventral so le; C: end plate of a podia ; D: suppor ting plates of the podia ; E: dorsal sca le; F: dorsa l 
knobbed button. 
I I 
I 04 C. MASSIN 
Acknowledgements 
It is a pleasure to thank H. ZIBROWIUS who invited me 
to study the holothurians collected during the Expedition 
CS96 of RIV/ Urania; Ph . WILLENZ for critically reading 
the manuscript and N. COM INA RDI for welcoming me in 
the Laboratoire des lnvertebres Marins et Malacologie at 
the MNHN of Paris. 
II 
References 
ALVA, V. 199 1. On three species of Mediterranean echinoderms. 
Scientia Marina, 55(2): 459-462. 
BECKERS, J.M ., BRASSEURS, P. & NIHOUL J.C.J. 1997. Circulation 
of the western Mediterranean: from global to regional sca les. In : 
EROS 2000 (European River Ocean System). ·The western 
Mediterranean, MARTIN J.M. (ed.). Deep-Sea Research II, 44(3-4): 
531-549. 
1/B . 
. 
A-D 100 pm 
Fig. 3. - Psolidium complanatum . Ossic les. A: arched perforated plates of the dorsal pod ia; 8 : cups of the dorsal podia; C: plates 
of the introvert; 0: rods of the tentacles . 
First record of a Psolidae m the Mediterranean Sea I 05 
CHERBONNIER, G. 1956. Les Echinodermes de Tunisie. Bulletin 
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PEREZ-RUZAFA, A. & LOPEZ-IBOR, A. 1988. Echinoderm fauna 
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Balkema, 141-149. 
C. MASSIN 
Section Malacologie 
IRSNB, 29 rue Vautier 
1000 Brussels, Belgium 
... 
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First record of a Psolidae (Holothuroidea, Echinodermata) in the Mediterranean Sea (Sicilian Channel)

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