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VERRUCAE ON SEA-FANS: UNEXPECTED ABUNDANCE OF THE BARNACLE CONOPEA CALCEOLA
(ELLIS) ON THE GORGONIAN EUNICELLA SINGULARIS (ESPER) IN THE MEDITERRANEAN SEA

Andrea Peirano 1*, Chiara Lombardi 1, Nicolò Ponzè 2 and Silvia Cocito 1
1 ENEA, Marine Environment Research Centre, La Spezia, Italy - andrea.peirano@enea.it

2 Area Marina Protetta Isole Egadi, Favignana (TP), Italy

Abstract
Colonies of the symbiotic Mediterrean gorgonian Eunicella singularis were found to host the warm-tropical barnacle Conopea
calceola on rocky bottoms in the Sicily Channel. Barnacle’ presence and abundance (some tens individuals per colony) is probably
due to increasing seawater temperatures, this ‘co-habitation’ supposedly representing a strategy for C. calceola species’ survival
and a further threat for E. singularis in an increasingly warming Mediterranean Sea.

Keywords: Crustacea, Sicily Channel, Cnidaria, Global change, Alien species

Introduction tropical C. calceola has a wide distribution extending from the eastern
The barnacle Conopea calceola (Ellis), living on gorgonians, has been Atlantic coast to the Indian Ocean, and further to the seas bordering S.E.
reported present, yet rare in Southern Italian coasts ([1], [2]). Records are Asia ([3]). Present occurrence and abundance of this barnacle may be
given here on monospecific, dense stands of candelabra-like Eunicella compared with those of other warm-water species such as Solidobalanus
singularis (Esper) hosting the barnacle, found in the Sicily Channel. fallax (Broch), which is found inhabiting the British sea-fan Eunicella
verrucosa ([4]). As for S. fallax, C. calceola ubiquitous presence observed in
Material and methods the last few years is probably due to increasing seawater temperatures,
A biodiversity survey was carried out in May 2012 at Favignana Island favoring species widespread and making it more detectable. In light of
(Marine Protected Area of Egadi Islands, Sicily Channel, Italy). In 13 serious threats affecting the Mediterranean white gorgonian E. singularis
localities, rocky bottom communities were video-surveyed along transects such as the extensive mortalities that occurred in the past decade ([5]), the
spanning on the whole a 0 to 60 m depth range. Video sampling (30 min per increase in C. calceola abundance could signify a further problem for E.
transect) was performed with a full-HD camera equipped with a wide-angle singularis. This ‘co-habitation’ may represent a strategy for C. calceola
lens recording nearly 0.75 m2 at a distance of approximately 50 cm. survival in the changing Mediterranean Sea.

Results and Discussion Tab. 1. Localities, depth range, number of E. singularis colonies and number
A total of 570 E. singularis colonies were surveyed, of which 24.6 % were of colonies (%) with C. calceola.
seen to host C. calceola (Tab. 1). The majority of E. singularis colonies
living on bottoms between 15 and 30 m were characterized by tens of
‘verrucae’ barnacle housings (Fig. 1).

Fig. 1. Colony of Eunicella singularis on a flat rocky bottom at Favignana, References
Egadi Island, Sicily Channel (South Western Mediterranean) colonized by
more than 12 individuals of the barnacle Conopea calceola that form visible 1 - Relini G., 1980. Cirripedi Toracici. Guide per il riconoscimento delle
verrucae. specie animali delle acque lagunari e costiere italiane. AQ/1/91. 2. Cons. Naz.
Ric., Genova: 117.
By sampling a few E. singularis colonies, gorgonian tissue was observed to 2 - Relini G., 2010. Check-list of the Flora and the Fauna in Italian Seas.
wrap C. calceola shell with the exception of a small opening which ensure Biol. Mar. Medit., 17 (1) part II: 466-470.
barnacle feeding. The presence of alive individual within the shell suggested 3 - Stubbings H.G., 1967. The Cirriped fauna of tropical West Africa. Bull.
that the white gorgonian is a suitable substrate for the barnacle. Warm- Br. Mus. nat. Hist. (Zool.) 158(6): 227-319.
4 - Southward A.J., Hiscock K., Moyse J. and Elfimov A.S., 2004. Habitat
and distribution of the warm-water barnacle Solidobalanus fallax (Crustacea:
Cirripedia). J Mar Biol Ass UK, 84: 1169-1177. <\/div>
5 - Ferrier-Pagès C., Tambutté E., Zamoum T., Segonds N., Merle P.L.,
Bensoussan N., Allemand D., Garrabou J. and Tambutté S., 2009.
Physiological response of the symbiotic gorgonian Eunicella singularis to a
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586 Rapp. Comm. int. Mer Médit., 40, 2013

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