MEDUSIVOROUS FISHES OF THE LIGURIAN SEA 2. THE SPECIALIST, SCHEDOPHILUS MEDUSOPHAGUS COCCO, 1839

Fulvio Garibaldi *, Lidia Orsi Relini and Giulio Relini Università di Genova, DIP.TE.RIS., Centro di Biologia Marina del Mar Ligure - garibaldi.f@libero.it

 Abstract From 2004 onwards, several adult specimens of the cornish blackfish Schedophilus medusophagus were sampled in the Ligurian Sea: these fish represent first adult captures in the whole Mediterranean. The presence of the mauve stinger Pelagia noctiluca in the stomach contents of one specimen is described. The fish was eating a large number of entire jellyfish and showed in the caudal portion of the stomach a coloured concentrate of this food.Keywords: Medusae, Fishes, Pelagic, Ligurian Sea

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Schedophilus medusophagus was described by Cocco [1] in Sicily. The specific name was questioned by Günther [2] because “the fish could draw but little nourishment from jellyfish”. Only one century later, the value of pelagic cnidarians as food for vertebrates was fully understood. Ates [3] was able to list 75 species of medusivorous fishes; 15 of them were reported to have their stomach filled solely, or for a considerable part, with jellyfish remains. Fish belonging to the family Centrolophidae are recognized as specialists in the association with jellyfish during their juvenile and young adult phases, so that the term "medusafish" was coined for them [4]. Four species are present in the Mediterranean: Centrolophus niger (Gmelin, 1789), Hyperoglyphe perciformis (Mitchill, 1818), S. ovalis (Cuvier, 1833) and S. medusophagus Cocco, 1839. The latter was recorded in Western Mediterranean [5] and Adriatic Sea [6; 7; 8], but it is still a poorly known species because most specimens collected to date are juveniles [4] and sometimes larvae. Past Mediterranean literature and iconography [9; 10], always relate to juveniles as well as the records, until the beginning of the millennium. In recent times, and especially from 2004 onwards, an important sampling of S. medusophagus was carried out in the Ligurian Sea. This abundance could be related to jellyfish (Pelagia noctiluca) blooms that occurred in the last few years in the Western Mediterranean. At the best of authors knowledge, a collection of many adult fish is unprecedented both in Mediterranean and in the adjacent Atlantic.

Fig. 1. The adult female Schedophilus medusophagus caught off Sanremo on 28 June 2006 One of these specimens, a female, 64 cm TL, caught off Sanremo on 28 June 2006 (Fig. 1), gave the opportunity to observe the stomach content consisting solely of P. noctiluca, for a total volume of 400cc (Fig. 2).  The cephalic portion of the stomach showed several complete individuals of P. noctiluca (umbrellas plus manubrium with oral arms). An ink-like liquid completely filled the caudal part of the stomach, showing evidences that, during the digestion, the pigments of P. noctiluca are transformed into a violet fluid that colours the entire gut.

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Fig. 2. Stomach content of the adult S. medusophagus from the Ligurian Sea, showing entire undigested P. noctiluca specimens and product of digestion (black spot at the bottom of the picture)

References 1 - Cocco A., 1839. Sopra un nuovo genere di pesci della famiglia dei Centrolofini e di una nuova specie di Trachurus. L’Innominato, Messina, 3, 56-59. 2 - Günther A., 1882. Description of a specimen of Schedophilus medusophagus, a fish new to the British fauna. Trans. Zool. Soc. London, 11: 223-224. 3 - Ates R.M.L., 1988. Medusivorous fishes, a review. Zool. Meded., 62: 29-42. 4 - Haedrich R.L., 2002. Centrolophidae. Medusafishes (ruffs, barrelfish). p. 1867-1868. In: K.E. Carpenter (ed.) FAO species identification guide for fishery purposes. The living marine resources of the Western Central Atlantic. Vol. 3: Bony fishes part 2 (Opistognathidae to Molidae), sea turtles and marine mammals.  5 - Haedrich R.L., 1986. Family: Centrolophidae and Nomeidae. In: Whitehead P.J.P., Bauchot M.L., Hureau J.C., Nielsen J., Tortonese E.(eds.), 1984-86. Fishes of the north-eastern Atlantic and Mediterranean. UNESCO, Paris. 6 - Ninni E., 1912. Catalogo dei pesci del Mare Adriatico. Venezia. 7 - Onofri, L. 1986. The rare saw-cheeked fish (Schedophilus medusophagus Cocco, 1839) (Pisces: Centrolophidae in the central Adriatic. Zbornik Matice Srpske za prirodne Nauke/ Proc. Nat. Sci., Matica Srpska, 70: 135-141. 8 - Dulcic, J., 1998. First record of the cornish blackfish Schedophilus medusophagus (Pisces: Centrolophidae) larvae from the Adriatic Sea. J. mar. biol. Ass. U.K., 78: 1035-1038. 9 - Bini G., 1968. Atlante dei pesci delle coste italiane. Mondo Sommerso ed. Print offset, Roma, vol. 6: 177 pp. 10 - Tortonese E., 1975. Fauna d’Italia. Osteichthyes (Pesci Ossei), Calderini, Bologna, Vol. 11: 636 pp.

525Rapp. Comm. int. Mer Médit., 39, 2010

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