Stragulum bicolor, Ofwegen, Van, 2011

Ofwegen, Van, 2011, A probably invasive new genus and new species of soft coral (Octocorallia: Alcyonacea: Clavulariidae) from Brazil, Zootaxa 3107, pp. 38-46 : 39-40

Stragulum bicolor n. sp.

( Figs. 1–4 )

Material: Holotype: RMNH Coel. 39693, colony and three microscope slides, Brazil, Paraná, Paranaguá, growing on polyethylene plates, Iate Clube de Paranaguá, coll. M.A. Haddad, 20 May 2009.

Paratypes: RMNH Coel. 39694, six colonies, same data as holotype; RMNH Coel. 39695, six colonies, Brazil, Santa Catarina, Itapoá, Pedra do Meio e Terceira Pedra, coll. M.A. Haddad, 28 March 2009; RMNH Coel. 39696, four colonies, Brazil, Rio de Janeiro, Baía de Sepetiba, coll. J.S. Vianna da Silva, December 2005; RMNH Coel. 39697, three colonies, Brazil, Santa Catarina, Itapoá, Pedra do meio e Terceira Pedra, coll. M.A. Haddad and L. Altvater, 9 May 2009; RMNH Coel. 39698, two colonies, Brazil, Paraná, Guaratuba, Cabaraquara, coll. L.M. Hostin, 12 June 2002; RMNH Coel. 39699, three colonies, Brazil, Paraná, Paranaguá Bay, growing on polyethylene plates, coll. L. Altvater, April 2007; RMNH Coel. 39700, two colonies, Brazil, Paraná, Paranaguá Bay, coll. M.A. Haddad, April 2007; RMNH Coel. 39701, seven colonies, Brazil, Paraná, Paranaguá Bay, coll. M.A. Haddad, May 2007; DZoo-Cn 223, two colonies, Brazil, Paraná, Guaratuba, Cabaraquara, Coll. L.M. Hostin, 12 June 2002; DZoo-Cn 314, three colonies, Brazil, Paraná, Paranaguá Bay, artificial substrate, coll. L. Altvater, 9 May 2009; MNRJ 5125, one colony, Brazil, São Paulo, Cananéia, coll. A.C. Morandini, 14 February 2000; MNRJ 7058, one colony, Brazil, Paraná, Rasa da Cotinga Island, Paranaguá Bay, coll. Y.A.G. Tavares, April 2000; MZUSP 356, Brazil, São Paulo, Cananéia, coll. A.C. Morandini, determined as Erythropodium caribaeorum by H.K. Boscolo, on oyster shells and piers, 13 December 2000; MZUSP 357, Brazil, Ceará, Aracati, 8 March 2001, coll. T.M.C. Lotufo, determined as Erythropodium caribaeorum by Lotufo & H. Matthews-Cascon, on intertidal beach rocks, 8 March 2001; MZUSP 358, Brazil, São Paulo, Cananéia, coll. E.P. Grande, determined as Erythropodium caribaeorum by H.K. Boscolo, 27 April 2002; MZUSP 360, Brazil, São Paulo, Cananéia, coll. A.C. Morandini, determined as Erythropodium caribaeorum by H.K. Boscolo, on oyster shells and piers, 24 March 2003.

Description. The holotype consists of an encrusting colony overgrowing barnacles, it is the largest specimen examined, measuring 5.5 by 3 cm in diameter and 1 mm thick ( Fig. 1 a). Most polyps are retracted, forming coenenchymal mounds that are conical, closely set to each other, and up to about 1 mm high; although a few hardly project above the colony surface.

In the upper layer of the coenenchyme and the larger part of the coenenchymal mounds are branched sclerites, crosses, radiates ( Fig. 1 b), and spindles ( Fig. 2 a); the smallest radiates are 0.05 mm long, the largest radiates and the spindles 0.15 mm long. Transitional forms between spindles and crosses also occur. The top of the coenenchymal mounds has smaller, less tuberculate radiates, branched forms and spindles, up to 0.10 mm long ( Fig. 2 b). The base of the colonial membrane has fused sclerites ( Fig. 2 c), which do not extend into the coenenchymal mounds.

Colour. The preserved holotype is red with white polyps; the colour is confined to the sclerites, which are all reddish.

Etymology. The species name is the Latin bicolor , of two colours, referring to the two colony colours found in the examined material, red and white ( Fig. 4 ).

Variability. One colony of RMNH Coel. 39699, two colonies of RMNH Coel. 39700, and one colony of RMNH Coel. 39701 are completely white; all sclerites colourless. The colony shape and sclerites are the same for all specimens.

Habitat, distribution and abundance. Figure 3 and Table 1 summarize the collection data of S. bicolor n. gen., n. sp. along the Brazilian coast. In the State of Paraná, South of Brazil, Yara A.G. Tavares firstly found the colonies among littoral loose organic material, which was collected by net trawls on a sandy bottom, along the boundaries of Cotinga Island and in the Sucuruí Channel, in April 2000 and May 2002, respectively. Both places are inside Paranaguá Bay, the largest estuarine system in the South of Brazil. Colonies were covering stems of the octocoral Leptogorgia setacea (Pallas, 1766) and bark portions from mangrove trees. On June 3rd 2002, Leonardo M. Hostin found the species in Guaratuba Bay, a smaller estuary at the southern littoral of Paraná, also on organic material. They brought the specimens to M.A. Haddad, at the Paraná Federal University, who suspected the species was unknown to the Brazilian coast.

Colony samples from Cananéia (São Paulo) and Aracati (Ceará) had been deposited in the Museum of Zoology of the São Paulo University (MZUSP), as Erythropodium caribaeorum (Duchassaing & Michelotti, 1860) . On the coast of Rio de Janeiro, Julieta S.V. Silva found the species in 2005, on island beach rocks, port structures and artificial fouling plates, inside Sepetiba Bay.

In March 2004, again on the coast of Paraná, some colonies were scrapped from piers of the Paranaguá Yacht Club ( Neves et al. 2007), and in April 2007, Stragulum bicolor n. gen., n. sp. dominated the fouling community on polyethylene plates, ropes and granite plates hanging down from the Yacht Club piers and pontoons ( Cangussu et al. 2010), also growing mainly on bryozoans and barnacles, not directly on the plates. This Club is inside Paranaguá Bay, neighbouring Cotinga Island, the first place where the species had been collected, and the Port of Paranaguá, one of the largest of the Brazilian coast.

In May 2008, M.A. Haddad found the species on natural substrata at the sea coast, on intertidal beach rocks of Itapoá (at the neighbour State of Santa Catarina), nearly 50 km south of Guaratuba Bay. Numerous dark red colonies, nearly two to five centimetres wide were encrusting seaweed stems, and barnacles, mussels, and other organisms on the rocks. She then sent some samples of the invasive species to L.P. van Ofwegen.

As described above, Stragulum bicolor n. gen., n. sp. rather suddenly appeared in many places along the Brazilian coast, from the tropical waters of the Northeast State of Ceará (04°33’S) to the Southern State of Santa Catarina (26°07'S), mainly in port areas. We can highlight the inexistence of colonies on acrylic plates submerged monthly during one year (1987/1988), in Paranaguá Bay ( Correia & Silva 1990). One of the three places these authors put their experiments was very nearby the Yacht Club where M. A. Haddad first found the new species ( Cangussu et al. 2010) on artificial substrata.

Vessels are vectors of introduction and distribution of notable invasive species ( Floerl & Inglis, 2003), while ports and marinas are sources of dispersion of native species and also gateways to alien ones; the new surfaces available in the form of artificial substrates may help the recruitment ( Carlton, 1985). The behaviour of S. bicolor n. gen., n. sp. has many features of an invasive species; rapidly colonizing artificial substrate in port areas, reproducing, perhaps sexually, and then spreading itself to natural beach rocks along the coastline.

One other possibly invasive octocoral species has been reported from Brazilian waters, Chromonephthea braziliensis ( Ofwegen, 2005) . It was initially found in 1997, in Arraial do Cabo, Rio de Janeiro, not that far from one of the localities where Stragulum bicolor n. gen., n. sp. was found. Ferreiro (2003) suggested C. braziliensis probably was introduced by oil platforms via fouling, and maybe the same applies for S. bicolor n. gen., n. sp.

Figures

FIGURE 1. Stragulum bicolor n. gen., n. sp., a, holotype RMNH Coel. 39693; b, branched sclerites, crosses and radiates of upper layer.

FIGURE 2. Stragulum bicolor n. gen., n. sp., sclerites of holotype RMNH Coel. 39693; a, spindles and branched forms of upper layer; b, sclerites of top of the coenenchymal mounds; c, fused sclerites from base of colony.

FIGURE 4. Live colonies of Stragulum bicolor n. gen., n. sp.; a, on polyethylene plates, overgrowing barnacles; b – c, overgrowing bryozoans and growing around the actinia Diadumene sp. (photographed through the eyepiece of a stereomicroscope).