BioInvasions Records (2013) Volume 2, Issue 3: 233–237 Open Access doi: http://dx.doi.org/10.3391/bir.2013.2.3.10 © 2013 The Author(s). Journal compilation © 2013 REABIC

Rapid Communication

Occurrence of the alien (H. Milne Edwards, 1853) () and sea hare dactylomela Rang, 1828 (Opistobranchia) in shallow marine waters north of Island (, , )

Claudius Pirkenseer University of Fribourg, Faculty of Sciences, Unit Earth Sciences, Chemin du Musée 6, CH-1700 Fribourg, Switzerland E-mail: [email protected]

Received: 13 June 2013 / Accepted: 9 August 2013 / Published online: 19 August 2013

Handling editor: Vadim Panov

Abstract

Percnon gibbesi (H. Milne Edwards, 1853) (Decapoda, ) and Aplysia dactylomela Rang, 1828 (Opistobranchia, ) are reported for the first time from shallow coastal waters between Pounta and Elafonisos village (, Greece). The occurrence of the crab unsurprisingly bridges findings from Antikithyra Island to the south and the Mani coast to the west, while the presence of the sea hare links records from the Messinian Gulf, Paros Island, and western Crete. Key words: non-indigenous ; Greece; Laconian Gulf; Aplysia dactylomela; Percnon gibbesi

initially recorded from the central Mediterranean Introduction (Relini et al. 2000) and in Greece from the north- eastern Messiniakos Gulf in 2004 (Thessalou- The most recent comprehensive overview of Legaki et al. 2006), showing an eastward- alien taxa in Greek waters lists a total of 237 directed expansion pattern (Katsanevakis et al. species (Zenetos et al. 2011), with 60 taxa being 2011). Since then, the species has been reported recorded from the and 76 in the south along the southern Messinian coast, the Mani . Percnon gibbesi (H. Milne Edwards, Peninsula, Antikithira Island, the Cyclades 1853) (Decapoda, Plagusiidae) and Aplysia dacty- archipelago, and Crete (Thessalou-Legaki et al. lomela Rang, 1828 (Opistobranchia, Aplysiidae) 2006; Katsanevakis 2011; Katsanevakis et al. 2010, were recorded in shallow waters between Elafonisos 2011; Nicolaidou et al. 2012; Pirkenseer 2012) Island and Pounta beach (Laconia, Greece) in (Figure 1, large map). summer 2012. Both species are considered It is generally assumed that the sea hare established biota in the eastern Mediterranean by Aplysia dactylomela is a circumtropical species Zenetos et al. (2007, 2011). The true provenance (e.g. Eales 1960). However, a recent molecular of the sea hare is still uncertain (e.g. Yokes data set suggests the need to re-evaluate the 2006; Pasternak and Galil 2010). The mode of Aplysia, implying independent taxonomic introduction of the crab via larval drift, aquarium status of Atlantic and Pacific “Aplysia dactylomela” trade, or ballast water into the Mediterranean populations, and a possibly synonymy of the latter also remains controversial (Yokes and Galil 2006; population with A. pulmonica (Alexander and Cannicci et al. 2008; Elkrwe et al. 2008; Valdés 2013). The known distribution of alien Katsanevakis et al. 2011). Aplysia dactylomela seems to be restricted to the Percnon gibbesi is widely distributed in the central and eastern Mediterranean (westernmost Atlantic, including the Americas, the Caribbean, record Lampedusa Island; Crocetta and Colamonaco the African west coast, and most of the Islands 2010; Pasternak and Galil 2010), and might thus (Manning and and Holthuis 1981). The species was be of Indo-Pacific origin.

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Figure 1. Distribution of Percnon gibbesi and Aplysia dactylomela along the coast north of Elafonisos Island (lower left, inset; Georeference: Appendix 1) and in the SE Ionian and S Aegean Sea (occurrences after Thessalou-Legaki et al. 2006; Pasternak and Galil 2010; Katsanevakis 2011; Katsanevakis et al. 2010, 2011; Nicolaidou et al. 2012; Pirkenseer 2012); points = local occurrences (georeferenced), black lines = established according to Katsanevakis et al. 2012.

It has been spotted irregularly and mostly in An outthrust, slightly tilted rock layer single occurrences in Greek waters, e.g., in the (locality 2, Figure 1) runs quasi-parallel to the Messinian Gulf, western Crete, and the Cyclades northern Elafonisos village beach at a distance of archipelago (Zenetos et al. 2007, Pasternak and 20–40 m from shore. It provides a hard substrate Galil 2010, Katsanevakis 2011, Nicolaidou et al. for sessile biota and abundant horizontal crevices 2012). as hiding places (Figure 2d) for Percnon gibbesi. The rock layer is overgrown only by a thin algal Methods and Study Area film, serving as feeding ground for the crab. The site is surrounded by a sandy to slightly muddy The study area is situated west of southern soft bottom with sparse cover (e.g. Laconian peninsula between the Island of locality 3 on Figure 1) in water depths between Elafonisos and the Pounta hamlet, west of the 1–1.5 m. The water is relatively clear, except town of Neapolis (Peloponnese, Greece; Figure when turbidity is induced by wave action. 1). Data were obtained by in-situ observation and Despite intensive human activity, common underwater photography during repeated free- smaller fish as well as molluscs, Bryozoa and diving and snorkelling surveys in depths up to 4 Actinaria were relatively abundant. m from July to August 2012. Abundance of Large round boulders densely overgrown by Percnon gibbesi was estimated along a 100 m macroalgae (Cystoseira spp.), extremely clear section on the coast north of Elafonisos village water, strong currents, and small size (approx. (Figure 1, please see annex 1) during several 420 m) characterize the (artificial?) habitat sampling events. (Figure 2A) at locality 3 near the southernmost

234 Occurrence of alien species in coastal waters of Elafonisos Island, Greece

tip of Pounta beach. Except for some small fish (e.g. Diplodus spp., Sarpa salpa) close to the boulders, the surrounding sublittoral sand flats associated to the Pounta beach complex was nearly devoid of macrofauna (Figure 2B).

Results and discussion Percnon gibbesi The crab Percnon gibbesi (Figure 3) was recorded from the localities 1 and 2 (Figure 1, annex). The morphology of the observed specimens agrees with the taxonomic description in Relini et al. (2000). Occurrences of P. gibbesi at the northern Elafonisos village beach (locality 2) reached densities (mainly in or close to crevices) of approx. 1–2 specimens/m2 along the outthrust rock layer, which is comparable to the lower end of densities reported from well established Mediterranean localities (e.g. up to 3 /m2, Deudero et al. 2005; about 1 crab/m2, Thessalou-Legaki et al. 2006; 1.6–11.9 crabs/m2, Sciberras and Schembri 2007; up to 10 crabs/m2, Pirkenseer 2012). Occurrence in locations lacking macroalgae and providing abundant hiding space (crevices) as well as the hiding behaviour agree with published reports (e.g., Pipitone et al. 2001; Sciberras and Schembri 2008; Katsanevakis et al. 2010). Due to the relatively low density, the crabs in most cases were observed feeding individually or in pairs on microalgae and retreated quickly into crevices when approached. A single specimen of P. gibbesi (Figure 3) was observed in the small patch of boulder habitat at the southernmost tip of Pounta beach (locality 1) at about 3 m water depth, a location characterized by a thick growth of macroalgae (Cystoseira spp.). The specimen’s isolated occurrence is a bit puzzling, but may represent the first foothold in colonizing the substrate offshore of Pounta beach like the uncolonized rocky area east of the Pounta ferry jetty and approx. 100 m west of locality 1 (Figure 2c).

Aplysia dactylomela A single specimen of the large sea hare Aplysia dactylomela was found in locality 3 (Figure 1, annex 1) on muddy sand with sparse seagrass Figure 2. Boulder habitat at the southernmost tip of Pounta beach cover at about 2 m water depth (Figure 4). Its (A), extensive sand bottom habitat surrounding Pounta beach (B), large size (approx. 20 cm in contracted state), uncolonized rock slab habitat approx. 100 m west of the boulder habitat at Pounta beach (C), and crevices in colonized rock slab coloration (black rings connected by a network habitat parallel to the Elafonisos village beach (D) (Images by C. of black lines on a pale yellowish background), Pirkenseer). and body morphology agrees with the amended

235 C. Pirkenseer

Crete). Due to low numbers of the crab Percnon gibbesi and the single record of Aplysia dactylomela, an additional survey will be carried out in 2013 to verify the establishment of continuous and stable populations, and the possible colonization of adjacent suitable habitats in the area (e.g. Lefki beach area).

Addenum July 2013 Unsurprisingly, the crab Percnon gibbesi has indeed been spotted in the rocky area just adjacent east of Lefki beach in small numbers (see Appendix 1, and locality 4 on large map) on two occasions. The continued presence of the crab at Figure 3. Single Percnon gibbesi specimen in the boulder habitat the Elafonisos village beach is confirmed. at the southernmost tip of Pounta beach; image by C. Pirkenseer.

Acknowledgements

Two anonymous reviewers are thanked for providing useful comments and suggestions concerning manuscript form and content.

References

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Appendix 1. Distribution of the two non-indigenous species, north of Elafonisos village (Laconia, Greece).

Species Percnon gibbesi Aplysia dactylomela

Map No. 1 2 4 3 100 m long outthrust rock few large boulders layer of about 4-8 m width (artificially placed?) on the small cove adjacent and close to the northern Locality parallel to the northern southernmost tip of Pounta east of Lefki beach Elafonisos village beach Elafonisos village beach, 5 – beach, close to shore 40 m from shore crevices between large crevices between rock slabs, flat boulders and sparse seagrass meadow boulders, rich vegetation with thin algal cover and few crevices in solid rock over sandy, muddy Habitat and strong coastal current, sessile biota, clear to turbid walls, partly overgrown substrate, clear to turbid extremely clear water water by macroalgae water some (up to ca. 1 specimen / Abundance single 5 specimens single m2), strongly variable Time 10:24 AM numerous sightings afternoon 5:02 PM Date / Period 02.08.2012 27.07. – 04.08.2012 30. – 31.07.2013 30.07.2012 9 runs on the sand flats Runs single, about 1 hour 9 runs along the rock layer 2 spot encounters adjacent to the beach Depth (ca.) 3 m 0.15 – 1.0 m 0.3 – 1.0 m 2 m area around Latitude, °N 36.515803 36.476106 36.510413 36.509561 Longitude, °E 22.984668 22.975522 22.983286 22.978066

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