Indo-Pacific gastropod species in the Levantine and Aegean Seas

The present study reports the occurrence of three Indo-Pacific gastropod species at new localities in the Mediterranean Sea. Chromodoris quadricolor was recorded on the 29 May 2004 in the eastern Medi-terranean, which is the third report of the species from the Mediterranean Sea. Finella pupoides and Syrnola fasciata are collected from the several sites in the Aegean Sea between 1997 and 2002. The morphological, ecological and distributional characteristics of these species are described.


Introduction
Since the opening of the Suez Canal in 1869, which connected two different zoogeographical regions, the eastern Mediterranean Sea is colonized by species of Indo-Pacific origin.Although the number of immigrant species was initially low, their number has increased especially during the last decade.Now, more than 300 Lessepsian immigrants are known in the Mediterranean.Among these non-indigenous species, the molluscs are most numerous and many studies have focused on them.
Most of the Mediterranean alien molluscan species (including the Lessepsian immigrants and the species which have been carried by shipping or mariculture) have been incorporated by Zenetos et al. (2003) in the recently published mollusc part of the "CIESM Atlas of Exotic Species in the Mediterranean".They listed a total of 126 species of Indo-Pacific origin and a few additional migrants from the other parts of the world.They also rejected 26 Indo-Pacific species, due to various reasons such as unconfirmed records, mis-identifications and species of an unclear origin.Soon thereafter, Mienis (2004) reported 23 new records for the Mediterranean Sea and additional data for 11 species, which were overlooked by Zenetos et al. (2003).
Although some of the immigrants constitute local populations near the Levant entrance of the Suez Canal, others have expanded their distributional ranges to the western Levantine Sea and to other regions of the Mediterranean system.A recent study reported the presence of the Lessepsian mantis shrimp, Erugosquilla massavensis (Koossmann 1880) in the Marmara Sea (Katagan et al. 2004), where the surface water is of Black Sea origin, and the bottom is of Mediterranean origin.In addition, two Polychaeta species, Leonnates persicus Wesenberg-Lund 1949 and Pseudonereis anomala Gravier 1900 were reported from Izmir Bay (Aegean Sea) by Çinar et al. (2002) and Çinar and Ergen (2005), respectively.Some mollusc species, like Cerithium scabridum stated by Albayrak (2001) from Gökçeada (North Aegean Sea), Fulvia fragilis (Bivalvia) reported by Vardala-Theodorou (1999) and Öztürk and Poutiers (2005) from Elefsis and Izmir Bay, respectively, are also Lessepsian immigrants which have enlarged their distributional ranges to the Aegean Sea.Among Lessepsian fishes, 19 species have also reached to the Aegean Sea, some of which have established populations in the central and northern Aegean Sea (Bilecenoglu et al. 2002).
Among the Turkish coasts, the highest number of alien species are known from the Levantine coast.A total of 277 alien species have been reported from the Turkish coasts (of which 90 are molluscs) and 216 alien species (84 are molluscs) occur in the Levantine Sea (see the addendum given by Çınar et al. 2005).The introduction of alien species is an ongoing process and numbers are increasing day by day.For example, Çeviker and Albayrak (2006) have reported three new alien molluscs for the Turkish fauna.
In the present study, two gastropod species, Finella pupoides and Syrnola fasciata, are being reported for the first time from the Aegean Sea.Furthermore, we provide some ecological and distributional features of Chromodoris quadricolor (Gastropoda) as a first record from the eastern Mediterranean Sea.

Materials and Methods
The samples, in which F. pupoides and S. fasciata were found, was collected from the Fethiye Bay (Levantine Sea) in 1997, and at the Salih Island coast near Bodrum (southern Aegean Sea coast of Turkey) in 2001 (Figure 1).The sampled material was studied within the framework of a project supported by TUBITAK [Project No: TBAG 2343 (103T154)].The material taken from Salih Island mainly comprised of leaves and roots of

Results and Discussion
Finella pupoides Adams, A. 1860 (Gastropoda: Scaliolidae) (Figure 2) Of 11 specimens investigated in this study, one specimen (shell 2.3 mm in height, with series of indistinct brown patches on a whitish background) was encountered at station 1 on sandy-muddy substrate with Posidonia oceanica remainders; one specimen (shell 2.2 mm in height, with a shell colour pattern as it is in the former specimen) was found at station 2 on Posidonia oceanica leaves and roots with sandy and muddy substrata; one specimen (shell 3.1 mm in height with brownish colour) was sampled at station 3 from Posidonia oceanica leaves and roots with sand; and 8 specimens (largest 2.6 mm in height, with shells colour patterns similar to the specimens sampled at station 1 and 2) were found at station 4 in muddy substrate.
According to Barash and Danin (1992, p 76), the Indo-Pacific range of Finella pupoides is as follows: Gulf of Suez, Red Sea, Persian Gulf, India and Japan.In the Mediterranean Sea, this Lessepsian species has been known so far only from the Levantine Sea, where it is commonly encountered along the eastern and northeastern coasts and Cyprus (Zenetos et al. 2003, p 73).This record extends its distribution in the Mediterranean system to the Aegean Sea.
F. pupoides was first recorded in the Mediterranean during 1958 from the Israeli coast of the Levantine Sea (Barash and Danin 1977).Although its distribution was initially restricted, it has expanded its distributional area in the last 15 years westwards in the Levantine Sea and to the Aegean Sea according to Tringali and Villa (1990), Engl (1995) and the present study.Its successful dispersion may probably be due to its long planktonic larval stage, during which it can be transported to remote sites by water currents, as well as in ballast water of ships.It should be noted that two ports (Adabükü and Kuyucak) (Figure 1) are located close to Salih Island, where F. pupoides and S. fasciata were sampled.
Syrnola fasciata (Jickeli 1882) (Gastropoda:Pyramidellidae) (Figure 3) One specimen of this species (shell 4.7 mm in height with two brownish cords on a hornywhitish background on the body whorl) was encountered at station 3 in areas with Posidonia oceanica leaves and roots with sand This probably Lessepsian migrant (not recorded so far in the Suez Canal) seems to have the same distributional pattern as Finella pupoides.It has been reported from the eastern and northeastern coasts of the Levantine Sea and all around Cyprus (in Zenetos et al. 2003, p 153).This distant locality in the present study enlarges its distribution to the Aegean Sea.
Syrnola fasciata was first found in the Mediterranean Sea in 1958 from the Israeli coast (Haifa) and in 1963 from the Turkish coast of the Levantine Sea (Aartsen et al. 1989, p 70).The expansion of this probably Lessepsian species to the west in the Levantine Sea appears to be similar to the F. pupoides according to information given by Tringali and Villa (1990) and Engl (1995), and the species recently reached the Aegean Sea (present study).
Remark: in the faunal assemblage of the autumn 2001 samples taken at station 1, a total of 689 individuals belonging to 35 species (including F. pupoides and S. fasciata) have been identified.Among them Bittium latreillii (Mollusca) was the dominant species, followed by Echinocyamus pusillus (Echinodermata).
A single specimen of this species was encountered and photographed at station 5, on rocks covered by algae in an area with sandgravel bottom, at a distance of approximately one mile to the Kemer marina (Antalya).The colour pattern of the specimen coincides well with the specimens from Red Sea, especially, with those reported by Cattaneo-Vietti (1986) from the Ligurian Sea.
According to Zenetos et al (2003, p 195), in the Red Sea, this species can be found on shallow water coral reefs and feeds on sponges, similar to other Chromodorid species.Chromodoris quadricolor originally described from the Red Sea and subsequently reported from Tanzania (Rudman 1977), has an elongate, dorsoventrally flattened and smooth body.Its mantle is brightly coloured, with four distinct colour bands (Figure 4).The dorsal part of the mantle consists of two blue and three black bands which are wider than blue ones.The bands are surrounded by a narrow white and a wide orange band, with a peripheral lining in white colour.The side of the foot, which can be seen when the animal is crawling, has the same colour as the notum.The orange colour of the lamellated rhinophores and branchial plume is darker than the mantle.
This species naturally occurs in the western Indian Ocean and the Red Sea.In the Mediterranean, it was first reported by Cattaneo-Vietti (1986) from Capo Mortola in the Ligurian Sea (northwestern Mediterranean) and subsequently by Ben Souissi et al. (2004) from the Biban Lagoon (Tunisia).C. quadricolor is here reported from the eastern Mediterranean for the first time.
As for its occurrence in the Mediterranean, Zenetos et al. (2003, p 195) indicated the mode of introduction of this species as unknown, but possibly being an accidental release from a tropical aquarium.The area, where the single specimen has been found (station 5) is along a shipping route and because the region is open to the tourism, no mariculture activities are in close vicinity.Its mode of introduction as proposed by Zenetos et al. (2003, p 195) should be considered as questionable.In contrast, Ben Souissi et al. (2004, p 312) assume Lessepsian migration as its mode of introduction.Further specimens collected from other localities in the Mediterranean may reveal a clearer picture of the mode of introduction.
There are many Chromodoris species in the world's oceans and the most important reliable criterion used for species identification is the colour pattern of the notum, foot, oral tentacles, gills and rhinophores (Rudman 1973, p 176) (Dekker and Orlin 2000, p 36), this is the only species that has immigrated into the Mediterranean.
According to Rudman (1977), C. quadricolor has been misidentified as Chromodoris africana Eliot 1904 in several studies such as with some reports from the Red Sea.According to the same author (p 374), C. quadricolor differs from C. africana by its colour, body shape and radula.Although C. quadricolor has four colours (black, blue, orange and white), C. africana does not have blue colour on the notum.
Despite some of the immigrants may thrive in their new environment by displacing the native fauna components, so far no native Mediterranean species is reported as endangered by nonnative species (Gofas and Zenetos 2003).The number of the immigrant species into the Mediterranean will probably increase in the future and parallel to the species richness increasing, the gene pool of the recipient regions will also change.

Figure 1 .
Figure 1.Map of the study area with location of sampling stations