Rhizaxinella elongata (Ridley and Dendy, 1886)

Topaloğlu, Bülent & Evcen, Alper, 2014, Updated checklist of sponges (Porifera) along the coasts of Turkey, Turkish Journal of Zoology 38 (6), pp. 665-676 : 672-675

Rhizaxinella elongata (Ridley and Dendy, 1886)

Material examined: One specimen from Saros Bay (station 1), 100–200 m depth, bottom-trawling (see Figure 1 ) .

Description: The species is a yellowish gray, stalked, oval, solid sponge. It has fine hispid surface and firm consistency. The body is solid, elongated, up to 6 cm long. Spicules: Styles and tylostyles, long, smooth, in 3 categories: long styles: 1750–2000 × 14–16 µm, intermediate styles: 500–2000 × 5–6 µm, and small tylostyles: 200–400 × 3–6 µm ( Figure 4 ). Previously it has been reported from the eastern Mediterranean Sea ( Carteron, 2002).

Terpios gelatinosa (Bowerbank, 1866)

Material examined: Many specimens from Ildırı Bay, Çeşme (station 2), 0–10 m, scuba diving (see Figure 2 ).

Description: It is recognizable by its blue colors. The blue or orange-yellow color persists in alcohol and in dried specimens. Oscules are minute, not distinct to the naked eye. Surface is smooth and hispid, quite thin. Spicules: only tylostyles (200–480 × 4–8 µm), have welldeveloped head. Tylostyle’s apex of the lobes is divided in various ways. Lobate swellings are a characteristic feature of the genus Terpios . Forming the skeleton, spicules are connected to each other in the form of a brush ( Figure 5 ). Terpios gelatinosa is very common on rocky substrata and the undersides of boulders. In the Mediterranean it occurs on algae and other sponges, and it occurs on the Aegean coasts and islands, where it has been recorded in various habitat types by several authors ( Pérès and Picard, 1958; Voultsiadou, 2005; Gerovasileiou and Voultsiadou, 2013).

The pioneer studies on sponges along the coasts of Turkey were carried out by Colombo (1885), Ostroumoff (1894, 1896), and Demir (1952 –1954). The species Geodia baretti was listed in the Sea of Marmara in the previous checklist by Evcen and Çınar (2012), based on reports by Colombo (1885), Ostroumoff (1894, 1896), and Demir (1952 –1954). The global distribution of the species is in the Arctic, Norway, Sweden, and North Atlantic (according to World Porifera Database, 2014). The orthotrien spicules that Demir (1952 –1954) mentioned in the description of the species are characteristic to Geodia cydonium . Topaloğlu (1999) also pointed out this fact after personal communication with RVM Van Soest. However, Geodia gigas and Geodia placenta are considered synonyms of Geodia cydonium (Jameson, 1811) ( Cárdenas, 2010; Cárdenas et al., 2013). Therefore, G. baretti , G. gigas , and G. placenta were eliminated from the checklist.

Ostroumoff (1896) reported 2 new species from the Sea of Marmara. These [ Cometella stolonifera ( Ostroumoff, 1896) and Suberites appendiculatus ( Ostroumoff, 1896) ] are actually considered to be nomen nudum ( Evcen and Çınar, 2012). According to the World Porifera Database, however, Oceanapia robusta (Bowerbank, 1866) (given by Ostroumoff, 1896) has not been recorded from the Mediterranean Sea. Therefore, O. robusta was removed from the checklist.

The highest number of species was reported from the Aegean Sea ( Sarıtaş, 1972, 1973, 1974; Kocataş, 1978; Yazıcı, 1978; Ergüven, 1988; Ergen and Çınar, 1994; Ergen et al. 1994; Kocak et al., 1999; Topaloğlu, 2001b; Çinar et al., 2002). While the Mediterranean records of Lissodendoryx isodictyalis and Rhabderemia indica (given by Sarıtaş, 1972, 1973, 1974) are considered invalid, Clathrina coriacea ( Ergüven, 1988) has not been recorded in the Mediterranean Sea according to the World Porifera Database (2014). The number of publications on sponges in the Aegean Sea is relatively high compared to the other coasts of Turkey. The area also has many suitable habitats for sponges, like rock reefs and islands. Three new records of sponges are also being reported from the Aegean Sea in the present study.

The sponge species from the Levantine Sea were reported by Gruvel (1931), Gözcelioğlu (2011), and Evcen and Çınar (2012). According to Evcen and Çınar (2012), the biodiversity of sponges has rarely been a subject of study in the Levantine Sea. The authors reported 29 sponge species in the area, 8 of which were new records for the marine fauna of Turkey. Gözcelioğlu (2011) reported 27 sponge species from the Aegean and Mediterranean coasts of Turkey and 5 of those species were new records for the marine fauna of Turkey. In total, 49 sponge species have been reported from the Levantine Sea coast of Turkey.

Only 2 species [ Dysidea fragilis (Montagu, 1814) and Suberites domuncula (Olivi, 1792) ] were reported from the western Black Sea coast of Turkey by Topaloğlu et al. (2013). Kaminskaya (1968) reported 26 sponge species, of which 5 species were endemic, for all of the Black Sea. The western part of the Black Sea may be more diverse than the eastern part for sponge species due to Mediterraneanoriginated currents that flow to the Black Sea via the İstanbul Strait.

The highest number of sponge species was reported from the Aegean Sea (82), where many suitable habitats for sponges exist, like rock reefs and islands. This is followed by the Sea of Marmara (63), where the sponge species were mostly sampled from the islands. The Sea of Marmara is called the Turkish Straits System (TSS) together with the Çanakkale and İstanbul Straits. This area also represents a biological corridor, a barrier, and a transitional zone between the Mediterranean and Black sea basins. On the other hand, the straits allow the acclimatization of certain species of Mediterranean origin such as decapod crustaceans, anthozoans, and sponges penetrating to the Sea of Marmara and Black Sea ( Öztürk and Öztürk, 1996). Therefore, many benthic species were not able to pass through the TSS and populated in the Black Sea. According to Oğuz and Öztürk (2011), one-third of benthic and pelagic taxa were able to migrate and settle successfully in the Black Sea.

According to data available, the hotspot area in terms of sponge species richness is Gökçeada, where more than 27 species were found in 2 grids (15 × 15 km) ( Figure 6 ). The other areas with relatively high numbers of sponge species are Edremit Bay , İzmir Bay, and Kaş. Almost all areas of the Black Sea (except for 2 grids) and the majority of areas of the other seas remain unexplored in terms of sponge species .

This study compiled the diversity of sponge studies for the Turkish marine fauna. Some authors reported sponge species in some specific areas, such as Ergüven et al. (1988) for Gökçeada, Topaloglu (2001a) for the Sea of Marmara, and Evcen and Çınar (2012) for the Levantine Sea. Evcen and Çınar (2012) presented a checklist for sponge fauna of Turkey with 116 species. The present study has increased the number of sponge species known from the coasts of Turkey to 131. We think that sponges are actually more diverse. More studies are needed, especially for the Black Sea coast. In this way, the actual number of sponge species in Turkey will be available, and their function in the marine ecosystem will become clearer.

Acknowledgments

We are grateful to 2 anonymous referees for their constructive comments. This work was partially supported by TÜBİTAK (Project Number: 111Y141). We thank Prof

Figures

Figure 1. Sampling stations for 3 new records (1: station 1, Saros Bay, 2: station 2, Çeşme).

Figure 2. The number of sponge species according to seas.

Figure 4. A) Photograph of Rhizaxinella elongata. B) Spicules of Rhizaxinella elongata: 1- long tylostyles, 2- intermediate tylostyles, 3- small tylostyles. Scale: 1- 300 µm, 2- 100 µm, 3- 50 µm. C) Overview of spicules.

Figure 5. A) Photograph of Terpios gelatinosa. B) Spicules of Terpios gelatinosa: tylostyles. Scale: 100 µm. C) Overview of spicules.

Figure 6. The number of sponge species along the coasts of Turkey. Each grid is 15 × 15 km in dimension.