Aquatic Invasions (2006) Volume 1, Issue 4: 241-244 DOI 10.3391/ai.2006.1.4.7 © 2006 The Author(s) Journal compilation © 2006 REABIC (http://www.reabic.net ) This is an Open Access article 241 Research article Indo-Pacific species in the Mediterranean. 5. Chrysallida micronana nom. nov. for Chrysallida nana (Hornung and Mermod, 1924) (Gastropoda: Pyramidellidae) Bilal Öztürk 1* and Jacobus J. van Aartsen 2 1 Ege University, Faculty of Fisheries, Department of Hydrobiology, 35100 Bornova, Izmir, Turkey E-mail: bilal.ozturk@ege.edu.tr 2 National Museum of Natural History Naturalis, P.O.Box 9517, NL2300 RA Leiden, The Netherlands E-mail: vanaartsen@hetnet.nl *Corresponding author Received 13 November 2006; accepted in revised form 28 November 2006 Abstract The occurrence of the alien species Chrysallida micronana [nom. nov. for Chrysallida nana (Hornung and Mermod, 1924) not Adams, A., 1861] (Gastropoda: Pyramidellidae) in the Mediterranean was investigated. In studies performed between 1997 and 2000, a total of 6 specimens were encountered from the Turkish coast of the Levantine and Aegean Seas. Descriptions of morphological features of the shell, along with the ecological and distributional aspects of the species are provided. Key words: Mollusca, Gastropoda, Pyramidellidae, Pyrgulina nana, Chrysallida micronana, nomen novum, alien species, Mediterranean Sea Introduction The genus Chrysallida Carpenter 1856 is one of the genera within the Pyramidellidae with many representatives in the Mediterranean Sea (Sabelli et al. 1990). Since Nordsieck's study in 1972, the first modern reviser of the genus Chrysallida, a lot of research covering this genus was realized, including some revisions (e. g. van Aartsen 1977, van der Linden and Eikenboom 1992, Nofroni and Tringali 1995, van Aartsen and Menkhorst 1996, Peñas et al. 1996, Micali and Nofroni 2004). As for the Mediterranean fauna, the Chrysallida species distributed in this ecosystem are heterogeneous concerning their origin. Although some of them are Atlanto- Mediterranean, boreal or endemic in the Mediterranean, others are alien species, reached into the Mediterranean by various means. Nowadays, according to Mienis (2004), three alien Chrysallida species (C. fischeri, C. maiae and C. pirinthella) are known from the Mediterranean, inhabiting the Levantin Basin. The first two species of which are considered to have entered into the region through the Suez Canal and the third one to have been transferred possibly via the Suez Canal. These species also have been reported from the Turkish Levantine coast in various studies (Tringali and Villa 1990, Micali and Palazzi 1992, Buzzurro and Greppi 1995) performed in the area during the last two decades. Among the samples taken from Turkish coasts between 1997 - 2000, another alien Chrysallida species was found at two stations along the Turkish Levantine and Aegean Sea coasts. The present study, which is the fift of the series Indo-Pacific species in the Mediterranean fallowing Aartsen 2002; Aartsen 2006; Aartsen and Goud 2006 and Aartsen and Hori 2006, is dealing with this additional species, being reported for the first time from the Mediterranean.