New data on Roxania Leach, 1847 (Gastropoda: Heterobranchia) from the Sea of Marmara based on materials of the Russian expedition in 1894

Abstract

Heterobranch specimens of the genus Roxania collected during the Russian expedition (1894) aboard the Turkish steamship Selânik to the Sea of Marmara are found in the collection of the Zoological Institute of the Russian Academy of Sciences (Saint Petersburg). One of the aims of the expedition was investigation of the fauna of the Sea of Marmara including its deepest zone to compare with the Black Sea. In 1896 A.A. Ostroumoff published a report on the expedition. Heterobranch mollusks of the genus Roxania are represented in our material by two lots from the first voyage of the expedition to the archipelago of the Prince Islands. The specimens were identified by K.O. Milaschewitsch as Roxania utriculus (Brocchi, 1814) and “Cryptaxis imperforatus n. sp.”, but a description of the last taxon has not been published. In this study, the specimens labeled by Milachewitch as Cryptaxis imperforatus n. sp. were identified as belonging to Roxania monterosatoi Dautzenberg et H. Fischer, 1896. The species is recorded for the Sea of Marmara for the first time; the description and illustrations of the species are presented. Most species of gastropod mollusks collected during the expedition including all samples of Roxania were represented by empty shells. Taxonomical value of the columella morphology in Roxania species is discussed. Based on this character the species of the genus can be divided into two groups: R. utriculus species group (mouth channeled) and R. monterosatoi species group (mouth without a channel). Morphological and molecular phylogenetic investigations are needed to clarify the status of these two groups.