Zoologica Scripta, Vol. 16, No. 3, zyxwvutsr pp. 209-222 1987 Printed in Great Britain 030&3256/87 $3.00 zy + .OO Pergamon Journals Ltd. z 0 1987 The Norwegian Academy of Science and Letters z Comparative electrophoretic analyses of three European z Carinarion species (Mollusca, Pulmonata, Arionidae) THIERRY BACKELJAU, SAYED ZABIHULLA AHMADYAR, MARCEL SELENS, JAN VAN ROMPAEY and WALTER VERHEYEN zyxwv Accepted 4 August 1986 Backeljau, T., Ahmadyar, S. zyxwvuts Z., Selens, M., Van Rompaey, J. & Verheyen, W. 1987. Compara- tive electrophoretic analyses of three European Carinarion species (Mollusca, Pulmonata, Arionidae).-Zool. Scr. 16: 209-222. Digestive gland esterases and albumen gland proteins of Arion (Carinarion) fasciatus, A. (C.) circumscriptus, A. ( C . )silvaticus, A. (Kobeltia) hortensis, A. (K.) distinctus and A. (K.) intermedius were studied using vertical polyacrylamide gel electrophoresis (PAGE) and isoelectric focusing (IEF). Each of the three Carinarion forms revealed characteristic and nearly monomorphic electrophoretic profiles. Yet some variation was also observed. Within each form the mean intraspecific similarities, calculated from IEF profiles, were high in comparison with similar figures for A. hortensis and A. distinctus. The interspecific similarities, however, were low and of about the same magnitude as those of the Kobeltia species. These results are discussed in the light of the reproductive biology of the Carinarion spp. It seems convenient to retain the three names A. fasciatus, A. circumscriptus and A. silvaticus, even though these do not necessarily refer to actual biological species. Thierry Backeljau, Sayed Zabihulla Ahmadyar, Marcel Selens, Jan Van Rompaey & Walter Verheyen, Laboratorium voor Algemene Dierkunde, Rijksuniversitair Centrum, Groenenborger- laan 171, B-2020 Antwerpen, Belgium. Introduction The slug genus Arion FCrussac, 1819 is usually divided into several subgenera (Hesse 1926), one of which is Carinarion Hesse, 1926. In western Europe this subgenus contains three forms, formerly considered as one or two species, which are treated as three separate species according to current taxonomic practice [A. (C.) fasciatus (Nilsson, 1823), A. (C.) circumscriptus Johnston, 1828 and A. (C.) silvaticus Lohmander, 1937; see, for example, WaldCn 1969; Chichester & Getz 1973; Wiktor 1973; Likharev & Wiktor 1980; Kerney et al. 1983; Grossu 1983; Gittenberger et al. 19841. However, the systematic relationships between these forms, which were originally distinguished by Lohmander (1937), are by no means well understood (Schmid 1972) and no one so far has been able to present convincing evidence to support their specific status. Because of this, Chichester (1967) started an elec- trophoretic analysis of albumen gland proteins of North American specimens of the three forms. According to Chichester & Getz (1969), WaldCn (in zyxwvu litt.) and Chiches- ter himself (in litt.), the result of these investigations clearly demonstrated the specific identity of the three forms. Unfortunately these data were never published, as no comparable information from Europe was available (Chichester in litt.) More recently, McCracken & Selander (1980) pub- lished an extensive electrophoretic survey of North American Carinarion spp. investigating the population genetics of these slugs. However, they did not mention which enzymes were studied nor which loci revealed possible specific differences. In addition, it is theoretically possible that American Carinarion populations have suf- fered from founder effects, since they were introduced into North America from native European stocks (Chichester & Getz 1969). Of course this may affect the systematic interpretation of electrophoretic data, because the investigated populations will not necessarily reflect the species’ gene pools in a representative way. Evidently this comment also applies to Chichester’s (1967) work. Therefore, Foltz et al. (19824 performed a comparable electrophoretic analysis of British and Irish Carinarion, the results of which they interpreted as indicating that the North American populations have not been influenced by founder effects. However, as we will point out in this paper, their results may just as well indicate the contrary. Moreover, Foltz et al. (19824 did not include A. fasciatus in their study. Thus, despite the above mentioned electrophoretic surveys, the systematics of the Carinarion forms are still problematic. Evidently this situation hampers further research on these slugs. The aims of the present contribu- tion may be summarized as follows: (1) to compare Chichester’s (1967) work with an analogous study of European Carinarion spp., (2) to search for possible species specific electrophoretic patterns, (3) to present a formal, but still preliminary account of the systematic relationships between the three forms and (4) to compare and evaluate the use of different electrophoretic techniques in systematic research. It should be emphasized that the terms ‘intra-’ and ‘interspecific’ will 209 Zoologica Scripta 16