661 ISSN 0032-9452, Journal of Ichthyology, 2006, Vol. 46, No. 8, pp. 661–667. © Pleiades Publishing, Inc., 2006. Original Russian Text © D.D. Zworykin, S.V. Budaev, A.A. Darkov, K.F. Dzerzhinskii, B.A. Lyovin, M.V. Mina, 2006, published in Voprosy Ikhtiologii, 2006, Vol. 46, No. 5, pp. 694–701. Lake Tana, the largest lake in Ethiopia, is situated at the altitude of 1786 m above sea level and has an area of 3156 km 2 and a maximum depth of 14 m (Chorowicz et al., 1998). As in other African lakes (Mina et al., 1998), the “large African Barbus” (sensu Banister, 1973) are represented by numerous forms, some of which differ significantly in their external morphology. As a result of many years of studies, Nagelkerke and Sibbing (1997, 2000) concluded that Lake Tana is inhabited by 15 barb species, 14 of which these authors considered as morphotypes (forms of uncertain status, Nagelkerke et al., 1994). Earlier, in a revision of large barbs from Eastern and Central Africa, Banister (1973) identified all species of Lake Tana barbs as a single spe- cies Barbus intermedius Rüppell, 1836. Even earlier, Brunelli (1940) suggested that some forms are true spe- cies whereas others are morphs of a single species. The hypothesis that Lake Tana barbs represent dif- ferent biological species, that is, boundless species sensu Mayr (1974), presupposes that they are reproduc- tively isolated. Studies of the major hystocompatibility complex suggest that there may be reproductive isolation between some of them (Dixon et al., 1996; Kruiswijk et al., 2005), because individuals of different morphotypes may have no common alleles of the same gene. Nonetheless, the mechanisms of reproductive isola- tion between morphotypes, especially spawning in the same river, require specific studies. Nagelkerke and Sibbing (1996) suggested that reproductive isolation between morphotypes depends on differences in spawning time; Palstra et al. (2004) thought that indi- viduals of different morphotypes spawn at different times and in different places. However, Dgebuadze et al. (1999) have shown that individuals of different morphotypes ready for spawning may be present in the spawning grounds at the same time. They suggested that even though temporal and spatial segregation of barb morphotypes from Lake Tana could facilitate their reproductive isolation, this segmentation could hardly prevent their interbreeding (p. 420), and the results of experimental spawnings (Alekseyev et al., 1996) revealed no postzygotic isolation between them. It was concluded that if there is reproductive isolation, it should be based mainly on differences in spawning behavior (Dgebuadze et al., 1999, p. 417). The same authors particularly noted that visual discrimination is very difficult because water in the spawning river is extremely turbid, the fish spawn mostly at the dark time, and the morphotypes have no specific visual dis- crimination signs (stripes, spots, etc.) Thus, it is reasonable to suppose that if reproductive isolation does exist, it should be based on prezygotic mechanisms and involve chemoreception. The signifi- cant role of chemical signals in mate choice is well doc- umented in fish (Partridge et al., 1976; Ryan, 1990; Andersson, 1994; Sorensen and Stacey, 1999). Even in cichlids (fam. Cichlidae), in which mate choice is pri- marily based on vision, chemoreception plays an important role (Crapon de Caprona, 1974; Jordan et al., 2003). Moreover, chemoreception helps fish of many species to distinguish mature conspecifics of the oppo- site sex from mature individuals of closely related spe- cies (McLennan, 2004; Wong et al., 2005). In this study, we assessed the role of chemical sig- nalization in the reproductive behavior Lake Tana barbs. We tried to determine whether the barbs use Assessment of the Role of Chemoreception in the Mate Choice in Barbs of the Barbus intermedius Complex from Lake Tana, Ethiopia D. D. Zworykin a , S. V. Budaev a , A. A. Darkov a , K. F. Dzerzhinskii a , B. A. Lyovin a , and M. V. Mina b a Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Leninskii prospekt 33, Moscow, 119071 Russia b Kol’tsov Institute of Developmental Biology, Russian Academy of Sciences, ul. Vavilova 26, Moscow, 119991 Russia E-mail: zworykin@zevin.ru Received July 4, 2005 Abstract—The role of chemoreception in mate choice was studied in barbs of the complex Barbus intermedius from Lake Tana. It was found that chemical communication may be used in reproductive interactions of the barbs, and that males are responsible for the choice. Mature males tend to prefer ripe females and avoid both immature females and mature males, or are indifferent to them. It was shown that selectivity in mate choice by certain barb morphotypes could reduce the probability of interbreeding between different morphotypes, but not pro- vide for reproductive isolation between them. It was hypothesized that the mate groups are finally formed as a result of direct interactions between potential partners, mediated by tactile reception or specific behavioral patterns. DOI: 10.1134/S0032945206080133