English: Title: Bulletin of the British Museum (Natural History) Zoology Identifier: bulletinofbritis5556farn (find matches) Year: 1989-90 (1980s) Authors: Farn, Alexander E Subjects: Publisher: London : Butterworths Contributing Library: Natural History Museum Library, London Digitizing Sponsor: Natural History Museum Library, London View Book Page: Book Viewer About This Book: Catalog Entry View All Images: All Images From Book Click here to view book online to see this illustration in context in a browseable online version of this book. Text Appearing Before Image: MONGOLIAN FISHES 195 Text Appearing After Image: Fig. 15 Oreoleuciscuspotanini 'Dwarf Form', lateral view (65 & 52 mm SL; BMNH 1986.8.28: 1048-1053). species (i.e. Oreoleuciscus potanini and Oreoleusicus pewzowi: Vasil'eva, 1982 & 1985; with judgement being reserved until further analysis of the possibility of a third i.e. Oreoleuciscus humilis: after Berg, 1948 and Dashadorzh et al., 1969), or a single polymorphic species (i.e. Oreoleuciscus potanini: Jorgansen, 1940; Kafanova, 1961; Svetovidova, 1965; Gun- drizer, 1976; Dgebuadze & Ryadov, 1978; Dgebuadze, Ermuhin, Lapin, Ryabov & Trophimenko, 1979; Borisovets etal., 1984 & 1985; Shatunovskii, 1983 & 1985). 'Ichthyophagous', 'phytophagous', 'sharp-snouted' and 'dwarf forms' of the polymorphic Oreoleuciscus potanini were described by Shatunovskii (1983), who considered them to occur throughout the water bodies of the Central Asian basin. Borisovets et al. (1985) added a 'lake form'. It is confined, together with the 'dwarf form', to the isolated water bodies of the Gobi Valley (i.e. Dolin and Hangiyn systems, see Dgebuadze, 1986, and above), whilst the other forms (i.e. 'ichthyophagus', 'phytophagous' and 'sharp-snouted') are restricted to the water bodies of the Great Lakes Valley (i.e. Kbodo and Dzavkhan River systems: Borisovets et al., 1985; Shatunovskii, 1985; and see above p. 194). The two distinct Oreoleuciscus species recognised by Vasil'eva (1985) were '... clearly differentiated' on the basis of only a single character: fusion or segmentation and branch- ing of anterior dorsal fin rays (Vasil'eva, 1985: 31, fig. 2). Analysis of this feature among my specimens from the confined population of Boon Tsagaan Nuur, revealed it to be ontogeneti- cally variable; this seriously diminishes its diagnostic value. The fishes of Boon Tsagaan Nuur were originally identified by Dashdorzh et al. (1969) as Oreoleuciscus pewzowi. The morphological variability of the specimens caught during this survey supports the view of a single morphologically plastic species and they are identified as the 'lake form' of O.potanini. This species susceptibility to sexual dimorphism or ecopheno- typic variation is recognised and associated with ontogenetic stage and reproductive state, or food source and other environmental stresses. A morphocline of intermediate stages, transitional between the forms described by Shatunovskii (1983) can be clearly recognised and lends support to the view of Borisovets et al. (1985) and Shatunovskii (1985) of a distinct 'lake form' in Boon Tsagaan Nuur. This 'form' appears to be present in other Gobi Valley lakes (e.g. Tsatsin Tsagaan Nuur) as specimens collected by the American Museum Asiatic Expedition (see Andrews, 1932 and AMNH specimens 10915, 10918, 11052, 11055, 11057, 11059, 11068, 11094 & 11111) exhibit a similar range of characters. Unfortunately, I have not had the opportunity to examine Oreoleuciscus material from the Great Lakes Valley of Western Mongolia (i.e. the 'ichthyophagous', 'phytophagous' or 'sharp-snouted forms'). Oreoleuciscus potanini Kessler, 1879 'Dwarf Form' Fig. 15 Note About Images Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.