科研之友
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摘要
The species of Pseudexostoma are restricted to the upper Salween (Nujiang) and one upper branch of the Irrawaddy (Dayinjiang) rivers in China. It includes only two subspecies P. yunnanensis yunnanensis (Tchang) and P. yunnanensis brachysoma Chu. After comparing their morphology, it is discovered that they can be distinguished easily by the structure of lower lip, the shape of premaxillary tooth band, the number of branched pelvic fin rays and meristic and mensural characteristics. These two taxa are recognized as distinct species. A third species is known from Nujiang basin of China. The new species, Pseudexostoma longipterus, can be distinguished from P. yunnanensis by the following combination of characteristics: posterior margin of lower lip with three notches, depth of middle notch shallower than depth of lateral ones (vs. same depth); length of two smaller median lobes of lower lip longer than lateral lobes (vs. same length); pelvic fin i, 3-4 (vs. i, 5); base of adipose fin longer (37.8-45.1% SL vs. 28.8-39.8); caudal peduncle more slender (depth of caudal peduncle 4.6-6.1% SL and 19.6-30.8% in length of caudal peduncle vs. 6.4-8.3 and 32.6-42.7); premaxillary tooth band with 16-18 tooth (vs. 18-22); premaxillary tooth band divided into two isolated patches (vs. patches partially connected). It differs from P. brachysoma in having longer pectoral, pelvic and caudal fins (pectoral fin 30.1-31.3% SL vs. 24.9-29.8, pelvic fin 23.1-24.3% SL vs. 16.1-22.9, caudal fin 18-19.6% SL vs. 13.6-17.9); bigger eyes and a wider interorbital width (eye diameter 8.2-10% HL vs. 5.8-7.8, interorbital width 25.5-30.8% HL vs. 19.7-24.7). The geographical and ecological isolation led to speciation in Pseudexostoma.
- 出版日期2007-2-28
- 单位西南林业大学
