文獻來源: Cox Fernandes, C., Lundberg, J.G. and Sullivan, J. P. 2009. Oedemognathus exodon and Sternarchogiton nattereri (Apteronotidae, Gymnotiformes): the case for sexual dimorphism and conspecificity. Proceedings of the Academy of Natural Sciences of Philadelphia, 158: 193-207.裸背電鰻科(=光背電鰻科)的頭型與吻部的極端雌雄二型性, 以及不同雄性個體間極大的多態型在1990年代之後開始被發掘並正視其對分類系統的影響, Cristina Cox Fernandes則是近年對於這個議題研究最力的學者, 無論是黑傑克飛刀, 火鶴飛刀或是恐龍飛刀都是她近年的重要研究成果. 在這篇文章中她與她的同事闡明了豬鼻飛刀(Oedemognathus exodon)(亦稱腫齒裸背電鰻)與納氏寬兇裸背電鰻(Sternarchogiton nattereri)其實是同一個物種, 而雄性齒列的誇張外翻則可能與種內競爭有關. Sazima雖然在1983年對於食鱗性魚類的整理中列舉了豬鼻飛刀, 但是這項推測目前並沒有被任何的(包括我們的)飼養經驗所證實. 台灣在近幾年所進口的"龍鱗飛刀"(如下圖)是否為Sternarchogiton nattereri則還需要進一步的鑑定.
Abstract
Oedemognathus exodon, a monotypic genus and species of Amazonian apteronotid electric fishes, is based on a single specimen with uniquely externalized jaw teeth projecting from a bulbous snout. Recently, many additional specimens of Oedemognathus, all mature males, have been collected in the Amazon by trawling in channels and seining in floating vegetation mats. These new specimens were collected with many monomorphic female, male and immature specimens of Sternarchogiton nattereri, a related and similar species. On this basis we suggested a hypothesis of sexual dimorphism and conspecificity for O. exodon and S. nattereri. Although this idea has been taxonomically accepted by recent authors with treatment of O. exodon as a junior synonym of S. nattereri, the evidenciary basis for this remains unpublished. Herein we present that evidence. In addition to being associated at sexual maturity during breeding season, S. nattereri and O. exodon are closely similar in external and internal morphology, pigmentation, and mitochondrial cytochrome b sequences. Furthermore, we observe that the striking dentition, jaw and snout morphology of Oedemognathus has its developmental origin in mature males that are equal, or nearly so, in size to non-dimorphic S. nattereri.
