Skip to main content Skip to main navigation menu Skip to site footer
Type: Article
Published: 2021-08-20
Page range: 509-536
Abstract views: 479
PDF downloaded: 261

A descriptive and comparative neurocranium morphology of Anguilliformes fishes in Taiwan waters

Department of Aquaculture, College of Life Sciences, National Taiwan Ocean University, Keelung, 20224, Taiwan
Institute of Ocean and Earth Sciences, Universiti Malaya, Kuala Lumpur 50603, Malaysia
Department of Aquaculture, College of Life Sciences, National Taiwan Ocean University, Keelung, 20224, Taiwan. Center of Excellence for the Oceans, National Taiwan Ocean University, Keelung, 20224, Taiwan.
Pisces Anguilliformes eel osteology neurocranium morphology


Taiwan is one of the richest in the world in terms of eel fauna. In this study, we examined the osteological and morphological characteristics of eels under order Anguilliformes. Furthermore, we focused on the neurocranium of total of 30 Anguilliformes fishes under family Congridae (10), Muraenesocidae (1), Muraenidae (7), Nemichthyidae (1), Nettastomatidae (2), Ophichthidae (5), Synaphobranchidae (4), which are caught in Taiwanese waters. This paper shows the results of a comparative study on osteological characters of the neurocranium including the ratio of seven length characters using its NCL (neurocranium length), NCW (neurocranium width), OBL (orbit length), MFW (maximum frontal width), NCDB (neurocranium depth at basisphenoid), PEVW (premaxilla-ethmovomer width) and mPOBL (mid pre-orbital length), and 20 morphological diagnostic characters for 30 eel species. Results shows that species under family Nemichthyidae and Nettastomatidae have the highest values on the ratio of NCL/MFW, NCL/NCDB, and NCW/mPOBD. In morphological characters, it shows that species of the same family mostly share similar formation of the PEV plate and frontal structure. The usage of the length measurements and morphological diagnostic characters of neurocranium allowed for a more in depth understanding of how similar or different these eels can be. The neurocranial description and morphological characters may prove valuable for identification purposes and might be necessary tool for further studies on the status of order Anguilliformes.



  1. Arai, T., Chin, T.C., Kwong, K.O. & Azizah, M.N.S. (2015) Occurrence of the tropical eels Anguilla bengalensis bengalensis and Anguilla bicolor bicolor in Peninsular Malaysia and implications for eel taxonomy. Marine Biodiversity Records, 8, e28. [published online]
    Asano, H. (1962) Studies on the congrid eels of Japan. Bulletin of the Misaki Marine Biological Institute, Kyoto University, 1, 1–143.
    Barnard, K.H. (1923) Diagnoses of new species of marine fishes from South African waters. Annals of the South African Museum, 13 (14), 439–445.
    Belouze, A. (2001) Comprehension morphologique et phylogenetique des taxons actuels et fossiles rapportes aux anguilliformes (Poissons, Teleosteens). Documents des laboratoires de géologie Lyon. No 158. Doctoral dissertation, Université Claude-Bernard Lyon 1, U.F.R. des sciences de la terre, Villeurbanne, 401 pp.
    Bleeker, P. (1852a) Bijdrage tot de kennis der ichthijologische fauna van de Moluksche Eilanden. Visschen van Amboina en Ceram. Natuurkundig Tijdschrift voor Nederlandsch Indië, 3 (2), 229–309.
    Bleeker, P. (1852b) Bijdrage tot de kennis der Muraenoïden en Symbranchoïden van den Indischen Archipel. Verhandelingen van het Bataviaasch Genootschap van Kunsten en Wetenschappen, 25 (5), 1–76.
    Böhlke, E.B. (1982) Vertebral formulae for type specimens of eels (Pisces: Anguilliformes). Proceedings of the Academy of Natural Sciences of Philadelphia, 134, 31–49.
    Böhlke, E.B., McCosker J.E. & Böhlke, J.E. (1989) Family Muraenidae. In: Böhlke, E.B. (Ed.), Fishes of the Western North Atlantic. Memoirs of the Sears Foundation for Marine Research. Vol. 1. Part 9. Sears Foundation for Marine Research, New Haven, Connecticut, pp. 104–206.
    Brevoort, J.C. (1856) Notes on some figures of Japanese fish taken from recent specimens by the artists of the U. S. Japan Expedition. In: Perry, M.C., Narrative of the Expedition of an American Squadron to the China Seas and Japan, performed in the years 1852, 1853, and 1854 under the command of Commodore M. C. Perry, United States Navy, by order of the Government of the United States, 2, 253–288.
    Castle, P.H.J. (1968) The congrid eels of the western Indian Ocean and the Red Sea. Ichthyological Bulletin, Department of Ichthyology, Rhodes University, 33, 685–726.
    Castle, P.H.J. & Smith, D.G. (1981) A revision of nettastomatid eel genera Nettastoma and Netttenchelys (Pisces: Anguilliformes), with descriptions of six new species. In: Smith, D.G., Böhlke, J.E. & Castle P.H.J., Proceedings of the Biological Society of Washington, 94 (2), 535–560.
    Chen, H.-M. & Loh, K.-H. (2007) Gymnothorax shaoi, a new species of moray eel (Anguilliformes: Muraenidae) from southeastern Taiwan. Journal of Marine Science and Technology, 15 (2), 76–81.
    Chen, H.-M., Loh, K.-H. & Shao, K.-T. (2008) A new species of moray eel, Gymnothorax taiwanensis, (Anguilliformes: Muraenidae) from eastern Taiwan. Raffles Bulletin of Zoology, 19, 131–134.
    Chen, H.-M., Shao, K.-T. & Chen, C.-T. (1996) A new moray eel, Gymnothorax niphostigmus, (Anguilliformes: Muraenidae) from northern and eastern Taiwan. Zoological Studies, 35 (1), 20–24.
    Chulin, A.K. & Chen, H.-M. (2013) Comparative morphological study of otoliths in Taiwanese Anguilliformes fishes. Journal of Marine Science and Technology, 21, 77–85.
    De Schepper, N., Adriaens, D. & De Kegel, B. (2005) Moringua edwardsi (Moringuidae: Anguilliformes): Cranial specialization for head-first burrowing? Journal of Morphology, 266 (3), 356–368.
    De Schepper, N., De Kegel, B. & Adriaens, D. (2007) Pisodonophis boro (Ophichthidae: Anguilliformes): Specialization for head-first and tail-first burrowing? Journal of Morphology, 268 (2), 112–126.
    Eagderi, S. & Adriaens, D. (2014) Cephalic morphology of Ariosoma gilberti (Bathymyrinae: Congridae). Iranian Journal of Ichthyology, 1 (1), 39–50.
    Ege, V. (1939) A revision of the genus Anguilla Shaw. Dana Rep, 16, 8–256.
    Froese, R. & Pauly, D. (2020) FishBase. WorldWide Web Electronic Publication. Version May 2010. Available from: (accessed 27 July 2021)
    Garman, S. (1888) On an eel from the Marshall Islands. Bulletin of the Essex Institute, 20: 114–116.
    Gosline, W.A. (1967) Reduction in branchiostegal ray number. Copeia, 1967 (1), 237–239.
    Günther, A. (1877) Preliminary notes on new fishes collected in Japan during the expedition of H. M. S. ‘Challenger.’. Annals and Magazine of Natural History, Series 4, 20 (119), 433–446.
    Günther, A. (1887) Report on the deep-sea fishes collected by H. M. S. Challenger during the years 1873-76. Report on the Scientific Results of the Voyage of H. M. S. Challenger, 22 (57), 1–268.
    Ho, H.C., Smith, D.G., Tighe, K.A., Hibino, Y. & McCosker, J.E. (2018) Checklist of eels of Taiwan (orders Anguilliformes and Saccopharyngiformes): An update. Zootaxa, 4454 (1), 5–17.
    Homayuni, H., Marjani, M. & Mousavi-Sabet, H. (2013) Descriptive key to the otoliths of three Sardinella species (Pisces, Clupeidae) from the northern Oman Sea. AACL Bioflux, 6 (3), 211–221.
    Huang, J.-F., Ho, H.-C., Chang, Y.-H., Smith, D. G. & Chen, H.-M. (2018) Two new species of the conger eel genus Bathycongrus (Anguilliformes: Congridae) from Taiwan. Zootaxa, 4454 (1), 107–117.
    Hulet, W.H. (1978) Structure and functional development of the eel leptocephalus Ariosoma balearicum (De La Roche, 1809). Philosophical Transactions of the Royal Society of London. B, Biological Sciences, 282 (987), 107–138.
    Inoue, J.G., Miya, M., Miller, M.J., Sado, T., Hanel, R., Hatooka, K. & Tsukamoto, K. (2010) Deep-ocean origin of the freshwater eels. Biology Letters, 6 (3), 363–366.
    James, P.S.B.R. (1985) Comparative osteology of the fishes of the family Leiognathidae part I: Osteology. Indian Journal of Fisheries, 32 (3), 309–358.
    Johnson, J.Y. (1862) Descriptions of some new genera and species of fishes obtained at Madeira. Proceedings of the Zoological Society of London, 2 (2), 167–180.
    Johnson, G.D., Ida, H., Sakaue, J., Sado, T., Asahida, T. & Miya, M. (2012) A ‘living fossil’ eel (Anguilliformes: Protanguillidae, fam. nov.) from an undersea cave in Palau. Proceedings of the Royal Society B: Biological Sciences, 279 (1730), 934–943.
    Jordan, D.S. & Snyder, J.O. (1901) A review of the apodal fishes or eels of Japan, with descriptions of nineteen new species. Proceedings of the United States National Museum, 23 (1239), 837–890.
    Kamohara, T. (1938) On the offshore bottom-fishes of Prov. Tosa, Shikoku, Japan. Maruzen Kobushiki Kaisha, Tokyo, 86 pp.
    Kanazawa, R.H. (1958) A revision of the eels of the genus Conger with descriptions of four new species. Proceedings of the United States National Museum, 108 (3400), 219–267.
    Karrer, C. (1983) Anguilliformes du Canal de Mozambique (Pisces, Teleostei). Faune Tropicale, 23 (1982), 1–116.
    Klausewitz, W. & Eibl-Eibesfeldt, I. (1959) Neue Röhrenaale von den Maldiven und Nikobaren (Pisces, Apodes, Heterocongridae). Senckenbergiana Biologica, 40 (3/4), 135–153.
    Lacepède, B.G.E. (1803) Histoire naturelle des poissons. Hureau & Monod 1973. Vol. 2. Chez F. G. Levrault, Paris, 323 pp.
    Loh, K.-H., Chen, I.-S., Randall, J.E. & Chen, H.-M. (2008) A review and molecular phylogeny of the moray eel subfamily Uropterygiinae (Anguilliformes: Muraenidae) from Taiwan, with description of a new species. The Raffles Bulletin of Zoology, 19, 135–150.
    Lopez, J.A. & Westneat, M.W. (2007) The phylogenetic affinities of the mysterious anguilliform genera, Coloconger and Thalassenchelys as supported by mtDNA Sequences. Copeia, 2007 (4), 959–966.[959:TPAOTM]2.0.CO;2
    McClelland, J. (1844) Apodal fishes of Bengal. Calcutta Journal of Natural History, 5 (18), 151–226.
    McCosker, J.E. (1998) Eels and their allies. In: Paxton, J.R. & Eschmeyer, W.N. (Eds.), Encyclopedia of Fishes. 2nd Edition. Academic Press, San Diego, California, pp. 85–90.
    McCosker, J.E. & Ho, H.-C. (2015) New species of the snake eels Echelus and Ophichthus (Anguilliformes: Ophichthidae) from Taiwan. Zootaxa, 4060 (1), 71–85.
    Mehta, R.S. (2009) Ecomorphology of the moray bite: relationship between dietary extremes and morphological diversity. Physiological and Biochemical Zoology, 82 (1), 90–103.
    Mehta, R.S. & Wainwright, P.C. (2007) Raptorial jaws in the throat help moray eels swallow large prey. Nature, 449, 79–82.
    Nelson, G.J. (1966) Gill arches of teleostean fishes of the order Anguilliformes. Pacific Science, 20, 391–408
    Ramos-Castro, M., Chen, H.-M. & Mao, B.-S. (2020) Descriptions of neurocranium morphology in 34 species of moray eels (Muraenidae) found in Taiwan. Zootaxa, 4810 (1), 81–109.
    Reece, J.S., Bowen, B.W., Smith, D.G. & Larson, A.F. (2010) Molecular phylogenetics of moray eels (Muraenidae) demonstrates multiple origins of shell-crushing jaw (Gymnomuraena, Echidna) and multiple colonizations of the Atlantic Ocean. Molecular Phylogenetics and Evolution, 57, 829–835.
    Richardson, J. (1845) Ichthyology. Part 3. In: Hinds, R.B. (Ed.) The Zoology of the Voyage of H.M.S. Sulphur, under the Command of Captain Sir Edward Belcher, R.N., C.B., F.R.G.S., etc., during the Years 1836–42. Vol. 1. Smith, Elder and Co., London, pp. 99–150.
    Richardson, J. (1848) Fishes. The Zoology of the Voyage of H. M. S. Samarang; under the Command of Captain Sir Edward Belcher, during the years 1843–1846. Reeve & Benham, London, pp. 1–28.
    Robins, C.R. (1989) The phylogenetic relationships of the anguilliform fishes. In: Böhlke E.B (Ed.), Fishes of the Western North Atlantic. Orders Anguilliformes and Saccopharyngiformes. 1 (Part 9). Sears Foundation for Marine Research, New Haven, Connecticut, pp. 9–23
    Robins, C.H. & Robins, C.R. (1971) Osteology and relationships of the eel family Macrocephenchelyidae. Proceedings of the Academy of Natural Sciences of Philadelphia, 1971, 127–150.
    Rosenblatt, R.H. (1967) The osteology of the congrid eel Gorgasia punctata and the relationships of the Heterocongrinae. Pacific Science, 21 (1) 91–97.
    Rüppell, W.P.S. in Klunzinger, C.B. (1871) Synopsis der Fische des Rothen Meeres. II. Theil. Verhandlungen der K.-K. zoologisch-botanischen Gesellschaft in Wien, 21, 441–688.
    Santini, F., Kong, X., Sorenson, L., Carnevale, G., Mehta, R.S. & Alfaro, M.E. (2013) A multi-locus molecular timescale for the origin and diversification of eels (Order: Anguilliformes). Molecular Phylogenetics and Evolution, 69 (3), 884–894.
    Stransky, C. (2005) Geographic variation of golden redfish (Sebastes marinus) and deep-sea redfish (S. mentella) in the North Atlantic based on otolith shape analysis. Journal of Marine Science, 62 (8), 1691–1698.
    Tang, K.L. & Fielitz, C. (2013) Phylogeny of moray eels (Anguilliformes: Muraenidae), with a revised classification of true eels (Teleostei: Elopomorpha: Anguilliformes). Mitochondrial DNA, 24 (1), 55–66.
    Tawa, A., Kobayakawa, M., Yoshimura, T. & Mochioka, N. (2012) Identification of leptocephalus larvae of the tiger moray Scuticaria tigrina (Anguilliformes; Muraenidae) based on morphometric and genetic evidence. Ichthyological Research, 59 (4), 378–383.
    Temminck, C.J. & Schlegel, H. (1846) Pisces. In: Siebold, P. F. de (Ed.), Fauna Japonica, sive descriptio animalium, quae in itinere per Japoniam, jussu et auspiciis, superiorum, qui summum in India Batava imperium tenent, suscepto, annis 1823–1830 collegit, notis, observationibus et adumbrationibus illustravit Ph. Fr. de Siebold. Parts 10–14. Apud Arnz et Socios, Leiden, pp. 173–269.
    Tuset, V.M., Piretti, S., Lombarte, A. & González, J.A. (2010) Using sagittal otoliths and eye diameter for ecological characterization of deep-sea fish: Aphanopus carbo and A. intermedius from NE Atlantic waters. Scientia Marina, 74 (4), 807–814.
    Vasconcelos, A.J.M. & Molina, W.F. (2009) Cytogenetical studies in five Atlantic Anguilliformes fishes. Genetics and Molecular Biology, 32 (1), 83–90.
    Watanabe, S., Aoyama, J. & Tsukamoto, K. (2004) Reexamination of Ege’s (1939) use of taxonomic characters of the genus Anguilla. Bulletin of Marine Science, 74, 337–351.
    Watanabe, S., Aoyama, J. & Tsukamoto, K. (2009) A new species of freshwater eel Anguilla luzonensis (Teleostei: Anguillidae) from Luzon Island of the Philippines. Fisheries Science, 75, 387–392.
    Wang, C.H., Kuo, C.H., Mok, H.K. & Lee, S.C. (2003) Molecular phylogeny of elopomorph fishes inferred from mitochondrial 12S ribosomal RNA sequences. Zoologica Scripta, 32 (3), 231–241.