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Abstract

Otoliths are calcareous structures found in the labyrinth membrane in the otic capsules of teleost fishes and are constituted of three pairs: the sagittae, lapilli and asterisci. They have long been recognized as being species specific. A comparative morphology of the sagittae, asterisci and lapilli among six eel species of Anguilliformes belonging to the Family Congridae, Muraenesocidae and Muraenidae was studied. A total of 64 specimens belonging to Bathyconger wallacei (n = 23), Conger japonicus (n = 9), Muraenesox cinereus (n = 10), Echidna polyzona (n = 4), Gymnothorax eurostus (n = 4) and Gymnothorax reticularis (n = 14) were collected from Tungkang, Chengkung, Changbin and Nanfangao, Taiwan, during the months of January and February 2013. The three pairs of otoliths were extracted from the otic capsules of the eels and observed by light and scanning electron microscopy. The morphology of the sagitta showed differences in shape among B. wallacei, C. japonicus, M. cinereus and G. reticularis, but similar shapes between E. polyzona and G. eurostus. While the morphology of the lapillus showed some similarities in shape among B. wallacei and C. japonicus and among M.cinereus, E. polyzona, G. eurostus and G. reticularis. The results also showed that the asteriscus is capable of conveying species specific information, with the asteriscus of each species varying in form. The three otolith types were the largest in C. japonicus and M. cinereus and the smallest in E. polyzona, G. eurostus and G. reticularis. The usage of the three pairs of otoliths allows for a more informative differentiation between the Anguilliformes species in Taiwan.

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