Abstract
Although tropical anguillid eels account for two-thirds of all species in the genus Anguilla, the information on the species diversity, geographic distribution, and life histories of the tropical eels is very limited. Recent studies suggested that accurate species identification in the tropical anguillid eels needs a validation by molecular genetic analysis after morphological observation. Two anguillid eels found in Sabah, Borneo Island, were firstly identified as Anguilla marmorata Quoy et Gaimard, 1824 using morphological analysis and further analysis of mitochondrial 16S ribosomal RNA (16S rRNA) sequences confirmed the morphological species identification. The presently reported study represents the first description of A. marmorata in Sabah, Borneo Island. One-year survey suggests that representatives of A. marmorata found in the region might belong to the North Pacific population in the westernmost distribution.
Highlights
This paper describes the first confirmed record of a tropical anguillid eel, Anguilla marmorata Quoy et Gaimard, 1824, from Borneo Island
The fin difference index (FDI), which is the distance between the verticals from beginning of the dorsal fin (Z) to the anus relative to the total length (TL) (Ege 1939), was calculated as follows: FDI = 100Z ·TL–1
Resin blocks were processed routinely and paraffin blocks were sectioned at 5 μm and stained with haematoxylin-eosin for histological observation
Summary
Total length (TL) [mm] Body weight [g] Gonad weight [g] Head length (HL) [mm] Predorsal length (PD) [mm] Preanal length (PA) [mm] Distance between verticals through anus and origin of dorsal fin (AD) [mm] Predorsal length without head length (PDH) [mm] Preanal length without head length (TR) [mm] Distance from tip of lower jaw to corner of mouth (LG) [mm] Distance from perpendicular through eye centre (DEG) [mm] Length of intermaxillary-vomerine band (LV) [mm] Length of left maxillary band (LM) [mm] Number of teeth of mid part of maxillary band (NMM) [mm] Width of mid part of maxillary band (WMM) [mm] Fin difference index (FDI) [%] PA ÷ TL [%] HL ÷ TL [%] TR ÷ TL [%] PDH ÷ TL [%] Patten of colour marking of skin Sex Gonadosomatic index [%] Gonad maturity stage. 1867; based on their variegated skin and narrow maxillary SB-1 had high GSI (2.93%) and final stage of maturation bands of teeth (Ege 1939, Arai 2016, Arai and Wong 2016) of stage V (Fig. 3, Table 1). It suggests that the eel attained (Table 2). The eel specimen of SB-2 had group of the genus Anguilla with their variegated skin and the GSI value of 0.04 and the maturation stage was stage broad maxillary bands of teeth (Table 2). The geographical distribution of anguillids in Molecular identification based on 16 rRNA gene has combination with key morphological characteristics confirmed that both specimens are A. marmorata with helped to identify the eel species. Representatives of the 99% maximum identity matches with reference data in second group, A. bengalensis labiata and A. reinhardtii GenBank
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