Short Communication |
Corresponding author: Takaomi Arai ( takaomi.arai@ubd.edu.bn ) Academic editor: Nina Bogutskaya
© 2017 Siti Raudah Abdul Kadir, Mohamad Hafiz Farhan Abdul Rasid, Kok Onn Kwong, Li Lian Wong, Takaomi Arai.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Abdul Kadir SR, Abdul Rasid MHF, Kwong KO, Wong LL, Arai T (2017) Occurrence and the ecological implication of a tropical anguillid eel Anguilla marmorata from peninsular Malaysia. ZooKeys 695: 103-110. https://doi.org/10.3897/zookeys.695.13298
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Recent studies suggested that accurate species identification in the tropical anguillid eels based on morphological examination requires confirmation by molecular genetic analysis. Previous studies found that two tropical anguillid eels, Anguilla bicolor bicolor and A. bengalensis bengalensis, were found in peninsular Malaysia (West Malaysia) based on morphological and molecular genetic analyses. This study is the first record of A. marmorata in peninsular Malaysia confirmed by both morphological and molecular genetic analyses. The present study also suggests that accurate tropical eel species identification is difficult by morphological identification alone; therefore, molecular genetic analysis is needed for precise species confirmation.
Anguillid eel, giant mottled eel, molecular, species identification, tropical fish
The anguillid eels of the genus Anguilla Schrank are widely distributed throughout the world. These eels have a catadromous life history, migrating between inland or coastal growth habitats and offshore spawning locations. Nineteen species or subspecies of Anguilla have been reported worldwide, thirteen of which occur in tropical regions. Of the thirteen species/subspecies found in tropical areas, seven species/subspecies inhabit western Pacific around Indonesia and Malaysia: A. celebesensis Kaup, A. interioris Whitely, A. bengalensis bengalensis Gray, A. marmorata Quoy & Gaimard, A. borneensis Popta, A. bicolor bicolor McClelland and A. bicolor pacifica Schmidt (
Molecular phylogenetic research on freshwater eels have revealed that tropical eels are the most basal species originating in the Indonesian and Malaysian regions and that freshwater eels radiated from the tropics to colonize temperate regions (
In the present study, two anguillid specimens were collected and examined from the Pondok Upeh River, Penang Island. As
Two anguillid specimens were collected by hook and line by local people in the Pondok Upeh River in Penang Island of peninsular Malaysia on 2 April 2015 (Fig.
External measurements follow
Morphometric characteristics of Anguilla marmorata and A. bengalensis bengalensis as revealed by molecular genetic analyses.
Specimen number | SP26 | TB316 |
Species by molecular genetic | A. marmorata | A. bengalensis bengalensis |
Species by morphology | A. celebesensis | A. marmorata |
Measurements (mm) | ||
Total length (Lt) | 904 | 889 |
Standard length (SL) | 886 | 975 |
Body weight (g) | 2335 | 1579 |
Head length (HL) | 136 | 127 |
Predorsal length (PD) | 303 | 259 |
Preanal length (PA) | 403 | 395 |
Length of intermaxillary-vomerine band (LV) | 28.7 | 24.9 |
Length of left maxillary band (LM) | 30.9 | 32.1 |
Number of teeth of mid part of maxillary band (NMM) | 5 | 1 |
Width of mid part of maxillary band (WMM) | 4.4 | 1.1 |
FDI (%) | 11 | 15 |
Two mitochondrial genes, cytochrome oxidase c subunit 1 (COI) and 16S ribosomal RNA (16S rRNA), were used. DNA was extracted from a dorsal fin clip of each specimen using Gentra Puregene Tissue Kit (QIAGEN, USA), according to the manufacturer’s instructions. Total DNA concentration and quality was quantified using BioPhotometer Plus spectrophotometer (Eppendorf, Germany). Both mitochondrial cytochrome COI and 16S rRNA genes were amplified using primer pairs (Table
Gene | Primer Sequences | Sources |
---|---|---|
Cytochrome oxidase subunit I (COI) |
FF2d: 5’TTCTCCACCAACCACAARGAYATYGG3’ FR1d: 3’CACCTCAGGGTGTCCGAARAAYCARAA5’ |
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16S rRNA |
L2510: 5′CGC CTG TTT ATC AAA AAC AT 3’ H3080: 5′ CCG GTC TGA ACT CAG ATC ACG T 3′ |
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The two specimens examined in this study had variegated markings on the body (Fig.
Anguilla marmorata and A. bengalensis bengalensis collected in the Pondok Upeh River in Penang Island of Peninsular Malaysia. A Anguilla marmorata (904 mm in TL) B Anguilla bengalensis bengalensis (889 mm in TL) C Wide maxillary bands of teeth of A. marmorata D Narrow maxillary bands of teeth of A. bengalensis bengalensis. DNA was extracted from dorsal fin clip of each specimen, and hence the posterior dorsal fin of each specimen is lacking.
SP26 was assigned into the first species group of the genus Anguilla (A. celebesensis, A. interioris, A. megastoma Kaup, A. luzonensis Watanabe, Aoyama and Tsukamoto) based on the variegated skin and wide maxillary bands of teeth (
The geographical distribution of anguillids is used in combination with key morphological characteristics to determine the classification of each species into four groups. Within the first group, A. interioris, A. megastoma, A. luzonensis exist in New Guinea, Solomon Islands, New Caledonia, Fiji Islands, Cook Islands, and northern Philippines (
Within the second group, A. bengalensis labiata and A. reinhardtii exist in the mid-southeastern region of Africa and eastern Australia and Tasmania, respectively (
A total contrast was found in the species identification outcomes in the molecular genetic analysis when compared to the morphological observation. As shown in Table
Validation of species identity of collected specimens based on mitochondrial cytochrome oxidase subunit I (COI) and 16S ribosomal RNA (16S rRNA) genes using BLAST search in GenBank.
The findings from this and previous studies (
In previous studies, Anguilla marmorata was reported to exist in Langkawi Island, peninsular Malaysia (
According to
This study was financially supported by the Ministry of Higher Education Malaysia under the Fundamental Research Grant Scheme (Vot Nos. 59281 and 59406) and Universiti Brunei Darussalam under the Competitive Research Grant Scheme (Vot No. UBD/OVACRI/CRGWG(003)/161101).