46
Table 9. Matrix genetic distance between all of species-subspecies on genus Anguilla. Grey highlights one is species-subspecies during this study. Standar errors SE was showed above diagonal. Analysis conducted under Kimura 2-parameter
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 1. A. b. bicolor
0,004 0,011 0,008 0,008 0,008 0,008 0,010 0,009 0,011 0,010 0,010 0,011 0,011 0,008 0,010 0,009 0,010
2. A. b. pacifica 0,023
0,011 0,008 0,008 0,009 0,008 0,010 0,009 0,011 0,010 0,010 0,011 0,011 0,008 0,010 0,010 0,010
3. A. borneensis 0,103 0,100
0,010 0,009 0,010 0,010 0,011 0,010 0,011 0,011 0,010 0,010 0,010 0,010 0,010 0,010 0,010
4. A. celebesensis 0,077 0,074 0,089
0,008 0,008 0,008 0,008 0,009 0,011 0,010 0,008 0,008 0,010 0,009 0,009 0,008 0,009
5. A. interioris 0,067 0,063 0,081 0,062
0,007 0,007 0,009 0,006 0,011 0,010 0,009 0,010 0,011 0,007 0,010 0,009 0,010
6. A. marmorata 0,072 0,070 0,087 0,065 0,048
0,008 0,010 0,007 0,011 0,011 0,008 0,009 0,011 0,008 0,011 0,010 0,010 7. A. n. nebulosa
0,063 0,063 0,092 0,068 0,051 0,057 0,009 0,008 0,011 0,010 0,009 0,009 0,010 0,008 0,010 0,009 0,010
8. A. megastoma 0,089 0,087 0,096 0,061 0,075 0,072 0,080
0,011 0,010 0,011 0,010 0,010 0,012 0,010 0,010 0,009 0,010 9. A. luzonensis
0,075 0,070 0,088 0,075 0,043 0,053 0,056 0,090 0,011 0,010 0,009 0,010 0,010 0,008 0,011 0,010 0,011
10. A. mossambica 0,101 0,101 0,097 0,096 0,098 0,096 0,099 0,093 0,102
0,010 0,010 0,011 0,011 0,011 0,010 0,010 0,010 11. A. rostrata
0,097 0,094 0,098 0,094 0,096 0,090 0,092 0,104 0,093 0,095 0,010 0,011 0,007 0,010 0,010 0,010 0,010
12. A. reinthardtii 0,083 0,083 0,087 0,070 0,076 0,063 0,068 0,079 0,075 0,088 0,091
0,009 0,011 0,009 0,010 0,009 0,010 13. A. japonica
0,102 0,096 0,094 0,073 0,082 0,074 0,076 0,079 0,085 0,093 0,094 0,062 0,011 0,010 0,011 0,009 0,011
14. A. anguilla 0,108 0,101 0,095 0,101 0,095 0,095 0,097 0,104 0,092 0,102 0,046 0,096 0,099
0,011 0,011 0,010 0,011 15. A. obscura
0,068 0,062 0,088 0,074 0,056 0,060 0,063 0,083 0,058 0,104 0,092 0,075 0,084 0,096 0,011 0,010 0,011
16. A. a. australis 0,095 0,089 0,079 0,076 0,085 0,086 0,091 0,085 0,096 0,084 0,084 0,080 0,087 0,086 0,097
0,008 0,001 17. A. diefenbachii
0,079 0,075 0,077 0,061 0,073 0,079 0,069 0,074 0,076 0,081 0,078 0,072 0,074 0,079 0,080 0,061 0,008
18. A. a. scimidthi 0,094 0,088 0,080 0,075 0,084 0,085 0,090 0,083 0,095 0,084 0,082 0,079 0,088 0,085 0,095 0,001 0,060
Table 10 Genetic distance within species and sub species.
Species Genetic distance within
species SE
A. marmorata
0,0055 0,0013
A. interioris
0,0058 0,0015
A. n. nebulosa
0,0035 0,0011
A. b. pacifica
0,0040 0,0010
A. b. bicolor
0,0080 0,0018
A. celebesensis
0,0063 0,0015
A. borneensis
0,0013 0,0010
A. marmorata LOM.1 A. marmorata PAP.12 SANG.5
A. marmorata BAL.42 A. marmorata AMB.21 LAS.89 PAL.5 PAP.2.8 BAL.29 POIG.1.17 INO.47
A. marmorata BAL.5 LOM.3.4 LAS.161.32 POS.18 A. marmorata PAP.6
A. marmorata BAL.30 A. marmorata PAL.3
A. marmorata OBI.11 A. marmorata BAL.1 AMU.32
A. marmorata LAS.149.3 A. marmorata BAL.51.7 LAS.120.77 LOM.6.7 PAP.1 SANG.10 PEL.501.126 POS.24
A. marmorata PAL.1 A. marmorata BAL.8
A. marmorata POS.20 A. marmorata LOM.5 BAL.12.21A MEN.2 POS 57B OBI.4
A. marmorata POS.1 A. marmorata SANG.8
A. marmorata PAL.4 A. marmorata LAS.1 POS.7
A. marmorata PAP.7 A. marmorata AMU.46
A. marmorata LAS.124 A. marmorata POIG.8
A. marmorata PEL.12
Cla de 1
A. marmorata BAL.50 LAS.104 SANG.1 INO3 A. marmorata INO.1
A. marmorata A. marmorata POS.72
A. marmorata MEN.5 A. marmorata PAP.16
A. marmorata BEN.6 PEL.183 A. marmorata PAP.5
A. marmorata AMB.63 A. marmorata PAP.9
A. marmorata BEN.23 A. marmorata AMB.7
A. marmorata BEN.20.24.30.2 MEN.23.41.17 PEL.257.17.192 ACE.35 A. marmorata BEN.31
A. marmorata ACE.36 A. marmorata MEN.27
A. marmorata PAP.4 A. marmorata MEN.32A OBI.1
A. marmorata POS.2 A. marmorata POS.3
Cla de 2
C
Figure 7. Neighbor Joining NJ phylogentic tree of all sequence in this study based on 950 bp of mitochondrial DNA cyt b gene fragmen under Kimura 2-parameter model up
75.
la de 1
A.interioris MEN.4 A.interioris MEN.44
A.interioris PAP.15 A.interioris MEN.2A POS.57A
A.interioris PAP.11
Cla de 2
A.interioris MEN.13 A.interioris MEN.26
A.interioris MEN.1 A.interioris
A.interioris MEN.12 A.interioris PAP.13
A.interioris PAP.14 POS.9
Cla de 3
A. n. nebulosa PEL.96 A. n. nebulosa PEL.161
A. n. nebulosa PEL.113 A. n. nebulosa BEN.15
A. n. nebulosa PEL.52 A. n. nebulosa
A. n. nebulosa ACE.24 LOM.2 PEL.132 A. b. pacifica DONG.11
A. b. pacifica POIG.15 A. b. pacifica BEG.3
A. b. pacifica BEG.4 A. b. pacifica DONG.1.14.16 POIG.5 OBI.3.9
A.b.pacifica A. b. pacifica BEG.1
A. b. pacifica DONG.2 A. b. pacifica DONG.4
A. b. pacifica OBI.7 A. b. pacifica BEG.8
A. b. bicolor PEL.425 A. b. bicolor BAL.16
A. b. bicolor ACE.32 PANG.11 A. b. bicolor PAD.73 PEL.238
A. b. bicolor BEN.63 A. b. bicolor ACE.5
A. b. bicolor PEL.85.96 A. b. bicolor PAD.9
A. b. bicolor CIL.13 A. b. bicolor PANG.3
A. b. bicolor PAD.87 PEL.35 A. b. bicolor POS.16
A. b. bicolor PEL.8 A. b. bicolor ACE.9
A. b. bicolor PEL.298 A. b. bicolor BAL.21
A. b. bicolor BAL.3 A. b. bicolor PEL.105
A. b. bicolor PEL.14
Cla de 1
A. b. bicolor PAD.48 A. b. bicolor ACE.17
A. b. bicolor CIL.5 A. b. bicolor PEL.360
A. b. bicolor MEN.32 A. b. bicolor PAD.17
A. b. bicolor ACE.11 A. b. bicolor PAD.96
A. b. bicolor PAD.14 A. b. bicolor AN.927 PEL.404
A. b. bicolor PEL.63 A. b. bicolor PEL.92
A. b. bicolor PAD.3 PEL.71 A. b. bicolor ACE.29
A. b. bicolor BAL.49 A. b. bicolor CIL.2
A. b. bicolor PEL.4 A. b. bicolor BEN.39
A. b. bicolor PANG.18 A. b. bicolor PAD.60
A.b.bicolor A. b. bicolor PANG.2
A. b. bicolor PEL.339 A. b. bicolor AN923.930 CIL.10 PAD.16.31.7.56 PANG.8 PEL.500.175.390 BAL 35
A. b. bicolor BAL 55 A. b. bicolor PAD.3.75
A. b. bicolor PEL.8.308
Cla de 2
A. celebesensis BEN.33 A. celebesensis INO.20
A. celebesensis POS.16A
Cla de 1
A.celebesensis POS.25 AMU.49 A. celebesensis POS.9
A.celebesensis
Cla de 2
A. celebesensis POS.17 A. celebesensis POS.10
A. celebesensis AMU.14.1 POS.11 INO.14 A. celebesensis POS.19
Cla de 3
A.mossambica
A. borneensis MAH.1 A. borneensis MAH.2
A.borneensis A. borneensis MAH.3
Serrivomer sector
99 99
90 99
99 90
99 99
90 99
99 86
95
0.08 0.06
0.04 0.02
0.00
47
Relationship among and within species was also supported by Kimura 2- parameter genetic distances we present genetic distance within and between
species on Table 9 and Table 10 respectively. A. b. bicolor and A. b. pacifica has closed relationship genetic distance 0,023 than other pairs. Whereas farthest
genetic relationship we found between A. borneensis with other species, there were 0.081, 0.087, 0.089, 0.092, 0.100 and 0.103 with A. interioris, A.
marmorata, A. celebesensis, A. n. nebulosa, A. b. pacifica and A. b. bicolor respectively.
Allopatric Divergence of A. bicolor The construction a NJ phylogenetic tree of all speciemen on this study
confirming a significant genetic differentiation between A. b. bicolor and A. b. pacifica that supported by strong bootstrap value were 100 replications and low
genetic distance between two subspecies. A. b. pacifica is composed the population from eastern part of Indonesia water Bengalon, Donggala, Poigar and
Obi, see location in Appendix 1. The nucleotide divergence within this subspecies is ranked between 0-3. Accordance table frequence haplotype, A.
b. pacifica have one common haplotype Hap. 70 that share on all population. While A. b. bicolor is composed the population from western part of
Indonesia water Aceh, Padang, Bengkulu, Pelabuhan Ratu, Cilacap, Pangandaran and Bali, see location in Appendix 1. The nucleotide
differentiation within this subspecies is ranked between 0,2-3 Table.11 Accordance table frequence haplotype, A. b. bicolor also have one common
haplotype Hap. 120 that share on all population. The NJ phylogenetic tree of cyt b also reveal important genetic divergence for two clade of A. b. bicolor with
strong bootstraps; 82 bootstrap replications for clade B1 and 86 for clade B2 Figure 7. Both of clade was supported by nonsynonymous mutation on codon
161 with a change Glycine G on clade 1 into Tryptophan W on clade 2. Genetic distance of two clade is 0,0180 SE=0,003 under K2P analysis. Even A.
b. bicolor separated two distinct monophyletic clade however not supported by unique distribution, probably they plays the sympatric speciations.
Allopatric speciation has led mutations on cyt b sequences of A. b. bicolor were 16 nucleotide of 1042 sequence. Table 12 showed the mutation position on
cyt b sequence on this study. Nonsynonymous mutation n=3 also found on cyt b
48
sequence of A. b. bicolor and A. b. pacifica that alter amino acid differences Table 12.
Table 11 Intraspecific genetic differentiation measured within A. bicolor species
No Sub species
Sample site n
specimen analysed
Nhp
π 1
A. b. bicolor Aceh 6
6 0,871
2 A. b. bicolor
Padang 16 10
0,572 3
A. b. bicolor Bengkulu 2
2 1,344
4 A. b. bicolor
Pelabuhan Ratu 27
22 2,632
5 A. b. bicolor
Pangandaran 5 4
0,557 6
A. b. bicolor Cilacap 5
5 0,729
7 A. b. bicolor
Bali 6 5
0,723 8
A. b. pacifica Bengalon 4
4 0,464
9 A. b. pacifica
Donggala 8 6
0,247 10
A. b. pacifica Obi 2
1 0,000
11 A. b. pacifica
Poigar 4 4
3,439 Total 16
85 69
11,578
Average
6,27 1,053
nucleotide divergence π of A. b. bicolor n=67 = 1,061 and A. b. pacifica n=18 = 1,037
Table 12. Mutation on nucleotide sequence above and amino acid below between A. b. bicolor and A. b. pacifica
198 306
447 464
582 600
675 693
709 723
750 780
828 840
882 900
A. b. bicolor
T G
C C
G G
G A
A T
T T
C T
C G
A. b. pacifica
C A
T T
A A
A G
T C
C C
T C
T A
A. b. bicolor
A. b. pacifica
Methionin M
Isoleucine I
Leucine L
Nucleotide mutations nt‐
Amino acid mutations codon‐
Serine S
Leucine L
Isoleucine I
153 231
237
A Wide Distribution of A. marmorata A. marmorata was found nearly in all sampling locations except Padang,
Cilacap, Pangandaran and Bengalon due to the limitations of this study. Alignment of 1042 bp of cyt b from 92 individuals of A. marmorata which
collected from 16 locations has 99 polymorphic sites 10,42. The quantities of nucleotide diversity from each population presented in Table 13 with rank 0,08-
6,9. Nucleotide diversity average were 0,973±0,004 . A branch of A.
marmorata on NJ phylogenetic tree Figure 4 was supported by 100 replications bootstrap. This branch separated into two clades but by weak support bootstrap
72 and 56 for clade 1 and clade 2 respectively. Clade 2 run into nonsynonymous mutation from clade 1 where Isoleucine I on codon 120 change being
Methionine M.
49
A. marmorata has three common haplotypes Hap5, 6, 17 and 27 were share on wide populations. Nevertheless this species also have a specific
haplotype that found only in specific region, such as Hap48 only found in the western part of Indonesian waters and absent in eastern part of Indonesia,
whereas Hap13 found only in eastern part of Indonesian waters and absent in western part of Indonesia.
Table 13 Intraspecific genetic differentiation measured within A. marmorata species
No Code
Sample site n
speciment analized
Nhp
1 Ace Aceh
2 2
6,910 ± 0,03455 2
Men Mentawai
8 5
0,295 ± 0,00073 3
Ben Bengkulu
7 4
0,084 ± 0,00028 4
Pel Pelabuhan Ratu
7 4
2,221 ± 0,01246 5
Bal Bali
12 10
1,401 ± 0,00902 6
Lom Lombok
6 5
0,313 ± 0,00103 7
Las Lasusua
9 6
0,288 ± 0,00060 8
Pal Palu
4 4
0,400 ± 0,00086 9
Pos Poso
9 8
0,538 ± 0,00107 10
Sang Sangata
5 5
0,365 ± 0,00079 11
Poig Poigar
3 2
0,192 ± 0,00090 12
Amu Amurang
2 2
0,384 ± 0,00192 13
Ino Inobonto
3 3
0,448 ± 0,00083 14
Obi Obi
3 3
0,576 ± 0,00202 15
Amb Ambon
3 3
0,576 ± 0,00193 16
Pap Papua
9 8
0,581 ± 0,00073 16
92 74
15,572 ± 0,0697 4,63
0,973 ± 0,0044 π
Total Average
Discussion
This is the first study of phylogenetic relationship and genetic diversity based on mitochondria DNA cytochrome b gene of Anguilla that covering all of
the geograpical distribution in Indonesian waters. According to Avice et al. 1986, providing an adequate description of the genetic structure of populations
that responsible for a given genetic architecture and evolutionary factors is an important objective of population genetics. In this study we present genetic
diversity and phylogenetic relationship among and within species in genus Anguilla to understanding the evolutionary process of Anguillid that inhabit in
Indonesia waters.
50
Genetic diversity Seven species of Indonesian tropical eel shows a higher haplotype
diversity at the cyt b locus range 0,93 to 1,00 compare to same locus in another species, Anguilla anguilla in eropa range 0,62 to 0,82, Daemen et al. 2001;
0,78 by Avise et al. 1998 and almost as same as with A. japonica 0,97 by Sang et al. 1994 and 0,96 by Ishikawa et al. 2001. The haplotype variation we
observed at the cyt b locus was 63,4 considerable 135 haplotype, in 213 eel specimens, this different haplotype is lower than other species as follow
Japanese flounder 98, N=82, Fuji and Nishida 1997, Japanese eel 98, N=55, Ishikawa et al. 2001. The molecular marker used in this study cyt b
showed high level of polymorphic site 20,48 compared with D-loop locus on other Anguilla, A. japonica 11 , Sang et al. 1994 and 17, Ishikawa et al.
2001 and A. anguilla 0,4 by Daemen et al. 2001. Sequence divergence in this study 0,1-1,06 lower with A. japonica 1,1-1,6, Ishikawa et al. 2001 and
higher than A. anguilla 0,2-0,5, Daemen et al. 2001. The comparison indicated that Indonesian tropical eel has various of
haplotype and frequency of variable site relatively higher than temperate eel A. anguilla and as same as Japan eel A. japonica, nevertheless the degree of
sequence difference and haplotype different among Indonesia ees almost lower than other species. If there was any genetic heterogenity on Indonesia eel
species, the level of nucleotide diversity should be also high, this variability pattern probably reflect the history of the Anguilla that they were migrated from
the sea to the freshwater on their life cycle, so the specimen collection should be represent the seasion or using more specimen is needed. It is could be seen on
genetic diversity of A. boorneensis and A. n. nebulosa that have a few amount of specimen, so the genetic diversity of both species is still questionable. In
addition, the causes of low nucleotide diversity of A. borneensis may be due to single panmictic population or single spawning population, A. borneensis is an
endemic species from Borneo Aoyama et al. 2001 and Minegishi et al. 2005 with narrow dispersal. According to Ryman and Utter 1986, mating between
related individuals is inbreeding, this caused by narrow dispersal of species, so high probability to mates in the next generation. Inbreeding will be decreasing
genetic diversity Frankham 2002. The cyt b sequence of Indonesian tropical eel reveal high and significant
differences of genetic variation among seven species that observed on this study,
51
this is expected for marine fish which often using mtDNA as genetic markers because their ability to detect the population structure Ryman and Utter 1986.
Number transitions and transversions suggested that few multiple substitutions have occurred at most nucleotide position. This suggests that
substitutions at the variable position are not saturated, indicating that interspecific genetic distance observed in this study could be used to phylogenetic
construction and that genetic divergence among the taxa could be used for molecullar clokcevolutionary time calibrations Lydeard and Roe 1997.
Phylogenetic and Evolution According to Minegishi et al 2005 and Aoyama 2003 one the one hand
which causing the discrepancies determine of the basal species on the previous phylogenetic study be caused the outgroup setting. In this study we used three
species suggested by Inoue et al. 2004 that conger eel Conger myriaster, cutthroat eel Synaphobrancus kaupii and sawtooth eel Serrivomer sector as
outgroup, if the construction of phylogenetic trees using the three species separately as outgroup, will be obtained three phylogenetic with different of
topologies and basal species candidates. However, if three species used simultaneously as outgroup will be obtained phylogenetic tree as same as
topologies of Synaphobranchus kaupi species as out group, so it concluded using Synaphobranchus kauphi as outgroup most reliable.
A. b. bicolor A. b. pacifica
Figure 8. Dendogram of genetic distance of Indonesian tropical eel based on cyt b sequence,
red font : cyt b sequence from this study and black one: based on
sequence from GenBank.
AP007247 A. obscura
A. interioris
A B 4 6 9 4 3 7
A. luzonensis A. n. nebulosa
A. marmorata A. celebesensis
A P 0 0 7 2 4 3
A. megastoma
A B 0 3 8 5 5 6
A. japonica
A P 0 0 7 2 4 8
A. reinhardthii
Indo-Pacific Group
A P 0 0 7 2 4 0
A. diefenbachii
A P 0 0 7 2 3 4
A. a. australis
A P 0 0 7 2 3 5
A. a. scimidthi
Oceanic Group
A. borneensis
A P 0 0 7 2 3 3
A. anguilla
A P 0 0 7 2 4 9
A. rostrata
Atlantic-Group
AP007244 A. mossambica
A P 0 0 7 2 5 0
Serrivomer s
A B 0 3 8 3 8 8 1
Conger myaster 0.12
0.10 0.08
0.06 0.04
0.02 0.00
52
53 The topology of tree suggested that A. mossambica as basal species.
This topology almost same with the phylogenetic tree that constructed by Minegishi et al. 2005 based whole mt-DNA. Beside that the same topology of
tree, this study also found three clade of geographical distributions; Atlantic group A. anguilla and A. rostrata, Oceanic group A. dieffenbachii, autralis A. australis
and A. a. schmidtii and Indo-Pacific group A. celebesensis, A. megastoma, A. nebulosa nebulosa, A. bicolor bicolor and A. b. pacifica Figure 8. Indicating
that marker cyt b which used in this study is more reliable for phylogenetic relation.
Estimation of the divergence time of Anguilla had been calculated by Minegishi et al. 2005. The beginning of speciestion of extant angillid species
was around 20 million years ago Mya and the estimate divergence between genus Anguilla and Serivormer sector was 52 Mya. Whereas A. b. bicolor and A.
b pacifica indicated as two last species which separated around 1,6 Mya. Interestingly, the branch topology of A. b. bicolor on Figure 7 was
separated into two mayor clades that supported by the high bootstrap 93, each clade have two nucletide diagnostic Table 8 even they dont have
subspecies nucleotide diagnostic. This indicated A. b. bicolor had two population structures. According to Li 1942 a basic of evolution process in the evolutions
of DNA sequence is the change in the nucleotide with time. The change of nucleotide sequence will separate the new sequence from the old one. After the
separation of two nucleotide sequences, each sequence will start accumulating nucleotide subtitutions and two sequences will diverge from each other. Initially,
every subtitution will increase the dissimilarity between two sequences.
V. Population Genetic Structure of Tropical eel Anguilla bicolor in Indonesia Water
Abstract
The objective of this study was to reveal the population structure of shortfinned eel, Anguilla bicolor, that inhabit in Indonesia water. The genotypes of
seven microsatellite DNA were analysed for 180 specimens collected from 10 representative location where two subspecies have been found. Analysis with
seven microsetallite loci showed Expected He and observed Ho heterozigosities of each locus range range from 0,594 to 0,921 and from 0,250 to
1,000 respectively. Significant deviation from H-Wequilibrium were detected in 26 out of 70 cases which AjTR 04 and Aro 63 locus were more informative
demonstrated with the higher average number of alleles. Whereas the genetic divergence and genetic distance between A. bicolor was from 0,20 to 5,52
and 0,241 to 0,869 respectively.
Key word; Microsatellite, A. bicolor bicolor, A. bicolor pacifica, population
structure and tropical eel.
Introduction
The shortfinned eel, Anguilla bicolor, has a relatively wide geographic distribution compared to the 19 species and subspecies of genus Anguilla, it is
distributed longitudinally from the eastern coasts of Africa through the seas around Indonesia to New Guinea in Pacific Ocean Ege 1993. The wide
distribution of A. bicolor is one of the characteristics of marine fishes including large population sizes and pelagic eggs and larvae Palumbi 1994; Ward 1994.
These characteristics, combined with the lack of physical barrier in the oceans, lead to the expectation of weak or no population structure Waples 1998.
Freshwater eels of the genus Anguilla are catadromous fish with long spawning migrations at various scales, expanding from a few hundred for tropical
eel to thousands of kilometers for temperate eel Aoyama 2009. Besides the distance migration, differences between tropical and temperate eel species occur
in the pelagic larval duration, distribution range and spawning season Arai et al. 1999, 2000. Geographic distribution of each tropical Anguillid species partly or
completely overlaps with at least one other congener in spawning area, growth 54
habitat or both, during their life cycle Aoyama 2009, questionning the origin of species distinction.
Most of freshwater eels are considered to form randomly mating panmictic populations. The mechanism producing panmixia is that individual from different
area spawn in common area in the ocean Avise et al. 1986. Two or more species have been regarded as completely panmictic, each comprising a single
and randomly mating population A. anguilla and A. rostrata as temperate species; A. borbneensis at least, as tropical species. However, recent evidence
from studies of microsatellite variation of European eel has challenged this model Wirth and Bernatchez, 2001; Daemen et al. 2001; Maes Volckaert
2002. Wirth and Bernatchez 2001 found that populations of European eel show slight but significant, genetic differentiation and genetic distance between
population, this was interpreted as geographical heterogeneity and geographic distance. This implies restricted gene flow and lack of random mating between
eels from different population. But this hypothesis has then been contreadicted by considering that the observed disequilibrium should be due to temporal
differences between samples Dannewitz et al. 2005 ; Maes et al. 2006; Pujolar et al. 2006. This question is still discussed.
Ege 1939 has described A. bicolor as composed of two subspecies, A. bicolor bicolor in the Indian Ocean and A. bicolor pacifica in the western Pacific
Ocean and the sea around the northern part of Indonesia. Allopatric distribution has led to differences in the morphology of both subspecies, Ege 1939 noticed
slight differences in their means and ranges of total number of vertebrae. Indonesia is an important biogeographic crossroad for ichthyofauna, the
western part of Indonesia is connected with Indian Ocean and the eastern one was connected with the Pacific Ocean. Concerning the widespread distribution of
A. bicolor, this exceptional geographic distribution and structure made this species an important model for eel biology understanding. While investigated at
its whole distribution scale Minegishi et al. 2011, nothing is known in Indonesian waters, such as the exact distribution and lineages differentiation
among Indonesian rivers. Beside, this species was also an important commercial fish because of its distribution and abundance.
In recent years, scientists have begun using microsatellites as a way to study within species evolution. Microsatellites are widely used as markers for
studying genetic mapping, population structures and evolutionary genetics Whirt 55