Phylogeography of tropical eel (Anguilla spp) in Indonesia Waters

Abstract

The freshwater eels (Anguilla spp: Anguillidae) are popular as a commercial important food, because of good nutritional value. These fish are also a well known for their unique catadromous life histories. These species breed far from offshore after migrate thousands kilometers from their growth habitats in freshwater and estuarine to their spawning area in oceanic waters. Most of the investigations concerning eels are concentrated on temperate species, in the north hemisphere mainly because of the economic importance of these species. Nowadays, the population of temperate eel, dramatically decrease is caused by habitat damage, illegal fishing and climatic changes in the ocean. As a consequence, tropical eels become important eel nowadays in the market, as well as the research on tropical eels become a new challenge. One of primary problems in tropical eels is that they have overlapping range of most morphological character, so species identification on this genus are no more sufficient. Then molecular approaches have been proposed for eel identification. This study has four main objectives: (1) to establish quick methods of identification of tropical eels; (2) to understand exact distribution and dispersal of tropical eel in Indonesia water; (3) to reveal the phylogenetic relationship among population in Indonesia and (4) to uncover population genetic structure of Anguilla bicolor between two Ocean. All of information obtained in this study revealed the conservation management of tropical eel in Indonesia water. The semi-multiplex method was proposed in this study has demonstrated the efficiency for in identifying seven species and sub-species of tropical eels with only one step PCR. By using this method, one could reduce the number of necessary sequences while the results are very sure for each species determination (we easily identified 1112 specimens). All of species were obtained in this study showed overlapping morphology and distribution. Especially for small specimens (mainly glass eels), the molecular method appears as indispensable. This method has proven to be most simple, quicker, lower cost (no acrilamide migration), specific/sensitive, and highly reliable way. The geographic distribution of tropical eels of the genus Anguilla in Indonesian waters was establish by identified genetically of all sample that obtain during this study. The genetically identification applied the semi-multiplex PCR method that recently developed in this study. We recognized four species and subspecies with wide distribution: A. b. bicolor, A. b. pacifica, A. marmorata and A. interioris, two species with limited distribution, close to endemism: A. celebesensis and A. borneensis and one subspecies A. nebulosa nebulosa that is only spread in river flowing into Indian Ocean. The phylogenetic relationship and genetic diversity was cosntructed and calculated based on mitochondria DNA cytochrome b gene sequence of Anguilla that covering all of the geograpical distribution in Indonesia waters. 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. Seven species of Indonesian tropical eel showed a higher haplotype and nucleotide diversity at the cyt b locus with haplotype and nucleotide diversity (π) were 0,98 and 4,57% respectively. Phylogenetic tree showed A. borneensis a likely most basal species in Indonesia water. The economic important 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. 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 from 0,594 to 0,921 and from 0,250 to 1,000 respectively. All off locus showed high polymorphic. Based on FST value and clustering test, there is no structure and fragmentation of A. bicolor in Indonesia water. A critical first step in species conservation is to gain a clear understanding of its taxonomy. Considering Indonesian waters that are inhabited by several sympatric species of tropical eels, almost all morphological character in this genus are overlapping. So a rapid and efficient identification technique is needed. Semi multiplex PCR that has been developed in the present study has successfully distinguished seven species that inhabit the waters of Indonesia through one-step PCR. After established the identification species subspecies methods then we constructed distribution and dispersal pattern, phylogenetic relationship among species that inhabit Indonesian water and population genetic structure of species that have widespread distribution. All of information obtained in this study was needed for conservation management of anguillid in Indonesian water.