Occurrence and ecological implication of a tropical anguillid eel, Anguilla marmorata, in Brunei Darussalam, Borneo Island

Abstract

Tropical anguillid eels account for two-thirds of the 19 species in Anguilla Schrank, 1798. However, information on the species diversity, geographical distribution, and life histories of the tropical eels is very limited. Recent studies suggested that morphological species identification of the tropical anguillid eels should be validated by molecular analysis for accurate identification. After surveying for three years, two anguillid eels were found in Brunei Darussalam, Borneo Island. They were firstly identified as Anguilla marmorata Quoy & Gaimard, 1824 using morphological analysis and further gene analysis of cytochrome c oxidase subunit I (COI) confirmed the species identification. This study is the first comprehensive description of A. marmorata in Brunei Darussalam, Borneo Island. Furthermore, it is also the first study to validate two anguillid eels collected from the tropical Bonin Islands of Japan as A. marmorata by means of morphological and COI analyses. The molecular phylogenetic tree and haplotype network analyses suggest that A. marmorata found in Brunei Darussalam would belong to the North Pacific population of the westernmost distribution.

Contrasting patterns of genetic population structure in tropical freshwater eels of genus Anguilla in the Indo-Pacific

“…These findings suggest that the transportation of the leptocephali of A. marmorata to the Sumatra and Java islands was likely not from this spawning site in the Indian Ocean but was possibly from the Pacific Ocean. Anguilla marmorata is also distributed in Brunei Darussalam [ 39 ] and Sabah of Malaysia [ 40 , 41 ] on Borneo Island, and on Bali and Lombok islands of Indonesia, which are near the Sumatra and Java islands ( Figure 1 ). Oceanic currents flow from the North Pacific and South Pacific oceans through off eastern Borneo Island (Makassar Strait) and off northern Australia to the Sumatra and Java islands [ 42 ] ( Figure 1 ).…”

Ecology and evolution of migration in the freshwater eels of the genus Anguilla Schrank, 1798

“…Thus far, six possible dispersal routes have been proposed: (1) the Tethys Sea route ( Bastrop et al., 2000 ; Aoyama et al., 2001 ); (2) the Cape of Good Hope route ( Minegishi et al., 2005 ; Tseng, 2016 ); (3) the Central American Isthmus route (Panama route) ( Lin et al., 2001 ; Teng et al., 2009 ); (4) the Arctic route ( Minegishi et al., 2005 ; Tseng, 2016 ) ( Figure 2 ); (5) multidirectional dispersion ( Minegishi et al., 2005 ); and (6): multiple radiation events ( Lin et al., 2001 ; Teng et al., 2009 ). Appropriate molecular phylogenetic studies suggest that the genus Anguilla originated from the tropical Indo-Pacific region and that A. borneensis or A. mossambica may be an ancestor distributed across the Indo-Pacific Ocean ( Aoyama et al., 2001 ; Lin et al., 2001 ; Minegishi et al., 2005 ; Teng et al., 2009 ; Tseng, 2016 ; Zan et al., 2020 ). It is absolutely certain that the Indo-Pacific region is the original central location of speciation in anguillid eels.…”

“…Phylogenetic relationships with integration of current distributions can provide valid information for the movement, dispersion and migration of species. Based on molecular phylogenetic studies of anguillid eels, A. borneensis and A. mossambica are believed to be the most plausible ancestral species ( Aoyama et al., 2001 ; Lin et al., 2001 ; Minegishi et al., 2005 ; Teng et al., 2009 ; Tseng, 2016 ; Zan et al., 2020 ), which distribute in the Indo-Pacific Ocean. The Indo-Pacific Ocean is considered as an origin of speciation in anguillid eels, and tropical ones are certainly more closely connected to the basal form than temperate ones.…”

Contribution of migratory types to the reproduction of migrating silver eels in a tropical eel, Anguilla bicolor bicolor

“…Of those tropical species, seven species were found around Indonesia in the western Pacific [ 4 , 5 ]. Tropical eels are believed to be originated in the Indonesian region as the most basal species and thereafter the catadromous eels dispersed to the temperate regions from the tropics [ 6 , 7 ]. Therefore, tropical eels could be more firmly associated to the ancestor of eels than temperate species.…”