Spawning by the European eel across 2000 km of the Sargasso Sea

Miller, Michael J.; Westerberg, Håkan; Sparholt, Henrik; Wysujack, Klaus; Sørensen, Sune Riis; Marohn, Lasse; Jacobsen, Marianne; Freese, Marko; Ayala, Daniel Jiro; Pohlmann, Jan‐Dag; Svendsen, Jon Christian; Watanabe, Shun; Andersen, Lone B.; Tsukamoto, Katsumi; Munk, Peter; Hanel, Reinhold

doi:10.1098/rsbl.2018.0835

Cited by 61 publications

(47 citation statements)

References 23 publications

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“…Given the pronounced overlap of spawning region of the two Atlantic eel species and the seeming continuity of the ca. 2,000 km long frontal system in which spawning takes place (Kleckner & McCleave, ; Miller et al, ; Munk et al, ; Schmidt, ), this would seem an ideal candidate for sympatric speciation to have occurred, as also implied in one of the scenarios originally suggested by Avise et al (). Our study nevertheless refutes the possibility of strict sympatric speciation and rather points towards allopatric speciation followed by secondary contact.…”

Section: Discussionmentioning

confidence: 87%

Speciation history of European (Anguilla anguilla) and American eel (A. rostrata), analysed using genomic data

Nikolic¹,

Liu

Jacobsen

et al. 2020

Molecular Ecology

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Speciation in the ocean could differ from terrestrial environments due to fewer barriers to gene flow. Hence, sympatric speciation might be common, with American and European eel being candidates for exemplifying this. They show disjunct continental distributions on both sides of the Atlantic, but spawn in overlapping regions of the Sargasso Sea from where juveniles are advected to North American, European and North African coasts. Hybridization and introgression are known to occur, with hybrids almost exclusively observed in Iceland. Different speciation scenarios have been suggested, involving either vicariance or sympatric ecological speciation. Using RAD sequencing and whole‐genome sequencing data from parental species and F1 hybrids, we analysed speciation history based on the joint allele frequency spectrum (JAFS) and pairwise sequentially Markovian coalescent (PSMC) plots. JAFS supported a model involving a split without gene flow 150,000–160,000 generations ago, followed by secondary contact 87,000–92,000 generations ago, with 64% of the genome experiencing restricted gene flow. This supports vicariance rather than sympatric speciation, likely associated with Pleistocene glaciation cycles and ocean current changes. Whole‐genome PSMC analysis of F1 hybrids from Iceland suggested divergence 200,000 generations ago and indicated subsequent gene flow rather than strict isolation. Finally, simulations showed that results from both approaches (JAFS and PSMC) were congruent. Hence, there is strong evidence against sympatric speciation in North Atlantic eels. These results reiterate the need for careful consideration of cases of possible sympatric speciation, as even in seemingly barrier‐free oceanic environments palaeoceanographic factors may have promoted vicariance and allopatric speciation.

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Section: Discussionmentioning

confidence: 87%

Speciation history of European (Anguilla anguilla) and American eel (A. rostrata), analysed using genomic data

Nikolic¹,

Liu

Jacobsen

et al. 2020

Molecular Ecology

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“…Superimposed in (B) the square study area and the trajectory of Dennis and Floyd, with colour coding as defined in Figure 1A and American eels (Anguilla anguilla Linnaeus 1758 and A. rostrate LeSueur, respectively) (Schmidt, 1923;van Ginneken and Maes, 2005;Friedland et al, 2007;Miller et al, 2019a). Spawning and retention of larvae are associated with relatively productive zones that may enhance feeding opportunities (Kleckner and McCleave, 1988;Munk et al, 2010).…”

Section: Climatological Analysis Of Sea Surface Temperature and Chlormentioning

confidence: 99%

Oceanic response to the consecutive Hurricanes Dorian and Humberto (2019) in the Sargasso Sea

Avila-Alonso¹,

Baetens²,

Cárdenas³

et al. 2020

Preprint

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Abstract. Understanding the oceanic response to tropical cyclones (TCs) is of importance for studies on climate change. Although the oceanic effects induced by individual TCs have been extensively investigated, studies on the oceanic response to the passage of consecutive TCs are rare. In this work, we assess the upper oceanic response to the passage of the Hurricanes Dorian and Humberto over the western Sargasso Sea in 2019 using satellite remote sensing and modelled data. We found that the combined effects of these slow-moving TCs led to an increased oceanic response during the third and fourth post-storm weeks of Dorian (accounting for both Dorian and Humberto effects) because of the induced mixing and upwelling at this time. Overall, anomalies of sea surface temperature, ocean heat content and mean temperature from the sea surface to a depth of 100 m were a 50, 63 and 57% smaller (more negative) in the third/fourth post-storm weeks than in the first/second poststorm weeks (accounting only for Dorian effects) of Dorian, respectively, while surface chlorophyll-a (chl-a) concentration anomalies, the mean ch-a concentration in the euphotic zone and the chl-a concentration in the deep chlorophyll maximum were 16, 4 and 16% higher in the third/fourth post-storm weeks than in the first/second post-storm weeks, respectively. The sea surface cooling and increased biological response induced by these TCs were significantly higher (Mann-Whitney test p < 0.05) as compared to climatological records. Our climatological analysis reveals that the strongest TC-induced oceanographic variability in the western Sargasso Sea can be associated with the occurrence of consecutive TCs and long-lasting TC forcing.

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“…The spawning areas of A. anguilla and A. rostrata were discovered in the Sargasso Sea of the Atlantic Ocean ( Schmidt, 1922 ). The spawning sites are located thousands of kilometres far from their continental growth habitats in Europe and North America ( Schmidt, 1922 ; Miller et al., 2019 ), demonstrating that the Atlantic eels assemble prominently large-scale spawning migrations. The European eel spawns across at least a 2000-km area of the Sargasso Sea ( Miller et al., 2019 ).…”

Section: Evolution Of Oceanic Migrationmentioning

confidence: 99%

“…Among the 19 species/subspecies, the spawning migration patterns of A. anguilla and A. rostrata in the Atlantic Ocean and A. japonica in the northern Pacific Ocean have been studied due to their long distances and commercial importance of the species. A. anguilla and A. rostrata migrate more than 2000–8000 km for spawning migration in the Sargasso Sea ( Schmidt, 1922 ; Miller et al., 2019 ). The spawning area of A. japonica has been consequently discovered in the northwestern Pacific Ocean, and the eel migrates approximately 2000–4000 km to its growth habitat ( Tsukamoto, 1992 ).…”

Section: Introductionmentioning

confidence: 99%

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

Arai

2020

Heliyon

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Scientists have long sought to uncover the secrets of the migration of anguillid eels, genus Anguilla . As catadromous fishes, anguillid eels spend most of their lives in freshwater until they return to their spawning grounds in the tropics, although part of the population never enters freshwater and instead resides in brackish and marine areas close to coastlines. Molecular phylogenetic research suggests that anguillid eels originated from deep-ocean midwater marine anguilliform species and that tropical eels originating from the Indo-Pacific region are the most basal species of anguillid eels. Anguillid eels left the tropical ocean to colonize temperate areas. The yearly spawning of tropical species and constant larval growth throughout the year extend to periods of recruitment in continental habitats to last all year for tropical eels. Tropical eels such as A. celebesensis and A. borneensis have relatively short migrations periods of less than 100 km to their spawning grounds. Conversely, the temperate European eel A. anguilla travels the longest distances and migrates more than 5000 km across the Atlantic Ocean to spawn in the Sargasso Sea. The ancestral state of migration in the genus Anguilla may have been local, short-scale and nonseasonal spawning migration throughout the year as defined in tropical eels. With the expansion of dispersion of global oceanic migration across the world, migration scales can gradually change. Temperate anguillid eels migrate thousands of kilometres from spawning areas to coastal and inland water habitats while retaining spawning areas in tropical areas, accompanied by seasonal downstream and spawning migrations with consequences for seasonal recruitment. Recent advances and the availability of electronic tags such as pop-up satellite archival tag could reconstruct the entire spawning migration from continental growth habitats to spawning sites with detailed migration behaviours and routes. Migration ecology and mechanisms throughout the life of anguillid eels have gradually been revealed in recent decades.

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Spawning by the European eel across 2000 km of the Sargasso Sea

Cited by 61 publications

References 23 publications

Speciation history of European (Anguilla anguilla) and American eel (A. rostrata), analysed using genomic data

Speciation history of European (Anguilla anguilla) and American eel (A. rostrata), analysed using genomic data

Oceanic response to the consecutive Hurricanes Dorian and Humberto (2019) in the Sargasso Sea

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

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