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Updated: Jun 17, 2026
08:24
Handling and Treatment of Male European Eels (Anguilla anguilla) for Hormonal Maturation and Sperm Cryopreservation
Published on: January 28, 2018
Deep-ocean origin of the freshwater eels
Jun G Inoue1, Masaki Miya, Michael J Miller
1Ocean Research Institute, The University of Tokyo, Tokyo 164-8639, Japan. j.inoue@ucl.ac.uk
Biology Letters
|January 8, 2010
Summary
Freshwater eels originate from the deep ocean, not the seabed. Phylogenetic analysis reveals their deep oceanic origin, linked to midwater eel species, explaining their unique migratory behavior.
Area of Science:
- Marine Biology
- Evolutionary Biology
- Genomics
Background:
- Freshwater eels (genus Anguilla) exhibit a catadromous life cycle, migrating between freshwater and oceanic spawning grounds.
- Their evolutionary origin and phylogenetic placement within the predominantly marine Anguilliformes order remain unclear.
- Understanding this origin is key to deciphering their enigmatic migratory behavior.
Purpose of the Study:
- To determine the phylogenetic position of freshwater eels within the Anguilliformes.
- To reconstruct the ancestral habitat of freshwater eels.
- To elucidate the evolutionary origins of their catadromous life cycle.
Main Methods:
- Phylogenetic analysis of whole mitochondrial genome sequences.
- Inclusion of 56 species representing all 19 anguilliform families.
- Reconstruction of ancestral growth habitats using the resulting phylogenetic tree.
Main Results:
- Freshwater eels form a highly supported monophyletic group with oceanic midwater eel species.
- Phylogenetic analysis places freshwater eels at an apical position within the Anguilliformes.
- Habitat reconstruction indicates an origin from the midwater of the deep ocean.
Conclusions:
- Freshwater eels evolved from a deep oceanic, midwater-dwelling ancestry.
- This deep-sea origin likely explains their unique migratory behavior and spawning in the open ocean.
- The study provides strong evidence for the evolutionary retention of ancestral spawning behaviors.
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