Overview

Brief Summary

Living Fossil

Protoanguilla palau is a species of eel, the only species in the genus Protoanguilla (lit., "first eel") which is in turn the only genus in its family, Protoanguillidae. The Palauan primitive cave eel (Protanguilla palau) has an evolutionary history that dates back some 200 million years. Individuals were found swimming in March 2010 in a deep underwater cave in a fringing reef off the coast of Palau. The body is very small and slender, about 18 cm long. They have a second premaxilla and under ninety vertebrae, features previously found only in fossilized eels. Their full set of gill rakers in their branchial arches have never previously been found in an eel but are common in bony fish. It is so different from all other living eels that scientists estimate that it must have diverged from the others around 200 million years ago, during the Mesozoic Era. It thus has not only its own species, but its own genus and family as well, and has been referred to by scientists as a "living fossil".

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Comprehensive Description

Biology

Cave species (Ref. 87802).
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Distribution

Asia: Republic of Palau. Presently known from a western fringing reef of Ngemelis Island, in a reef cave at 35 m depth.As an elopomorph, it almost certainly has a leptocephalus larval form, and letptocephali (particularly those of anguilliforms) are known to have long planktonic durations (2–10 months). Accordingly, the authors believe that Protoanguilla probably has a considerably broader distribution than currently known, even though no leptocephali matching its unique meristic formula (fewer than 90 vertebrae, more than 170 dorsal fin and anal fin rays) have been identified in extensive worldwide larval fish collections. In any case, historically, the Protoanguilla lineage, estimated to have diverged ca 200Ma, must have been much more widely distributed, because the Palau-Kyushu Ridge formed only around 60–70 Ma (Ref. 87802).
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Physical Description

Size

Max. size

17.6 cm TL (female)
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Diagnostic Description

Gill opening terminates as ovoid tube with low, fringed collar; pseudobranch present; knob-like, toothed gill rakers present; premaxilla present, autogenous; symplectic autogenous; metapterygoid present; anterior end of vomer with small, ovoid, autogenous toothplate; body relatively short, total vertebrae 87 or fewer (79–87, mean ¼ 83.3); hypurals 3 and 4 not fused to each other; pterosphenoid not excluded from posterior margin of orbit (Ref. 87802).
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Ecology

Habitat

Environment

reef-associated; marine; depth range 35 - ? m (Ref. 87802)
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Evolution and Systematics

Evolution

Divergence Time

The divergence time analyses are based on the topology that places Protanguilla as the sister group of all other eels. The resultant timetree indicates that Protanguilla diverged from other eels during the Triassic–Jurassic boundary around 220 Ma. (Johnson et al, 2011)

  • Johnson, G. David, Hitoshi Ida, Jiro Sakaue, Tetsuya Sado, Takashi Asahida and Masaki Miya. 2011. A ‘living fossil’ eel (Anguilliformes: Protanguillidae, fam. nov.) from an undersea cave in Palau. Proceedings of the Royal Society B. vol. 279 no. 1730 934-943.
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Molecular Biology and Genetics

Molecular Biology

Barcode data: Protoanguilla palau

The following is a representative barcode sequence, the centroid of all available sequences for this species.


No available public DNA sequences.

Download FASTA File
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Statistics of barcoding coverage: Protoanguilla palau

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 1
Specimens with Barcodes: 1
Species With Barcodes: 1
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Conservation

Threats

Not Evaluated
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Wikipedia

Protanguilla

Protanguilla palau is a species of eel, the only species in the genus Protanguilla (first eel) which is in turn the only genus in its family, Protanguillidae. Individuals were found swimming in March 2010 in a deep underwater cave in a fringing reef off the coast of Palau.[1]

Characteristics

The body is very small and slender, about 18 cm long.[2][3] They have a second premaxilla and under 90 vertebrae, features previously found only in fossilised eels. Their full set of gill rakers in their branchial arches have never previously been found in an eel, but are common in bony fish.[4] It is so different from all other living eels, scientists estimate it must have diverged from the others around 200 million years ago, during the Mesozoic Era. It thus has not only its own species, but its own genus and family, as well, and has been referred to by scientists as a "living fossil".[3]

References

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