Skip to main content

Advertisement

Log in

Positive buoyancy in eel leptocephali: an adaptation for life in the ocean surface layer

  • Original Paper
  • Published:
Marine Biology Aims and scope Submit manuscript

Abstract

Many planktonic organisms have adaptations such as floats or lighter substances to obtain buoyancy to help them remain in the surface layer of the ocean where photosynthetic primary production occurs and food is most abundant. The almost totally transparent eel larvae, called leptocephali, are a unique member of the planktonic community of the surface layer, but their ecology and physiology are poorly understood. We conducted a comparative study on the specific gravity of planktonic animals including 25 taxa of 7 phyla of marine invertebrates and 6 taxa of leptocephali (vertebrate) to gain a broad perspective on the buoyancy of the eggs and larval stages of the Japanese eel. The specific gravity values of the various freshly caught marine invertebrate taxa varied widely from 1.020 to 1.425, but leptocephali had some of the lowest values (1.028–1.043). Artificially cultured live leptocephali had even greater buoyancies with specific gravities of 1.019–1.025 that were close to or lower than seawater, and their buoyancy showed ontogenetic changes among the different early life history stages. Leptocephali appear to have a unique mechanism of buoyancy control by chloride cells all over body surface through osmoregulation of body fluid contained in the extracellular matrix of transparent gelatinous glycosaminoglycans filling their bodies. This adaptation is likely a key factor for their survival by helping them to remain in the surface layer where food particles are the most abundant, while being transparent for predator avoidance. The ontogenetic change in buoyancy of eel eggs, leptocephali and glass eels likely enhances their larval survival, transport, and recruitment to terrestrial freshwater habitats.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Subscribe and save

Springer+ Basic
$34.99 /Month
  • Get 10 units per month
  • Download Article/Chapter or eBook
  • 1 Unit = 1 Article or 1 Chapter
  • Cancel anytime
Subscribe now

Buy Now

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5

Similar content being viewed by others

References

Download references

Acknowledgments

We thank the captain and crew of the R/V Hakuho Maru for assistance in making the plankton collections, the other scientists onboard for assistance in collecting and sorting the plankton samples, and T. Horita, curator of the Toba Aquarium, for kindly providing us a reared moon jelly.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Katsumi Tsukamoto.

Additional information

Communicated by U. Sommer.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Tsukamoto, K., Yamada, Y., Okamura, A. et al. Positive buoyancy in eel leptocephali: an adaptation for life in the ocean surface layer. Mar Biol 156, 835–846 (2009). https://doi.org/10.1007/s00227-008-1123-8

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s00227-008-1123-8

Keywords