Decades old fish puzzle solved!

International collaboration between scientists in Australia, the USA and Japan has resulted in one of the most amazing biological discoveries in decades.

A juvenile cetomimid whalefish, Gyrinomimus sp

A juvenile cetomimid whalefish, Gyrinomimus sp
Bruce Robison © Monterey Bay Aquarium Research Institute

The seven scientists have shown that what were previously recognized as three distinct families of deep-sea fishes are in fact only one. The whalefishes (family Cetomimidae) are all female, the smaller bignose fishes (family Megalomycteridae) are all male and the bizarre tapetails (family Mirapinnidae) are larvae.

The remarkable combination of developmental transformations and sexual dimorphism (differences between the sexes) the authors have documented are unparalleled within vertebrates.

The road to this discovery was long and winding. The scientists had studied the families individually over many years. Detailed analyses of changes in the anatomy of specimens as they transform from larvae to females and males were made on some recently captured fishes after DNA indicated one larva was similar to a female. Closer study of older museum specimens identified two specimens transforming from larvae to males.The recently captured specimens also allowed new DNA analyses of all three life stages. In a wonderful piece of good luck towards the completion of the research, a specimen which was transforming from a juvenile (tapetail) to a female (whalefish) was caught in the southeast Atlantic in late 2007.

A final twist to the story is that the small males do not eat after maturing. Reproduction and the search for a female are fueled entirely by a huge liver.

The deep-sea midwaters of the ocean between sunlit surface waters and the bottom constitute the largest and most poorly known and sampled ecological area on earth. There are many more discoveries to be made in this little-sampled zone.

Publications From This Research:
Johnson, G.D., Paxton, J.R., Sutton, T.T., Satoh, T.P., Sado, T., Nishida, M. & M. Miya. 2008. Deep-sea mystery solved: astonishing larval transformations and extreme sexual dimorphism unite three fish families. Biology Letters. http://dx.doi.org/10.1098/rsbl.2008.0722.


Mark McGrouther , Collection Manager, Ichthyology
Last Updated:

Tags fishes, ichthyology, tapetail, whalefish, Cetomimidae, puzzle,

2 comments

Mark McGrouther - 8.08 AM, 20 August 2009
Hi Sascha. Thank you for your comment. Yes, the authors have done an amazing job. I certainly agree with your suggestion that the support staff and volunteers perform a vital role. One of my colleagues, who is a research scientist, made a similar statement at a recent event.
Sascha Schulz - 9.08 PM, 19 August 2009
I think all the scientists involved in this project deserve a great deal of kudos for their many years of dedication and perseverance in the face of continual budget cuts and funding shortages. But something that isn't mentioned here is the tireless work of collection managers, technicians and volunteers who work behind the scenes of the world's museums. Without them, our taxonomists would be even more restricted than they are now. Well done the lot of you!

Report misuse