The Conundrum of the Gap in the Spine of the Barbeled Dragonfish Finally Solved

Old drawing of dragonfish

The conundrum of why a particular group of deep sea fish have a gap between their skull and spinal columns has finally been solved by a crack team of researchers, which include representatives from the Natural History Museum.

It appears that the Barbeled Dragonfish also have a number of bones missing which would normally connect their skulls to their spine, and this has been puzzling researcher for quite some time.

There are a total of 28 genera of these fish, which represent over 270 species, and all of them have this same gap. However, are these missing bones always the cause?

An international group of scientists including Dr. Nalani Schnell, of the University of Tubingen; Dr Ralf Britz, of the Natural History Museum; and Dr. David Johnson, of the smithsonian Institution in Washington DC.

Together they performed the most in depth and comprehensive study for this group.

They stained the fish so that their bones and nerves would show up in different colors, so they could discern them properly.

The researchers discovered that the bones were one missing in 2 of the different genera of barbeled dragonshish, Chauliodus, and Eustomias and in the Leptostomias gladiator as well. The loss of these bones occurred naturally as they evolved.
Dr Britz explains, ‘In stomiids [barbeled dragonfishes are in the Family Stomiidae], vertebrae develop in an unusual fashion from back to front, which facilitated the loss of front vertebrae. They have failed to form in development leaving a gap between the skull and backbone.

However, the gap in the spine of the other barbeled dragonfish is caused by a lengthening of the notochord.

There you have it… Mystery solved.