MadSci Network: Zoology

Re: How do black dragon fish look after their young

Date: Mon Oct 18 07:00:22 2004
Posted By: Rob Campbell, Postdoctoral researcher, Biological Oceanography
Area of science: Zoology
ID: 1098072636.Zo


I assume you're referring to Melanostomias valdiviae, or a very similar member of the (generally very creepy looking!) family Stomiidae (both links are from FishBase, a very handy online database about known fish species). Like you wrote, most Stomiids (pronounced "Stow-mee-id" by the way) live in the deep ocean, and not very much is known about their biology. They are solitary and not particularly abundant, so they can be quite difficult to catch. Really the only way to catch them is to trawl for them with nets, and as a consequence they're usually not in very good shape when they arrive at the surface.

For the most part fish have external fertilization, that is to say that gametes (eggs and sperm) are released by females and males into the water, and fertilization occurs outside of the body. Most fish do not exercise any care of their young, who are basically on their own from the egg stage onward (with a very heavy mortality as a result of that). There are a few exceptions to that - some fish are known as livebearing, and actually retain their eggs internally until they hatch (sort of like giving birth). Some of the more common aquarium fish like swordtails and guppies are livebearers, as are some Scorpaenids (Rockfishes). Some other families of fish take care of their larvae in nests - Centrarchids (bass and sunfishes) and Cichlids are known for this for instance. Often, the male is responsible for guarding the larvae, and they may forgo feeding for weeks or months to do this (they also sometimes mouthbrood - keep the larvae safe within their mouth - which is also not conducive to eating!). Most fish that take care of their young are what we call demersal - they live their lives at or near the bottom. Dragonfish, on the other hand, are pelagic.
So, my educated guess would be that they do not take care of their offspring in any way. Looking around in FishBase, I did find one species within the family Stomiidae, Idiacanthus antrostomus which has a reference as having pelagic larvae (there may be others if you look through other species in the family), which you could call weak evidence for other species within the family.

Hope that helps!
Rob Campbell, MAD Scientist

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