Take a look at this illustration and tell me what you see. I had to give it a second glance because of something odd about fish #4. It is drawn with its head pointing down toward the seafloor. At first I assumed it was just the artist making an economy of space in the composition. Then I realized that it is not just a representation of the animal itself but also an illustration of its behavior. Look closely at those finger-like rays of the pectoral fins. Fish #4 is doing a “handstand.” But why?
The image comes from a Japanese Web site on deep-sea fishes. The one doing a handstand is a Salmon Snailfish (Careproctus rastrinus), a scorpaeniform marine fish in the family Liparidae. Members of the snailfish family are some of the deepest living fish ever filmed. My curiosity piqued, I soon found that the two most common characteristics given for this species is that it is poorly understood and has a tadpole-shaped body. Fortunately for my interest, a pair of enterprising Japanese researches were more thorough in their investigations, plunking a few Salmon Snailfish into a tank to watch their feeding behavior. It turns out these fish have taste buds on the tips of their pectoral fin rays and use them to find food. Sakurai and Kido observed these animals hovering over the bottom of the tank, head downward with their fins splayed out and the tips touching the bottom. When the tips contacted food on the substrate, the fish immediately sucked it into their mouths. In captivity they were fed krill and greenling. In the wild these animals enjoy a typically scorpaeniform diet of small crustaceans, worms and other invertebrates.
Sakurai and Kido did histological analysis of the fins, jaws and head. They found pear-shaped taste buds in the epidermis of the lower lobe of the pectoral fins and around the mouth. Other liparidid fish share a similar arrangement to their pectoral fins. The researchers concluded that the natural feeding behavior of this group might be similar to Careproctus rastrinus.
Additional Notes
- I’ve found nothing definitive about how the snailfish got its name. Presumably the smaller, shallower water species were the first specimens encountered. These have a rather slug-like appearance, often spiral their tail around to their head and have an adhesive fin on their abdomen reminiscent of a goby. Some members are also know to hang out in mollusk shells. If anyone has a more definitive etymology, let me know.
- Following Gorton’s Law (any fish, no matter how rare or unusual, should not go uneaten), there are a couple of Web sites that detail what these animals taste like and how best to prepare them. These are also in Japanese.
- For the more taxonomically inclined who like their molecular analysis separate from their morphological characteristics, here is a recent slideshow on the Phylogeography of the Careproctus rastrinus Species Complex (Liparidae) in the western North Pacific (PDF). See also, Phylogeny of the snailfishes (Teleostei: Liparidae) based on molecular and morphological data.
- My thanks go out to Rick Hibpshman of Crappy Wildlife Photography for permission to reproduce his picture of a Salmon Snailfish. You can see additional images of other snailfish species on his Flickr page.
Research Blogging
This marks my first official Research Blogging post. If I messed up the format for posting, please let me know. I’ve also started using an application on my Mac called Bookends. It is a program for aggregating, notating and formating citations and has been a real boon to my blogging research. While using its integrated online search feature, I decided that Google Scholar is my new best friend. I know that will be old hat to the veteran science bloggers, but Google Scholar is a great resource for the casual science/nature blogger operating outside the networks of academia. Fortunately I can get full access to some journals through the research library at work. But it is still a pain to bump up against the pay-wall of the journal publishers and not be able to read an article. It has given me a greater appreciation for the openness of the Public Library of Science and their kin.
Sakurai, Y, & Kido, K (1992). Feeding behavior of Careproctus rastrinus (Liparididae) in captivity Ichthyological Research, 39 (1), 110-113 : 10.1007/BF02905640