Q: My six- and four-year olds would like to know if "octopus have teeth"? (Margie, Fallston, Maryland)
A: An octopus has up to four kinds of teeth (none like ours), and, like birds, has a beak which can tear pieces from prey, and even break shells. The beak is below his eye (see image) where his eight legs join his head like wheel spokes to a hub.
Cracking a crab's shell is easy work for an octopus' strong beak (made of the same hard stuff as a lobster's shell). One shell-crushing bite can kill a crab.
On the other hand, a clam's shell defeats the beak. But the octopus still wins, because, he does have teeth, indeed, depending on the species: up to four types. He may start the hole with saw-like teeth on his tongue (the radula) "but most of the drilling is carried out by the salivary papilla [small teeth-like bumps in his mouth]," emails biologist Roy Caldwell, a professor at the University of California at Berkeley. He uses these and more teeth located at the turned-inside-out tip of the salivary duct to drill the actual hole. The salivary teeth also push corrosive saliva forward to the drill site, where the saliva attacks the shell. Then, having penetrated the shell, the octopus sucks out clam flesh. Here's a diagram (courtesy of the Tree of Life) showing the beak, salivary gland and duct.
Furthermore, besides those three possible kinds of teeth, sucker rims are "armed with hooks or teeth" in some octopus, Caldwell says. That makes four possible kinds of small teeth — not like ours but effective.
How does an octopus fare against a 5-foot shark and her thousands of sharp teeth? Click the video to see. Courtesy of Stevan Hogg and the Seattle Aquarium.
Roy Caldwell, "Death in a Pretty Package: The Blue-Ringed Octopuses." Freshwater and Marine Aquarium Magazine, 23 (3): 8-18.
Octopus digestive system, Tree of Life
Octopus gnashers (beak), Pharyngula
Octopodids, Australian Biological Resources Study
Giant Pacific octopus, National Parks Conservation Association
Q: Does eye color affect vision? (Colleen, Austin, Texas)
Q: Does the color of the eye affect the way you see? Do more people with one color of eyes see better or worse then people with a different color? (Alyssa, Laredo, Texas)
A: Light-eyed people are more sensitive to light, because they have few pigments to protect their eyes from sunlight exposure. So, such people can encounter sun-related problems, like developing cataracts, as they age.
Eye color may affect vision involved in sports (more about this in a moment). Albinism certainly affects vision acuity.
Albinism (an inherited condition where the person is born either completely lacking or has little pigment in his eyes, skin or hair) can be linked with eye problems. Albinism exists in many forms; most (especially the oculocutaneous form) are linked with vision problems. The oculocutaneous albino may have light sensitivity, a lack of visual acuity, and erratic eye movement. In the USA, about one in 17,000 people is an albino.
Finally, "There have been some reports about eye-colour effect on reaction time. However, these reports are mixed, about half see some effect, the others not," e-mails biologist Richard A. Sturm, principal research fellow of the Institute for Molecular Bioscience at the University of Queensland in Australia. "I'm no expert in the area, but I suspect there's some truth in it." This is interesting, because surely vision influences how fast we react to something.
Sturm sent me eight reaction-time studies, of which five found that eye color affected how well people reacted in various sports. In general, light eyed people did better on self-paced tasks (bowling, golf, pitching baseballs), and dark-eyed people did better on reactive tasks (boxing, hitting a ball, defensive football positions). Here's a few of the results:
• Dark-eyed men (61 college students tested at the University of Louisville, Kentucky) hit a tennis ball better than light-eyed men in forehand rallies.
• Light-eyed kids did better at self-paced activities; dark-eyed youngsters did better at reactive activities (Fort Hays State University, Kansas)
• Dark-eyed students hit a target with a frisbee more times than light-eyed students.
By the way, two other investigations found a correlation between eye color and behavior. Blue-eyed children in these studies were more inhibited than brown eyed children.
How does albinism affect the eyes? About vision
Ball color, eye color and a reactive motor skill, Percept Mot Skills
(Answered December 18, 2006)
April Holladay, science journalist for USATODAY.com, lives in Albuquerque, New Mexico. A few years ago Holladay retired early from computer engineering to canoe the flood-swollen Mackenzie, Canada's largest river. Now she writes a column about nature and science, which appears Fridays at USATODAY.com. To read April's past WonderQuest columns, please check out her site. If you have a question for April, visit this informational page.
NOTE: This article has been updated to reflect that all albinos have vision problems. The original story stated that only the oculocutaneous form is linked with vision problems