Mystery Bones

Since my walk to North Beach two days ago I’ve been doing some sleuthing. I was curious about the bones I had found and brought them to my fellow naturalists. We looked at them in awe and confusion questioning, “Bird, fish, alien species, fossil?”. We ooood and ahhhed and looked at them under our hand lenses, but no one seemed to know for certain. One friend suggested sturgeon, which lead me in the right direction. I sent my photos to the state fish biologist who was a bit perplexed and then I turned to Google. My search ended with the freshwater drum. They do exist in Lake Champlain and my esteemed fish biologist confirmed it. The strange looking bone with the holes (tooth sockets) is a plate for pharyngeal teeth that drum fish use to grind up their food (mollusks). These teeth are found deeper in the mouth cavity than typical teeth in a location similar to the roof of our mouths. The other bones are the operculum or gill cover, vertebrae and ray fins (on oak leaf).

The freshwater drum also has a special bone made of calcium carbonate and a gelatinous matrix, which is found in the inner ear. The bone, termed otolith, is a balance and gravity center for living in the aquatic world. These structures start off small and grow as the fish grows. Scientists use otoliths to age fish just as dendrologists age trees. They cut the otoliths in half and study the annual rings which indicate age, stress and also environmental pollution. The stone is a creamy white and is used in jewelry as a good luck charm. I tried to find one for myself, but I guess I’ll have to stick with my pharyngeal plate and call it good. After all, it was a great excuse to get outside and spend time with my two favorite animals.