Heart Without a Head

Fingernail clam adult and offspring - clip from video

Linda Bower* still has her camcorder focused in her neighbor’s farm pond and sent me this story.

This time I was watching fingernail clams (smaller than your little finger’s nail). These bivalve mollusks are in the Sphaeriidae family which includes 12 species in North America. Their more exotic relatives include octopi, cuttlefish and squid. Yes, you read that right. The clams in our ponds are related to some of the most fascinating and intelligent ocean creatures.

According to the Museum of Zoology, University of Michigan, the taxonomy of Sphaeriidae is in a “confused state” even though they are abundant and widespread. It is futile to attempt identifying to a species without a microscope. How did they become widespread without wings? I’m glad you asked. Clam babies can clamp directly onto feathers, mobile aquatic insects, amphibians, or plants that birds inadvertently carry with them. Some species are ingested by ducks, but not digested, and are “released” in a new location.

If you are new to freshwater clams like me, these facts may be of interest:
· Fingernail clams don’t have a head, but they do have a heart.
· They have a muscular appendage called a, “Foot” that is used to move around.
· The mantle (inner lining that sticks out from the shell) can sense touch and light.
· Their two-siphon system allows for feeding and breathing through one siphon, and eliminating  
  out of the other siphon.
· They are filter feeders on very small pieces of organic matter and mini-plankton.
· They are a food source for fish, crayfish, aquatic amphibians, waterfowl and shore birds.
· They are self-fertilizing hermaphrodites.
· The dastardly Zebra Mussels are capable of crowding them out.

Linda's video of an adult and baby fingernail clam gives us a good view of the foot, mantle and siphon. Clams don’t move very quickly, so let’s just say it is relaxing to watch, especially with the music Linda selected.

* Linda Bower is a member of our Springfield Plateau Master Naturalists with a passion for capturing pond wildlife in videos.  More of her video's are at Nature in Motion.