Around Halloween some people delight in the shivers that slightly gross or scary things send down our backs. I personally always felt that spiders do not deserve the unfriendly reception many give them (they are very interesting and occupy an important niche in their ecosystem). However, this column is about marine animals and phenomena in the ocean, so I’ll leave the spiders alone. While I did consider writing about spider crabs, or decorator crabs, eventually I settled on an animal from an altogether different genus. What could be creepier than worms? Especially when they are really large worms.
Last summer, my son went to a summer camp in Kachemak Bay and went camping across the bay from Homer. On a tide pool expedition the kids found large red ribbon worms. I can just imagine how these animals attracted middle school-age boys with a fascination for anything slimy, gooey or squishy. Ribbon worms, in contrast to bristle worms, have no body segmentation and are often very elastic. A contracted worm of just a few inches might stretch to over a foot in length when fully extended. There is a large species of ribbon worm in the North Pacific that has been measured at over 100 feet long. Most of the close to 1,000 described species worldwide, however, are much smaller and many are microscopic, living on seaweeds or in the small spaces between sand grains. Some are parasitic, feasting on another animal without killing it, and some live peacefully in the mouth opening of sea anemones for a home with free food delivery.
By far the majority of ribbon worms are predators, hunting small crustaceans and other worms. Their bodies have a unique built-in weapon for hunting their prey. It is called a proboscis and is a projectile, sometimes armed with spikes, and often equipped with a poison to subdue the unlucky prey. The proboscis is shot out of a special opening above the mouth, and retracts into the worm’s body when not in use. Many ribbon worms have eyes and some can smell their food. Others just crawl along until they chance upon something edible to shoot their proboscis at.
Generally, ribbon worms come as male or female, but in the off-season for mating, their gonads are undeveloped. Sexual reproduction usually occurs through external fertilization when a female lays eggs and a male adds his sperm. However, there is another way in which one half and one half makes two: If a ribbon worm breaks apart, both pieces can regenerate into a new worm.
The life of a worm is dangerous, because many animals favor them as a snack or for dinner. Since many ribbon worms live in the muddy areas of shallow bays, low spring tides often expose millions of them, and migrating birds have adapted their travel routes to make rest stops at those mud flats and fill up on worms. Recently I had a chance to go on a fishing trip and we pulled up a few black rockfish. Their mouths were full of, you guessed it, ribbon worms. While they are not my choice for a favorite animal, they certainly have their place in the ecosystem. So, if spiders don’t give you the creeps, how about slimy, stretchy, meat eating, red, orange, black or purple ribbon worms with a weapon to shoot out, grab and poison their prey? Happy Halloween!