By Laura Lukas
Is it possible for any one person to know every species on Earth? The answer is a resounding no, for many reasons. My alma mater required students to take only 1/3 of the biology courses offered to science majors, so it's no surprise I struggle to keep my (many phyla of) worms straight from each other and worms from clam worms (which are annelids), clams, clam shrimp, and shrimp. [Somewhat sarcastically speaking of course!] Would the other 2/3 of courses have prepared me for what I see at the museum?
Working behind the scenes in the museum's ichthyology collection I am exposed to various treasures. Recently I've been finding invertebrate symbionts attached to fish hosts. One invertebrate with a particularly interesting life history is the tongue eating isopod; it literally looks like a tongue until you take a second look and see a bug like creature. This crustacean eats the tongue of a fish, and leaving a host with a life-long companion whether it wants it or not.
Other fish symbionts appear to be slightly less invasive. While looking over a sunfish, I noticed an object attached to the fish near the tail region. It seemed out of place and I dismissed it for an ID tag we sometimes attach to fish. Upon closer examination, I realized it was a parasite. The parasite looked very strange, so my colleagues and I were determined to ID it. We came to the conclusion that the parasite was an anchor worm. Rather than falling into the "true worm" phylum – rather many worm phyla – the anchor worm is the reproductive female form of a copepod, which is a crustacean!
A few weeks later I noticed another "worm" attached to a different fish, this time a marine species. Interestingly, the two copepods were found at different salinities, and showed obvious morphological differences. The freshwater copepod was more of a soft Y; the saltwater copepod was stiff and more cylindrical.
I was given the opportunity to remove the "worm" from its saltwater host. Using my expert surgery skills, I dug into the fish until finding the anchor portion. The anchor structure of the copepod was buried under the skin of fish at almost 1.5 times the length of the exposed body.
It seems there is no shortage in finding new (to me) species at work. These animals have evolved such curious lifestyles. It just goes to show how unique life is, and begs the question as to why these anchor worms began attaching themselves to fish in the first place. Food and transportation all in one package? Pretty tempting, if I do say so myself.