A Few Words About Words
Scientists, you’ve got to love us. We use a whole lot of big words to describe everything, even ourselves. For example, I’m a paleontologist (someone who studies fossils), a geologist (someone who studies the Earth), and a taxonomist (someone who spends way too much time classifying organisms according to their presumed natural relationships). If you’re a taxonomist like me, it means whenever you work on a new group of organisms, you need to learn a whole new vocabulary. It’s kind of like learning a foreign language. Ever wonder where these words come from and why they are necessary? Well…I’ll tell you.
I’m currently working on a group of organisms known as entocytherid ostracods (seed shrimp… though technically they aren’t shrimp… don’t get me started). Entocytherid ostracods are ectosymbionts of other crustaceans… Just stop with the jargon already and get to the point!
One of the new words I’ve recently learned is “amiculum”, which comes from Latin, meaning a mantle or cloak. So why not just use mantle or cloak? Well, there’s a story behind that. Back in the day, 1955 to be exact, Horton Hobbs Jr. described a particular piece of anatomy seen in adult female entocytherid ostracods as the “ruffled skirt.” Though other authors, Crawford (1959), Hobbs and Walton (1960), followed suit, a problem arose in 1961, when Hobbs and Walton discovered an entocytherid “species” with a decidedly “unruffled skirt!” These authors explain it this way …”it seems inappropriate to refer to it as an unruffled, ruffled skirt. Although neither the minute structure, nor its function is understood, to aid in the preparation of future descriptions we propose that it be designated the amiculum (L.-a mantle).”
Thus the term amiculum is now part of the entocytherid vernacular, which is probably a good thing because there are several genera of entocytherid ostracods whose adult females have neither an unruffled ruffled skirt, nor a ruffled skirt. In fact some wander around with no skirts at all. Oh the humanity!
Though I admit I find this all very entertaining, I find it even more fascinating that to this day, over a half century later, we still don’t know what the purpose of this structure is. The ammiculum is only seen in adult, usually gravid (full of eggs), females. Not all entocytherid genera have this structure. Though it sits in the same portion of the carapace (shell) as the copulatory complex of the males, it is highly unlikely the amiculum is the female equivalent, because mating/impregnation seems to occur before this structure is developed.
I have plenty of unsupported theories on the subject, but all are pure speculation. Ask me if you’re interested. But I can say entocytherids are weird, and gravid female entocytherids are particularly peculiar. There is one genus, Entocythere, where adult females not only develop an amiculum, they also grow what I like to call an extra “happy hand” on their antennae. What’s the point in that?
Crawford, Jr., E.A. (1959) Five new ostracods of the genus Entocythere (Ostracoda, Cytheridae) from South Carolina. Publications of the University of South Carolina (III, Biology) 2, 149–189.
Hobbs, Jr., H.H. (1955) Ostracods of the genus Entocythere from the New River system in North Carolina, Virginia, and West Virginia. Transactions of the American Microscopical Society 74, 325–333.
Hobbs, Jr., H.H. & Walton, M. (1960) Three new ostracods of the genus Entocythere from the Hiwassee drainage system in Georgia and Tennessee. Journal of the Tennessee Academy of Science 35, 17–23.
Hobbs, Jr., H.H. & Walton, M. (1961) Additional new ostracods from the Hiwassee drainage system in Georgia, North Carolina, and Tennessee. Transactions of the American Microscopical Society 80, 379–384.