Dominica Flat Worm ID

At 25 feet, sand, heavy turtle grass:

Thanks, Bud

Bud, we have got to raise some money & get you a good invert book! This is a ribbon worm, phylym Nemertea, not a flatworm which is phylum Platyhelminthes. Not sure, but that might be the recently described Micrura rubramaculosa which was named for the red leopard-like coloration. Would you send me a high-res file? If I can spot one particular feature it will let me know that at least the genus is probably right. lharris[at]nhm[dot]org

Thanks for sending the files. Unfortunately, the worm has one of the ends broken off & I can't see the other so I've no way to be sure about the genus.

Leslie,

That is too bad. When I first spotted it, it was being dive bombed by some razor fish. At one point is was up in the water column swimming like crazy but not going anywhere. I chased off the fish and when it began burrowing in the sand I thought all was well. Are these worms able to regenerate their missing parts?

Bud

The front end can regenerate the back portion. Whether a middle piece or a posterior piece can regrow the head depends on what kind of worm it is. In polychaetes - the worm group I know best - some cirratulids reproduce by splitting into pieces as small as 2-3 segments and regrowing both ends. Some polychaetes can only regrow the head if the break is within a certain anterior region of the body.

Hi Leslie,

I was on the road chasing interstitial nemerteans and must have deleted this post in my rush to get through email.

M. rubramaculosa is a good guess. Meg agrees, though it seems to be bigger than any we found in rubble. We would be interested in the size - turtle grass generally is about 5mm or more wide?

Many of the burrowing nemerteans can regenerate both head and tail on a midbody piece as long as both of the lateral nerve cords are present, but a head has the greatest potential for successfully regenerating the missing body.

Interesting observation about the fish pecking at it, because most nemerteans are chemically defended and very distasteful to potential predators. If this had been non-defended it probably would have been swallowed instantly. However, that doesn't mean that a fish can't do some serious damage while trying to figure out if the worm can be eaten. Of course, a few bottom-feeding fish have overcome the taste problem and do eat the worms. Some of the worms most susceptible to predation break spontaneously into many pieces, each acting like a lizard tail; possibly this gives the head region a greater chance at survival or just allows some fragments to escape rather than giving a fish one easy meal.

You lucky stiff. I haven't been out of the museum in nearly two long boring years....... Glad to have you back! )