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Saturday, March 29, 2014

Coming to you from Westfield, MA


This is an interesting nemertean, or ribbon worm, that Eric found in a kelp holdfast a couple of weeks ago.  When fully extended, it was ~8 cm long.

The first features we noticed were the chocolate brown coloration, the cream-colored rings, and the bright white borders to the head.  

When viewed from the side, we were impressed with this ribbon worm's extremely long cephalic grooves (see below) look for the slit or furrow along the lower edge.



At the posterior end there was a long appendage called a caudal cirrus (next picture).



After looking at all of these features and checking The Light and Smith Manual (2007), we were pretty sure this was Micrura wilsoni.  We looked for photographs online to confirm, but unfortunately couldn't find any pictures.  Eventually we located a copy of Wesley Coe's Nemerteans of the West and Northwest Coasts of North America (1905) with its wonderful set of color plates.

And there was Micrura wilsoni on Plate 3! 

Modified from Coe, W.R. (1905). Nemerteans of the West and Northwest Coasts of North America.  Bulletin of the Museum of Comparative Zoology 47: 1-319.


If you look closely at the drawing above, you can see a red spot at the back edge of the head.  We wondered what that was, so we read the species description.  Coe and the illustrator were highlighting the rosy-colored brain of Micrura wilsoni!  Could we see the brain in this individual?  Sure enough, in the right light, a reddish glow was visible (see below).


A few more fun things about Micrura wilsoni

Sometimes it would contract and look somewhat like a leech:



Other times it would move via peristalsis a series of wave-like muscle contractions: 



We wondered who Micrura wilsoni was named after.  Surprisingly, there's a connection to western Massachusetts!  Coe says: 

"The species is named in honor of Prof. C. B. Wilson, of Westfield, Mass., well known for his work on Nemertean development, to whom I am indebted for several specimens of this and of other Nemerteans, and for valuable notes on a number of the species described in this paper."


P.S.  Last March, we found a different species of Micrura in a kelp holdfast.  Click here for pictures of Micrura verrilli. 

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