Suckers for the low zone

This might be tough, but do you want to guess what type of animal this is?  This is a close-up view of one end of the animal:

 

If you think that looks like a sucker, you're right!  It's a magnified view of a caudal sucker (the tail end).

Here's a look at the other end:

 

If you think that looks like a sucker, you're right again!  ;)  It's a magnified view of an oral sucker (the mouth end). 

I'll also tell you that this is a marine invertebrate.  So you need to visualize an animal with suckers at both ends...

Are you ready for the answer?

The next photo will reveal the entire animal after Eric discovered it attached to a rock in the low intertidal zone:

 

If you think that looks like a leech, you're right!  This is Trachelobdella oregonensis.   It was ~30 mm long when outstretched.

The diagram below highlights some of the main features of this species.  Look for (1) overall dark coloration; (2) the pale caudal sucker; (3) the small oral sucker with lighter patterning; and (4) 10 pairs of "pulsatile vesicles" = the bumps along the sides.

 

Modified from The Light and Smith Manual (edited by James Carlton) 

And here's a view of the leech while it was attached to the side of a bowl by its caudal sucker.

 

Although this individual was not attached to a fish, Trachelobdella oregonensis is known to be a parasite on a specific fish host — Cabezon (Scorpanichthys marmoratus).

The Light and Smith Manual states that this species has only been found from the central Oregon coast.  However, I searched the Smithsonian's invertebrate collection, and two California locations are represented: Crescent City and Pacific Grove.  So this record from 26 November 2015 could be a first for the Bodega Bay area.  [Yes, we found this leech on Thanksgiving (after our holiday meal) — there are so many interesting things to discover in the low intertidal zone that we couldn't resist a short field trip during one of the better low tides of the year!]

One more quick fact: Of ~700 species of leeches worldwide, only ~100 of those are marine.