Amphiporus bimaculatus Coe, 1901 Common name(s): Two-spotted ribbon worm, chevron ribbon worm, thick amphiporus
Synonyms: Nipponemertes bimaculatus, Amphiporus angulatus, Collarenemertes bimaculata
Phylum Nemertea Class Anopla  Order Hoplonemertea  Family Amphiporidae
	Amphiporus bimaculatus, probably an anterior fragment
	(Photo by:  Dave Cowles, July 2012)

Description:  This Nemertean worm is a light brown or brownish orange dorsally, and pale cream or light orange ventrally.  The dorsal side of the head is lighter in color but has two well-defined darker or even black spots or pigment patches next to the lighter dorsal midline of the head.  This is likely the reason for the 'bimaculutus' in the name.  Numerous eyes (up to 25-30 per side) can be found along the sides of the head.  They also have several eyes just lateral to the posterior end of the pigment patches on the head.  The pigment patches often taper out to a sharp point in front.  The center of the dorsal side behind the head has two light stripes (marked by slight ridges in this individual), separated by a dorsomedian darker line.  This line fades out farther back on the body.  Length up to 12 cm and up to 6 mm wide and 2 mm thick.  

How to Distinguish from Similar Species:  M. verrilli has a brown or purple dorsum with regularly spaced white, transverse lines and an orange triangle on the dorsal head.

Geographical Range:  Northern Alaska to northern Mexico

Depth Range:  Intertidal to 137 m

Habitat:  Have been found under rocks, among hydroids, and on piers

Biology/Natural History:  The individual above has probably lost the back part of its body.  The mid-dorsal stripe on its head seems to be on a double ridge which extends back posterior to the head (photo). 
 

References:

General References:
  Lamb and Hanby, 2005

Scientific Articles:
Coe, Wesley R., 1901.  Papers from the Harriman Alaska Expedition.  XX. The Nemerteans.  Proc. Wash. Acad. Sci. 3: pp 1-110

Web sites:
Amphiporus bimaculatus page on Lifedesks: Nemertea

General Notes and Observations:  Locations, abundances, unusual behaviors:

The animal has a pair of raised longitudinal middorsal ridges (colored white on its head).  The ridges, separated by a darker pigmented area, continue back along the body for several times the length of the head then fade out.
This individual is hard to focus on because it is crawling rapidly.  Photo by Dave Cowles, July 2012 

This view of the side of the head shows rows of numerous black eyes.  Photo by Dave Cowles, July 2012 

This view of the underside of the head (the worm is crawling on the water's surface film) shows the anterior but ventral mouth.  Photo by Dave Cowles, July 2012 

Salish Sea Invertebrates web site provided courtesy of Walla Walla University