Leggy

A couple of nights ago I promised to share more information about this sea spider:

 

We're slowly trying to document the diversity of local sea spiders.  Maddy spotted this one in July and we hadn't knowingly observed this species yet, so Eric took some photos for the record.  Meet Ammothea hilgendorfi!  The entire sea spider is ~12 mm across (from leg tip to leg tip).

 

Sea spiders aren't necessarily easy to photograph, but these are terrific shots (thanks to Eric's patience!).

Below is a series of images showing some of the distinguishing features used to identify Ammothea hilgendorfi to species.  First, a diagram so you know what to look for:

Modified from Cole, Leon J. 1904. Pycnogonida of the west coast of North America. Harriman Alaska Expedition, Volume 10: pp. 249-298. 

Look for the eyes (two are visible from the side, a pair of circles on a small raised cone) and the abdomen (also a raised projection, at the end opposite the eyes):

 

Next, here's a view of the proboscis.  Look for the large white tubular structure projecting forward — it's below and extends out in front of the eyes.  The proboscis is used in feeding (suctioning and pumping). Although it's not visible, there's a small, triangular mouth at the far end of the proboscis.  (Sea spiders are parasitic on other animals like hydroids, bryozoans, and sea anemones.)

 

Eric also captured a nice view of one of the claws (at the tip of a leg).  It reminded me of the claw of a sloth — useful for grasping limbs.  In this case the sea spider might hold on to the branches of colonial animals such as hydroids:

 

You can compare the photos of these features to the diagram above to see that they are a good match for this species.

Many thanks to Maddy for spotting this intriguing pycnogonid and to Eric for the photos!