Fantastically spinose

 

Recently, Maddy found several of these sea spiders (pycnogonids) living among low intertidal tunicates on Bodega Head.   This species is very distinctive among our local sea spiders because of the many spines covering its body.  Below is a close-up view of the top surface of the sea spider.  Notice the numerous cactus-like spines around the legs and abdomen:

 

As Joel Hedgpeth noted in his 1951 paper on the sea spiders of Dillon Beach, this species is “fantastically spinose” and so it seems appropriate that it is named Nymphopsis spinosissimum!  

The drawing below from Hilton (1942) shows the spiny body plan of this species.  You can also see another important distinguishing feature of this species — the three tubercles (tower-like structures) in a row on the upper surface of the sea spider:

Modified from: Hilton, W.A. (1942) Pycnogonids from the Allan Hancock Expeditions. Reports of the Allan Hancock Pacific Expedition 5 (9): 277–339.

In the side view below, you can see the spiny abdomen in the back (it looks like a finger pointing to the left), then the three spiny tubercles in a row, and lastly the ocular tubercle at the front (the projection on the right side with reddish coloration bearing the shiny eyes). 

Finally, here’s a head-on view of the sea spider, showing its grasping claws (chelicerae) and the ocular tubercle above:

 

It seems possible that all of these sharp spines might help defend the sea spider against being eaten, but very little is known about the biology of this species.    

Many thanks to Maddy for finding these sea spiders and Eric for taking the excellent photographs!