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!
3 comments:
SUCH a beautiful and interesting creature!
And it was wonderful to see mention of Joel Hedgpeth, who I knew quite well and admired enormously when I was in high school. This gave me a little side-trip down memory lane.
Fantastic creature. Its tiny ocular tubercles hardly seem matched to the relatively huge snappers. Reminds me of a human in a tiny cab operating a huge crane.
Thank you for the fantastic photos!
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