Hawaii pycnogonids sea spiders

hawaiisfishes.com

Sea Spiders not in Hawaii's Sea Creatures
Sea Spiders, so called because they have four pairs of legs, are small marine arthropods of the class Pycnogonida. They are thought to be related to spiders and horseshoe crabs. The Bishop Museum's list of pycnogonids known in Hawaii is here

Chuck Babbitt

Sea Spider (unidentified)
Chuck Babbitt photographed this small animal in 65 feet of water at a spot he calls Disneyland, straight out from the new Disney resort at Ko Olina, West Oahu, and sent me the photo to ID. It seems to be a pycnogonid, more commonly known as a "sea spider." and can be identified as such by its four pairs of long, slender legs (although a few pycnogonids have 5 or 6 pairs of legs). Small and well camouflaged, these tiny, slow-moving predators are noticed only by the most sharp-eyed of divers. Most species are probably less than 1/2 in long. According to the Bishop Museum, there are about 15 known species of sea spiders in Hawaiian waters, but I don't have a clue how to figure out which one this is. I didn't even think to mention these obscure animals in my book Hawaii's Sea Creatures. Thanks, Chuck, for bringing them to my attention!

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David Rolla

On February 6, 2016 I received more photos from David Rolla of what might be the same unidentified species. This individual was carrying a large white egg mass under its abdomen. David wrote:

At the end of a dive today, I found a sea spider ... The photo on your site is familiar to me...Chuck Babbitt is a friend, and I was diving with him the day we found the one in his photo. Coincidentally, he took us out on his boat today and I found another one…not so tiny.

This one appears to be very similar to the previous one — except larger. I’d estimate the size at 1/2” across. It was actively crawling along the mooring line at about 85’ on the deep LCU wreck on the west side of Oahu. It also appeared to have a solid white body, but now as I take a close look at my photo and Chuck’s photo, I believe it is carrying something…perhaps an egg mass, or a big meal?

I’m guessing we still don’t know which of the 15 species this could be…just thought you may be interested to see this one.

David Rolla

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After seeing David Rolla's photos, Cory Pittman wrote that he had photos of several other sea spiders found in algae washes done by him and Pauline Fiene over the years. Cory writes:

There are actually quite a few species in Hawaii (most small and cryptic). Like John, however, I have no idea about identification. Several small ones are fairly common in my algae washes and I have photos of three or four. My largest reaches about 20 mm in leg-spread and is peculiar in that its body is transparent and its digestive system is dark green. It's a Halimeda-dweller. So, that might provide camouflage. But, I also wonder if it's retaining chloroplasts--perhaps picked up secondarily from its prey since they're all supposed to be predators.

The first two shots are of small animals (around 4-5 mm in leg spread, if I recall correctly--I didn't record it at the time). They were both from an algae wash taken at Maliko Bay, Maui at 3-9 m on April 19, 2008.

Cory Pittman

The next two are of the large, Halimeda-dwelling species I mentioned.

The first animal had a leg spread of about 16 mm. It was from pooled algae washes taken by Pauline and me in a Halimeda kanaloana bed at a depth of 6-14 m about 3.5 km north of Hekili Point, Maui on October 11, 2003.

The second animal had a leg spread of about 15 mm. It was from an algae wash taken by Pauline (with me sorting) in a Halimeda kanaloana bed at a depth of 8-11 m at Wahikuli, Maui on Nov. 6, 2010.

Cory Pittman

Cory Pittman
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