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Some interesting crabs not in Hawaii's Sea Creatures

GIANT ELBOW CRAB
Rhinolambrus contrarius (?)
Family Parthenopidae
     John Earle spotted this amazing animal sitting motionless in silty sand at a depth of about 60 ft. off Kahe Point, O`ahu. He called me over then touched it lightly with his wand whereupon it spread its arms menacingly in a span of at least 12 in. Having never seen anything like it before, I decided to collect it in case it was a species not known in Hawai`i. Picking it up was easy but holding it for any length of time was not; it seemed to be able to reach me with its pincers no matter where I grasped it. Eventually we got it into a bag, and, once ashore, into a bucket.
     When I got home I put an airstone in the bucket and started looking in books to see what it might be. Clearly, it belonged to the crab family Parthenopidae, commonly known as "elbow crabs." A 1965 book (long out of print) by Spencer Wilkie Tinker got me pretty close to the answer. The book is titled "Pacific Crustacea, an Illustrated Handbook of the Reef-Dwelling Crustacea of Hawaii and the South Seas" and on p. 88 it shows a photo of the crab, or something very much like it, under the name Lambrus (Rhinolambrus) longispinis. Tinker called it the Long-Spined Parthenopid Crab Of it he says:
    "The carapace of shell of this crab is covered with tubercles and short spines. The front legs or chelipeds are large and are also covered with tubercles and spines, of which those along the angles of these legs are triangular in shape. The walking legs are slender, quite smooth, and marked with encircling bands of color. The carapace measures about two inches in width. This is an Indo-Pacific species which extends from Hawaii southward to Australia, westward to Japan, through the East Indies, and across the Indian Ocean to the coast of Africa.
     This rare crab has been retrieved from rocky bottoms at depths of about one hundred feet."
     I took photos of the crab and sent them to the world's expert on parthenopids, Dr. Swee Hee Tan of the National University of Singapore. However, it was the weekend and I didn't expect Dr. Tan to answer for a couple of days. Since the crab was in Tinker's book I figured it there was no reason to keep it, so the following day John Earle and I returned it to the spot where we had captured it.
    Soon afterwards I got an answer from Dr. Tan. He thought it looked like Rhinolambrus contrarius but of course couldn't be sure without a specimen. I notified Dr. Peter Castro, who is working on crabs at the Bishop Museum; he said that Rhinolambrus contrarius is not presently known from the Hawaiian Islands. So, it looks like it's at least possible that it's a different species than the one pictured in Tinker's book, which, come to think of it, did seem to have thicker chelae (pincers). Also, Tinker's animal came from rocky bottom whereas this crab was in soft silty sand and nowhere near rocks. On the other hand, Tinker's description of the banded legs was perfect. So in the end we don't know what it is. It could well be a new record for Hawai`i but we won't know until another is found and collected as a specimen. I have here proposed the common name Giant Elbow Crab, just in case it is not the same as Tinker's animal. Dr. Tan, however, says that in terms of leg span there are probably larger elbow crab species in Japan and the Mediterranean.

July 15, 2007 update: Kent Backman writes from Kaua`i:

I saw a odd looking horned helmet in the sand at 130 ft, which turned out to be odd because it was (temporarily?) cohabitating with this strange looking crab. With its two large arms folded, it was about the breadth of the horned helmet…14 inches or so. But when I approached with my video camera to get a macro shot, the arms popped out and it attacked in a very quick defensive maneuver.

I am quite positive I have not seen this guy before. I would have liked to collect it, but my hour+ deco in ripping current was hard enough as it was. I would have had to somehow kill that crab in order to bring it up safely. He was very defensive!.

Here is a link to my video, alas with only visible light…not so good at 130 ft.

http://www.veoh.com/videos/v1159909rJCYf7tD

KING KONG CRAB
Daldorfia rathbunae (?)
Family Parthenopidae
I photographed this crab at Makua, Oahu, in about 30 ft. In the original ed. of Hawaii's Sea Creatures I showed a similar but smaller crab which I erroneously called the Horrid Elbow Crab with the scientific name Daldorfia horrida, but it has turned out to be the recently-named Daldorfia dimorpha (Tan & Ng, 2007). In the revised edition I kept the photo but called it "Holcom's Elbow Crab" (Daldorfia sp.) after diver Ron Holcom, who collected the animal and showed it to me. However, Tinker's 1965 book "Pacific Crustacea..." lists Daldorfia horrida as occurring in Hawaii and mentions that it grows to a width of 4 in. I suspect the crab above is the same species that Tinker shows in his book. He calls it the "Horrid Parthenopid Crab" and writes:

Like most parthenopid crabs, the surface of this species is rough. It is covered with rough elevations and depressions and with smaller tubercles and pits. The chelipeds (claws) are usually unequal in size, and the walking legs bear spines which grow in such a way that they form a perforated margin along the upper edge of the leg. The carapace is somewhat five-sided and is four inches in width.

This crab is an Indo-Pacific species... (and) is reported to live on bottoms of mud or broken shells from shallow water to depths in excess of three hundred feet.

However, Dr. Swee Hee Tan of the National University of Singapore says that as far as he knows the true D. horrida does not occur in Hawai`i and the crab which Tinker illustrates and describes is actually D. rathbunae.

Below is another photo, taken by John Earle at Makua, Oahu at a depth of 40 ft.

Ghost Crab juvenile
Ocypode sp.
Ray Farm took this wonderful picture of a small crab on a beach near Honokohau Harbor, on the Kona Coast of the Big Island; Dr. Peter Ng of the National University of Singapore identified it as a small ghost crab. Two species of ghost crabs are known in Hawai`i but it's not clear which one this represents. Ray writes: "It is a very small crab (less than 1 inch across including the legs) with some of the most amazing camouflage that I have ever seen. I'm not sure whether it truly matches the mixture of white, black, and beige sand particles or if it is somewhat transparent and you actually see the sand particles through the body and legs. Whatever the case, nature certainly is protecting the little guy from predators. We could see him when he moved, but he disappeared when he stopped. I just took a picture of the area where I thought he had stopped and found him in the picture."

Viaderiana taeniola (Rathbun, 1906)
family Pilumnidae
top photo: J.Hoover Wai`anae, O`ahu. 100 ft.
bottom photo: Tina Owens, Kona, Hawai`i.

Nucia speciosa Dana 1852
family Leucosiidae
O`ahu. collected by Darrell Takaoka

Parapilumnus sp
family Goneplacidae
photos: Tina Owens, Kona, Hawai`i. Tina calls this the "Crusader Crab" because of the red cross on its back. I sent the photo to Dr. Peter Ng in Singapore who replied. "Your crusader crab is interesting!!! It may well be a rather rare animal called Parapilumnus. See my attached picture of a specimen from Guam. It is rare and if you have the specimen - PLEASE send it to me - it is not Pilumnidae but Goneplacidae. An odd animal by all regards, and the genus currently has only 2 species."

So, if anyone comes across one of these, please collect it, freeze it and contact me. It could be a new species! It could be named after YOU!