The Perigrinations of the Amazing Mr. Hazlett or a report on Homing Instinct in Calcinus hazletti

Hazlett's Hermit Crab, Ca hazletti, Kailua Pier  2/23. 2012

    Two days ago, I swam the Ironman side of the Kailua Pier.  The water was more than a little cloudy, but cleared adjacent to the pier.  As usual, I finished in this clear water looking for immature butterflyfish and, increasingly, hermit crabs.  To my delight, I spotted a moderately sized Triton shell, about 1 1/2 inches, coated in pink coraline algae,  perched atop a a coral head.  Recognizing this for a probable hermit crab, I dove and gently pried the little fellow loose.  To my delight, this was a hermit.
   Washing back and forth in the water, I examined my prize.  He was extremely brave, mounting repeated sorties against my fingers.  Cangrejo bravo!  Were this little fellow a bull, he should have found himself in the ring in Sevilla facing Belmonte.  He had a purplish carapace and chelipeds (claws) tipped with white and purple.  To my immediate vision, he appeared almost black and hairy.  I thought I had a new species of crab for my personal list.  I took a few macro pictures while holding the crab in my left hand and then swam towards shore, looking for a place to set the hermit down and get a better picture.

The pink algae encrusted triton, home to a hermit crab.

     I decided  to set him on the old part of the pier, that offers an  irregular surface at the level of the water.  I did this , but my plan was immediately quashed; a small wave came and washed the crab into the water before I could get any more pictures.  I searched for him underwater, but he was no where to be found.
     That afternoon we looked at the pictures.  As always, the camera doesn't lie; I had found a moderately large Hazlett's Hermit Crab...a fairly common species. 
     The next day I swam again at the pier and first checked out the spot where the Hazlett's had washed  away the day before.   I then went back to the coral head where he was first spotted.  This was easily located as I had carefully noted its position the day before, just opposite the small ladder descending to the boarding area for the cruise tenders. I had marked the spot carefully,  intending to return the crab to his home territory (only to be foiled by the shell washing into the sea.)

Hazlett's Hermit Crab, Ca. hazletti,  2/24  Same shell, same crab.

   Low and behold, a very similar crab was on the same coral head, within two feet of where I had found the crab on a previous day.  As I was messing with the camera, preparing to photograph the crab, two brown gentleman leaped from the pier to within a foot or so of my distracted corpus.  "Holy Shit!" I exclaimed through my snorkel as they swam away giggling.  It always gives me pleasure to provide others a chance for mirth.  Or to put it another way, what a couple of complete assholes.
    Digression aside, here is the picture of the encrusted triton shell on the coral head.  and here is the best photo of my new friend.   There is no doubt in my mind that we are looking at the same triton shell and, therefore, the same hermit crab.  (Look at the pattern of little shells growing on the big shell.)  I hope you like that second picture, I think its the bomb!
   I had the chance to read a PhD thesis on the web.  The author talks about a certain species of hermit navigating a meter in search of food.  He points out that crabs are known employ chemical and celestial information in their navigation.  How sensitive these receptors must be!  The distance that this small hermit traversed in less than 24 hours was roughly 20 meters.  Not only do we have an amazing example of homing instinct, but an admirable example of determination and stamina. 

Cangrejo Bravo gores a spear fisherman in Sevilla

    Suffice it to say, on this day I replaced him in the exact spot from which he was plucked.  There was a hunting Whitemouth Moray in the same coral head, but I was confident that cangrejo bravo could take care of himself.   I was careful not to get bit on his behalf, although it probably would have served me a lesson!

jeff

 This blog is dedicated to the late Patsy McLaughlin, a giant in the field of hermit crab biology.  Not only did she identify our Calcinus revi, she did her best to make me a better scientist. 
j