Harlequin Shrimps!

As scuba divers, we are fortunate to glimpse the wonders of life under water. The variety is astounding, but one of the coolest critters is the Harlequin Shrimp; the endemic Hawaiian species is known as Hymenocera Picta. These spectacular little shrimp are white with beautiful purple and orange markings. They also have large, flat pincers that they wave about in the water which makes them look more like flowers than shrimp. They only grow to about 2 inches, but they are powerful hunters of sea stars, including the notorious Crown of Thorns.

Over my career, I have had an opportunity to observe Harlequins a number of times. When I began my Open Water Scuba Instructor career, I dove at Ulua Beach with my students several times a week. One day I found a couple of these shrimp in a beautiful coral head out on the second reef. There was a little one and a big one (in my experience, I have always observed Harlequins living in pairs). The male is generally smaller than the female, although I have seen many pairs that appeared to be the same size. Over time, I watched the little one get bigger and bigger until it became the same size as the big one. Sometimes I would see part of a sea star caught in the coral with the shrimp. These shrimp usually capture their prey alive and take them back to their home in the coral, where they keep them alive and devour them over several days.

Eventually, one of the Harlequins disappeared (did the female eat the male?). There was only one left for some time, but then there was a little one again. I watched it over time as well, and it eventually became the same size as the bigger one, just like before. According to John Hoover, (Hawai’i’s Sea Creatures) Harlequin Shrimp “may be territorial”. Knowing, this, I was able to visit the Harlequins’ home repeatedly and watch this cycle occur several times until one day they were just gone. I never saw them in that coral head again.

Another interesting encounter was toward the end of a night dive, again at Ulua Beach. We were in about ten feet of water with a little bit of surge going on. There on the rubble was a Harlequin Shrimp pulling along an upside-down sea star known as a Spotted Linckia with its bright pink spots. The shrimp keep the sea stars upside-down so they cannot grip onto anything. Every now and then the surge rolled both the shrimp and the sea star over. The Harlequin picked itself up, turned the sea star on its back, and started dragging the sea star again. This happened several times while my buddy and I looked on, completely enthralled. Finally, our diminishing air supply dictated that we go to shore and leave the wondrous world of the Harlequin Shrimp behind.

If you are interested in learning more about the marine life living just a dive away, I recommend the PADI Underwater Naturalist course, or the PADI Project AWARE Fish Identification course. See you underwater!

And of course, if you’ve got Harlequin Shrimp stories to share, we’d love to hear them!

Aloha, Teri