DIVE DRY WITH DR. BILL #875: I'LL "PREY" FOR YOU: MANTIS SHRIMP
It has been years since I've written about a critter commonly found on some of our sandy bottoms here on Catalina. No, I'm not refering to the sandy bottoms in a Coppertone ad of years gone by. I'm talking about ocean floors with soft sediment. No, I'm not going to get too "sedimental" in this column. I'll focus on the critter itself.
I'm talking about the California mantis shrimp (Hemisquilla californiensis). I was surprised to note in Jernsen, et al.'s otherwise excellent guide Beneath Pacific Tides that they lumped this arthropod with the true shrimps. It is NOT a decapod crustacean. It belongs in the Order Stomatopoda, not Decapoda. They've been there for 340 million years!
I can't remember ever seeing a mantis shrimp in our local dive park, but they can be seen frequently in other dive sites such as Willow Cove and Hen Rock (to name just a few). Often the first clue to their presence is a round hole in the sand, often rimmed with stones or shells. I'm not sure of their purpose, but they may help prevent the sand from caving into the burrow. If you are lucky, you may see the head of the mantis shrimp peeking out from the hole.
If you are really lucky, you might find one out in the open looking for food early in the morning or late afternoon. They tend to take mid-day "siestas" in their burrows... a practice I'm finding quite pleasant as I "mature." I was at Hen Rock one afternoon when I spotted a male out in the open as I descended. It was in full mating "plumage" and wandering away from its burrow, presumably in search of a mate. I spent the entire dive with it and ended up with 29 minutes of video footage.
On another dive south of Avalon, I was buddied up with Dave Bower. As we descended, we saw another one out in the open at about 70 fsw if memory serves me well (good luck with that, Dr. Bill!). Before we reached it, we penetrated one of the coldest thermoclines I've ever dived through. Needless to say I didn't spend much time filming as my hands (and teeth) chattered and I got ice cream headaches.
Now mantis shrimp are "well-armed" (or should I say well-legged?) as two of their forward appendages are modified for capturing prey and defense. One group has them modified into hardened calcium carbonate clubs that they bash their hard-shelled prey with. These are the "clubbers" (also known as smashers). The second group has them modified into powerful grasping claws that look like a praying mantis (but it should be "preying" mantis!). These are the "spearers."
Mantis shrimp have extremely good vision... far better than mine! We Homo sapiens have a mere three types of color receptors (cones) that sense mainly in the red, green and blue regions of the visual light spectrum. The stomatopods have 16 attuned to many different wavelengths including UV and infrared. This makes them exceptional hunters... and also facilitates the use of complex behaviors in courtship and combat (aren't they both the same?). No wonder I rarely win in those battles!
My dives in tropical waters such as the Philippines have exposed me to a number of other species of mantis shrimp. As is usual in the tropics, many are quite colorful. As I filmed them, I noticed what appeared to be a trend in eye shape. Clubbers often appear to have spherical eyes whereas spearers have oblong ones. Apparently this is due to their different feeding strategies.
Some of my friends in the Philippines like to eat mantis shrimp. I never tried them and stuck to decapods like crabs rather than stomatopods. Apparently when they are sold live in markets, the individual mantis shrimps are placed in plastic bottles to prevent them from killing one another. And a word to the wise... don't put them in aquariums with other critters or you may have nothing left but the mantis after a while.
© 2020 Dr. Bill Bushing. For the entire archived set of over 850 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Burrow bordered by shells and mantis shrimp poking out of burrow; two males out in the open; feeding structures and eyes of spearers and clubbers.
It has been years since I've written about a critter commonly found on some of our sandy bottoms here on Catalina. No, I'm not refering to the sandy bottoms in a Coppertone ad of years gone by. I'm talking about ocean floors with soft sediment. No, I'm not going to get too "sedimental" in this column. I'll focus on the critter itself.
I'm talking about the California mantis shrimp (Hemisquilla californiensis). I was surprised to note in Jernsen, et al.'s otherwise excellent guide Beneath Pacific Tides that they lumped this arthropod with the true shrimps. It is NOT a decapod crustacean. It belongs in the Order Stomatopoda, not Decapoda. They've been there for 340 million years!
I can't remember ever seeing a mantis shrimp in our local dive park, but they can be seen frequently in other dive sites such as Willow Cove and Hen Rock (to name just a few). Often the first clue to their presence is a round hole in the sand, often rimmed with stones or shells. I'm not sure of their purpose, but they may help prevent the sand from caving into the burrow. If you are lucky, you may see the head of the mantis shrimp peeking out from the hole.
If you are really lucky, you might find one out in the open looking for food early in the morning or late afternoon. They tend to take mid-day "siestas" in their burrows... a practice I'm finding quite pleasant as I "mature." I was at Hen Rock one afternoon when I spotted a male out in the open as I descended. It was in full mating "plumage" and wandering away from its burrow, presumably in search of a mate. I spent the entire dive with it and ended up with 29 minutes of video footage.
On another dive south of Avalon, I was buddied up with Dave Bower. As we descended, we saw another one out in the open at about 70 fsw if memory serves me well (good luck with that, Dr. Bill!). Before we reached it, we penetrated one of the coldest thermoclines I've ever dived through. Needless to say I didn't spend much time filming as my hands (and teeth) chattered and I got ice cream headaches.
Now mantis shrimp are "well-armed" (or should I say well-legged?) as two of their forward appendages are modified for capturing prey and defense. One group has them modified into hardened calcium carbonate clubs that they bash their hard-shelled prey with. These are the "clubbers" (also known as smashers). The second group has them modified into powerful grasping claws that look like a praying mantis (but it should be "preying" mantis!). These are the "spearers."
Mantis shrimp have extremely good vision... far better than mine! We Homo sapiens have a mere three types of color receptors (cones) that sense mainly in the red, green and blue regions of the visual light spectrum. The stomatopods have 16 attuned to many different wavelengths including UV and infrared. This makes them exceptional hunters... and also facilitates the use of complex behaviors in courtship and combat (aren't they both the same?). No wonder I rarely win in those battles!
My dives in tropical waters such as the Philippines have exposed me to a number of other species of mantis shrimp. As is usual in the tropics, many are quite colorful. As I filmed them, I noticed what appeared to be a trend in eye shape. Clubbers often appear to have spherical eyes whereas spearers have oblong ones. Apparently this is due to their different feeding strategies.
Some of my friends in the Philippines like to eat mantis shrimp. I never tried them and stuck to decapods like crabs rather than stomatopods. Apparently when they are sold live in markets, the individual mantis shrimps are placed in plastic bottles to prevent them from killing one another. And a word to the wise... don't put them in aquariums with other critters or you may have nothing left but the mantis after a while.
© 2020 Dr. Bill Bushing. For the entire archived set of over 850 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Burrow bordered by shells and mantis shrimp poking out of burrow; two males out in the open; feeding structures and eyes of spearers and clubbers.
