DIVE DRY WITH DR. BILL #744: NUDIS!
No, I didn't mispell that title. For my readers with well-developed prurient interests, sorry... this will not be a column focused on naked women (or men). Of course the subjects I will be talking about lack clothes, but how many marine critters are you aware of that shop at Pierre Cardin, Christian Dior or Ralph Lauren... or even Costco, Marshalls or Ross? And, as you shall learn, they'd have a hard time chosing which gender clothing they needed!
I'm referring to the marine gastropods (snails) known as nudibranchs, sometimes disgustingly referred to as sea slugs. Their name comes from the fact that their gills are naked (good thing ours aren't). Of course many of the snails you are familiar with are encased in shells, but nudis lack such protection. These colorful creatures are a focus for many underwater photographers. Unfortunately even my high definition video camera can't capture their beauty, so once again I turn to my friend and talented underwater imager, Kevin Lee (DiverKevin).
Since escargot is a delicacy for many marine animals (and I even tasted them at the Drake Hotel in Chicago as Packy Offield's guest), how come these snails choose to live without protection? Well, if you were to try eating one, like my marine biologist icon Edward F. "Doc" Ricketts of Cannery Row fame reportedly did, you'd apparently find many of them just don't taste very good.
Other species of nudis which feed on marine life with stinging cells such as hydroids or anemones are capable of incorporating these cells (called nematocysts) into their own bodies without triggering the sting. They then defend themselves using the nematocyts from their own prey! Pretty cool. Too bad I can't do that myself with my steaks or Thai green curry.
So why are so many nudis so colorful, and therefore attractive to underwater photographers. It is called warning coloration. By adorning their bodies with beautiful pigmentation these snails tell potential predators they do not represent a tasty snack. When a fish tries to eat one, it spits it out and (hopefully) remembers not to eat another one with the same coloration. It's kind of like me when I munch down on a pickle or asparagus... even though they aren't beautifully adorned.
Let's get back to the nudi thing. I said it refers to the snail's naked gills. There are essentially two types of nudis based on their gill structure. One group, the dorids, has its gills arranged in a circle toward the rear of the body. They can be retracted so an inquisitive fish doesn't nip them off. Another group, the aeolids, have their gills (called cerata) spread all over their dorsal or upper surface.
I mentioned previously that nudis would have a hard time shopping for clothes due to their gender identity. All the ones I've encountered are neither male nor female. Instead they are both... and at the same time! Nudibranchs are simultaneous hermaphrodites. Although they possess both male and female genitalia, they are not able to fertilize their own eggs. That would be way too easy! However, when they are out on the town... er, reef... any member of their species they encounter would be a suitable mate!
When nudis do "the wild thing," they line up on their right sides (head to tail). The male organ of one couples with the female organ of the other. In the past I've referred to this as "double your pleasure, double your fun!" I hope my friends in the Wrigley family won't object to my using that phrase.
© 2017 Dr. Bill Bushing. For the entire archived set of 750+ "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Dorid nudibranchs on top and aeolid nudibranchs on bottom. Note location of gills (cerata). All photos courtesy of Kevin Lee.
No, I didn't mispell that title. For my readers with well-developed prurient interests, sorry... this will not be a column focused on naked women (or men). Of course the subjects I will be talking about lack clothes, but how many marine critters are you aware of that shop at Pierre Cardin, Christian Dior or Ralph Lauren... or even Costco, Marshalls or Ross? And, as you shall learn, they'd have a hard time chosing which gender clothing they needed!
I'm referring to the marine gastropods (snails) known as nudibranchs, sometimes disgustingly referred to as sea slugs. Their name comes from the fact that their gills are naked (good thing ours aren't). Of course many of the snails you are familiar with are encased in shells, but nudis lack such protection. These colorful creatures are a focus for many underwater photographers. Unfortunately even my high definition video camera can't capture their beauty, so once again I turn to my friend and talented underwater imager, Kevin Lee (DiverKevin).
Since escargot is a delicacy for many marine animals (and I even tasted them at the Drake Hotel in Chicago as Packy Offield's guest), how come these snails choose to live without protection? Well, if you were to try eating one, like my marine biologist icon Edward F. "Doc" Ricketts of Cannery Row fame reportedly did, you'd apparently find many of them just don't taste very good.
Other species of nudis which feed on marine life with stinging cells such as hydroids or anemones are capable of incorporating these cells (called nematocysts) into their own bodies without triggering the sting. They then defend themselves using the nematocyts from their own prey! Pretty cool. Too bad I can't do that myself with my steaks or Thai green curry.
So why are so many nudis so colorful, and therefore attractive to underwater photographers. It is called warning coloration. By adorning their bodies with beautiful pigmentation these snails tell potential predators they do not represent a tasty snack. When a fish tries to eat one, it spits it out and (hopefully) remembers not to eat another one with the same coloration. It's kind of like me when I munch down on a pickle or asparagus... even though they aren't beautifully adorned.
Let's get back to the nudi thing. I said it refers to the snail's naked gills. There are essentially two types of nudis based on their gill structure. One group, the dorids, has its gills arranged in a circle toward the rear of the body. They can be retracted so an inquisitive fish doesn't nip them off. Another group, the aeolids, have their gills (called cerata) spread all over their dorsal or upper surface.
I mentioned previously that nudis would have a hard time shopping for clothes due to their gender identity. All the ones I've encountered are neither male nor female. Instead they are both... and at the same time! Nudibranchs are simultaneous hermaphrodites. Although they possess both male and female genitalia, they are not able to fertilize their own eggs. That would be way too easy! However, when they are out on the town... er, reef... any member of their species they encounter would be a suitable mate!
When nudis do "the wild thing," they line up on their right sides (head to tail). The male organ of one couples with the female organ of the other. In the past I've referred to this as "double your pleasure, double your fun!" I hope my friends in the Wrigley family won't object to my using that phrase.
© 2017 Dr. Bill Bushing. For the entire archived set of 750+ "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Dorid nudibranchs on top and aeolid nudibranchs on bottom. Note location of gills (cerata). All photos courtesy of Kevin Lee.
