DIVE DRY WITH DR. BILL #879: MYSTERIES OF THE DEEP, PART II
Einstein reportedly once said "The most beautiful thing we can experience is the mysterious. It is the source of all true art and science." There are so many mysteries about marine life that I've tried to solve in my 50+ years as a marine biologist. Many I know I'll never find answers to, even if I get reincarnated as... a marine biologist! However, some seem within reach during my limited lifetime.
One involves two related species of sea cucumbers (aka holothurians). I've observed both in the waters around Catalina Island over the years. I've even filmed both and sent images of them to some of the top sea cucumber experts in North America. None of them have offered an answer since a positive ID usually involves sampling the spicules that comprise their "skeleton" and allows them to be included with the sea stars, sea urchins and brittle stars. Since I found both species in marine protected areas, I wouldn't feel right taking samples.
The first species I observed was at Twin Rocks along Catalina's leeward coast. Initially I thought it was just part of the algal turf on the rocks there. Then it showed some movement. I investigated further and was surprised to find it was indeed a sea cucumber... with various algae growing on it! As I positioned it on the rocks to get a better shot (naughty Dr. Bill), it began a defensive strategy familiar to most marine biologists. It expelled long white streams known as Cuvierian tubules.
Now marine biologists are well aware that many sea cucumbers have devised another strategy to distract predators. When approached by one or bothered by a nosy marine biologist or, as I found out one day, subjected to thermal stress, they eviscerate their intestines out through their anus. Hopefully the predator chows down on that instead of the cuke as it makes its slow escape.
Now that approach has a serious drawback. To fully take advantage of any munchies ingested at the oral end, the intestines are necessary to extract nutrients. When they are eviscerated, it takes time to regrow a new set. Given my colon cancer, I wish evolution had instilled that talent in me, too. Some species, mostly in the genus Holothuria in our waters and also the tropics, have devised a better method. They produce Cuvierian tubules in ducts adjacent to the intestines. When these are released, the cuke still has its intestines intact and the predator has a tasty (and very sticky) snack.
Now the second sea cucumber that no one could identify is most likely also in the genus Holothuria as it, too, released Cuvierian tubules when I molested... er, examined... it. The only place I've seen this specimen is in our own dive park and only on night dives. I quickly found out why. When I'd encounter one, it would quickly disappear by withdrawing into the soft sediment. Apparently this species is light sensitive and nocturnal. By capturing two of these with my quick hands, I was able to extract them from the sand without causing any damage and filmed them.
I'd prefer not to go to my grave (in the briny deep) without finding out the identity of these two cukes. As I mentioned, none of the specialists I've contacted were able to ID them. Certainly someone out there knows and marine biologists should want to know their identity and where I have observed them. I could not find them in any of the field guides in my library.
© 2020 Dr. Bill Bushing. For the entire archived set of nearly 900 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Mystery sea cucumber #1 from Twin Rocks showing algae growing on it and expulsion of Cuvierian tubules.
Image caption: Light sensitive mystery sea cucumber from Casino Point dive park with feeding tentacles and Cuvierian tubules.
Einstein reportedly once said "The most beautiful thing we can experience is the mysterious. It is the source of all true art and science." There are so many mysteries about marine life that I've tried to solve in my 50+ years as a marine biologist. Many I know I'll never find answers to, even if I get reincarnated as... a marine biologist! However, some seem within reach during my limited lifetime.
One involves two related species of sea cucumbers (aka holothurians). I've observed both in the waters around Catalina Island over the years. I've even filmed both and sent images of them to some of the top sea cucumber experts in North America. None of them have offered an answer since a positive ID usually involves sampling the spicules that comprise their "skeleton" and allows them to be included with the sea stars, sea urchins and brittle stars. Since I found both species in marine protected areas, I wouldn't feel right taking samples.
The first species I observed was at Twin Rocks along Catalina's leeward coast. Initially I thought it was just part of the algal turf on the rocks there. Then it showed some movement. I investigated further and was surprised to find it was indeed a sea cucumber... with various algae growing on it! As I positioned it on the rocks to get a better shot (naughty Dr. Bill), it began a defensive strategy familiar to most marine biologists. It expelled long white streams known as Cuvierian tubules.
Now marine biologists are well aware that many sea cucumbers have devised another strategy to distract predators. When approached by one or bothered by a nosy marine biologist or, as I found out one day, subjected to thermal stress, they eviscerate their intestines out through their anus. Hopefully the predator chows down on that instead of the cuke as it makes its slow escape.
Now that approach has a serious drawback. To fully take advantage of any munchies ingested at the oral end, the intestines are necessary to extract nutrients. When they are eviscerated, it takes time to regrow a new set. Given my colon cancer, I wish evolution had instilled that talent in me, too. Some species, mostly in the genus Holothuria in our waters and also the tropics, have devised a better method. They produce Cuvierian tubules in ducts adjacent to the intestines. When these are released, the cuke still has its intestines intact and the predator has a tasty (and very sticky) snack.
Now the second sea cucumber that no one could identify is most likely also in the genus Holothuria as it, too, released Cuvierian tubules when I molested... er, examined... it. The only place I've seen this specimen is in our own dive park and only on night dives. I quickly found out why. When I'd encounter one, it would quickly disappear by withdrawing into the soft sediment. Apparently this species is light sensitive and nocturnal. By capturing two of these with my quick hands, I was able to extract them from the sand without causing any damage and filmed them.
I'd prefer not to go to my grave (in the briny deep) without finding out the identity of these two cukes. As I mentioned, none of the specialists I've contacted were able to ID them. Certainly someone out there knows and marine biologists should want to know their identity and where I have observed them. I could not find them in any of the field guides in my library.
© 2020 Dr. Bill Bushing. For the entire archived set of nearly 900 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Mystery sea cucumber #1 from Twin Rocks showing algae growing on it and expulsion of Cuvierian tubules.
Image caption: Light sensitive mystery sea cucumber from Casino Point dive park with feeding tentacles and Cuvierian tubules.
