DIVE DRY WITH DR. BILL #804: SEA CUKES
Some time ago I wrote about brittle stars, the interesting relatives of the sea stars (or starfish for the non-PC crowd). Today I thought I'd focus on another of this group's relatives, the sea cucumbers. Along with the sea urchins, they belong to the phylum Echinodermata or spiny skinned critters.
I'm quite sure my intelligent readers won't confuse them with terrestrial cucumbers. However, there are cultures which find them even more edible than the land-based veggies. I see sea cucumbers in the Asian markets of Little Saigon here in SoCal. I must admit, I have never tried their flesh. You can even buy them through Amazon.com these days! I'm sure you are aware that terrestrial cucumbers can become pickles (something else this finicky eater won't touch). The closest I've seen a sea cucumber come to that is when I "pickled" them for my biology lab collection.
You might ask why sea cucumbers are included with the other spiny skinned marine critters. Certainly sea urchins, sea stars and brittle stars are obvious members given their hard exoskeletons of calcium carbonate. However, sea cucumbers have soft, pliable bodies more akin to leather. You have to look "deep" inside to see the connection. They have numerous calcium carbonate structures known as ossicles or spicules which can be seen in the microscope image below.
The sea cukes are classified in the group Holothuroidea which was established by the French biologist Henri Marie Ducrotay deBlainville way back in 1834. They usually have elongated, cylindrical bodies that are unlike their other echinoderm relatives. However, like those relatives they usually exhibit the five part radial symmetry of most echinoderms. If you look closely, you may see five rows of tube feet or podia like those seen on sea stars, sea urchins and brittle stars. These are used for moving along the bottom or holding on to hard substrate.
Most cukes have a ring of "tentacles" surrounding the mouth which are used for feeding. These are actually modified tube feet. Some species use them to ingest sediment containing organic matter and other "tasty" goodies. They excrete the sediment and their poop is commonly seen on the bottom in our waters and elsewhere. Other species extend the tentacles to trap plankton drifting by. These cukes often burrow into the reef with only the tentacles exposed.
The tentacles are occasionally seen by fish as a tasty treat, so the sea cucumber is able to retract them into the body if danger threatens. Based on my observation, the cucumber species in our waters do not seem to have many predators. Most rest on the bottom with little obvious means of defense. One might think they contain toxins that potential predators avoid. And that would be correct since many have holothurin in their bodies. I have also seen an unidentified species in our waters that apparently allows algae to grow on its body surface, thus camouflaging it!
Another defense mechanism is accomplished by eviscerating their digestive tract or specialized cuvierian tubercules, part of the respiratory system. These often sticky structures occupy the predators attention and often deter it from attacking the body of the cuke. Both of these structures can then be regrown by the sea cucumber in a relatively short time.
Yet another defense mechanism I've observed in local species was seen in a yet unidentified critter that remains buried in the substrate during the day but comes out at night to feed. As soon as it detects my video lights, it immediately withdraws back into its hiding place. I have tried to get an identification of the species from several experts but none of them seemed to know what it is.
Despite these defenses, I have observed crabs feeding on them and have seen cucumbers with bite marks (probably from fish or crabs) and large patches of skin missing. During warm water episodes I have also seen signs of what may be a disease impacting them. During El Niño events, their echinoderm relatives like sea urchins and starfish are alsdo affected by similar diseases. Cukes from temperate waters like ours are also known to shut down many body functions during periods of elevated sea water temperatures.
I mentioned earlier that many species of sea cucumber are harvested for human consumption. Various cultures refer to it as as trepang, bêche-de-mer or balate. The Japanese eat sea cucumber raw as a form of sushi and the digestive tract is also eaten and known as konowata. Holothurians are also used in Chinese traditional medicine to treat a number of health issues such as fatigue, impotence, gingivitis and joint pain. Their bodies contain chemicals that help reduce inflammation and chondroitin sulfate which is a major component of collagen.
FOX News has even reported that sea cucumbers may be a treatment for certain forms of cancer. Western oncologists use chemotherapy and radiation, which kills cancer but also lowers the body's immune system. Eating sea cucumbers is reported to kill cancer cells while keeping the immune system functioning at an optimal level. Hmmm... perhaps I should stop by those Asian markets on my way to my next chemo session, or just order sea cucumber through Amazon prime!
© 2018 Dr. Bill Bushing. For the entire archived set of over 750 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Local warty sea cucumber and microscopic view of ossicles; cucumber tentacles extending from crevice to filter feed and cuvierian tubules being expelled by cucumber for defense.
Some time ago I wrote about brittle stars, the interesting relatives of the sea stars (or starfish for the non-PC crowd). Today I thought I'd focus on another of this group's relatives, the sea cucumbers. Along with the sea urchins, they belong to the phylum Echinodermata or spiny skinned critters.
I'm quite sure my intelligent readers won't confuse them with terrestrial cucumbers. However, there are cultures which find them even more edible than the land-based veggies. I see sea cucumbers in the Asian markets of Little Saigon here in SoCal. I must admit, I have never tried their flesh. You can even buy them through Amazon.com these days! I'm sure you are aware that terrestrial cucumbers can become pickles (something else this finicky eater won't touch). The closest I've seen a sea cucumber come to that is when I "pickled" them for my biology lab collection.
You might ask why sea cucumbers are included with the other spiny skinned marine critters. Certainly sea urchins, sea stars and brittle stars are obvious members given their hard exoskeletons of calcium carbonate. However, sea cucumbers have soft, pliable bodies more akin to leather. You have to look "deep" inside to see the connection. They have numerous calcium carbonate structures known as ossicles or spicules which can be seen in the microscope image below.
The sea cukes are classified in the group Holothuroidea which was established by the French biologist Henri Marie Ducrotay deBlainville way back in 1834. They usually have elongated, cylindrical bodies that are unlike their other echinoderm relatives. However, like those relatives they usually exhibit the five part radial symmetry of most echinoderms. If you look closely, you may see five rows of tube feet or podia like those seen on sea stars, sea urchins and brittle stars. These are used for moving along the bottom or holding on to hard substrate.
Most cukes have a ring of "tentacles" surrounding the mouth which are used for feeding. These are actually modified tube feet. Some species use them to ingest sediment containing organic matter and other "tasty" goodies. They excrete the sediment and their poop is commonly seen on the bottom in our waters and elsewhere. Other species extend the tentacles to trap plankton drifting by. These cukes often burrow into the reef with only the tentacles exposed.
The tentacles are occasionally seen by fish as a tasty treat, so the sea cucumber is able to retract them into the body if danger threatens. Based on my observation, the cucumber species in our waters do not seem to have many predators. Most rest on the bottom with little obvious means of defense. One might think they contain toxins that potential predators avoid. And that would be correct since many have holothurin in their bodies. I have also seen an unidentified species in our waters that apparently allows algae to grow on its body surface, thus camouflaging it!
Another defense mechanism is accomplished by eviscerating their digestive tract or specialized cuvierian tubercules, part of the respiratory system. These often sticky structures occupy the predators attention and often deter it from attacking the body of the cuke. Both of these structures can then be regrown by the sea cucumber in a relatively short time.
Yet another defense mechanism I've observed in local species was seen in a yet unidentified critter that remains buried in the substrate during the day but comes out at night to feed. As soon as it detects my video lights, it immediately withdraws back into its hiding place. I have tried to get an identification of the species from several experts but none of them seemed to know what it is.
Despite these defenses, I have observed crabs feeding on them and have seen cucumbers with bite marks (probably from fish or crabs) and large patches of skin missing. During warm water episodes I have also seen signs of what may be a disease impacting them. During El Niño events, their echinoderm relatives like sea urchins and starfish are alsdo affected by similar diseases. Cukes from temperate waters like ours are also known to shut down many body functions during periods of elevated sea water temperatures.
I mentioned earlier that many species of sea cucumber are harvested for human consumption. Various cultures refer to it as as trepang, bêche-de-mer or balate. The Japanese eat sea cucumber raw as a form of sushi and the digestive tract is also eaten and known as konowata. Holothurians are also used in Chinese traditional medicine to treat a number of health issues such as fatigue, impotence, gingivitis and joint pain. Their bodies contain chemicals that help reduce inflammation and chondroitin sulfate which is a major component of collagen.
FOX News has even reported that sea cucumbers may be a treatment for certain forms of cancer. Western oncologists use chemotherapy and radiation, which kills cancer but also lowers the body's immune system. Eating sea cucumbers is reported to kill cancer cells while keeping the immune system functioning at an optimal level. Hmmm... perhaps I should stop by those Asian markets on my way to my next chemo session, or just order sea cucumber through Amazon prime!
© 2018 Dr. Bill Bushing. For the entire archived set of over 750 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Local warty sea cucumber and microscopic view of ossicles; cucumber tentacles extending from crevice to filter feed and cuvierian tubules being expelled by cucumber for defense.
