 exploring, preserving and protecting the genetic diversity of the world's oceans
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OGL Newsletter
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Greetings!
Old man 2012 has been replaced by baby 2013 as we head into the new year, so what better time to talk about rejuvenation in the undersea world? Read below as we describe unique marine creatures who have managed to do what Botox and cod liver oil can't: literally reverse the maturation process. Perhaps one day mankind will figure out how to tap into this Fountain of Youth!
And, as always, follow our expeditions and other news from the marine world on our Facebook and Twitter pages!
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The Ocean's Immortals
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The "immortal jellyfish", also known as the "Benjamin Button jellyfish", Turritopsis dohrnii, is able to revert from its adult form (left) to a juvenile polyp state (right) when stressed. Photo: National Geographic
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They say that you are only young once, but not if you are Turritopsis dornii. This pea-sized hydrozoan found in the Mediterranean, Caribbean and off the coast of Japan, is known as the "Benjamin Button Jelly" because, like the movie character of the same name, it can live its life in reverse! Like other hydrozoans, Turritopsis dornii spawns to produce polyps that grow into new adult medusae. In 1988, Christian Sommer discovered that, unlike other hydrozoans, Turritopsis dornii does not always go on to get old and die. Instead, it can revert from its adult tentacle-bearing medusa stage back to its juvenile polyp stage! As exciting as this discovery was, its significance was not fully appreciated until recently.
The regeneration process from adult to polyp is now understood to be one of "transdifferentiation," where one cell type becomes another; a capability shared by stem cells in the human body. Stem cells are important because they can develop into any other type of cell or tissue. Scientists hope that by understanding how stems cells do this they can learn to help the body heal itself or even regenerate new tissues and organs. Cancer cells also behave a bit like stem cells gone awry, growing out of control and disrupting the delicate balance of cell birth and cell death that keeps healthy animals alive. So understanding the transdifferentiation process may help explain how normal cells become cancerous.
Kevin Peterson, a molecular paleobiologist from Dartmouth, recently revealed how micro-RNAs (miRNA) in cells act as on-off switches, causing cell differentiation (maturation) when on and causing return to a primitive, undifferentiated state when off. In the case of the hydrozoans, it's the stress of aging, food deprivation, or temperature modulation that turns the miRNA switch on. In the case of human cells, changes that that effect the miRNA switch can cause them to turn off, cells thus becoming undifferentiated and chaotic (i.e. cancerous). Peterson has been following the research of Daniel Martínez, a biologist at Pomona College who is studying these hydrozoans, in the hope of better understanding how this mechanism might contribute to human health and longevity.  | |
(Left) This purple encrusting sponge (Haliclona sp.) is renowned for its ability to regenerate, while (right) the red sea urchin (Strongylocentrotus franciscanus) has been recorded to live more than 200 years without indication of senescence. Photos: Mary Joe Adams and Dave Cowles
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The "Benjamin Button" jelly isn't the only seemingly ageless creature in the ocean. Porifera (sponges), in addition to both spawning and regenerating, are able to physically move individual cells away from danger or to cover up damaged regions of their bodies; only dehydration or freezing and subsequent cell rupture appear capable of killing sponges. In fact, some sponges have been found living near Antarctica with a lifespan greater than 1000 years! Demonstrating yet another youth-preserving mechanism, Thomas Ebert, professor of Biology at San Diego State, studied red and purple sea urchins (Strongylocentrotus franciscanus and purpuratus) known for their incredible longevity; it appears that these species can continue to live and spawn well over 200 years if left undisturbed with no sign of cell aging or death and replacement, growing steadily and consistently at a very slow rate independent of ocean conditions.
It may be some time still before mankind can fully comprehend how some marine life forms can remain forever young, and how we may best make use of this knowledge for our own rejuvenation and survival. In the meantime, there are always Botox and cod liver oil! ****
Read this article in the New York Times describing the history of research on the immortal jellyfish and what role miRNA from these hydrozoans can play in combating cancer in humans!
Find out more about the pharmaceutical potential of sponges in this fascinating article. Find out more about immortal sea urchins in this Science Daily article.
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New Publication for OGL and Collaborators!
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Tartralons in Teredinebacter turnerae shipworms inhibit transient microbes in the gut from scavenging glucose (left), and inhibit competing symbionts in the gill from utilizing resources there (right).
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Congratulations to OGL and collaborators on the Philippine Mollusk Symbiont project! January 3 marks the electronic release of a new publication:
Elshahawi SI, Trindade-Silva AE, Hanora A, Han A, Flores M, Vizzoni V, Schrago C, Soares C, Concepcion G, Distel D, Schmidt EW, Haygood MG (2013) . Boronated tartrolon antibiotic produced by symbiotic cellulose-degrading bacteria in shipworm gills. PNAS, Early Edition, 3 January.
Shipworms rely on bacterial symbionts in their gills to make enzymes that help them digest wood (cellulose), converting it to sugar (glucose). This paper presents the finding that shipworm symbionts also make antimicrobial compounds (tartrolons). It is proposed that the tartralons support the symbiosis by inhibiting growth of unwanted (non-symbiotic) bacteria that could compete with the symbionts for resources in the gills, as well as inhibiting growth of bacteria in the gut (cecum) that could compete with the host for glucose. This exciting news may have implications in the development of human antibiotics.
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Love in the Deep
In the spirit of Valentine's Day, join us next month as we observe the sensuous and sometimes risque amorous endeavors of some of our favorite ocean inhabitants. You might pick up some pointers to try out on your own special Valentine... or not!
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During mating season, the male octopus grows a special appendage on his third arm called a "hectocotylus", which he inserts into the female's gill to deliver sperm. The mating act can last up to two hours and can be repeated several times until eventually the male's hectocotylus breaks off. But never fear: he will regenerate a new one in the next mating season.
Photo: www.bjornstar.com
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Want to help OGL document and preserve the spectacular genetic diversity of our world's oceans? Visit http://www.oglf.org/Support.htm
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