Science and the SeaAuthor: The University of Texas Marine Science Institute
17 Nov 2018

Science and the Sea

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The goal of Science and the Sea is to convey an understanding of the sea and its myriad life forms to everyone, so that they, too, can fully appreciate this amazing resource.

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    Hogfish and their Amazing Technicolor Skin

    Camouflage is one of the best evolutionary strategies there is for evading predators, and hogfish are masters of it. These pointy-nosed reef dwellers change skin color so rapidly to match their surroundings — literally in milliseconds — that it seems impossible for them to rely only on their eyes to perceive those surroundings.

    As it turns out, they don’t only use their eyes. Hogfish skin can “see” too. Scientists recently analyzed hogfish DNA and learned how this skin vision, called dermal photoreception, works. Hogfish skin cells include chromatophores, which contain a pigment that’s sensitive to light. When these cells sense light patterns, they can mimic those patterns by manipulating the distribution of their pigment, spreading it thin or clustering it together.

    But scientists also wanted to understand how hogfish skin detects light in the first place. Octopus and cuttlefish also rapidly change skin color to blend into their environments. Their skin uses the same basic mechanism that their eyes use. But that’s not how hogfish skin works. Duke University biologists compared genetic material in hogfish skin to genetic material in its retina, the sensory membrane at the back of the eye. They found the fish’s skin and eyes use different genes to detect light.

    Researchers are still studying the molecular chain reaction involved in this newly discovered form of dermal photoreception. They also want to learn how the hogfish combines visual information from the skin and eyes to match its coloration to the environment so quickly. As they learn more, they hope to discover whether this skin-sensing superpower helps hogfish in other ways too. Hogfish and their Amazing Technicolor Skin Hogfish

  • Posted on 01 Nov 2018

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    Sea Serpent…or Surreptitious Shark?

    Sailors’ lore about the ocean has captured popular imagination for centuries, from mermaids and sirens to the mythical Kraken. But often these stories are rooted in a case of mistaken identity. Tales of frightening sea serpents, for example, may have arisen in part from rare sightings of the elusive frilled shark, a long, slender fish that usually lives 400 to 4,200 feet below the surface.

    In fact, in the earliest existing written description of this bizarre creature, Pennsylvania zoologist Samuel Garman wrote in 1884, “its appearance in the forward portion of the body, particularly in the head, brings vividly to mind the triangular heads, deep-cleft mouths, and fierce looks of many of our most dreaded snakes.” The shark’s discovery led Garman to suggest that people should not dismiss too easily the possibility that a “serpent-like monster of the oceans” might actually exist.

    What makes these sharks so fierce are the 300 teeth that are arranged in 25 diagonal rows along its gaping mouth. The teeth all face backward, making it impossible for prey to back out of the shark’s jaws once snagged. Examinations of stomach contents suggest that squid and other cephalopods make up more than half the frilled shark diet. But scientists know almost nothing about their hunting habits.

    There is one problem, however, in blaming these serpentine predators for supposed sea serpent sightings. Although frilled sharks can grow as long as 6 feet, they more typically reach only 3 to 5 feet long, hardly the massive monster that superstitious sailors might fear. Are frilled sharks responsible for myths about sea serpents, or is that possibility a myth itself?

  • Posted on 01 Oct 2018

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    The Heat Is On…for Deep-Sea Skate Eggs

    If it took more than four years for your eggs to hatch, no one could blame you for seeking a way to speed things up. It appears that deepsea skates, a relative of sharks and rays, have found a way to do exactly that—by using the volcanic heat released from hydrothermal vents deep in the ocean.

    Water heated by Earth’s crust reaches the ocean through hydrothermal vents, where only creatures that have evolved to withstand the extreme temperatures typically live. But when scientists recently sent a remotely operated underwater vehicle (ROV) to explore the hydrothermal fields near the Galapagos Islands, they found several layers of large egg cases. They counted 157 of these cases, often called “mermaid purses,” and used the ROV to bring four of them back to the surface.

    The scientists analyzed the DNA and learned the eggs belonged to the skate species Bathyraja spinosissima. Though these skates live deeper than almost any other skate species, they have not been observed regularly near hydrothermal vents. Yet more than half the egg cases were found near the hottest vents. Could the skates be using heat from the vents to help their offspring develop more quickly? T

    hat’s what the biologists believe is happening, based on similar behavior of two other animals, a rare bird in the South Pacific and long-necked dinosaurs of the Cretaceous period. But their hypothesis is just that — a plausible idea the scientists must test through more observation and research. Hopefully they will learn whether deep-sea skates really are trying to skate past their extra-long incubation periods with a bit of help from Earth’s heat.

  • Posted on 01 Sep 2018

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    Jellyfish for Dinner

    It’s not just humans who enjoy a snack that jiggles and wiggles like gelatin does. To the surprise of scientists, it turns out several penguin species enjoy a bit of jellyfish in addition to their diet of fish, squid, krill and crustaceans. More than 350 hours of video footage from small “penguin cams” in the wild showed that Adélie, yellow-eyed, Magellanic and little penguins eat a wide range of gelatinous critters while hunting for other food.

    Scientists in five countries attached small cameras about the size of strawberries to the backs of 106 penguins at breeding sites throughout the southern hemisphere. Each camera only recorded one trip out to sea per penguin, but the videos revealed penguins going after gelatinous prey almost 200 times, including 187 jellyfish.

    Jellyfish are just one type of gelatinous marine animal, but other “gelata” species unrelated to the jellyfish ended up as penguin dinner too. Little and Magellanic penguins gobbled up 11 comb jellies. The penguins did not seem interested, however, in salps, which are gelatinous filter feeders that consume phytoplankton.

    Despite the number of jellyfish consumed, they were not a big part of the penguins’ diet. They made up only about 1-2 percent of total calories the birds ate. Still, with jellyfish populations soaring in recent years, penguins’ affinity for jellyfish may offer an abundant alternative food source when other menu items are scarce. But scientists don’t know whether huge blooms of jellyfish alone would be enough for penguins to survive if other food sources disappeared.

  • Posted on 01 Aug 2018

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    Some Hermit Crabs Buy Instead of Rent

    They say that home is where the heart is, and that is literally true with hermit crabs — they carry the shell that houses them wherever they go. Since hermit crabs steal their shells from other creatures, usually sea snails, their shells do not grow with them. So a hermit crab only leaves its shell when it has outgrown the home and moves into a larger one, sometimes even killing the shell’s current resident to acquire its new dwelling.

    But a newly discovered species of hermit crab does things a little differently. Instead of moving house after outgrowing one shell after another, the crab known to science as Diogenes heteropsammicola picks a home that grows with it—and involves a bit of quid pro quo. Researchers from Kyoto University in Japan discovered the new crab species living in “walking coral,” a type of solitary coral usually inhabited by marine worms called sipunculans. Normally, the worms receive protection from the coral and benefit the coral by moving it around, preventing it from becoming buried under sediment. It’s an ideal symbiotic relationship—enough so that these new hermit crabs found it a good deal too.

    Two types of walking corals will sometimes host a red and white D. heteropsammicola instead of a worm. Like sipunculans, these hermit crabs offer the living coral transportation, and they sweep away sediment that might otherwise threaten to bury the coral. The coral offers the crabs protection from predators, just as it does for sipunculans, while also growing with the hermit crabs. For this hermit crab species then, home is where the coral is.

  • Posted on 01 Jul 2018


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