Science and the SeaAuthor: The University of Texas Marine Science Institute
16 Aug 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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    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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    Revamping Their Venom

    One of the most effective treatments for a venomous bite or sting in humans is anti-venom, which is manufactured from the venom itself. But what if a creature’s venom changes over time? That’s exactly what scientists recently found in the starlet sea anemone, and it raises important questions about the way humans use venom, especially in medicine.

    The starlet sea anemone, found in shallow, brackish water along the East and West Coasts, is a relative of the jellyfish that can grow up to a little more than 2 inches long. A group of scientists studied this sea anemone, scientifically named Nematostella vectensis, throughout its life cycle to learn more about the venom it produces.

    The anemone starts out as a tiny oval larva, an attractive meal for predators passing by. But when a predator swallows the larva, it spits it back out because the larva’s powerful venom—passed along to it from its mother—is poisonous. Then, as the larva metamorphoses into an adult, the composition of its venom changes too. The adult starlet sea anemone is a predator that stings small fish and shrimp to feed on them. But even adults do not rely on producing just one type of toxin. The venom’s recipe shifts according to the anemone’s environment, diet and needs.

    Past research has found that cone snails and scorpions use one type of venom for defense and another for catching prey. The new findings from the starlet sea anemone suggest that other animals might also have different toxin concoctions—and that could mean new opportunities for researchers to develop new medicines.

  • Posted on 01 Jun 2018

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    Parrotfish Farmers Protect Coral

    Farmers don’t typically grow crops on all of their land simultaneously – they rotate crops and leave some land fallow so soil can recover and remain fertile. It turns out some herbivorous reef fish also understand not to over-harvest their food. They give it time to recover, which benefits them as well as the coral on which their food grows.

    This discovery began when scientists’ observed partially eaten patches of algae – the preferred food of parrotfish – on dead coral skeletons on the Palmyra atoll, about 1,000 miles south of Hawaii. Scientists continued observing these bald spots over time and saw steephead parrotfish gorging on one small patch of algae. But the parrotfish moved on to another patch of algae before wiping out the first spot. In fact, the fish did not return to that first patch until more algae grew back, and they defended it against other grazing critters, giving the algae time to recover. This same algae is usually toxic to juvenile coral. So, when parrotfish scrape away the algae, they create an algae-free spot where new coral larvae can survive and grow.

    But overfishing has reduced parrotfish populations. Researchers therefore tracked parrotfish movements over several years, hoping to gather information to help develop effective conservation strategies. Biologists learned for the first time that parrotfish travel up to a kilometer from their feeding grounds, most likely to spawn offshore. Knowing how far parrotfish range from their feeding area helps researchers determine how much space around a reef requires protection for conservation. But scientists don’t need to worry as much about conserving the algae since the parrotfish help with that.

  • Posted on 01 May 2018

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    This Cool Cucumber Regrows Itself

    You may have heard that starfish can regrow arms they’ve lost, but imagine a creature that can regrow nearly all its internal organs. Sea cucumbers have no brain, eyes or heart, but when they have to protect themselves, they turn themselves inside out and eject their intestines, reproductive organs and respiratory tissues. But these soft tube-shaped animals can regrow all that tissue within about six weeks. Researchers hope studying the sea cucumber’s remarkable regeneration abilities will offer insights for human medicine.

    Sea cucumbers are echinoderms, the same animal subgroup that includes starfish, sand dollars and sea urchins. Sea cucumbers don’t have shells for protection, like the other echinoderms. Instead, they shoot out their guts out at predators. But that means they must regrow those organs in order to survive. Scientists at the Chinese Academy of Sciences Institute of Oceanology wanted to know how this organ regeneration is possible, so they sequenced about 30,000 genes of the Japanese sea cucumber, about 92 percent of its entire genome.

    Then they compared its genetic makeup to genomes of other organisms to learn about the sea cucumber’s evolution. Researchers found that sea cucumbers branched off from other echinoderms about 479 million years ago and have far fewer genes than other echinoderms for turning biological material into hardened mineral. This biomineralization process builds echinoderms’ shells, or exoskeletons.

    The scientists also identified other genes that no other echinoderms have—probably the ones that allow them to regrow their innards. That brings us one step closer to understanding how these resilient critters regrow their insides — and it may help us learn more about repairing or growing human tissue.

  • Posted on 01 Apr 2018


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