Natures wonders: mucus mesh ocean grazers (Introduction)

by David Turell , Wednesday, May 09, 2018, 17:44 (2388 days ago) @ David Turell

Just when you thought the bush of life couldn't get any crazier, it has:

https://cosmosmagazine.com/biology/meet-the-ocean-creatures-that-use-a-mesh-of-mucus-to...

"But the ocean has its own suite of grazers, with very different — even bizarre — body forms and feeding techniques. Instead of teeth, one group of these invertebrates uses sheets of mucus to consume huge quantities of tiny plant-like particles. In our new paper, my colleagues and I suggest a new categorization for this overlooked group: “mucous-mesh grazers,” in recognition of their unusual feeding strategy.

"Unlike the mucus in our noses, which appears amorphous and blobby, the mucous sheets of these ocean grazers can be structured into ornate meshes and nets. These mucous sheets can function like a filter to ensnare food as small as bacteria. The grazers themselves are mammoth in comparison: up to 10,000 times bigger than their food. If people ate food that small, you’d be picking salt and sugar grains off your dinner plate.

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"Mucous-mesh grazers include salps, pyrosomes, doliolids, pteropods and appendicularians. They are typically centimeters in length, roughly spanning the size of your fingernail to the size of your hand. Some form colonies comprised of many individuals in long chains that can be much longer. These creatures are large and watery compared to their hard-bodied planktonic counterparts. If you stepped on one, it would squish, not crunch. A mostly water body enables them to grow large quickly.

"Mucous-mesh grazers are free floating and suited to the open ocean. They live far from shore, where food is scarce and often small. The tiny holes and fibers of their mucous meshes enable them to capture microscopic particles, which they subsequently swallow, sometimes along with the mucus.

"Unlike spiders that spin their feeding webs, these grazers have a special organ, called an endostyle, that secretes their mucous mesh. Depending on the grazer, the mucous mesh can be located either inside or outside the body. One group, for example, secretes a mucous bubble big enough for the animal to live inside like a house. Another group, nicknamed sea butterflies, secrete mucous webs that attach to their wing-shaped feet. These mucous webs range in size from an inch to over 6 feet.

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"Picky eating by mucous-mesh grazers may have profound implications for biogeochemical cycles, particularly in light of shifting ocean conditions. Environmental factors like ocean temperature, availability of nutrients and the type and amount of prey present influence when and where mucous grazers appear, how long they stick around and their impact on ocean food webs.

"A more tropical species of mucous-grazing pyrosomes (Pyrosoma atlanticum) provides a case study. Typical in warmer waters as far north as Southern California, they confounded scientists and fishermen alike when they appeared off the Oregon coast in 2014.

"No one knows why the pyrosomes appeared, but ocean temperatures warmed around the same time. Like other mucous-mesh grazers, the fine pyrosome filter allows them to graze on the smaller particles that are associated with warmer, less nutrient-rich surface water – prey too small for most other animals to catch. Along with other researchers along the West Coast, my lab is actively working to understand why the pyrosomes appeared, how they might affect the marine ecosystem, and if they will persist."

Comment: Mucus is a common product among organisms. This is a neat adaptation.