Natures wonders: Hydra new mouth every meal (Introduction)

by David Turell , Thursday, March 10, 2016, 05:38 (3178 days ago) @ David Turell

This tiny invertebrate has stingers on its arms, makes a new mouth each time it catches prey to eat:-http://www.livescience.com/53980-terrifying-mouth-of-a-hydra.html?cmpid=NL_LS_weekly_2016-3-09-"Hydra vulgaris is a tiny, tentacled freshwater invertebrate. It has a tubular body measuring less than 0.5 inches (1.3 centimeters) in length, with a grasping footlike appendage at one end and a ring of tentacles covered in sharp barbs at the other. If a small shrimp touches those tentacles, the hydra's barbs paralyze the prey. That's when the smooth expanse of skin at its head rips open to expose a mouth, which gulps down the prey and then reknits itself closed without a seam to show that there was ever a mouth at all.-***-"Collins examined hydra mouths on a cellular level, genetically engineering hydras to have colorized layers of skin tissue throughout its body, so that she and her colleagues could better track cellular activity in the mouth area during feeding.-"The researchers quickly discovered that the cells weren't rearranging — they were deforming.-"'When the mouth is closed, the cells have a roundish appearance," Collins said. "As [the mouth] opens, cells stretch dramatically, going from a roughly spherical to an ellipsoidlike shape."-***-"A hydra would trigger the stretching with electrical signals, which then cued muscular pulses that pulled its mouth open, Collins said. The muscle contraction was a key part of the mouth-opening process, the researchers found — if a hydra was given a muscle relaxant, its mouth wouldn't open."-Comment: Arrived about 600 million years ago. Not very complex compared to Cambrians which appeared 60 million years later with little phenotypic changes in-between.