In contrast, appendicularians retain the look of a tadpole as they grow to adulthood and swim freely in the upper waters. They live their adult lives attached to the seafloor. Most ascidiaceans begin their lives looking like a tadpole and morph into the barrel-shaped adults. There are two main tunicate lineages, ascidiaceans (often called “sea squirts”) and appendicularians. One of the siphons draws in water with food particles through suction, allowing the animal to feed using an internal basket-like filter device. An adult tunicate’s basic shape is typically barrel-like, with two siphons projecting from its body. Tunicates are truly strange creatures that come in all shapes and sizes and have a wide variety of lifestyles. In a new study in Nature Communications, Nanglu and co-authors describe the new fossil, named Megasiphon thylakos, revealing that ancestral tunicates lived as stationary, filter-feeding adults and likely underwent metamorphosis from a tadpole-like larva. … It’s just as cool,” said Nanglu, a postdoctoral researcher in the Department of Organismic and Evolutionary Biology. “This animal is as exciting a discovery as some of the stuff I found when hanging off a cliffside of a mountain. But his latest subject may hold first-place status for a while: a 500-million-year-old fossil from the tunicates, a wonderfully weird group of marine invertebrates.
Karma Nanglu says his favorite animal is whichever one he’s working on.
