Enlarge / That blue tube is actually a very close relative of vertebrates.Gerard Soury
Beneath the waves, there are strange, almost alien creatures that raise questions about the evolution of life on Earth and our own earliest origins. The answers might be hiding in tunicates.
Tunicates are filter-feeding invertebrates that include sea squirts and salps. The more common ascidiacean species are sessile and attach to rocks or the seafloor, while the appendicularian species swim freely. Yet all of them spawn as larvae that vaguely resemble tadpoles. Motile tunicates tend to grow into something that looks like a larger version of
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