notochord

The Bizarre World of Pelagic Invertebrates

I have come to view the oceans as an immense bowl of salty soup. Billions of creatures ride its currents, some visible to the naked eye, but many so tiny they can only be seen under a microscope. Some creatures will eventually settle down and live their adult lives far from where they started out. Others will spend their entire lives offshore. The latter — in particular invertebrates that spend their lives adrift in the ocean — is what this article is about. Many are […]

Tunicates: The Surprisingly Complex Sea Squirts

Of all the marine animals in the world, tunicates are vetebrates’ closest relatives and that includes the class Mammalia (us). Both tunicates and mammals are members of the phylum Chordata. Both have a notochord (a cartilaginous skeletal rod) when they are embryos. The notochord is lost as most tunicates grow older but it segments and turns into a backbone in mammals and other vertebrates. Tunicates further belong to the subphylum Tunicata and the class Ascidiacea. The latter includes 2,500 to 3,000 species, about 90 of […]

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