Friday Harbor Marine Laboratories, University of Washington
San Juan Island, Washington
Archival Pigment Print
This is one of those surprising facts that invertebrate zoologists take delight in sharing with the uninitiated: Sea squirts like the one you see here (looking more exotic vegetable than animal) are the invertebrate group most closely related to vertebrates—that is, to salmon, lizards, hawks, and humans. The evidence for this link is apparent when we look at the squirt’s fish-like larva, a swimming stage that shares key traits with primitive vertebrates: a notochord, dorsal nerve cord, and gill slits. The adult stage, however, lacks a notochord and nerve cord and lives attached to rocks. To feed, it creates a current by drawing seawater in one opening and ejecting it out the other, removing food particles from the flow.