As the senior aquarist of animal health at Birch Aquarium at Scripps Institution of Oceanography, Maddy Tracewell often gets a close-up look at some of the ocean’s most captivating and odd creatures.

An Oklahoma family has come to grips with its new reality after acquiring an octopus to raise as a pet, only for her to stunningly produce a small army of hatchlings. “In case it wasn’t already ...