WASHINGTON, D.C.—No bigger than a thumb, the Hawaiian bobtail squid needs all the help it can get to survive. Researchers have long known that this cephalopod, Euprymna scolopes, houses bioluminescent bacteria in a special light organ just for that purpose. The light helps camouflage the squid from predators below, and the squid has specific proteins to aim this spotlight. Now, researchers have discovered that the bobtail hosts other bacterial guests as well—and may depend on them to keep squid eggs safe. Many octopuses watch over their eggs as they develop. Not the bobtail squid, which leaves its eggs unattended on coral reefs. Yet it does have a small gland in its reproductive tract whose function has been a mystery for almost a century. Curious about this gland, microbiologists isolated DNA from it, identifying about a dozen types of microbes. These microbes are deposited in the jelly encasing the squid’s eggs. Now, the researchers have treated bobtail squid eggs with antibiotic and left them in seawater. In just 11 days, the eggs became coated with a “fuzz” of fungi and suffocated, they reported this week at the Frontiers in Phylogenetics meeting at the National Museum of Natural History here. Further tests show that some of the bacteria in the gland are very similar genetically, but have different abilities to inhibit fungi and seem to do a good job keeping eggs clean. Thus, aside from being an unusual example of a host tapping different bacteria for different purposes, the egg-protecting microbes may offer new opportunities to look for novel antifungal compounds.