Brooding in a gonatid squid off northern Japan.

Brooding of egg masses by a squid in Japan is described. Brooding females were photographed in situ, and the females, their eggs, and their hatchlings were collected. The squid had all undergone gelatinous degeneration and swam slowly and continuously by undulating the fins and expelling water sporadically through the funnel. Eggs were held together by a dark, viscous material that formed a single-layer, sheet-like mass, from which hatchlings were seen to emerge. The annual appearance of brooding females in surface waters during spring suggests that they transport their egg masses from deep water to the surface before the eggs hatch. Genetic analyses identified the squid as Gonatus madokai (family Gonatidae), now the second gonatid and third squid known to brood.