The best known species is T. pellucida. Juveniles begin an ontogenetic descent reaching bathypelagic depths as adults where they mate and spawn. Peculiar glands develop on the mantle of females at maturity that may produce a pheromone (Voss, 1985). In the dark, spacious waters of the bathypelagic zone locating a mate can be difficult. Presumably the production of a chemical attractant (pheromone) combined with the luminescence provided by the arm-tip photophores solves this problem. During mating discharged spermatophores (spermatangia) attach to the dorsal surface of the female then penetrate through the mantle wall and apparently discharge sperm into the mantle cavity (Voss, 1985). Females apparently spawn once then die.