As they mature they migrate to progressively greater depths, an ontogenetic descent, and this reaches to about 1500 m, the depth at which the largest individual collected to date was recorded, it had a mantle length of 243mm and was a subadult.
The passage describes the movement of these creatures from shallower to deeper waters as they grow, reaching a depth of approximately 1500 meters where the largest specimen ever found was recorded. This individual measured 243 mm in mantle length and was a subadult.