As they mature they migrate to progressively greater depths , an ontogenetic descent .
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 .
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 .