Discovery of adipocyte-like accessory reproductive cells in male giant squid

Some deep-sea squids are different from most other cephalopods, but similar to most animals, in their method of utilizing male genitalia. We conducted anatomical investigations of the male reproductive tract in the giant squid, Architeuthis dux and found that the lumens of the spermatophoric complex are filled with a myriad of lipid droplet-enriched cells. These cells have a spherical shape, consisting of a nucleus, lipid droplets making up approximately 25% of the cell, and well-developed rough endoplasmic reticulum. Chemical and proteomic analyses identified fatty acids and many abundant proteins that are common in their muscle tissues and mammalian adipocytes, respectively.