Deep-sea records of shells of Argonauta nouryi Lorois, 1852 (Mollusca, Cephalopoda, Argonautidae) in western Mexico

ABSTRACT Empty shells, also known as egg cases, of females of the epipelagic cephalopod Argonauta nouryi were collected in deep sea off the coast of western Mexico, in two localities at 1535–1542 m and 1858–1879 m depth. A total of 30 shells (length 28 to 53 mm), most of these entire, were examined and represent the second record of A. nouryi empty shells in deep sea, below 200 m depth. It is suggested that entire shells found on the sea bottom indicates that the individuals were not consumed by apex predators but rather died of natural causes or penetrate into the very shallow, wide, hypoxic or even anoxic core of the Oxygen Minimum Zone, a habitat hostile for the argonauts which feature high metabolic rate and high aerobic demand.