Reproductive systems of rare adult specimens of the deep-sea squid genera Chiroteuthis, Mastigoteuthis, Liocranchia, and Bathoteuthis were collected in 2006 and 2015 in the different research surveys in the Atlantic Ocean between 46°40′S and 17°11′N.

We describe a new species, Mastigoteuthis microlucens, of the family Mastigoteuthidae from the tropical North Pacific. Its most distinctive morphological character is the presence of microscopic photophores in the integument. Morphological data indicate

Mastigoteuthid squids are ecologically important, being prey to many apex predators, yet the diversity and systematics of the family remain poorly understood. Delicate by nature, they are often damaged during capture; there is a need to accurately identify