Mariaglaja tsurugensis is a species of sea slug, or "headshield slug", a marine opisthobranch gastropod mollusk in the family Aglajidae.

[1] This species lives from Tanzania to Australia.

[2] Mariaglaja tsurugensis is a simultaneously hermaphroditic species.

[3] Contrary to classic theoretical predictions, Sprenger et al. (2011)[3] have shown for the first time that the mating rate is largely unresponsive to variations in mate availability in this simultaneous hermaphrodite.

[3] With mating rates being close to the female fitness optimum, their findings challenge the prevailing notion of male-driven mating rates in simultaneous hermaphrodites, and call for complementary investigations of mating-rate effects on fitness through the male sexual function.