About Octopus tehuelchus d'Orbigny
This is a small to medium-sized octopus species with a maximum total length of approximately 20 cm (8 in). It has a globular, smooth-surfaced mantle, and its head is slightly narrower than the mantle. The species has prominent eyes surrounded by small granulations. The mantle opening is wide, and the funnel is long. The neck is constricted, and the eight arms measure between two-thirds and three-quarters of the total length of the rest of the animal. The second arm pair is the shortest, while the fourth arm pair is the longest. In males, the hectocotylus develops on the right third arm, and males also have enlarged suckers. Octopus tehuelchus is native to the subtropical southwestern Atlantic Ocean. Its geographic range stretches along the coasts of Brazil and Argentina, between 30°S and 44°S latitude, and between 50°W and 65°W longitude. It inhabits the intertidal zone and shallow subtidal zone, reaching depths of around 90 m (300 ft). It lives over reefs and sandy seabeds, and often hides in crevices, under boulders, and inside empty mollusc shells. This octopus feeds on crabs and small clams, and it is known to drill through gastropod shells to extract hermit crabs living inside. Off the coast of Argentina, this species is heavily preyed on by young sharks. Breeding occurs between autumn and spring. Like many other octopus species, the female selects a shelter to brood a batch of eggs. Females usually choose an invertebrate shell as a shelter: small individuals typically select gastropod shells such as those of Zidona dufresnei, Odontocymbiola magellanica or Buccinanops cochlidium, clam shells such as those of Pitar rostratus or Amiantis purpurata, or large barnacles from the genus Balanus. Medium-sized individuals prefer shells of the oyster Ostrea puelchana, while the largest individuals build their own shelters from shell fragments and other materials. Overall, the oyster Ostrea puelchana is the most favoured shelter, and the majority of eggs are deposited inside the oyster's concave valve.
