Host-parasite relationship Octopus tehuelchus – Aggregata valdessensis in Patagonian coast, southwestern Atlantic Ocean

•Aggregata valdessensis causes damage to Octopus tehuelchus tissues evidenced by hypertrophy of host cell, destruction of host tissues and inflammation host responses.•Males octopuses were most infected.•Octopus tehuelchus infected by Aggregata valdessensis showed a lower RNA/DNA ratio.