Step 1: Understanding the Concept:
Parasitic crustaceans represent a significant group of pests in freshwater aquaculture, with specific attachments and lifecycles on their hosts.
Step 2: Detailed Explanation:
- Assertion A: Lernaea (commonly known as the anchor worm) is a highly common crustacean parasite infecting freshwater carps.
The adult female attaches to the fish skin, causing lesions, hemorrhages, and secondary bacterial infections.
Hence, Assertion A is true.
- Reason R: Lernaea is an ectoparasite, not an endoparasite.
The female parasite inserts its modified anchor-like head into the skin and musculature of the host, but its long, cylindrical body and egg sacs remain fully exposed on the outside of the fish. It is not found inside internal organs.
Hence, Reason R is false.
Step 3: Final Answer:
Assertion A is true but Reason R is false, which corresponds to option (C).