This disease is caused by a parasitic crustacean (copepod).

• A. Ichthyophthiriasis
• B. Trichodiniasis
• C. Anchor parasite
• D. Fungal infection

Answer: (C)

The situation describes a disease caused by a crustacean parasite, specifically a copepod. The anchor parasite, or anchor worm disease, is produced by Lernaea species. These parasites attach to the fish with a rootlike “anchor” and protrude a hooked or filamentous body part, causing tissue damage, irritation, and increasing the risk of secondary infections. That crustacean origin is what sets this disease apart from the others listed.

Ichthyophthiriasis, for example, is caused by a protozoan parasite (Ichthyophthirius multifiliis) and appears as numerous tiny white spots on skin and gills. Trichodiniasis is also due to a protozoan, Trichodina, causing irritation, often on gills. Fungal infections, like those from Saprolegnia, are caused by water molds (fungal-like organisms) and show cottony growth on fish surfaces. The key here is recognizing the parasite’s crustacean (copepod) nature, which points to anchor parasite as the correct cause.