Long-nosed spider crab

The Long-nosed spider crab (Macropodia longirostris) belongs to the order Decapoda and the family Inachidae. Within the context of marine aquaculture, this crustacean is recognized for its potential to act as a pest, particularly affecting underwater farming systems that cultivate specific species of marine algae.

The primary crops threatened by this species include various edible and industrial seaweeds. The crabs feed on the delicate tissues of young plants, significantly stunting their development and reducing the harvestable biomass, which directly affects the economic efficiency of marine farms.

The biological cycle involves planktonic larval stages (zoea and megalopa) followed by a settlement phase where juveniles anchor themselves to the benthos. Adults are known for their exceptional camouflage abilities, often making it difficult for farm managers to detect them until damage to the crop has already occurred.

The damage caused by Macropodia longirostris includes mechanical grazing on the thallus, which compromises the structural integrity of the seaweed. These wounds create entry points for opportunistic pathogens, leading to secondary infections and tissue necrosis that can spread through the plantation.

Effective pest management involves physical barriers, such as fine-mesh protective screens, to exclude crabs from the cultivation area. Furthermore, regular inspection and mechanical removal of individuals, combined with maintaining optimal environmental conditions that discourage crab colonization, remain the most viable strategies for crop protection.