Spider crabs are marine crustaceans known for their long, spindly legs and often camouflaged bodies. These creatures, which include the enormous Japanese spider crab, can appear intimidating due to their size and shape. Spider crabs are neither venomous nor typically aggressive toward people. They rely on physical defenses and camouflage for protection.
The Definitive Answer: Venom vs. Mechanical Defense
A creature is considered venomous only if it produces a toxin in a specialized gland and possesses a delivery system, such as a fang or stinger, to actively inject that toxin. Spider crabs, as crustaceans, lack this biological mechanism and cannot inject toxins into a person or predator.
Their primary form of defense is purely mechanical, relying on their tough exoskeletons and large claws, or chelae, especially in male crabs. A provoked crab will use its claws to pinch or crush defensively. While the largest species have immense size and powerful claws, the resulting injury to a human would be a physical wound, such as a bruise or laceration, not a chemical one.
Understanding the Toxicity Distinction
The question of danger requires distinguishing between being venomous and being poisonous. A venomous animal injects a toxin, while a poisonous animal contains a toxin that harms another organism when ingested or absorbed through touch. Spider crabs are not poisonous either, meaning they do not contain toxins harmful if eaten.
Several common species are commercially fished and considered a delicacy in many regions. The European spider crab (Maja squinado) and the Japanese spider crab (Macrocheira kaempferi) are prized for their sweet meat. Health issues related to consumption typically stem from improper handling, such as eating spoiled meat.
Common Species and Encounter Safety
The term “spider crab” covers a wide range of species, including decorator crabs and the massive Japanese spider crab. The common spider crab (Libinia emarginata) is found along the Atlantic coast and is generally slow-moving. These crabs are non-aggressive and prefer to avoid confrontation, using natural camouflage to hide.
If encountered in the wild, the simplest safety measure is to observe it without disturbing it. They only use their claws defensively when threatened or handled carelessly. If a spider crab must be handled, wear thick gloves to protect against a defensive pinch. Handling the crab by the rear of its shell, away from the powerful claws, is the safest way to prevent injury and ensure the animal can be released unharmed.