Octopuses are intelligent and adaptable marine predators, playing a significant role in ocean food webs. While their diet is broad, encompassing bivalves, gastropods, and fish, crabs represent a particularly common and challenging prey item. The unique physical and behavioral adaptations of octopuses allow them to successfully hunt and consume these armored crustaceans.
Locating and Securing Prey
Octopuses employ a sophisticated array of senses to locate crabs. Their highly sensitive suckers function as both touch and taste receptors, detecting subtle chemical cues and textures. This chemoreception, combined with acute vision, helps them pinpoint potential prey hidden in rocky crevices or sandy bottoms.
They use various strategies to approach their targets. Ambush predation is common, with octopuses blending seamlessly into their surroundings. They also forage actively, exploring the seafloor or using jet propulsion.
Some intertidal octopuses even venture out of water briefly, pursuing crabs. Once within striking distance, the octopus pounces or jets forward, swiftly enveloping the prey. Powerful, adhesive suckers firmly grasp and immobilize the crab.
Neutralizing the Crab’s Defenses
After capture, the octopus uses its strong arms and suckers to maintain a secure hold, preventing retaliation from the crab’s claws. It maneuvers the crab to expose vulnerable areas, like the soft membrane at its joints or its underside. This minimizes injury risk from the crab’s defenses.
The octopus then delivers a potent neurotoxin. This venom, contained within its saliva, paralyzes or kills the crab. In some cases, the octopus bites the crab directly to inject the venom. The neurotoxin begins to liquefy the crab’s internal tissues, preparing it for consumption.
For crabs with tough shells, many octopuses breach the exoskeleton. They drill a small, oval hole into the shell. This is done using minute teeth on their salivary papilla or radula. An enzyme in their saliva dissolves the shell’s calcium carbonate, easing penetration. Once a hole is created, venom is injected, paralyzing the crab and aiding internal tissue breakdown.
Processing and Consuming the Meal
At the center of its arms, an octopus has a chitinous beak, resembling a parrot’s. This beak is a primary tool for processing prey, used to bite, tear flesh, and break open softened or drilled crab shells. Its tough, fingernail-like composition withstands the rigors of dismembering crustaceans.
Further aiding in consumption is the radula, a ribbon-like organ equipped with rows of serrated teeth. The radula works to scrape and transport the softened crab meat into the digestive system. It efficiently shreds the internal tissues, acting like a conveyor belt to move the meal towards the esophagus.
The octopus selectively consumes the edible soft tissues of the crab, leaving behind indigestible shell fragments. Digestive enzymes in its saliva break down the crab’s internal structure into a more liquid form, often described as a “milkshake.” After the meal, the octopus discards the remaining shell fragments, which are frequently found in neat piles outside its den, indicating recent feeding activity.