The term “ocean mantis” refers to mantis shrimp, a group of marine crustaceans from the order Stomatopoda. They are not true shrimp but are distant relatives known for being highly efficient predators. Their biological systems set them apart from other marine life, making them a subject of scientific interest.
Extraordinary Vision Capabilities
The visual system of the mantis shrimp is one of the most complex in the animal kingdom. Their eyes, mounted on stalks, can move independently of each other, rotating up to 70 degrees. Each eye is divided into three sections, giving them trinocular vision and depth perception within a single eye. This means a mantis shrimp can still judge distance effectively even if it were to lose one eye.
While human eyes have three types of photoreceptor cells for color, mantis shrimp possess between 12 and 16. This array of photoreceptors enables them to see a spectrum of light that includes ultraviolet and infrared wavelengths. They are also capable of detecting polarized light, a rare trait among animals. This ability is used for communication with other mantis shrimp, signaling from a distance to avoid territorial disputes.
The processing of this visual information is also unique. Instead of sending all raw data to the brain for interpretation, much of the processing occurs within the eyes themselves. This decentralized approach allows for faster reaction times, which is an adaptation for a predator that relies on quick strikes.
The Powerhouse Claws
A primary feature of the mantis shrimp is its set of raptorial appendages, which are modified claws used for hunting and defense. There are two classifications for these predators based on their claws: “smashers” and “spearers”. Spearers possess a sharp, barbed appendage designed to impale and snag soft-bodied prey. In contrast, smashers have a club-like appendage used to bludgeon and hammer hard-shelled prey.
The strike of a smasher is one of the fastest movements in the animal kingdom, reaching speeds of up to 51 miles per hour. This velocity is achieved through a spring-loaded mechanism in their arms. The force of the impact is capable of breaking the shells of mollusks and even the glass of an aquarium.
A consequence of this high-speed strike is the formation of cavitation bubbles. As the claw moves through the water, it creates a low-pressure area that vaporizes the water, forming a bubble. The collapse of this bubble generates a secondary shockwave that can stun or kill prey, even if the initial strike misses. This means the prey is hit twice: once by the claw and again by the force of the imploding bubble.
Natural Environments and Prey
Mantis shrimp are found in the shallow tropical and subtropical waters of the Indian and Pacific Oceans. Their habitats range from coral reefs and rock crevices to burrows they excavate in sandy or muddy seabeds. These burrows serve as a refuge from predators and a place to consume prey. Most species are solitary and territorial, defending their homes from intruders.
The diet of a mantis shrimp is directly related to its claw type. Smashers specialize in feeding on hard-bodied animals like crabs, snails, oysters, and other mollusks. Their powerful blows allow them to access a food source that is unavailable to many other predators.
Spearers, on the other hand, target softer prey. They are ambush hunters, often concealing themselves in sand or crevices before lunging out to impale passing fish, worms, and shrimp. As carnivores, mantis shrimp play a role in their local ecosystems by regulating the populations of the species they prey upon.
Diversity Within Mantis Shrimp
There are more than 500 known species of mantis shrimp, and new ones are regularly discovered. These species exhibit a diversity in size, with some measuring less than an inch while the largest recorded specimen reached 46 centimeters in length. This variation allows them to occupy a wide range of ecological niches.
Coloration is another area of diversity. Many species are colored in muted browns and greens that blend with their surroundings, while others are vibrantly colored. The peacock mantis shrimp, for example, displays a combination of bright red, green, orange, and blue hues. This coloration can be used for signaling and attracting mates.
While the “smasher” and “spearer” claw types are consistent, there are subtle morphological variations among species. These differences in claw shape and size are adapted to their specific prey and habitats. This diversity highlights the evolutionary success of these crustaceans in marine environments.