Mantis Shrimps: Stomatopoda
MANTIS SHRIMPS: StomatopodaNO COMMON NAME (Nannosquilla decemspinosa): SPECIES ACCOUNTS
PEACOCK MANTIS SHRIMP (Odontodactylus scyllarus): SPECIES ACCOUNTS
Typical mantis shrimps have long bodies that are cylinder-shaped or slightly flattened from top to bottom. They vary considerably in color, depending on the species or the individual. Some are brightly colored, while others are marked so that they blend in with their surroundings. At the front of the head are moveable segments that bear the eyestalks and two pairs of antennae. The antennae are sensitive to odors and disturbances in the water.
Mantis shrimps have the most highly developed eyes of all crustaceans, and their vision is excellent. Each compound eye is made up of multiple lenses. The eyes are often iridescent, appearing like jewels, and are mounted on the end of a periscope-like stalk to give them a clear view in all directions. A specialized band of lenses across each eye is unique and divides the eyes into three distinct visual regions. Mantis shrimps have the ability to see shapes accurately under all light conditions and to gauge distances, allowing them to use their lightning-quick raptorial limbs with deadly accuracy. The middle band of lenses is used to see infrared, visible, and ultraviolet light. The other two regions can see polarized light. Polarized light travels in parallel planes. Parts of the antennae and tails of mantis shrimps reflect polarized light and may provide them with the ability to locate and communicate with one another.
A shieldlike carapace (CARE-eh-pes) covers the thorax or midbody, and the abdomen is distinctly segmented. The thorax has eight pairs of limbs. The first five pairs, the maxillipeds (mack-SIH-leh-pehds), are associated with the mouth and are used for prey capture and eating. The second pair of maxillipeds is very conspicuous and resembles the front legs of a praying mantis. They are called grabbing, or raptorial (rap-TORE-ee-all), limbs and are used to stab or club prey. When not in use, they are kept folded like jack knives under the head and body. Mantis shrimps can replace lost or damaged raptorial limbs. Damaged limbs are forcibly removed with the other maxillipeds. The lost limb is replaced with the next molt and grows to full size after three more molts. Three more pairs of maxillipeds follow the raptorial limbs. The remaining three pairs of thoracic midbody limbs are used for walking.
The abdomen has five pairs of leaflike limbs called pleopods (PLEE-oh-pawds). They are used for swimming and also have gills for breathing. The abdomen ends in a large, fanlike tail made up of the flat tail segment, and a pair of appendages, or uropods (YUR-oh-pawds).
Male and female mantis shrimps are easily distinguished. Males have a pair of long, slender sperm-transferral organs located at the bases of the last pair of walking legs. The female's reproductive organs appear as a narrow slit that opens underneath the body between the first pair of walking legs. In some species the males have larger bodies than the females, with larger raptorial limbs and tails.
Mantis shrimps live in the ocean off nearly all landmasses in tropical and subtropical waters.
Most mantis shrimps prefer to live in shallow tropical or subtropical seas, but a few species live in cooler waters of the sub-Antarctic. They are usually found along the shore in habitats affected by the tides or just beyond. Some species dig or occupy abandoned burrows with several entrances in muddy or sandy sea bottoms down to 33 feet (10 meters) below the surface. Other species live in hollows among rocks and corals.
Mantis shrimps are predators that hunt and kill animals for food. They attack fish, mollusks, and other crustaceans.
BEHAVIOR AND REPRODUCTION
The behavior of mantis shrimps is defined by their raptorial limbs. Species with toothed or spiny limbs grab and stab their prey and are called spearers. Spearers lie in wait at the entrance to their burrows in mud or sand and wait for a soft-bodied fish or shrimp to come within range. Mantis shrimps that use their raptorial limbs like clubs are called smashers. Smashers actively search for prey, usually animals with hard bodies or shells, crippling them with powerful blows. They drag their smashed victims into hollows among rocks and coral before they begin eating. Depending on the species, resting animals plug the entrance to their burrow with rocks or with their raptorial limbs or tail.
Some species of mantis shrimps are nocturnal (nahk-TER-nuhl), or active only at night, especially on moonlit nights. Others are diurnal (die-UR-nuhl), or active during the day. Still others species are crepuscular (kreh-PUS-kyuh-lur), coming out only just after sunset or before sunrise.
Most mantis shrimps live alone, but males and females will come together briefly only to mate. Males and sometimes females will actively seek a mate. Males perform elaborate mating behaviors to attract the attention of the female. Females will accept one or more males as mates during this time. In a few species, males and females mate for life, a period that may last 15 to 20 years. These life-long mates share one burrow. The females tend to the eggs, while the male hunts for himself and his mate.
Males and females mate belly to belly. Males deposit sperm directly into the female where it is stored in a special pouch just inside the opening to her reproductive organs. The eggs are fertilized inside her body just as they are being laid. The eggs may not be laid right away. The female may choose to wait until ocean currents are available for dispersing the eggs. Eggs are glued together in a mass and take anywhere from 10 days to two months to hatch. During this time the female carefully tends the eggs and is guarded by the male. The hatchlings may leave the burrow immediately, or remain in the burrow for a week to two months.
Newly hatched mantis shrimps have long slender bodies and bulging eyes. They pass through several distinct developmental stages in about three months before reaching adulthood. Some species are benthic (ben-thik) and start out on the sea bottom. Others are pelagic (peh-LAJ-ihk) and immediately set off in the open sea. All species eventually develop into pelagic larvae (LAR-vee) or young and settle to the bottom as post-larvae. Postlarvae are very similar to the adults in both shape and behavior.
MANTIS SHRIMPS AND PEOPLE
Mantis shrimps are especially sensitive to pollution. Their presence or absence in coral reefs allows scientists to gauge the environmental health of the habitat. Some mantis shrimp species are popular pets in saltwater aquariums. Squilla mantis is a very tasty species. Efforts are underway to culture them as human food in the Mediterranean and Adriatic seas.
LIGHTNING FAST AND PACKS A PUNCH
The strike of the raptorial limbs of mantis shrimps is one of the fastest movements in nature. They can strike at prey in just 2 milliseconds. The blink of a human eye takes 100 milliseconds. Two of the larger smasher species, Hemisquilla ensigera and Odontodactylus scyllarus, can strike with a force nearly equal to that of a .22 caliber bullet and are known to have smashed the double-layered safety glass of public aquariums.
No mantis shrimps are considered endangered or threatened.
Physical characteristics: This small species measures up to 0.98 inches (25 millimeters) in length and is marked to match its background.
Geographic range: This species can be found off the Pacific coast of Panama.
Habitat: They live in shallow waters on muddy bottoms close to shore.
Diet: This species is a spearer that waits inside the entrance of its burrow to ambush soft-bodied fish and crustaceans.
Behavior and reproduction: When washed up on shore by high tides or storms, Nannosquilla decemspinosa turns itself into a wheel and rolls back to the water at 72 revolutions per minute, or 1.5 body lengths per second. If it slows down before reaching the shore, it uses its entire body as a spring to move upward and forward into the next roll.
Males actively search for females and engage in mating displays in front of their burrows. After mating, the male will guard the female until the larvae swim out to sea and then he leaves.
Nannosquilla decemspinosa and people: Its ability to roll like a wheel makes this species a scientific curiosity.
Conservation status: Nannosquilla decemspinosa is not considered endangered or threatened. ∎
Physical characteristics: The body of a peacock mantis shrimp reaches a length of 6.7 inches (170 millimeters). Males and females are distinctively colored. Mature males are bright green with crimson and blue appendages; females are more olive or brown. Young individuals are bright yellow.
Geographic range: This species is found in the Indo-Pacific Ocean, including Hawaii.
Habitat: They live on coral reefs.
Diet: The peacock mantis shrimp is a smasher that hunts hard-shelled animals like clams, snails, and crabs.
Behavior and reproduction: This species is usually diurnal, but may hunt at night during a full moon. They line their burrows with pieces of coral, rock, and shell.
Males actively search for females and engage in mating displays in front of their burrows. After mating, the male will guard the female until the larvae swim out to sea, and then he leaves.
Peacock mantis shrimps and people: This brightly colored species is popular with hobbyists who keep saltwater aquariums.
Conservation status: The peacock mantis shrimp is not considered endangered or threatened. ∎
FOR MORE INFORMATION
Caldwell, R. L., and H. Dingle. "Stomatopods." Scientific American 234 (1975): 80-89.
"Earth Almanac: Eyes and Claws of a Killer Shrimp." National Geographic 190, no. 3 (September 1996).
Patek, S. N., W. L. Korff, and R. L. Caldwell. "Biomechanics: Deadly Strike Mechanism of a Mantis Shrimp." Nature 428 (2004): 819-820.
Lurker's Guide to Stomatopods.http://www.blueboard.com/mantis/ (accessed on February 14, 2005).
Secrets of the Stomatopod.http://www.ucmp.berkeley.edu/aquarius/ (accessed on February 14, 2005).
Stomatopoda: Families.http://www.crustacea.net/crustace/stomatopoda/index.htm (accessed on February 14, 2005).