Mystacocarids: Mystacocarida

views updated

MYSTACOCARIDS: Mystacocarida

NO COMMON NAME (Derocheilocaris typicus): SPECIES ACCOUNT

PHYSICAL CHARACTERISTICS

Mystacocarids (my-stah-koh-KAR-ids) are small, wormlike crustaceans that reach up to 0.039 inches (1 millimeter) in length. Nearly one-third of their entire body length is made up of a head that is not covered with a shieldlike carapace (CARE-eh-pes). The eyes are simple and are not set on stalks. Each simple eye has only one lens. The head is sharply narrowed between the pairs of antennae. The first pair of antennae, or antennules (an-TEN-yuhls), is uniramous (YU-neh-RAY-mus), or not branched. The antennules are about half as long as the entire body. The second pair of antennae is branched, or biramous (BY-ray-mus). The jaws, or mandibles, are also biramous, while the second set of mouthparts, or maxillae (mack-SIH-lee), are uniramous. There are long, hairlike structures on the inside margin of the maxillae. The thorax has five segments. The first thoracic segment is not tightly joined, or fused, with the head. It has a pair of biramous limbs called maxillipeds (mack-SIH-leh-pehds). Maxillipeds work together with the mouthparts. Each of the four remaining thoracic segments has a pair of leglike limbs called pereopods (PAIR-ee-oh-pawds). The uniramous pereopods are sometimes used for grasping. The five abdominal segments do not have any appendages underneath. The tip of the abdomen ends in a large taillike segment, or telson. The telson is fused to the last abdominal segment. A well developed bladelike structure is found on either side of the telson.

GEOGRAPHIC RANGE

Mystacocarids are found along the coasts of the eastern and western Atlantic, southern South America, western Australia, and the Mediterranean Sea.

HABITAT

Mystacocarids live in the spaces between the grains of sand found along coastal beaches.

DIET

Mystacocarids probably eat algae (AL-jee) and bacteria living on the surfaces of sand grains.

BEHAVIOR AND REPRODUCTION

Mystacocarids use their antennae, mandibles, and slender bodies to burrow through the sand.

Both males and females are required for reproduction, but mating has never been observed by scientists. Females release fertilized eggs into the sand. The hatching larvae (LAR-vee), or young animals, do not resemble the adults. They molt, or shed their external skeletons (exoskeletons), several times, adding body segments and thoracic limbs as they grow.

MYSTACOCARIDS AND PEOPLE

Mystacocarids are of interest to scientists who want to learn more about how crustaceans live and reproduce.

MOUSTACHE SHRIMP, ANYONE?

The very first mystacocarids were described in 1943 from specimens collected in the sands of beaches along the coasts of Massachusetts and Connecticut. They were so different from other crustaceans that they had to be placed in a new order, the Mystacocarida. The name of the order is taken from the Greek words mystakos, meaning moustache, and karis, or shrimp. This refers to the long, moustachelike bristles found on the mouthparts.

CONSERVATION STATUS

No species of mystacocarids is considered threatened or endangered.

NO COMMON NAME (Derocheilocaris typicus): SPECIES ACCOUNT

Physical characteristics: Adults measure less than 0.039 inches (1 millimeter) in length. This species is distinguished by very small differences in the size and shape of their body structures. They also have grooves on the body with edges that resemble teeth. The mouthparts are bristly, and the bladelike structures on the tip of the abdomen are short.

Geographic range: Derocheilocaris typicus (abbreviated as D. typicus) lives along the Atlantic coast of the United States, from Cape Cod south to southern Florida.

Habitat: This species lives deeply buried in beach sand. They are sometimes found several feet (meters) inland, but still within the zone where the tides keep the sand wet.

Diet: They eat small bits of algae and bacteria between or living on the surfaces of sand grains.

Behavior and reproduction: They use their antennae to crawl between sand grains.

Eggs are laid in the sand. The larvae go through seven stages before reaching adulthood. Adults molt once.

Derocheilocaris typicus and people: This was the first mystacocarid ever to be discovered, resulting in the creation of a new order and subclass of crustaceans.

Conservation status: D. typicus is not considered endangered or threatened. ∎

FOR MORE INFORMATION

Books:

Brusca, R. C., and J. G. Brusca. Invertebrates. Second edition. Sunderland, MA: Sinauer Associates, Inc. 2003.

Periodicals:

Lombardi, J., and E. E. Ruppert. "Functional Morphology of Locomotion in Derocheilocaris typica (Crustacea: Mystacocarida)." Zoomorphology 100 (1982): 1-10.

Pennak, R. W., and D. J. Zinn. "Mystacocarida, a New Order of Crustacea from Intertidal Beaches in Massachusetts and Connecticut." Smithsonian Miscellaneous Collections 103 (1943): 1-11.