Mictaceans: Mictacea

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MICTACEANS: Mictacea

NO COMMON NAME (Mictocaris halope): SPECIES ACCOUNT

PHYSICAL CHARACTERISTICS

Mictaceans (mik-tah-SEE-ans) resemble long, slender shrimps. They range in length from 0.078 to 0.14 inches (2 to 3.5 millimeters). This species does not have a shieldlike carapace covering the head and segmented thorax. However, a plate does cover the head and the first segment of the thorax, which is tightly joined with the head. The head plate covers the sides of head and the bases of the mouthparts. Mictaceans may or may not have stalked eyes. The first pair of thoracic limbs is associated with the mouth. The remaining seven pairs are used for swimming. Pairs 1 through 5, or 2 through 6, are branched, or biramous (BY-ray-mus). Gills are absent. The abdomen is six-segmented. The first five abdominal segments have pairs of uniramous (YU-neh-RAY-mus) or unbranched appendages called pleopods (PLEE-oh-pawds). At the end of the abdomen is a pair of slender biramous appendages called uropods (YUR-oh-pawds). In between the uropods is a slender, taillike segment called the telson. The telson and uropods do not join together to form a fanlike tail.

GEOGRAPHIC RANGE

Mictaceans are found off the coasts of northeastern South America, southeastern Australia, Bermuda, the Bahamas, and the Cayman Islands.

HABITAT

Mictaceans are found in underground sea caves or deep-sea habitats.

DIET

No one is sure what mictaceans eat. The small body size and the shape of their mouthparts suggests that they scavenge dead plants and animals.

BEHAVIOR AND REPRODUCTION

The animals move both by walking and swimming. It is believed that males and females must mate to reproduce, but mating has never been observed.

MICTACEANS AND PEOPLE

Mictaceans are of special interest to scientists studying the lives and evolution of crustaceans. Evolution is how organisms slowly change and adjust to their environments over millions of years.

EXTINCTION IS FOREVER

Three-fifths of the world's mictaceans live in anchialine (aeng-KEY-eh-lihn) caves. Anchialine comes from Greek meaning "near the sea." Anchialine caves are formed when sea water floods underground spaces in limestone or volcanic rock. There is no surface connection with the ocean. These sometimes incredibly old habitats are home to many unusual animal species found nowhere else. Pollution, collapse, or other disturbances in caves might cause these animals to die out forever, or become extinct.

CONSERVATION STATUS

Only one species of mictacean, Mictocaris halope from Bermuda, is listed as Critically Endangered by the World Conservation Union (IUCN). This means that it faces extremely high risk of extinction in the wild.

NO COMMON NAME (Mictocaris halope): SPECIES ACCOUNT

Physical characteristics: The body is long, slender, and colorless. Adults measure 0.12 to 0.14 inches (3 to 3.5 millimeters) in length. The head has a beaklike projection, or rostrum. Working eyes are absent, but eyestalks are present. The inner branches of the uropod have two segments. The telson is spiny along its back margin.

Geographic range: Mictocaris halope is found in Bermuda.

Habitat: Mictocaris halope lives on or near rocks at the bottom of underground sea caves.

Diet: They may strain bits of plant food from the water.

Behavior and reproduction: This species spends most of its time swimming, but is occasionally found crawling over or resting on rocks. Mating has never been observed. Eggs are carried in a pouch, or marsupium (mar-SOUP-ee-uhm), formed by special plates on the leg bases. The young larvae (LAR-vee) hatch without their last pair of appendages.

Mictocaris halope and people: This species is not known to impact people or their activities.

Conservation status: This species is listed as Critically Endangered by the World Conservation Union (IUCN), which means it faces extremely high risk of extinction in the wild. Mictocaris halope is very sensitive to the water quality of the caves in which it lives. ∎

FOR MORE INFORMATION

Books:

Brusca, Richard C., and Gary J. Brusca. Invertebrates. Sunderland, MA: Sinauer Associates, 2003.

Periodicals:

Bowman, T. E., and T. M. Iliffe. "Mictocaris halope, a New Unusual Peracaridan Crustacean from Marine Caves on Bermuda." Journal of Crustacean Biology 5 (1985): 58-73.