Proturans: Protura

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PROTURANS: Protura

NO COMMON NAME (Sinentomon yoroi): SPECIES ACCOUNT

PHYSICAL CHARACTERISTICS

Proturans have three distinct body regions (head; thorax, or midsection; and abdomen), no wings, and six legs, but they are not considered true insects. They form a group closely related to insects that includes springtails (order Collembola) and diplurans (order Diplura). All of these animals have mouthparts located inside a special pocket in their heads.

Proturans are small, pale, secretive animals ranging in size from 0.024 to 0.06 inches (0.6 to 1.5 millimeters). The head is cone-shaped and lacks eyes or antennae (an-TEH-nee). The needlelike jaws are directed straight ahead, with only their tips visible outside the head. On the top of the head is a pair of slightly raised, ringlike structures that help proturans smell their surroundings by detecting the presence of chemical compounds.

The front legs are long and bristling with sensitive, hairlike structures. These are the proturans' most important sensory structures, and they are usually curled and held high above the body like antennae. All of the legs have five segments and are tipped with a single claw. The species that live on the soil surface have longer claws than the species that burrow through the soil. Adult proturans have an eleven-segmented abdomen tipped with a distinctive taillike structure. The first three abdominal segments each have a pair of segmented appendages (uh-PEN-dih-jehz), or limblike structures, underneath. Most species breathe directly through the exoskeleton, or outer skeleton, but a few proturans have respiratory system made up of an internal network of breathing tubes.

GEOGRAPHIC RANGE

Proturans are found around the world, except in the Arctic and Antarctic.

HABITAT

Protura usually prefer to live in moist habitats with lots of rotting plant materials. They are found in meadows or in leaf litter, rotten logs, soil, and moss in wooded areas. Some species live in parks and agricultural fields. Most proturans live near the soil surface, although some are found underground as deep as 10 inches (25.4 centimeters).

DIET

Little is known of the feeding habits of proturans. Their needlelike mouthparts suggest that they feed on fluids. A few species feed on fungus, organisms related to mushrooms. They are believed to suck fluids from threadlike structures that underground funguses use to obtain nutrients from the roots of plants.

BEHAVIOR AND REPRODUCTION

Proturans move slowly through the soil with their forelegs, or front legs, held out in front of the head, while the middle and hind legs are used for walking. Some species curl the tip of the abdomen over the head to discharge a sticky fluid in the direction of their enemies. Occasionally, proturans gather together in large groups, making them easy to see.

A TALE OF TELSON TAILS

The name Protura comes from the Greek words protos, meaning "first" and oura, or "tail." In Europe, Proturans are called telson tails. "Telson" is simply another word meaning "end," or tail, referring to the end segment of a proturan. The Italian scientist Antonio Sylvestri first discovered them in leaf litter in 1907 near Syracuse, New York. Since then they have been found throughout the world and are among the most abundant arthropods living in soil and leaf litter. Leaf litter samples collected in the eastern forests of North America sometimes have as many as 150 individual proturans, representing several different species.

The life cycles are known only for a few species. Among proturans, there is no courtship, or activities meant to attract a mate. Males deposit packets of sperm on the ground, which are later picked up by the females. Eggs are laid in early spring. Proturans are the only insectlike animals that add body segments and structures as they grow. Larval proturans, or young proturans, look very similar to the adults but have only eight abdominal segments. As they grow and molt, or shed and replace their skeletons, they add segments. Only after they molt for the fifth time do they reach adulthood. It is unknown whether proturans keep growing and molting after they become adults.

Species living close to the surface in cooler habitats produce one generation per year and spend the winter as adults, while species living deep in the soil may reproduce year-round. Some species spend the summer near the surface and migrate deeper into the soil with the approach of winter.

PROTURANS AND PEOPLE

Proturans are common in forest leaf litter. They help build nutrient-rich soils by breaking down dead plants. They are not considered pests.

CONSERVATION STATUS

No proturans are endangered or threatened.

NO COMMON NAME (Sinentomon yoroi): SPECIES ACCOUNT

Physical characteristics: The body is very spiny. The larvae (LAR-vee) have rows of small hairlike bristles on top of some of their abdominal segments.

Geographic range: This species lives in Japan.

Habitat: They live among the roots of bamboo on steep slopes with little leaf litter.

Diet: Nothing is known.

Behavior and reproduction: Nothing is known.

Sinetomon yoroi and people: The activities of this species are not known to affect people directly.

Conservation status: The species is not endangered or threatened. ∎