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Pauropoda

life science Maturity 7-9 Next article →

Pauropoda is a class of tiny, millipede-like arthropods within the subphylum Myriapoda. These small animals live in soil and leaf mold across the entire world. They are significant to science because they represent a unique group of manyriapods. Most species are incredibly small, measuring between 0.3 and 2 mm in length. Their name comes from the Greek words "pauros," meaning small or few, and "pous," meaning foot. This name describes their most famous trait: most adults have only nine pairs of legs. This is a much lower number than any other adult class of myriapods.

Pauropus amicus
Pauropus amicus

Anatomy in pauropods is quite specialized for their life in the soil. They are soft, cylindrical creatures that are usually white or brown. Interestingly, they lack both eyes and hearts. Instead, they rely on sensory organs to detect light. They also possess five pairs of long sensory hairs called trichobothria. These hairs are located throughout their various body segments. Their antennae are distinctive because they are segmented and biramous, which means they are branching. To identify different species, scientists look at the anal plate. This plate is unique to the class, and its specific shape and size help define each species.

Pauropus amicus
Pauropus amicus

Scientists have been documenting these creatures for over 150 years. The first species, Pauropus huxleyi, was described by Lord Avebury in 1866. He found the creature in his own garden in London. He described the animal as bustling, active, and neat. He even noted it seemed to have a look of cheerful intelligence. In 1870, a researcher named Packard discovered a species in North America. This finding proved that pauropods had a much wider range than just Europe. We also know they are ancient because of the fossil Eopauropus balticus. This prehistoric species was discovered preserved in Baltic Amber.

Pauropus amicus
Pauropus amicus

Taxonomists divide the class Pauropoda into two distinct orders. The first order is Hexamerocerata, which is mainly found in tropical regions. These pauropods are white, relatively large, and long. They have a strongly telescopic antennal stalk consisting of six segments. As adults, they possess twelve tergites and eleven pairs of legs. The second order, Tetramerocerata, is much larger and more diverse. It contains eleven different families, such as Pauropodidae, Brachypauropodidae, and Eurypauropodidae. This order has a subcosmopolitan distribution, meaning it is found in many parts of the world.

Pauropus amicus
Pauropus amicus

Within the Tetramerocerata order, the family Pauropodidae is the most massive. This single family includes 27 genera and 814 different species. Most adults in this order have nine pairs of legs. However, there are exceptions to this rule. Four specific genera—Cauvetauropus, Aletopauropus, Zygopauropus, and Amphipauropus—have only eight pairs of legs. Additionally, adult females in the genus Decapauropus can have either nine or ten pairs of legs. These adults also feature a telescopic antennal stalk with four segments and five or six tergites.

Pauropus amicus
Pauropus amicus

Growth in pauropods follows a process called hemianamorphosis. This means they continue to molt as adults, but they stop adding new legs or segments. The development begins when males place sperm packets on the ground for females to use. After fertilization, females deposit eggs on the ground. The embryo passes through a short pupoid stage before the first larval instar hatches. In the Tetramerocerata order, juveniles start with only three pairs of legs. They progress through stages with five, six, and eight pairs of legs. Eventually, they reach their adult leg count. In contrast, Hexamerocerata larvae start with six pairs of legs and grow to eleven.

Pauropus amicus
Pauropus amicus

In their daily lives, pauropods play a small but active role in the soil ecosystem. They live in densities of less than 100 individuals per square meter. They feed on fungi, mold, and sometimes the root hairs of plants. Because their bodies are too soft to dig, they must find other ways to move through the earth. They navigate through tiny crevices and follow plant roots. Sometimes, they follow these paths all the way down to the groundwater. Their movement is very specific, characterized by frequent changes in direction and sudden bursts of speed. They are also shy of light and will actively move away from it.

Pauropus amicus
Pauropus amicus
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