Mesothelae

Mesothelae is a suborder of spiders that is considered to be one of the most primitive groups within the order Araneae. These spiders are characterized by their segmented abdomens and the presence of a series of plates, or tergites, on the dorsal side of their abdomen. Mesothelae are primarily found in Southeast Asia and are known for their burrowing behavior.

Description

Mesothelae spiders are distinguished by several primitive features that are not found in more derived spiders. One of the most notable characteristics is the presence of abdominal segmentation, which is a trait shared with other arachnids but lost in most other spiders. The segmentation is visible as a series of hardened plates, or tergites, on the dorsal side of the abdomen.

These spiders have a relatively simple body plan compared to other spiders. Their chelicerae, or fangs, are oriented forward, a feature known as "orthognathous". This is in contrast to the "labidognathous" orientation seen in more advanced spiders, where the fangs are directed towards each other.

Habitat and Behavior

Mesothelae are primarily found in forested regions of Southeast Asia, including countries such as China, Japan, and Vietnam. They are burrowers, creating silk-lined burrows in the ground where they spend most of their time. These burrows are often camouflaged with debris and are used as a base for ambushing prey.

The spiders are nocturnal hunters, emerging from their burrows at night to capture prey. They rely on their silk to detect vibrations and movements of potential prey, which they then quickly subdue with their venomous bite.

Evolutionary Significance

The Mesothelae are of great interest to evolutionary biologists because they provide insight into the early evolution of spiders. Their primitive features suggest that they are a basal group, retaining characteristics that were likely present in the common ancestor of all spiders. Studying Mesothelae can help scientists understand the evolutionary transitions that led to the diversity of spider forms seen today.

Taxonomy

The suborder Mesothelae contains a single family, Liphistiidae, which includes several genera and species. The taxonomy of Mesothelae is based on both morphological characteristics and molecular data, which have helped clarify their relationships to other spider groups.

Conservation

Many species of Mesothelae are considered to be of conservation concern due to habitat loss and degradation. As forested areas in Southeast Asia are cleared for agriculture and development, the natural habitats of these spiders are being destroyed, leading to declines in their populations.

Also see

• Araneomorphae
• Mygalomorphae
• Spider anatomy
• Arachnid evolution