Peripatus: external morphology

 Peripatus, also known as velvet worms, are fascinating invertebrates that belong to the phylum Onychophora. 

Here are some key features of their external morphology:

Body Structure:

Peripatus has a soft and cylindrical body with a velvety appearance, covered in fine papillae or tubercles.

The body is divided into segments, giving it a segmented appearance, although the internal segmentation is not as pronounced as in true segmented worms.

Antennae:

They have a pair of antennae on the head, which are sensory structures used for detecting their environment.

Legs:

Peripatus has numerous paired, unjointed, and stumpy legs along the length of its body. These legs end in a claw or terminal pad.

The number of legs varies between species but can range from 14 to over 40 pairs.

Coloration:

Velvet worms come in a variety of colors, including shades of brown, red, and green.

Mouth and Jaw Structure:

They possess a retractable oral tube, which extends to capture prey.

Peripatus has a pair of powerful jaws that can inject a secretion to immobilize and digest their prey before ingestion.

Eyes:

Most species have simple eyes, often referred to as ocelli, which can detect light and dark but do not provide detailed vision.

Slime Glands:

Velvet worms have specialized glands that produce a sticky, adhesive slime. They use this slime for various purposes, including capturing prey and defending against predators.

Respiratory System:

They breathe through small pores on their exoskeleton called spiracles, allowing for gas exchange.

Reproduction:

Peripatus species are oviparous, meaning they lay eggs. The eggs are typically laid in protected locations, and the young undergo direct development without a larval stage.

Peripatus is often considered a "living fossil" because it shares features with both annelids (segmented worms) and arthropods. The unique combination of characteristics in their external morphology reflects their evolutionary significance and adaptation to their environment.