Dermal papillae (Onychophora)

For dermal papillae in humans or polychate worms, see Dermis § Dermal papillae, and Papilla (worms).

Dermal papillae on the peripatopsid velvet worm Ooperipatellus viridimaculatus

Dermal papillae are small protrusions on the cuticle of onychophorans, a group of animals commonly known as velvet worms. These structures give the group their common name, as they have a velvet-like feel when touched. Dermal papillae come multiple forms and cover the body of onychophorans in rings known as annulations.

Types

Primary papillae

Talk about structure and make a diagram showing differences between Peripatidae and Peripatopsidae primary papillae

• when found on distal part of foot known as distal papillae
• when found on basal part of foot known as basal papillae
• scale ranks are responsible for velvety feel

Type 1 sensilla

Type 1 sensilla are a specialized variant of primary papilla with a prominent apical piece covered in scales and a sensory bristle with a textured base. These papillae act as mechanoreceptors, giving the animals a sense of touch, and occur in peripatid velvet worms.

Type 2 sensilla

Type 1 sensilla are similar to type 1 sensilla but lack an apical piece and have a far longer bristle.

Spindle-shaped sensilla

Spindle-shaped sensilla are a modified version of Type 1 sensilla that have a large, spindle-shaped apical piece and a short, thorn-like bristle. Like regular type 1 sensilla, these also only occur in peripatid velvet worms. In life, spindle-shaped sensilla make up an array known as the antennal sensory field. This is located on the underside of the antennae on its proximal (closer to the base) portion.

Accessory papillae

Crater shaped papillae

• crater shaped papillae in Neopatida have a rudimentary apical piece, while those in basal Asian clade do not