Figure 2: Squirt system and papilla structure.
From: Oscillation of the velvet worm slime jet by passive hydrodynamic instability
(a) A haematoxylin and eosin-stained section of a Peripatus solorzanoi. The squirt system is composed of a large slime reservoir, re, whose length is depicted by a black arrow. The reservoir has a large diameter compared with the diameter of the duct that connects it with the oral papilla (black circle). (b) Longitudinal cut of an oral papilla of a Peripatus solorzanoi. Its wrinkled surface and sphincter-like tissues surrounding the inner duct are shown (scale 4mm). The black substance inside the duct corresponds to remnants of the slime. (c) Structure of a fresh oral papilla (red Peripatus solorzanoi) when deployed. Its semi-transparent and wavy structure is apparent (scale bar, 1 mm). (d) Oral papilla accordion structure of a Epiperipatus acacioi (scale bar, 200 μm). In this case the hinged accordion structure is resolved by scanning electron microscopy (Leica Leo 440) taken at 15 kV after coating with gold (~20 nm) in a Denton Desk IV gold sputter model. This specimen was used to confirm that the accordion-like structure present in Peripatus solorzanoi is generic to Onychophora regardless of its size. (e) Opening of the oral papilla D~350 μm and d~200 μm (scale bar, 100 μm).
