Figure 1.

Life Cycle and Developmental Plasticity of the Model Nematode Pristionchus pacificus

(A) The life cycle of P. pacificus consists of four juvenile stages (J1–J4) until sexual maturation (adult hermaphrodites). Like many nematodes P. pacificus can enter a long-living “dormant” dauer state that is resistant to harsh environmental conditions. The decision to continue through the direct life cycle or enter dauer is regulated by small-molecule-excreted ascarosides (chemical structure adapted from Butcher, 2017).

(B and C) (B) P. pacificus can also adopt one of two possible feeding structures; either a microbivorous narrow mouth (stenostomatous, St) or (C) an omnivorous wide mouth (eurystomatous, Eu) with an extra tooth that can be utilized to kill and eat other nematodes or fungi. White lines indicate the presence of an extra tooth (right side) in the Eu morph or its absence in the St morph, and the dorsal tooth (left side), which is narrow and elongated (flint-like) in St and hook like in Eu. Scale bar, 5 μM.

(D) P. pacificus is often found in a necromenic association with beetles (e.g., shown here Oryctes borbonicus, photo taken by Tess Renahan) in the dauer state and resumes the free-living life cycle upon beetle death to feed on the ensuing microbial bloom.

(E) RSC017 mixed-staged worms on agar plates.