Caenorhabditis elegans

It feeds on microbes and can reproduce in patches of decomposing plant material, linking its life cycle to short-lived food supplies.

An adult is about one millimetre long, with a protective cuticle outside the epidermis.

Body-wall muscles generate its characteristic bending movements; inside are digestive, reproductive and excretory systems.

Its transparency makes internal cells visible under suitable microscopy rather than leaving the animal as an opaque silhouette.

A muscular pharynx connects the mouth to the intestine and draws in liquid containing bacterial particles.

Repeated contractions retain particles while excess liquid is expelled; movements farther back carry food towards the intestine.

A grinder in the terminal bulb helps break up bacteria before they enter the intestine.

Food quality matters as well as quantity: different bacteria can support growth differently, and worms can change their feeding behaviour accordingly.

The species has self-fertilising hermaphrodites and males.

A hermaphrodite first produces sperm, then eggs, and can also mate with a male.

Hermaphrodites have two X chromosomes, whereas males normally have one and no Y chromosome.

After embryonic development, the worm passes through four larval stages, L1 to L4, before adulthood.

Each larval stage ends in a molt that replaces the cuticle.

When conditions deteriorate, developing larvae can instead enter dauer, a non-feeding, stress-resistant alternative to the usual third larval stage.

Dauer is reversible: favourable conditions allow feeding and development towards adulthood to resume.

Field sampling in France found C. elegans reproducing in rotten fruits and herbaceous stems, sometimes alongside C. briggsae.

Some populations contained actively developing worms without any dauer larvae, while larger populations included pre-dauer or dauer stages.

These observations support a life history with periods of growth in food-rich patches interrupted by pauses and dispersal, rather than permanent dormancy in soil.

The combination of transparency and a reproducible developmental lineage makes it possible to follow the fate of individual cells in a living animal.

Its feeding apparatus also connects a visible behaviour to a small neuromuscular system, allowing questions about movement and its control to be studied together.

NCBI places Taxonomy ID 6239 at species rank under Caenorhabditis; the closely related C. briggsae in the field study is a different species.

Félix and Duveau used mating or molecular tests because the two species could not reliably be separated by their similar morphology.

The authors recorded abundance and developmental stages in fresh field samples.

Colonisation, reproduction and dauer dispersal form an interpretation of these snapshots, not continuous tracking between patches.

Pharyngeal pumping and posterior-isthmus peristalsis are distinct movements; the latter follows only some pumps and transports retained food rearwards.

Consequently, counting visible pumps alone does not directly measure every step of food transport into the intestine.