FEEDING ON SLIME

Velvet worms are among the most extraordinary animals on earth! With a very simple body structure, these ancient animals have been living on our planet for nearly 500 million years. Despite their name, they are not actually worms. They are not insects either, but look like caterpillars, and belong to their own phylum called Onycophora. 

Onycophorans have a remarkable technique for hunting. To capture their prey, velvet worms eject a sticky, adhesive slime from their oral papillae, which are located close to their mouth. The sticky slime immobilizes the prey so that the velvet worm can then casually approach it. 

In a study of feeding behavior conducted in Costa Rica in 2019, researchers documented for the first time a form of parental feeding in velvet worms involving a socially transferred material. Barquero-Gonzales and colleagues showed that in some species, during the first two weeks after birth, the young only eat one thing: the threads of slime used by their parents to capture their prey! This is an unusual form of parental care, and noteworthy as an example of early evolution of a socially transferred material given how ancient these creatures are. 

The slime is composed of proteins and lipids, and although its original function may have been defense and prey capture, the components of the slime also represent a good quality food source. So far this is the only study documenting this behavior in velvet worms, so more work is needed to understand the nutritional importance of slime feeding in young velvet worms. 

Source: Barquero-González JP, Vega-Hidalgo A & Monge-Nájera J. (2019). Feeding behavior of Costa Rican velvet worms: food hiding, parental feeding investment and ontogenetic diet shift (Onychophora: Peripatidae). doi.org/10.22458/urj.v11i2.2195

Picture credits: Jose Pablo Barquero-Gonzalez