Convolutrillidae

Convolutrillidae is a family of acoelomorph flatworms. These small, marine invertebrates are characterized by their unsegmented bodies and lack of a coelom. Unlike other flatworms, they possess a simple, sac-like gut and lack a distinct anus. A key feature of Convolutrillidae is the presence of cilia covering their entire body, which aids in locomotion and suspension feeding. Their body plan is generally ovate or somewhat flattened.

Members of this family are typically found in shallow marine environments, often inhabiting sandy or muddy substrates. Some species are known to live in association with other marine organisms, such as sponges or algae, forming symbiotic relationships. The reproduction of Convolutrillidae is primarily sexual, with both hermaphroditic and gonochoristic species observed. Their life cycle is direct, meaning they hatch as miniature adults without a larval stage.

The diet of Convolutrillidae consists mainly of bacteria, diatoms, and other small organic particles suspended in the water column or found on sediment surfaces. They filter these food particles using their ciliary structures. Due to their small size and often cryptic habitat, research on Convolutrillidae is less extensive compared to more commonly studied invertebrate groups. However, they are considered important components of benthic ecosystems, contributing to nutrient cycling and serving as a food source for larger invertebrates. The taxonomic classification of Convolutrillidae is within the order Acoela, a group of basal bilaterians.