How do ascidians differ from appendicularians?

Ascidians and appendicularians differ significantly in their habitat, morphology, and feeding strategies within the subphylum Tunicata.

Key Differences

• Habitat and Lifestyle: Ascidians are primarily benthic and sessile as adults, often forming colonies that can reach two meters in length. In contrast, appendicularians are free-swimming, pelagic organisms that spend their entire lives in the open sea and do not form colonies.12
• Morphology: Adult appendicularians retain a form resembling the tadpole larvae of other tunicates, featuring a tail. Unlike ascidians, appendicularians lack a distinct atrium.12
• Feeding Mechanisms: Ascidians use an internal mucous sheet secreted by the endostyle to filter food from the water. Appendicularians employ a unique method: they secrete a complex, mucus-based "house" around their bodies. By undulating their tails, they create currents that draw water through a fine mucous net within this structure to trap nannoplankton.31

While both are chordates, their evolutionary adaptations reflect vastly different ecological niches.12