Didemnum

Didemnum is a genus of colonial ascidians, commonly known as sea squirts. These marine invertebrates belong to the family Didemnidae. Didemnum species are found in oceans worldwide, inhabiting a variety of substrates including rocks, pilings, and other sessile organisms. They are characterized by their communal living structure, where individual zooids are embedded within a shared tunic, a tough outer covering. This tunic can vary in texture and color, often incorporating sand or other foreign particles.

The feeding mechanism of Didemnum involves filter feeding, drawing water through a siphon and extracting plankton and other organic matter. Reproduction in Didemnum can occur both sexually and asexually. Sexually, they release gametes into the water column, and asexually, they can bud and fragment. Some species of Didemnum are known for their ability to overgrow and outcompete native species, leading to concerns about their invasive potential in certain regions. For example, Didemnum vexillum has been identified as an invasive species in several parts of the world, causing ecological and economic impacts. Research into their biology, ecology, and control methods is ongoing.