Veligerlarven

Veliger larvae, or Veligerlarven in some German sources, are a major larval stage of many molluscs, most notably marine gastropods and bivalves. They appear after the trochophore stage in lineages that produce a velum-bearing larva and play a key role in the dispersal and early development of the animal.

The defining feature of veligers is the velum, a pair of ciliated lobes that surrounds the mouth and acts as both a swimming organ and a feeding apparatus. The velum is usually well developed in free-swimming phases and allows the larva to capture food particles from the water. During this stage a shell begins to form at the edge of the mantle; in bivalves this shell is often referred to in sub-stages as prodissoconch I and II, while in gastropods the developing shell is called the protoconch. Internal organs and the foot also become more distinct as development progresses.

Development and life history vary among species. Many veligers are planktonic for days to weeks or months, feeding on microalgae and detritus, which facilitates wide dispersal. Others may be lecithotrophic (relying on yolk) and have shorter pelagic durations. Upon metamorphosis, the velum is reduced or lost as the larva transitions to the juvenile shell-bearing form, such as a snail or a bivalve youth.

Ecologically, veliger larvae contribute to the connectivity of populations across coastal and continental shelves and leave a rich fossil record, where protoconch and prodissoconch features help identify related groups. While most veligers are associated with marine molluscs, some freshwater lineages exhibit veliger-like stages, though many freshwater molluscs have alternative larval strategies.