Chaetopteridae

The Chaetopteridae are a family of marine filter-feeding polychaete worms that live in vertical or U-shaped tubes in tunnels buried in the sedimentary or hard substrate of marine environments. The worms are highly adapted to the hard tube they secrete. Inside the tube the animal is segmented and regionally specialized, with highly modified appendages on different segments for cutting the tunnel, feeding, or creating suction for the flow of water through the tube home. The modified segments for feeding are on the 12th segment from the head for members of this family.

==Larvae== Chaetopteridae larvae are the largest among the polychaete worms. The larvae will range in size from 0.4 mm to 2.5 mm (largest polychaete larvae reported having a maximum length of 12 mm; the late stage of an unknown phyllodocid species). Chaetopteridae larvae are barrel-like in form with one to two ciliated bands at the midsection. They also have a large buccal funnel. These larvae are often long lived and effectively disseminate, although are constrained geographically to their appropriate ranges for successful adult growth. The most common form of larval developmental plan for polychaetes is the trochophore larvae. The trochophore will add segments sequentially from a posterior growth zone to produce a nectochaete larva. Chaetopterus represents a distinct deviation from this general design. At no point in larval growth stages does the metatrochophore take on the clearly segmented form of the typical nectochaete larva. The 15 segments of Chaetopterus are formed by subdivision of existing anlage.