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Their mouths vary depending on their diet, since the group includes predators, herbivores, filter feeders, scavengers, and parasites. Most have a pair of jaws and a pharynx that can be quickly turned inside out, allowing the worm to grab food and pull it into the mouth.
Most species have external gills usually found on the parapodia and a well-developed, simple circulatory system. The nervous system consists of a single or double ventral nerve cord running the length of the body, with ganglia and a series of small nerves in each segment. The brain is relatively large, compared with that of other annelids, and lies in the upper part of the head.
Most polychaetes have separate sexes - male and female and the sperm and eggs are released into the surrounding water through ducts or openings. The fertilized eggs hatch into larvae, which float among the plankton, and eventually metamorphose into the adult form by adding segments.
Most species have external gills usually found on the parapodia and a well-developed, simple circulatory system. The nervous system consists of a single or double ventral nerve cord running the length of the body, with ganglia and a series of small nerves in each segment. The brain is relatively large, compared with that of other annelids, and lies in the upper part of the head.
Most polychaetes have separate sexes - male and female and the sperm and eggs are released into the surrounding water through ducts or openings. The fertilized eggs hatch into larvae, which float among the plankton, and eventually metamorphose into the adult form by adding segments.