What was the phylum Sipuncula originally classified as?

Originally classified as annelids, despite the complete lack of segmentation, bristles and other annelid characters, the phylum Sipuncula was later allied with the Mollusca, mostly on the basis of developmental and larval characters.

What kind of body wall does a sipuncula have?

Sipunculans have a body wall somewhat similar to that of annelids (though unsegmented) in that it consists of an epidermis without cilia overlain by a cuticle, an outer layer of circular and an inner layer of longitudinal musculature.

What is the role of the sipunculan in reproduction?

Most sipunculans are deposit feeders, extending the introvert to gather food particles and draw them into the mouth, and retracting the introvert when feeding conditions are unsuitable or danger threatens. With a few exceptions, reproduction is sexual and involves a planktonic larval stage.

When does the sipunculan retract into the mouth?

Where are the sipunculid worms used as food?

Sipunculid worms are used as food in some countries in south-east Asia. The Swedish naturalist Carl Linnaeus first described the worm Sipunculus nudus in his Systema naturae in 1767.

How big does a Sipunculus nudus peanut worm get?

Peanut worms are not considered endangered or threatened. Physical characteristics: Sipunculus nudus measures 6 to 10 inches (150 to 250 millimeters) long. The introvert is short, only one-third the length of the trunk, and lacks hooks.

How many species of Sipuncula worms are there?

The Sipuncula or Sipunculida (common names sipunculid worms or peanut worms) is a group containing 144–320 species (estimates vary) of bilaterally symmetrical, unsegmented marine worms. Sipuncula signifies “little tube or siphon”. Traditionally considered a phylum, they might be a subgroup of phylum Annelida based on recent molecular work.