Lancelet Habitat

The lancelets inhabit soft bottoms ranging from fine sand to coarse shelly sand or gravel in shallow coastal water. Lancelets lie buried beneath the ground, often with their mouths protruding above the surface, allowing them to take in water laden with food. They prefer shallow water and the most popular places to live as a lancelet are warm, sandy, shallow, protected coastal beaches.

Tunicate Habitat

Tunicates are sessile creatures meaning that they do not move. Their preferred habitat is attached to docks, boats, or rocks in protected sub-tidal zones. These marine creatures like shallow water and not too many disturbances.

Reproduction

Lancelets reproduce sexualy. There are two sexes in each species and the sperm and egg are simaltaniously released into the water where fertilization occurs. Tunicates on the other hand, reproduce a little differently. The gametes produce a larva which looks very similar to a tadpole that has a small spherical body with a long tail. These larvae are released from the tunicate and swim freely intil they find the perfect habitat to settle in. Within a few weeks the baby tunicate reaches it's full adult size and is able to begin it's own reproduction.

Feeding

The main structures that are used for feeding are the endostyle with mucous glands, the peripharyngeal grooves and dorsal grooves lined with cilia, the stigmata, and the esophagus. the tunicates excrete a mucus film to capture prey that has been sucked in with the water. This mucus is secreted by the endostyle continuously which is then moved by cilia into the brachial basket, to the dorsal groove, and finally to the esophagus .

Uniting Traits

Phylum Chordata (chordates) includes fish, frogs, birds, snakes, humans etc. This very diverse phylum is untied by four traits:
1. Notochord
2. Dorsal hollow nerve cord
3. Pharyngeal gill slits
4. Post anal tail
Many of these traits are only present in the embryo stage of life. The notochord is a long flexible support rod replaced by a back bone in humans. The dorsal hollow nerve cord (DHNC) runs along the dorsal surface just above the notochord. The front end of the DHNC developes into a brain. The pharayngeal gill slits are paired strucures in the pharyngeal or throat region. In terrestrial vertebrates, gill slits are only present during the embryonic stage. Last but not least, the post anal tail, is found in the larval or embryonic stages of invertebrate chordates.

Tunicates

Tunicates are small marine chordates that eat plankton they filter from the water. Their name is derived from a special body covering called the tunic. ONly the tadpole- shaped larvae of tunicates have a notochord and a dorsal hollow nerve chord. When most tunicate larvae mature they undergo metamorphosis and become sissile adults that grow into colonies attached to a solid surface. Both larval tunicates and adults filter feed and breed at the same time through a pharyngeal basket pierced by gill slits.

lancelets

Lancelets are small fish like creatures that live in the sandy bottom of shallow tropical oceans. unlike tunicates, adult lancelets have a definate head. They have a mouth that opens into a long pharyngeal region with up to a hundred pairs of gill slits. Lancelets feed by passing water through their pharynx, where food particles are caught in a sticky mucus. This music is swallowed into a digestive tract that starts at one end of the pharynx and continues straight through the animal to the anus. They have a simple, primative heart that pumps blood through vessels in a closed circulatory system. Unlike most vertibrates, lancelets have no jaw. Their mouth is composed of soft tissues. Lancelets also lack appendages and can move only by bending their bodies back and forth.