Lancelets

Definition

Lancelets are small, elongated marine animals that belong to the subphylum Cephalochordata. They are characterized by their notochord, which extends the length of their body and persists throughout their life.

5 Must Know Facts For Your Next Test

1. Lancelets possess all five key characteristics of chordates: a notochord, dorsal hollow nerve cord, pharyngeal slits, endostyle, and post-anal tail.
2. They are filter feeders, using cilia to draw water into their mouths and trapping food particles in mucus.
3. Lancelets are considered living fossils and provide important evolutionary insights into the early development of vertebrates.
4. Unlike vertebrates, lancelets lack a backbone but have segmented muscles called myomeres.
5. Their circulatory system is simple and lacks a true heart; instead, they rely on contractile vessels to move blood.

Review Questions

• What are the five key characteristics that lancelets share with other chordates?
• How do lancelets feed and what anatomical structures do they use for this process?
• Why are lancelets considered important for understanding vertebrate evolution?

Related terms

Notochord: A flexible rod made out of a material similar to cartilage that provides support in all embryonic and some adult chordate animals.

Cephalochordata:

A subphylum of chordates that includes lancelets, characterized by their blade-like shape.

Filter Feeding: A method of feeding where an organism strains suspended matter and food particles from water.