What is the Difference Between Lancelets and Tunicates?

Lancelets and tunicates are both marine chordates, but they have distinct differences in their morphology, structure, and lifestyle. Here are some key differences between lancelets and tunicates:

1. Subphylum: Lancelets belong to the subphylum Cephalochordata, while tunicates belong to the subphylum Urochordata.
2. Motility: Lancelets are motile, resembling fish in appearance and behavior, while adult tunicates are sessile and have a barrel-shaped body.
3. Notochord: The notochord in lancelets extends from the head to the tail, while in tunicates, the notochord is present only in the larval tail.
4. Segmentation: Lancelets have a segmented body with myomeric segments, while tunicates lack myomeric segmentation.
5. Excretory System: Lancelets have an excretory system with segmented kidneys and protonephridia, while tunicates lack these features.
6. Reproduction: Lancelets are gonochoric, meaning there are separate sexes, while tunicates are hermaphroditic, meaning they have both male and female reproductive organs.
7. Size: Lancelets are usually 1 to 8 centimeters long, while tunicates can vary in size.
8. Feeding: Both lancelets and tunicates are suspension feeders, filtering small particles of food from the water.

In summary, lancelets are motile, fish-like chordates with a segmented body, while tunicates are sessile, barrel-shaped organisms lacking segmentation. They both belong to the phylum Chordata but have distinct differences in their structure and lifestyle.

Comparative Table: Lancelets vs Tunicates

Here is a table summarizing the differences between lancelets and tunicates:

Lancelets belong to the subphylum Cephalochordata and are small, fish-shaped marine organisms. They are motile and have a notochord that extends from the head to the tail. Tunicates are part of the subphylum Urochordata and are sessile marine invertebrates. They have a notochord only in the larval tail and do not have myomeric segments or tunica.