Question

How many features of the amphioxus adult do you also find in the ammocoete, the larval form of a lamprey? Why do you think these similarities exist?

Answer 1

Following features are found in both amphioxus adult and ammocoete:

1. Velum
2. Oral tentacles(buccal cirri)
3. Pharynx
4. dorsal nerve chord
5. Notochord
6. doesal fins
7. myomeres (body muscle segments)

The similarities between the ammocoete larva and pmphioxus adults can be understood in the light of ontogeny recapitulating phylogeny by showing resmblence to a more primitive chordate in this case Amphioxus.Ernst Haeckel's theory of ontogeny recapitulates phylogeny states that from fertilization till gestation or hatching goes through resembling the stages of evolution in the animal's remote ancestor. Kollmann has described this retention of larval features as ' neoteny'.