Which statement describes the life-stage symmetry pattern of echinoderms?

Which statement describes the life-stage symmetry pattern of echinoderms?

• A. Larvae: Bilateral; Adults: Fivefold radial
• B. Larvae: Fivefold radial; Adults: Bilateral
• C. Larvae: Radial; Adults: Bilateral
• D. Larvae: No symmetry; Adults: Radial

Answer: (A)

Echinoderms start life with bilateral symmetry and later develop a pentaradial (fivefold) body plan as adults. In the larval stage, their bodies are bilaterally symmetric, which is common for many marine larvae. Through metamorphosis, they reorganize into a five-ray arrangement around a central axis, giving the characteristic pentaradial symmetry of the adult form. This pattern—bilateral in larvae, fivefold radial in adults—best fits what we observe in echinoderm development, such as sea stars, sea urchins, and their relatives.

Echinoderms start life with bilateral symmetry and later develop a pentaradial (fivefold) body plan as adults. In the larval stage, their bodies are bilaterally symmetric, which is common for many marine larvae. Through metamorphosis, they reorganize into a five-ray arrangement around a central axis, giving the characteristic pentaradial symmetry of the adult form. This pattern—bilateral in larvae, fivefold radial in adults—best fits what we observe in echinoderm development, such as sea stars, sea urchins, and their relatives.