Embryonic development of arthropods is:

• A. Protostome
• B. Deuterostome
• C. Spiral cleavage
• D. Radial cleavage

Answer: (A)

Arthropods develop as protostomes, meaning the mouth forms from the blastopore early in embryonic development and the cells divide in a spiral, usually determinate pattern. This developmental mode also often involves forming the body cavity (coelom) by schizocoely. In contrast, deuterostomes — such as chordates and echinoderms — show radial cleavage and the blastopore becomes the anus, with the mouth forming later. Spiral cleavage is a typical feature of protostomes, including arthropods, but the key classification for their embryology is protostome rather than deuterostome.