Q.76 The characteristic feature of deuterostomes is depicted by
(A) coelom formed by the hollowing out of a previously solid cord of mesodermal cells
(B) spiral and determinate cleavage
(C) formation of mouth from blastopore
(D) formation of anus from blastopore

Deuterostomes represent a key superphylum in animal development, distinguished by specific embryonic traits crucial for exams like NEET. The characteristic feature centers on blastopore fate, with option (D) as the correct choice.​​

Correct Answer
The correct option is (D) formation of anus from blastopore. In deuterostomes, the blastopore—the first embryonic opening—develops into the anus, while the mouth forms secondarily at the opposite end. This “second mouth” (deuteros = second, stome = mouth) trait separates them from protostomes.​

Option Analysis

• (A) coelom formed by the hollowing out of a previously solid cord of mesodermal cells: Incorrect. This describes schizocoely, typical of protostomes where mesoderm splits to form coelom. Deuterostomes use enterocoely, with coelom arising from gut pouches.​

• (B) spiral and determinate cleavage: Incorrect. Spiral, determinate cleavage (fixed cell fates early) defines protostomes. Deuterostomes exhibit radial, indeterminate cleavage, allowing regulative development.​

• (C) formation of mouth from blastopore: Incorrect. This is a protostome hallmark (“first mouth”). Deuterostomes reverse it, forming anus from blastopore.​

• (D) formation of anus from blastopore: Correct, as explained above. Seen in echinoderms, chordates (including humans).​

Protostome vs Deuterostome Table