Amphiblastula larva in sponges is
Poriferan embryology reveals diverse larval morphotypes including parenchymella solid stereoblastula and amphiblastula. Amphiblastula distinctive of calcareous sponges Class Calcarea and some Demospongiae characterized as hollow blastula with polarity one hemisphere composed small flagellated micromeres animal pole opposite large non-flagellated macromeres vegetal pole giving half-flagellated appearance. Free-swimming undergoes gastrulation by invagination of flagellated half then attaches metamorphoses into juvenile sponge. Polarity reflects axial specification. Presence exemplifies primitive
Ref: Brusca & Brusca, Chapter 7: Porifera amphiblastula larva Calcarea; NCBI Porifera
