What is the difference between amphiblastula and parenchymella sponge larvae?

The primary differences between the amphiblastula and parenchymella larvae in sponges lie in their physical structure and cellular organization.1

• Amphiblastula: This larva is oval-shaped and hollow, containing a central cavity. It is characterized by a distinct regional division: the anterior half consists of small, flagellated cells, while the posterior half is composed of larger, non-flagellated cells. It swims with the flagellated portion directed forward.12
• Parenchymella: This is the most common larval form among the Demospongiae. Unlike the hollow amphiblastula, the parenchymella is solid and compact. It features an outer layer of flagellated cells surrounding an inner mass of non-flagellated cells.1

During metamorphosis, these structural differences dictate how the adult sponge forms. In the parenchymella, the outer flagellated cells become the adult's choanocytes, while the interior cells give rise to the mesohyl and other adult tissues. In the amphiblastula, the choanocytes are derived specifically from the forward flagellated region, while the remaining adult structures develop from the posterior half.1