Final answer:
The totipotent sponge cell type that can become other cell types is the amoebocyte. Amoebocytes have multiple functions and can differentiate into various cell types within the sponge.
Step-by-step explanation:
The sponge cell type that is totipotent and can become other sponge cell types is the amoebocyte. Amoebocytes are stem-cell-like cells that have a variety of functions within the sponge, including nutrient delivery, egg formation, sperm delivery, and cell differentiation. They can differentiate into other cell types such as collenocytes, lophocytes, sclerocytes, and spongocytes. These different cell types contribute to the support and structure of the sponge.