Fertilization in sponges occurs in
Sponge reproductive biology includes retention of eggs internally because sessile filter feeders cannot copulate. Hermaphroditic sperm released via oscular current into seawater drawn into neighboring sponge through ostia where choanocytes phagocytose packets transform into carrier cells delivering sperm to oocytes in mesohyl. Therefore fertilization occurs internally within parental mesenchyme not externally broadcast. Cleavage holoblastic leads to amphiblastula larva released through osculum to swim briefly then settle. Internal fertilization ensures protection and nutritional support of gam
Ref: Brusca & Brusca, Chapter 7: Porifera internal fertilization mesohyl; Campbell Chapter 33
