Hatch-as-hatch-can: tricks of the trade in coleoid hatchlings (Mollusca: Cephalopoda)

All coleoid hatchlings have a special complex of glandular cells situated at the mantle tip, which store a hatching enzyme that is released at the close of embryonic development; it locally dissolves the chorion membrane and any surrounding envelopes, thus producing a hatch opening. In most coleoids the hatchling also uses auxiliary equipment and actions to effectively extract itself from the egg case. This article considers the co-aptation between parental (egg cases) and filial contributions (hatching gland etc) in different coleoid groups.