A flexible repertoire of wound closure strategies precedes whole-body regeneration

Wound closure is an essential aspect of regeneration, often serving as the first morphogenetic step preceding downstream events. Animals capable of whole-body regeneration can heal virtually any wound, but how the process of re-epithelialization compares across injury types remains understudied. Here, we investigate wound closure in the acoel Hofstenia miamia. We find that H. miamia deploy two distinct modes of closure, depending on which epithelial layers are injured. Regardless of geometry, wounds that injure the outer epidermis close by constriction. In contrast, damage to both the outer epidermis and pharyngeal epithelium induces long, actin-rich protrusions that form transient bridges across the wound prior to re-epithelialization. Muscle contraction is differentially required across conditions, and pharmacological inhibition of actomyosin contractility is sufficient to shift closure dynamics across epithelia. This work compares wound closure within the same animal, identifying a wide toolkit of repair strategies that appears independent of subsequent regenerative processes.