Abstract
Ophiocoma scolopendrina, a prevalent brittle star species in the southernmost intertidal zone of Qeshm Island, serves as an exemplary model for studying echinoderm arm regeneration processes within the Persian Gulf. To elucidate the regenerative mechanisms of these organisms, we conducted a comprehensive investigation of their regenerative structures from a histological perspective. The collected specimens were carefully acclimated to laboratory conditions in aerated seawater aquaria before being transferred to specially treated environments. Adhering to strict ethical protocols, we amputated the arms of the brittle stars and meticulously documented the subsequent regenerative changes at various intervals: 24 hours, 72 hours, and weekly up to six weeks post-amputation. Our findings reveal that Ophiocoma scolopendrina undergoes a triphasic regenerative pathway, encompassing a repair phase, an early regenerative phase, and an advanced regenerative phase. Notably, the temporal progression of these phases differs from that observed in other previously studied species. Initially, the brittle stars effectuate wound closure and healing of the autotomy plane through an epimorphic process, characterized by the migration of epidermal cells and re-epithelialization. Subsequently, the formation of a regenerative blastema within the bud initiates morphogenesis, followed by the differentiation and proliferation of blastemal cells, culminating in the development of the regenerated arm.