DATE2025.09.04 #Press Releases
The Mechanism of Comb Plate Retraction in a Ctenophore That Loses Its Combs
— Unraveling the Life History of a Deep-Sea Ctenophore Discovered by Emperor Showa —
Summary
A research group led by Professor Toru Miura, then-graduate student Ryosuke Kanahara, and Technical Specialist Hisanori Kōzuka of the Misaki Marine Biological Station, Graduate School of Science, The University of Tokyo, along with Curator Nobuya Yamauchi of Aquamarine Fukushima, has revealed the developmental process of growth and retraction of comb plates in the larval stage of Coeloplana, a member of the ctenophore phylum (Ctenophora) known for having been discovered by Emperor Showa.
Ctenophores are generally characterized by structures known as “comb plates,” composed of numerous cilia. These comb plates are present in the larvae of Coeloplana, but are entirely lost in the adult stage, which adopts a benthic (bottom-dwelling) lifestyle. Until now, the developmental process and mechanism of this retraction had remained unclear.
In this study, histological observations of larvae at different time points post-hatching revealed that Coeloplana possesses a mechanism that switches between comb plate growth and retraction, leading to the loss of these structures prior to settlement. The acquisition of this mechanism appears to be closely linked to the evolution of the species’ unique life history.
Future studies, including investigations into the underlying molecular mechanisms and comparative developmental analyses with other ctenophores, are expected to advance our understanding of the evolution of benthic lifestyles within this phylum.
Figure: Growth and Retraction of Comb Plates in Coeloplana
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Journals
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Journal name Zoological Science
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