Cuttlefish skin papilla morphology suggests a muscular hydrostatic function for rapid changeability

Area of Science:

• Marine Biology
• Animal Physiology
• Biophysics

Background:

• Coleoid cephalopods exhibit dynamic body pattern changes for camouflage and signaling.
• Benthic octopuses and cuttlefish can rapidly alter skin texture from smooth to rugose.
• The biomechanics of skin papillae, the organs enabling texture change, remain uninvestigated.

Purpose of the Study:

• To investigate the biomechanics of dorsal skin papillae in cuttlefish (Sepia officinalis).
• To elucidate the muscular and structural mechanisms underlying papilla extension and retraction.

Main Methods:

• Histological examination of preserved cuttlefish papillae (retracted and extended states).
• Utilized brightfield, confocal, and scanning electron microscopy.
• Analyzed the arrangement and function of dermal erector muscles and connective tissues.

Main Results:

• Papillae contain extensive dermal erector muscles, arranged circularly and diametrically.
• Papillae function as muscular hydrostats, with muscles controlling shape and movement.
• Structural light reflectors (leucophores, iridophores) create white tips; thinner connective tissue suggests elastic energy storage for retraction.
• Subepidermal muscles likely facilitate active papillary retraction.

Conclusions:

• Cuttlefish skin papillae are muscular hydrostats controlled by specialized dermal erector muscles.
• Papilla extension may store elastic energy for rapid retraction, contributing to dynamic texture changes.
• Understanding papilla biomechanics provides insight into cephalopod camouflage and signaling mechanisms.