Functional morphology of changeable skin papillae in octopus and cuttlefish

Meeting Abstract

P2.85  Sunday, Jan. 5 15:30  Functional morphology of changeable skin papillae in octopus and cuttlefish ALLEN, J.J.*; BELL, G.R.R.; KUZIRIAN, A.M.; VELANKAR, S.S.; HANLON, R.T.; Brown University, Providence, RI; Marine Biological Laboratory, Woods Hole, MA; Marine Biological Laboratory, Woods Hole, MA; University of Pittsburgh, PA; Marine Biological Laboratory, Woods Hole, MA

Benthic cephalopods are renowned for their adaptive camouflage behavior, including changing the 3-dimensional texture of their skin via malleable dermal papillae. We used brightfield, scanning electron and confocal microscopy to study papillae of different shapes, sizes and degrees of extension in six species: cuttlefish Sepia officinalis and S. apama and octopuses Octopus vulgaris, Macrotritopus defilippi, Abdopus aculeatus, and O. bimaculoides. Our results suggest two distinct biomechanic mechanisms of papilla extension: muscular hydrostatic movement and flexible tissue buckling. Most papillae are extended by the contraction of two sets of muscles: concentric circular dermal erectors lift the papilla away from the surface of the body while horizontal dermal erectors draw the papilla’s perimeter toward its core to determine shape. Retractor muscles attached to the papilla’s apex radiate basally toward its periphery; their contraction pulls the papilla flat by drawing the apex down toward the surface of the body while opposing and stretching the circular erectors. In these species, connective tissue infiltrated with mucopolysaccharides assists with structural support. Face ridge papillae in S. apama are different: contraction of underlying erector muscles causes buckling of the overlying skin layers, resulting in papilla extension. Flattening is achieved by the contraction of retractor muscles inserted at the edges of the reflective elements. In this species, leucophores are embedded in mucopolysaccharide-rich connective tissue, which contributes structural support. Study of papillae in the many so far unexamined species of cuttlefish and octopuses might reveal additional methods of soft tissue actuation.

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