title: The significance of pelvic fin flexibility for tree climbing fish.
abstract: In this article, we compare the characteristics of biomechanical attachment exhibited by two morphologically different mudskipper species, Boleophthalmus boddarti (with fused pelvic fins) and Periophthalmus variabilis (with unfused pelvic fins). P. variabilis is a tree and rock climber while B. boddarti dwells in the muddy shallows and is unable to climb. Our aim in this article is to determine whether it is predominantly chemical or morphological properties of the pelvic fins from each species that may allow P. variabilis to climb trees whilst preventing B. boddarti from doing the same. To fulfil our objective we perform friction and suction resistance tests, Fourier transform infrared spectroscopy of the mucosal secretions under the fins, direct geometrical measurements and finite element modelling. We find that B. boddarti has considerable resistance to pull-off forces, while P. variabilis has greater frictional resistance. Both species produce mucopolysaccaharides that we suggest aid Stefan adhesion to different substrates. P. variabilis fins are, nevertheless, considerably more flexible than those of B. boddarti and we conclude that P. variabilis is consequently able to maintain a more intimate surface area of contact with underlying material, which aids Stefan adhesion, increases frictional resistance, and helps it to climb trees.
authors.affiliation: Laboratory of Paper Coating and Converting, Centre for Functional Materials, Abo Akademi University, Porthaninkatu 3, 20500 Turku, Finland.
authors.forename: Adhityo
authors.initials: A
authors.lastname: Wicaksono
authors.affiliation: Laboratory of Animal Embryology, Faculty of Biology, Universitas Gadjah Mada, Yogyakarta, Indonesia.
authors.forename: Saifullah
authors.initials: S
authors.lastname: Hidayat
authors.affiliation: Laboratory of Paper Coating and Converting, Centre for Functional Materials, Abo Akademi University, Porthaninkatu 3, 20500 Turku, Finland; Laboratory of Animal Embryology, Faculty of Biology, Universitas Gadjah Mada, Yogyakarta, Indonesia.
authors.forename: Yudithia
authors.initials: Y
authors.lastname: Damayanti
authors.affiliation: Rapid Gain Global Corporation, Singapore.
authors.forename: Desmond Soo Mun
authors.initials: DS
authors.lastname: Jin
authors.affiliation: Laboratory of Paper Coating and Converting, Centre for Functional Materials, Abo Akademi University, Porthaninkatu 3, 20500 Turku, Finland.
authors.forename: Erly
authors.initials: E
authors.lastname: Sintya
authors.affiliation: Laboratory of Animal Embryology, Faculty of Biology, Universitas Gadjah Mada, Yogyakarta, Indonesia. Electronic address: bambang.retnoaji@ugm.ac.id.
authors.forename: Bambang
authors.initials: B
authors.lastname: Retnoaji
authors.affiliation: Laboratory of Paper Coating and Converting, Centre for Functional Materials, Abo Akademi University, Porthaninkatu 3, 20500 Turku, Finland. Electronic address: parvez.alam@abo.fi.
authors.forename: Parvez
authors.initials: P
authors.lastname: Alam
mesh_terms: D058500:Animal Fins / Q000502:physiology*; D000818:Animals; D001522:Behavior, Animal; D001696:Biomechanical Phenomena; D005399:Fishes / Q000502:physiology*; D009043:Motor Activity / Q000502:physiology*
keywords: Biomechanical attachment; Mucosal secretion; Mudskipper; Pelvic fin flexibility; Stefan adhesion