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How (and why) fins turn into limbs: insights from anglerfish

  • Blake V. Dickson (a1) and Stephanie E. Pierce (a1)

The fin-to-limb transition is heralded as one of the most important events in vertebrate evolution. Over the last few decades our understanding of how limbs evolved has significantly increased; but, hypotheses for why limbs evolved are still rather open. Fishes that engage their fins to ‘walk' along substrate may provide some perspective. The charismatic frogfishes are often considered to have the most limb-like fins, yet we still know little about their underlying structure. Here we reconstruct the pectoral fin musculoskeletal anatomy of the scarlet frogfish to identify adaptations that support fin-assisted walking behaviours. The data are compared to three additional anglerfish species: the oval batfish, which represents an independent acquisition of fin-assisted walking; and two pelagic deep-sea swimmers, the triplewart seadevil and ghostly seadevil. Our results clearly show broad musculoskeletal differences between the pectoral fins of swimming and walking anglerfish species. The frogfish and batfish have longer and more robust fins; larger, differentiated muscles; and better developed joints, including a reverse ball-and-socket glenoid joint and mobile ‘wrist'. Further, the frogfish and batfish show finer-scale musculoskeletal differences that align with their specific locomotor ecologies. Within, we discuss the functional significance of these anatomical features in relation to walking, the recurring evolution of similar adaptations in other substrate locomoting fishes, as well as the selective pressures that may underlie the evolution of limbs.

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Aiello, B. R., King, H. M. & Hale, M. E. 2014. Functional subdivision of fin protractor and retractor muscles underlies pelvic fin walking in the African lungfish Protopterus annectens. Journal of Experimental Biology 217, 34743482.
Bennett, M. B. 2000. Unifying principles in terrestrial locomotion: do hopping Australian marsupials fit in? Physiological and Biochemical Zoology 73, 726735.
Biewener, A. A., Thomason, J. J. & Lanyon, L. E. 1988. Mechanics of locomotion and jumping in the horse (Equus): in vivo stress in the tibia and metatarsus. Journal of Zoology 214, 547565.
Biewener, A. A. & Daley, M. A. 2007. Unsteady locomotion: integrating muscle function with whole body dynamics and neuromuscular control. Journal of Experimental Biology 210, 29492960.
Boisvert, C. A., Joss, J. M. & Ahlberg, P. E. 2013. Comparative pelvic development of the axolotl (Ambystoma mexicanum) and the Australian lungfish (Neoceratodus forsteri): conservation and innovation across the fish-tetrapod transition. EvoDevo 4, 3.
Clack, J. A. 2002. An early tetrapod from ‘Romer's Gap'. Nature 418, 7277.
Clack, J. A. 2005. Getting a leg up on land. Scientific American 293, 100107.
Clack, J. A. 2007. Devonian climate change, breathing, and the origin of the tetrapod stem group. Integrative and Comparative Biology 47, 510523.
Clack, J. A. 2009. The fin to limb transition: new data, interpretations, and hypotheses from paleontology and developmental biology. Annual Review of Earth and Planetary Sciences 37, 163179.
Clack, J. A. 2012. Gaining ground: the origin and evolution of tetrapods. 2nd edn. Bloomington, IN: Indiana University Press. 523 pp.
Coates, M. I., Ruta, M. & Friedman, M. 2008. Ever since Owen: changing perspectives on the early evolution of tetrapods. Annual Review of Ecology, Evolution, and Systematics 39, 571592.
Coates, M. I. & Clack, J. A. 1995. Romer's gap: tetrapod origins and terrestriality. Bulletin du Muséum National d'Histoire Naturelle, 4ème Série–Section C–Sciences de la Terre, Paléontologie, Géologie, Minéralogie 17, 373388.
Cole, N. J., Hall, T. E., Don, E. K., Berger, S., Boisvert, C. A., Neyt, C., Ericsson, R., Joss, J., Gurevich, D. B. & Currie, P. D. 2011. Development and evolution of the muscles of the pelvic fin. PLoS Biology 9, e1001168.
Consi, T. R., Seifert, P. A., Triantafyllou, M. S. & Edelman, E. R. 2001. The dorsal fin engine of the seahorse (Hippocampus sp.). Journal of Morphology 248, 8097.
Currey, J. D. 2013. Bones: structure and mechanics. Princeton, NJ: Princeton University Press. 435 pp.
Descamps, E., Sochacka, A., De Kegel, B., Van Loo, D., Van Hoorebeke, L. & Adriaens, D. 2014. Soft tissue discrimination with contrast agents using micro-CT scanning. Belgium Journal of Zoology 144, 2040.
Diogo, R., Johnston, P., Molnar, J. L. & Esteve-Altava, B. 2016. Characteristic tetrapod musculoskeletal limb phenotype emerged more than 400 MYA in basal lobe-finned fishes. Scientific Reports 6, 19.
Edwards, J. L. 1977. The evolution of terrestrial locomotion. In Hecht, M. K., Goody, P. C. & Hecht, B. M. (eds) Major patterns in vertebrate evolution, 553577. Boston, MA: Springer.
Edwards, J. L. 1989. Two perspectives on the evolution of the tetrapod limb. American Zoologist 29, 235254.
Ellerby, D. J., Spierts, I. L. & Altringham, J. D. 2001. Slow muscle power output of yellow- and silver-phase European eels (Anguilla Anguilla): changes in muscle performance prior to migration. The Journal of Experimental Biology 204, 13691379.
Flammang, B. E., Suvarnaraksha, A., Markiewicz, J. & Soares, D. 2016. Tetrapod-like pelvic girdle in a walking cavefish. Scientific Reports 6, 18.
Foster, K. L., Dhuper, M. & Standen, E. M. 2018. Fin and body neuromuscular coordination changes during walking and swimming in Polyterus senegalus. Journal of Experimental Biology 221(17), 113.
Fricke, H., Reinicke, O., Hofer, H. & Nachtigall, W. 1987. Locomotion of the coelacanth Latimeria chalumnae in its natural environment. Nature 329, 331333.
Froese, R. & Pauly, D. (eds) 2018. Fishbase. htttp://
Gans, C., Gaunt, A. S. & Webb, P. W. 1997. Vertebrate locomotion. Supplement 30: Handbook of Physiology, Comparative Physiology 3, 55213.
Gehrke, A. R., Schneider, I., de la Calle-Mustienes, E., Tena, J. J., Gomez-Marin, C., Chandran, M., Nakamura, T., Braasch, I., Postlethwait, J. H., Gómez-Skarmeta, J. L. & Shubin, N. H. 2015. Deep conservation of wrist and digit enhancers in fish. Proceedings of the National Academy of Sciences 112, 803808.
Goto, T., Nishida, K. & Nakaya, K. 1999. Internal morphology and function of paired fins in the epaulette shark, Hemiscyllium ocellatum. Ichthyological Research 46, 281287.
Gougnard, C. & Vandewalle, P. 1980. Déplacements terrestres de Clarias lazera (Pisces, Siluriformes, Clariidae). Annales de la Societe Royale Zoologique de Belgique 109, 141152.
Harris, V. A. 1960. On the locomotion of the mudskipper Periophthalmus koelreuteri (Pallas):(Gobiidae). Journal of Zoology 134, 107135.
Johanson, Z., Joss, J., Boisvert, C. A., Ericsson, R., Sutija, M. & Ahlberg, P. E. 2007. Fish fingers: digit homologues in sarcopterygian fish fins. Journal of Experimental Zoology Part B: Molecular and Developmental Evolution 308, 757768.
Johnels, A. G. 1957. The mode of terrestrial locomotion in Clarias. Oikos 8, 122129.
Kawano, S. M. & Blob, R. W. 2013. Propulsive forces of mudskipper fins and salamander limbs during terrestrial locomotion: implications for the invasion of land. Integrative and Comparative Biology 53, 283294.
King, H. M., Shubin, N. H., Coates, M. I. & Hale, M. E. 2011. Behavioral evidence for the evolution of walking and bounding before terrestriality in sarcopterygian fishes. Proceedings of the National Academy of Sciences 108, 21146–51.
King, H. M. & Hale, M. E. 2014. Musculoskeletal morphology of the pelvis and pelvic fins in the lungfish Protopterus annectens. Journal of Morphology 275, 431441.
Lauder, G. V., Madden, P. G. A., Mittal, R., Dong, H. & Bozkurttas, M. 2006. Locomotion with flexible propulsors: I. Experimental analysis of pectoral fin swimming in sunfish. Bioinspiration & Biomimetics 1, S25–34.
Lieber, R. L. 2002. Skeletal muscle structure, function, and plasticity. Philadelphia, PA: Lippincott Williams & Wilkins. 369 pp.
Lindsey, C. C. 1978. Form, function, and locomotory habits in fish. In Hoar, W. S. & Randall, D. J. (eds) Fish physiology. Volume VII, 1–100. New York, NY: Academic Press.
Lou, F., Curtin, N. A. & Woledge, R. C. 2002. Isometric and isovelocity contractile performance of red muscle fibres from the dogfish Scyliorhinus canicula. Journal of Experimental Biology 205, 15851595.
Lucifora, L. O. & Vassallo, A. I. 2002. Walking in skates (Chondrichthyes, Rajidae): anatomy, behaviour and analogies to tetrapod locomotion. Biological Journal of the Linnean Society 77, 3541.
Macesic, L. J., Mulvaney, D. & Blevins, E. L. 2013. Synchronized swimming: coordination of pelvic and pectoral fins during augmented punting by the freshwater stingray Potamotrygon orbignyi. Zoology 116, 144150.
McHorse, B. K., Biewener, A. A. & Pierce, S. E. 2017. Mechanics of evolutionary digit reduction in fossil horses (Equidae). Proceedings of the Royal Society, B 284, 20171174.
Miya, M., Pietsch, T. W., Orr, J. W., Arnold, R. J., Satoh, T. P., Shedlock, A. M., Ho, H. C., Shimazaki, M., Yabe, M. & Nishida, M. 2010. Evolutionary history of anglerfishes (Teleostei: Lophiiformes): a mitogenomic perspective. BMC Evolutionary Biology 10, 58.
Miyake, T., Kumamoto, M., Iwata, M., Sato, R., Okabe, M., Koie, H., Kumai, N., Fujii, K., Matsuzaki, K., Nakamura, C. & Yamauchi, S. 2016. The pectoral fin muscles of the coelacanth Latimeria chalumnae: functional and evolutionary implications for the fin-to-limb transition and subsequent evolution of tetrapods. Anatomical Record 299, 12031223.
Molnar, J. L., Diogo, R., Hutchinson, J. R. & Pierce, S. E. 2017. Reconstructing pectoral appendicular muscle anatomy in fossil fish and tetrapods over the fins-to-limbs transition. Biological Reviews 93, 10771107.
Monod, T. 1960. Apropose du pseudobrachium des Antennarius (pisces, Lophiiformes). Bulletin de l'Institut Français d'Afrique Noire 22, 620698.
Nakamura, T., Gehrke, A. R., Lemberg, J., Szymaszek, J. & Shubin, N. H. 2016. Digits and fin rays share common developmental histories. Nature 537, 225228.
Pace, C. M. 2009. Locomotion in amphibious fishes. Flagstaff, AZ: Northern Arizona University.
Pace, C. M. & Gibb, A. C. 2009. Mudskipper pectoral fin kinematics in aquatic and terrestrial environments. Journal of Experimental Biology 212, 22792286.
Pierce, S. E., Clack, J. A. & Hutchinson, J. R. 2012. Three-dimensional limb joint mobility in the early tetrapod Ichthyostega. Nature 486, 523526.
Pierce, S. E., Hutchinson, J. R. & Clack, J. A. 2013. Historical perspectives on the evolution of tetrapodomorph movement. Integrative and Comparative Biology 53, 209223.
Pietsch, T. W. & Grobecker, D. B. 1987. Frogfishes of the world: systematics, zoogeography, and behavioral ecology. Redwood City, CA: Stanford University Press. 420 pp.
Pridmore, P. A. 1994. Submerged walking in the epaulette shark Hemiscyllium ocellatum (Hemiscyllidae) and its implications for locomotion in rhipidistian fishes and early tetrapods. Zoology 98, 278297.
Renous, S., Davenport, J. & Bels, V. 2011. To move on immersed and emersed substrata: adaptive solutions in extant “fishes”. Mémoires du Muséum National d'Histoire Naturelle 201, 91128.
Romer, A. S. 1958. Tetrapod limbs and early tetrapod life. Evolution 12, 365369.
Ruta, M. & Wills, M. A. 2016. Comparable disparity in the appendicular skeleton across the fish–tetrapod transition, and the morphological gap between fish and tetrapod postcrania. Palaeontology 59, 249267.
Schneider, I. & Shubin, N. H. 2013. The origin of the tetrapod limb: from expeditions to enhancers. Trends in Genetics 29, 419426.
Shubin, N. H., Daeschler, E. B. & Jenkins, F. A. 2006. The pectoral fin of Tiktaalik roseae and the origin of the tetrapod limb. Nature 440, 764771.
Shubin, N. H. & Alberch, P. 1986. A morphogenetic approach to the origin and basic organization of the tetrapod limb. In Hecht, M. K., Wallace, B. & Prance, G. T. (eds) Evolutionary biology, 319387. Boston, MA: Springer.
Standen, E. M., Du, T. Y. & Larsson, H. C. E. 2014. Developmental plasticity and the origin of tetrapods. Nature 513, 5458.
Standen, E. M., Du, T. Y., Laroche, P. & Larsson, H. C. E. 2016. Locomotor flexibility of Polypterus senegalus across various aquatic and terrestrial substrates. Zoology 119, 447454.
Taft, N. K., Lauder, G. V. & Madden, P. G. A. 2008. Functional regionalization of the pectoral fin of the benthic longhorn sculpin during station holding and swimming. Journal of Zoology 276, 159167.
Wilhelm, B. C., Du, T. Y., Standen, E. M. & Larsson, H. C. E. 2015. Polypterus and the evolution of fish pectoral musculature. Journal of Anatomy 226, 511522.
Zuniga, A. 2015. Next generation limb development and evolution: old questions, new perspectives. Development 142, 38103820.
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