fish escapes to their advantage, snakes increase strike success and reduce handling time with head-first captures. The latter may, in turn, prevent snakes from becoming prey when feeding. Findings in these two unusual predators emphasize the importance of a multidisciplinary approach for understanding the evolution of brains and behavior.
Star-nosed moles and tentacled snakes each have novel sensory appendages protruding from their faces. These appendages give both animals a unique appearance unparalleled among their peers—no other mammal or snake has comparable appendages (Fig. 13.1). However, there is more than the bizarre appearance of these animals to attract our attention. Extreme sensory specializations often reveal general principles of nervous system function and organization that are less obvious in other species (Hodgkin and Huxley, 1952; Carr and Konishi, 1990; Heiligenberg, 1991; Bass and Zakon, 2005; Kawasaki, 2009; Konishi, 2010; Nottebohm and Liu, 2010). More generally, extremes in morphology provide informative case studies in evolutionary biology. Indeed, Darwin (1859) devoted a special section of On the Origin of Species by Means of Natural Selection to “Organs of extreme perfection and complication.” One can argue whether these unusual species seem in some way perfected, but surprisingly, the complexity of the mole’s star has been cited as evidence of a divine creator (Weston and Wieland, 2003).
My goal is to review recent studies of these two species beginning with star-nosed moles, the species for which we have the most information from many years of study. The mole’s nose is exceptional not only in appearance but also in the high density of mechanoreceptors that covers the nasal rays and the complexity of the modular neocortical network that processes touch information from the star. These findings make the question of how and why the star evolved even more mysterious. However, expanding studies to include the mole’s habitat and behavior in the context of optimal foraging theory (Stephens and Krebs, 1986) strongly suggests a selective advantage (the ability to specialize on very small prey) that led to the evolution of the star as the highest resolution touch organ among mammals. Another extension of the research to include comparative and developmental studies provides compelling evidence for how the star evolved (Gould, 1977; Catania et al., 1999).
Recent investigations of aquatic tentacled snakes reveal a very different use for sensory appendages (Catania et al., 2010). Rather than serving active touch, the snake’s tentacles seem to act as fish-detecting motion sensors. However, the most interesting finding from the tentacled snake is its remarkable ability to use fish escape responses to its advantage (Catania, 2009, 2010).