The brain and behavior of the tentacled snake

Abstract

Tentacled snakes (Erpeton tentaculatum) are aquatic predators that feed exclusively on fish. They have a unique pair of tentacles projecting from the face and an unusual J-shaped hunting posture. These features have been the subject of speculation for over a century. In a series of behavioral studies, tentacled snakes were found to exploit fish escape responses by startling fish toward their strike. This remarkable, deceptive behavior takes advantage of the stereotyped C-start escape response of fish. For some fish approach angles, snakes predicted future fish behavior and accurately struck at their moving head. These findings suggest tentacled snakes are acting as "rare enemies"--taking advantage of prey behavior that is usually adaptive for the prey species. Anatomical and physiological analysis showed the tentacles are densely innervated by the trigeminal nerve and are sensitive mechanoreceptors that respond to water movements. Mechanosensory information from the tentacles projects to the optic tectum in approximate register with vision, providing a mechanism for integrating visual and mechanosensory cues for identifying, localizing, and capturing prey.

Comparative morphology of snake (Squamata) endocasts: evidence of phylogenetic and ecological signals

“…B–D), the only specimen that has an endocast with the dorsal margin of the optic tectum located more dorsally than the dorsal margin of the cerebral hemispheres. Such features can be correlated to the special nature of E. tentaculatum , which is the only snake presenting a pair of appendages that protrude from the face (Catania, , ). The tentacles, useful to detect and locate preys, are innervated by trigeminal fibers to the optic tectum and could be responsible for its large size in E. tentaculatum .…”

The rostral neurovascular system of Tyrannosaurus rex

“…The nasopalatine nerve is also responsible for innervating most of the premaxilla in squamates and crocodilians, in which the ophthalmic branch of the trigeminal nerve and corresponding canals are comparatively shorter (Sedlmayr, 2002;Leitch and Catania, 2012;George and Holliday, 2013;Lessner and Holliday, 2020). The ophthalmic nerve nevertheless does reach the premaxilla in these taxa (Bellairs, 1949;Witmer, 1995;Dubbeldam, 1998;Sedlmayr, 2002;Hieronymus, 2019;Lessner and Holliday 2020) and even innervates the medial half of the tentacle in Erpeton tentaculatum (Catania, 2011).…”

Evolution of the eyes of vipers with and without infrared-sensing pit organs

“…This is a topic of substantial interest in sensory and evolutionary biology, and among vertebrates there are several striking instances of new and/or elaborated senses occurring in taxa in which other senses are degenerate. For example, echolocating bats and toothed whales have reduced visual and olfactory systems, respectively (Oelschläger, 1992;Jones, Teeling, & Rossiter, 2013;Hudson et al, 2014); the two trichromatic lineages of primates have a significantly more degenerate olfactory repertoire than other primates (Gilad et al, 2004); the mostly soil-dwelling caecilian amphibians have a reduced visual system but a unique, probably chemosensory and tactile tentacle (Himsted, 1996;Mohun et al, 2010); small-eyed star-nosed moles, naked mole-rats and duck-billed platypuses all have reduced vision and an elaborated somatosensory/electrosensory system (e.g., Pettigrew et al, 1998;Catania & Remple, 2004;Catania, 2011); and cave fish with reduced vision have hypertrophied mechanosensory lateral line systems and enhanced gustatory and possibly olfactory systems (e.g. Soares & Niemiller, 2013).…”