10. Sensory systems_FA2023 (1).pdf

MARI 3090 – Marine Mammalogy Dalhousie University Dr. Amanda Babin Fall 2023 uwphotographyguide.com Sensory Systems Senses • Vision (Photoreception) • Touch (Somatosensation) • Chemoreception • Smell (Olfactory) • Taste (Gustatory) • • • • • • Sense of time Echolocation Equilibrioreception (ba...

MARI 3090 – Marine Mammalogy Dalhousie University Dr. Amanda Babin Fall 2023 uwphotographyguide.com Sensory Systems Senses • Vision (Photoreception) • Touch (Somatosensation) • Chemoreception • Smell (Olfactory) • Taste (Gustatory) • • • • • • Sense of time Echolocation Equilibrioreception (balance) Magnetoreception (navigation) Baroreception (pressure/depth) Electroreception (electrical activity) teknear.com • Hearing (Auditory) • Many more! Function of Sensory Systems • To sense the environment and other animals’ behaviour in order to make appropriate decisions Vision • Visibility may be limited (light is gone within 200 m) • River dolphins have small eyes, Indus and Ganges dolphins only see light vs. dark • Eyes used for close range (hunting, social interactions) • There is less violet in sunlight than blue Less energy More energy • Thickened sclera • Spherical lens used for focusing, not the cornea (except River dolphins) • Iris opens wide in low light • Ciliary muscles: • None in cetaceans • Present in pinnipeds • No tears • Pad under eye secretes oil to protect from saltwater improve-vision-naturally.com The Eye Visual Acuity in Air and Water • Pinnipeds and dolphins have good visual acuity in air and water • Northern Elephant Seals adapt to changes in light levels within 6 min (humans 10-40 min) • Southern Elephant Seals are most sensitive to the wavelength of bioluminescent organisms • Adapted for low-light: Mark Fickett • Contract pupil in bright light • Reflective layer behind retina – tapetum lucidum • Cells in the retina: • Rods = low-light, black-and-white • Cones = bright-light, colour • Most terrestrial mammals are dichromats: • • • • L-cones = long-to-middle wave (red to green) S-cones = short wave (blue to UV) Manatees are dichromatic Some nocturnal mammals are monochromats (no S-cones) • Primates are trichromatic (2 types of L-cones for green and red) • Cetaceans and pinnipeds have lost their S-cones (rods compensate) • Mysticetes see colour better than odontocetes Philip Thurston Colour Vision Touch • Thigmotaxis – respond to touch with highly sensitive skin • Sensory hairs Evolution Evidence Reproduced with permission from Catherine Hood • Mysticetes have ~100 vibrissae around jaws • Odontocetes have a few vibrissae on their upper jaw (except River dolphins have more) • Sirenians have vibrissae on their muzzle • Sea otters most sensitive on paws Pinniped Vibrissae Reproduced with permission from Catherine Hood news.mit.edu • Mystacial vibrissae on muzzle (mv) • Supraorbital vibrissae above the eyes (sv) • Rhinal vibrissae at back of muzzle (rv) Smell • Mysticetes maintain some olfactory tissues • Plankton clouds? • Odontocetes unable to smell • Otariids better at smelling than phocids, both better than sirenians • Predatory detection, mother-pup recognition, social interactions • Sea otters and polar bears can smell well Taste • Functions: • Communication (urine) • Orientation (salinity gradients) • Seals are highly sensitive to differences in salinity – can tell a 4% difference vs. humans can tell an 18% difference lateet.com • Fewer taste buds than terrestrial mammals Hearing in Air medicalanatomy.net Hearing Underwater • No outer ear (except otariids) • Amphibious marine mammals maintain hearing in air • Ear canal blocked by wax and debris in cetaceans (vestigial) • Sound is conducted anteriorly through lower jaw (odontocetes) or laterally (mysticetes) Yamoto and Pyenson 2015 Electroreception in mammals • Platypus – pits in their bill similar to fishes • Echidnas – tip of snout • Guiana dolphin! Wikimedia Commons PatWeeSit Czech-Damal et al. 2012 Jakob Fahr • Hairless vibrissal crypts on the rostrum • Ampullary electroreceptors Take Home Messages • Vision is used for close range interactions • The ability to sense touch is called somatosensation, responding to touch is called thigmotaxis • Vibrissae are sensory hairs • Tapetum lucidum is a reflective layer behind the retina, a low-light adaptation • Hearing is the most important sense 1zoom.me Thank you!