Sensory Systems PDF - Marine Mammalogy FA2023
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Dalhousie University
2023
Dr. Amanda Babin
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Summary
This document is a lecture on sensory systems in marine mammals, presented by Dr. Amanda Babin at Dalhousie University during Fall 2023. It covers various senses, including vision, touch, hearing, smell, and taste, in different marine mammal species.
Full Transcript
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!