Animal SensesHasith V, Aron Milberg, Ted Tsien, Zack Hausle

Introduction

Catch-all term for sensory inputs not perceived by humans.

Two classes: - Similar to human senses, but information

capture and processing is different.

- Inputs vastly different from human perception, and used in unique ways.

Echolocation

Echolocation

• Also known as biosonar

• Used by shrews, bats, cetaceans

• Used for navigation, foraging

• Consists of emitting calls, interpreting received responses to detect obstacles in environment

Echolocation

• Bats are great example

• Highly specialized auditory systems

• From the innervation of the inner ear to the auditory cortex, the system is specialized to interpret these sounds

Echolocation

• Basilar membrane in cochlea (ear) has a much greater surface area for returning calls of biosonar

• This region of response is known as an “acoustic fovea.”

• Movement of this membrane stimulates inner ear neurons.

Echolocation

• Interneurons in inferior colliculus have a great sensitivity to time differences

• This indicates importance of timing in auditory response – qua echolocation

• Neurons in this region have a very low threshold of stimulation, indicating a reflexive physical response

Echolocation

• Auditory cortex is significantly larger in animals with echolocation

• Brains create “maps” of auditory response, such as frequency or amplitude

• Neurons vary across the maps to produce correlating varied responses

Echolocation

• Three major types of neurons: FM-FM, CF-CF, DSCF

• FM-FM respond to call and echo; find distance

• CF finds frequency through Doppler effect; velocity relative to target object

• DSCF responds to a combination of frequency and amplitude

Echolocation

• Some subterraneans use echolocation due to low visibility in water, water’s high conductivity of sound.

• Oilbirds and shrews use echolocation to navigate dark environs.

Echolocation

• Toothed whales (dolphins, purpoises, sperm whales) emit a focused beam of high-frequency clicks.

– modulated by an organ known as the 'melon'. acting like a lipid-form acoustic lens.

• Most toothed whales use clicks in a series, or click train, for echolocation, while the sperm whale may produce clicks individually.

• A repetition rate over 600 clicks/s is a burst pulse. The auditory cortex of bottlenose dolphins resolves individual clicks up to 600 per second,

– graded response for higher click rates.

Electroreception

• The ability to perceive electric impulses

• Common in aquatic creatures

• Ability is found in the “lateral line,” a line of receptors running down the length of the creature

Electroreception

• Passive involves detecting bioelectric fields generated by surrounding animals.

• Active has an animal generating a field, and detecting distortions – sharks have this

Electroreception

• Active relies on epithelial cells, which respond to changes in frequency in a large range

• Passive relies on ampullary receptors, which respond below 50Hz

• Both rely on stimulation of sensory neurons

Ampullae of Lorenzini

• Jelly-filled canals found on the head of the animal forming a system of sense organs.

• Each canal ends in groups of small bulges lined by the sensory epithelium. A small bundle of afferent nerve fibers innervates each ampullae.

• The ampullae are mostly clustered into groups.

– Same number of nerve fibers are dedicated to electroreceptors as are dedicated to the eye, ear

– determine the sensitivity and degree of acuity of that sensory organ.

– Ampullae of Lorenzini is at least as important to an animal as its eyes, ears, and the lateral line.

Chemoreceptors

Chemoreceptors

Turn chemical signal into action potentials

Olfactory or Gustatory Chemicals bind to the receptors,

opening chemical-gated channels. There are glutamate-gated channels for instance which release action potentials on stimulation from glutamate.

Worms

Entire bodies covered in Chemoreceptors.

Worms can taste everything around them, motivating them to move through soil and eating the different matter that surrounds their bodies.

Octopi

Octopi have their chemoreceptors on the end of their tentacles allowing them to taste and smell by moving their tentacles. This allows them to taste out the area in safety.

SnakesSnakes are rullllly cool. They smell and

taste with their tongues. They stick their tongue out while slithering to help facilitate the rooting out of prey.

The forked tongue of snakes allows them to detect the direction from which a smell originates

stereo perceptionPits in the roof of the snake's mouth

(Jacobson's Organs) allow it to sense taste and smell information.

Vomeronasal Organ

Picks up pheromones and other smells. It transmits smells immediately to

amygdala and further smell processing It is coupled to g proteins which it

released in a cascade as a chemical gated ion channel

EM Spectrum PerceptionEM Spectrum Perception

Notes on animal vision

Animal vision is comprised of many different spectra which humans cannot see. Color is the processing of waves as they hit the eye, and animals for different evolutionary reasons perceive these waves in entirely different ways

Hawk Vision

Hawks have 20/5 vision, meaning for every 5 feet that a human can see, a hawk can see 20

Has 1 million photoreceptor per square millimeter in its retina.

Penguin Vision

Penguin’s flat corneas allow them to see underwater

Penguins can also see in the ultraviolet range of color

Their blue photoreceptors are modified to a shorter wavelength, to accommodate for the blue of the ocean.

Tetrachromacy

• Ultraviolet is actually another variation of "normal" color vision.

• TetrachromacyFour independent channels for

conveying color• Four different types of cone

cells in the eye

Tetrachromacy

Approaches but is not infinite in color.

The additional type of cone cell provides for color detection of even shorter wavelengths, like ultraviolet.

Allows tetrachromats to distinguish colors that trichromats would perceive as identical.

Tetrachromats: Birds, Humans ... Shrimp?

• Most birds are tetrachromats:o Mating - Sexual Dichromatismo Food detection/recognition

• Humans are rumored to possess a mutable gene for tetrachromacy (but only on the X-chromosome)o Classical type2 Opsin Genes:

OPN1MW1 & OPN1MW2o Only females can possess different

copies of both genes, allowing for tetrachromacy

Yes, Shrimp, Mantis Shrimp

There is a suborder of shrimp (Unipeltata) that are polychromats, with the most complex eyes in the animal kingdom.

Hundreds of permutations of cone cells (16 types) and color filters (12 variations), plus oil drops (6 types) that also act as filters.

Each eye is divided into three parts by bands of specialized cells, resulting in trinocular vision per eye stalk.

Able to see all forms of polarized light (circular and linear polarization).

Mantis Shrimp: In depth• Composite eyes made up of ~10,000

apposition ommatidia• Each ommatidium's rhabdom holds 8

photoreceptor cells.o Each cell contributes one side to the

rhabdom (meaning rod in Greek), increasing its surface area to allow for ~60,000 microvilli or ~20,000,000 rhodopsin molecules

o Arranged in tiers• Differentiation of tiers in bands on the

eyes give rise to the Mantis shrimp's wide spectrum of visiono Six bands per eyeo Three tiers per band

http://en.wikipedia.org/wiki/File:Appostion_Eye.jpg

Bird Vision: In depth too• Most improved upon non-mammal

variants.o Anatomically improved from fish,

amphibian, and reptilian eyes. Highest eye size to body ratio Lens shifted forwards, allowing

for a larger field of focus.o Eyes optimized for higher spatial

resolution, in exchange for light sensitivity. Myopic in lower half, to be able

to view the horizon and the ground simultaneously

o Pecten oculi (the waffle) is actually the blood vessels.

• Sees ultraviolet and polarized light.• High acuity from high receptor density

Infrared Vision• Ability to detect thermal images, or heat

radiation given off by other animals.• Infrared spectrum

includes visible light spectrum, so naturally some animals should have infrared senses.

 • Only a few do, this is due

to the fact that these organs are highly specialized.

• Currently, the only confirmed animals with thermal vision are snakes:o Pitviperso Boao Pythons

Pit Vipers

Magnetoception/Magnetoreception• Magnetoception: the ability to detect a

magnetic field to perceive direction, altitude or location.

• Several species of fish (Chimaera), sharks, and Stingrays are able to detect subtle differences in electrical potential along its outer skin, and via other internal organs.o Ampullae of Lorenzini

o Mucus canals leading from the skin to internal sacs.

o Measure slight changes in the mucus' conductivity between the skin and the sacs. 

More Magnetoception• Bees have trace amounts of magnetite

arranged on a small group of neurons that depolarize the neurons when it aligns with the Earth's magnetic field.

• Grazing animals tend to position themselves along the magnetic field lines.

• European Robins have shown evidence to have an inclination compass.

• Certain species of sea turtles also seem to rely upon alignment with the magnetic poles of the earth for orientating.

Magnetoreception

• Magnetite is believed to play

a role.

• Bird have a large portion of their beak that's highly innervated and embedded with magnetite.

• Many animals with magnetoreception also possess trace amounts of magnetite.

• Humans, due to small quantities of magnetite, are believed to possess limited magnetoreception

Chicken Heads.

• Almost all birds that walk have a head-bobbing motion.

- attempt to keep motion parallax from affecting depth perception.

– Relies on the gait of the species.

• Synchronize visual and vestibular information.

– Feedback loop to keep the head steady.

Chicken Head Tracking.

Bibliography

http://animals.nationalgeographic.com/staticfiles/NGS/Shared/StaticFiles/animals/images/primary/great-white-shark.jpg