Marine Mammalogy Final Exam Review

Sensory Systems, Vision, Smell, Taste, Magnetic syst., Communication and Cognition, and Distributional Ecology

Definition of umwelt:

an animal’s perceptually limited construct of the world

Four essential elements of a sensory system:

Sensor, filter, transducer, and central processor

Purpose of sensor:

captures environmental signal (receptor)

Purpose of filter:

removes “junk” and passes signal (receptor)

Purpose of transducer:

converts a signal into an electrical impulse (nerves)

Purpose of central processor

receives signal and interprets it (brain)

Most important sense in marine mammals:

hearing

Sound in water travels __ times faster than air.

4.5

The frequency of sound is equal to

speed of sound (expressed by c) divided by wavelength (lambda)

Function of outer ear:

sound collector, contains ear flange and ear canal

Purpose of ear flange:

sound diffractor, aid in sound localization

Purpose of ear canal:

conveys sound to the middle ear

Purpose of the middle ear:

amplifies and tunes the signal, transforms sound into mechanical signals, which vary in stiffness, volume, and mass depending on the animal

The appearance of the middle ear:

an airy, bony lever and membrane

Adaptations in the middle ear of Odontocetes:

stiffened ossicular chains

Adaptations in the middle ear of Mysticetes:

large middle ear with flaccid tympanic membranes

What are the components of the inner ear?

fluid-filled, contains the vestibular system and cochlea

Purpose of inner ear

converts sound into electrical impulse

Describe the cochlea:

it is a hearing receptor that contains the basilar membrane and the organ of Corti

Function of vestibular system:

organs for orientation and balance

Adaptations in the external ears of marine mammals:

closure, wall-thickening, wax plugs

Adaptations in the middle ears of marine mammals:

thick mucosa, broad eustachian tubes

Describe Cetacean external ears

external canal plugged with cells and wax (tissue path for sound), no connection to tympanic membrane, pan bone that serves as a pathway to the middle ear

Describe Cetacean middle ears:

ossicles are fused, poorly understood

Describe Cetacean inner ears:

Cochlea similar to other mammals, has basilar membranes that create ultrasonic and infrasonic specialists

Describe Pinniped external ears:

pinnae reduced or absent, external ear canal open, can be voluntarily closed, ears not attached to skull

Describe Pinniped middle ear:

Similar to land mammals, mass suggests wider range of hearing

Describe Pinniped inner ears:

suggested to be high-frequency generalists, no evidence of infra or ultrasonic capabilities

Describe the ears of polar bears:

Not well known, studied in zoos

Describe the ears of sea otters:

Defined ear flap that folds during dives, auditory bullae attached to the skull, inner/middle ear similar to terrestrial animals

Describe Sirenian external ears

No pinnae, sound reception is unknown

Describe Sirenian middle ears:

Extensively modified, but the function is unknown, ossicles are loosely jointed, and staples are stiffened (like reptiles). The tympanic membrane is everted and keeled, with dual frequency sensitivity

Describe Sirenian inner ears:

mixture of aquatic and terrestrial, lacks infra and ultrasonic capabilities

Marine mammals are functionally ___.

Crepuscular

The two main eye components for detection and acuity:

The cornea and lens

Describe the cornea:

accounts for 2/3 of focusing power, loses focusing power underwater

Describe the lens:

stronger in marine mammals, severe myopia out of water

Why are the lens of Cetaceans special

They are spherical and lack ciliary muscles, their pupils contract horizontally

Describe the eyes of pinnipeds:

lens shape is intermediate, ciliary muscles to distort thick lens

Describe the vision of polar bears:

can see like terrestrial animals, little adaptation underwater

Describe the vision of sea otters

see well in water and air by changing the radius or the curvature of the lens

Describe the vision of Sirenians:

poor vision

Purpose of pigmented retina:

absorbs light and helps adapt to dark and light

Diffusion of chemicals is ___ times slower in water than air.

1000

Describe olfaction in odontocetes:

lack olfaction bulb

Describe olfaction in mysticetes and sirenians:

have rudimentary olfactory bulb

Describe olfaction of carnivora:

well-developed sense of smell

Describe gustation in odontocetes and sirenians:

taste buds and grooves in pits of tongue

Describe gustation in otariids:

have taste buds

Describe what gustatory elements marine mammals can detect

they can detect bitter compounds but not salty or sweet compounds

Describe the tactile senses of dolphins:

They have a sensor that detects pressure, which allows them to move away from high pressure and go to lower pressure

Describe the tactile senses of pinnipeds:

their highly innervated vibrissae, used to detect displacement and ice hole shaking

What effect does water have on magnetic flux density?

Little to no effect

How is magnetite formed?

Through biochemical processes within the body

Purpose of magnetite:

It accumulates in dense matter of cetacean brains, and it can be assumed that it serves as a magnetic detector to guide movements and positioning

Examples of aggressive visual signals:

blowing bubbles, snapping jaws, lunging, expanding pleats, shaking head

The three senses often most developed in marine mammals

Sight, touch, hearing

Optimal echolocation works if the object is ___ than the wavelength.

smaller

Definition of signal noise

The optimal sound to produce in order to project into the environment

Why are low frequency waves attenuated farther than high frequency waves?

High-frequency waves are rapidly dissipated into heat

Isolation/distress call:

vocal system for regaining contact

Brain size:

Pure mass of brain

Cepahlic volume

number of neurons

Cephalic index

brain to body weight ratio

Cephalic index in mammals

sirenians/mysticetes - lower than expected, pinnipeds - average, odontocetes - larger than expected

Example of marine mammal that recognizes themselves:

sea lions

What is the cortical surface area?

The surface area within the cephalic folds in the brain, greater in dolphins than in humans (because of auditory system)

Neocortex area to volume ratio:

The largest part of the cerebral cortex, dolphins have 1/3 more surface area, but ½ less thickness.