Vertebrates Exam 2

Salamander Families

Cryptobranchidae
Proteidae
Amphiumidae
Salamandridae
Plethodontidae

Cryptobranchidae

Aquatic but do not retain external gills as adults
Most respiration done through skin
Lungs function for buoyancy

Proteidae

Mudpuppies/waterdogs (Necturus)
Fully aquatic that retain external gills

Amphiumidae

Well developed lungs

Fully aquatic - can aestivate in mud for 2+ years

Salamandridae

Diverse family (55 species)

Bright coloration (aposematic warning of toxicity)

All produce toxic skin secretions

Textrodotoxins

Neurotoxin found in Salamandridae

100x more poisonous than potassium cyanide

Prevents action potentials from starting by blocking Na+ channels
Toxicity varies

What do male Red-Spotted Newts develop during breeding season?

Horny nuptial pads on their hind legs to help grasp the female

Plethodontidae

Lungless salamanders

380 species

Feeding specializations (tongue projection mechanism, no elongate ribs, hyobranchial apparatus)

Why is the tongue projection mechanism only possible in Plethodontidae

No lungs

Hyobranchial apparatus

Facilitates buccal pumping and could become co-opted for tongue projection

What allows tongue projection to be temperature independent?

The elastic recoil of collagen fibers within the muscle which store energy during excitation

How long before the tongue leaves the mouth are the tongue projector muscles activated?

80-180 milliseconds

What indicates a dissociation between muscle electrical activity and tongue action?

Collagen fibers within the muscle are stretched during excitation, storing energy before release

What mechanism propels the tongue out of the mouth?

The stored elastic energy in collagen fibers recoiling, rather than direct muscle contraction

Evolution of tongue projection in Plethodontinae

First ceratobranchial used in larval suction feeding

Second ceratobranchial elongated after metamorphosis

Tongue projection less extensive

Evolution of tongue projection in Hemidactyliinae

No aquatic larval stage

Second ceratobranchial elongated during embryonic development

Nasolabial grooves

Fluid drawn up into groove via capillary action

Drawn into nose via ciliary movement within nasal cavity

Chemicals pass over chemoreceptors in vomeronasal organ

Most salamanders have internal fertilization except…?

Cryptobranchidae

Sirenidae

Describe internal fertilization via spermatophore

Spermatophore = sperm cap on gelatinous base

Euproctus male deposits spermatophore on female then uses his feet to grasp spermatophore and insert into female

In most species female picks up sperm cap after courtship behavior between sexes

What are the different ways female salamanders obtain sperm from spermatophores?

Aquatic

Terrestrial

Courtship

How do female salamanders obtain sperm from spermatophores aquatically?

Male releases water-borne pheromones to coax female to pick up his spermatophore

How do female salamanders obtain sperm from spermatophores terrestrially?

Male undulates tale under female to ensure spermatophore transfer

How does courtship work for salamanders?

Pheromones delivered by males via mental gland under his chin

May be slapped on female which volatilizes molecules

Sometimes delivered directly into female’s blood system (facilitated by enlarged teeth)

Spotted Salamander Egg Masses

Eggs larger in size

Stay intact when pulled out of water

Have symbiotic relationship with green algae

What does the presence of green algae with Spotted Salamander eggs result in?

Embryos hatch earlier

Decreased embryonic mortality

Synchronous hatching

Later development stage at hatching

What are the benefits from the symbiotic relationship between Spotted Salamander eggs and green algae?

Algae use nitrogenous wastes from embryos

Embryos use increased oxygen produced by algae

Jefferson Salamander egg masses

Eggs smaller in size (laid in cylindrical tubes)

Loose or drippy when pulled out of water

General features of Anura

Globose body form

Males vocalize to attract females

Toads

Frogs

Locomotion via saltation (to leap)

General features of Toads

Stout bodied

Blunt head

Short legs

Make short hops

Terrestrial

General features of Frogs

Slightly more slender than toads

Long legs
Make long leaps

Can be terrestrial, arboreal, or aquatic

Urostyle

Fusion of posterior vertebrae and elongated ilium

What locomotion mechanisms allow Anurans to leap?

Urostyle

Fusion of tibia and fibula

Stiffened vertebral column

Strong forelimbs

Flexible pectoral girdle (to absorb impact of landing)

Eyes positioned anteriorly on head to enable binocular vision

What do Anurans use to stick to smooth surfaces?

Wet adhesion

How does wet adhesion work in Anurans?

Peg-like projections within epidermal layer trap mucous secretion

Intercalary cartilage increases range of motion while allowing toe pad to remain against surface

What is phragmosis and what type of frog uses it?

Blocking entrance of burrow with part of body

Casque-headed tree frog

Toxic skin secretions from what gland in anurans?

Parotid gland

What type of tongue projection?

Mechanical pulling (basal anurans)

What type of tongue projection?

Inertial elongator (derived anuran)

What type of tongue projection?

Ballistic projection (plethodontid salamander)

What type of tongue projection?

Hydrostatic elongator (some anurans)

Types of reproduction in Anura

Explosive breeding

Prolonged breeding

Characteristics of explosive breeding

Lasts only a few days

Breed in ephemeral aquatic habitats (ex. vernal ponds)

Males and females arrive simultaneously and in large numbers

Sex ratio close to 1:1

Mating success similar from one male to the next

Time is the main constraint on mating success

Characteristics of prolonged breeding

Breeding season may last several months

Males arrive first

Males often establish territories

Males always outnumber females who visit on one night

Male success is highly variable

Males compete for female via vocalizations

Females use multiple characters to decide suitor

What characters do female anurans use to evaluate a suitor’s call?

Pitch

Length

Repetition

Why is calling energetically costly for male anurans?

It depletes energy stores with long calls being the most costly

What percentage of glycogen stores can be depleted in a single night of calling?

Up to 50% in 2-4 hours of calling

What type of energetic investment do anurans use for calling?

Capital investment (stored energy)

How does the Borneo tree hole frog adjust its call?

It matches the frequency of its call to the resonant frequency of the tree hole

How do Agalychnis callidryas tadpoles avoid predation?

They hatch prematurely when predators vibrate the leaves/branches they are on

Modes of reproduction in Anurans that counteract egg predation

Skin brooding

Vocal sac brooding in males

Gastric brooding

Foam nest building

Describe gastric brooding (platypus frogs)

Female ingested fertilized eggs and swallowed them into her stomach

Stomach is normally functioning when eggs swallowed

Jelly substance surrounding eggs contained prostaglandin E2 (inhibited HCl production in stomach)

Once hatched tadpoles also released prostaglandin E2 from gills

What are the stages of foam nest building (tungara frogs)?

1. Bubble raft construction (no egg deposition)

2. Building foam with egg deposition (mixing is constant)

3. Building more foam but mixing events are intermittent with intervals increasing exponentially

Synapomorphies of Amniotes

Amniotic egg

Skin elaborations from keratin (skin, hair, feathers)

Costal rib ventilation of lungs (strong suction enables evolution of longer necks)

Complex innervation of forelimbs

What does complex innervation of forelimbs allow for in amniotes?

Complex control of limb manipulation

What are the three extraembryonic membranes of the amniotic egg and what do they do?

Chorion (surrounds entire contents of egg)

Amnion (inner membrane that surrounds just the embryo)

Allantois (storage for nitrogenous wastes)

Skull fenestration

Openings in the skull that made room for muscle bulging

Accommodates for increased muscle mass

How might skull fenestration have evolved?

No longer needed buccal pumping with costal ventilation providing large suction

Skull did not need to be as large

Muscles could diversify

What are the types of mammal-like reptiles (extinct)?

Pleycosaurs

Therapsids

Moschops

Cynodonts

Describe Pleycosaurs

Sailbacks of late Palezoic

Most were generalized carnivores

Some herbivores

Describe Therapsids

More derived than pleycosaurs

Increased metabolic rate (possibly homeothermic)

Heavy-bodied, large headed, stumpy-legged

Large temporal fenestra (suggests larger adductor muscles)

Heterodont dentition (incisors, canines, and molars)

Describe Cynodonts

Reduced body size

Multicusped cheek teeth

Probably laid eggs

Enlarged infraorbital foramen (space for snout nerves)

Nasal turbinates (scroll like bones in nasal passages that help to minimize water and heat loss)

Define synapsida

Mammals and their extinct relatives

List evolutionary trends in Synapsids

First amniotes to diversify in terrestrial habitats

Most were medium to large sized animals

Most lineages went extinct at end of Triassic period (those surviving were rat sized or smaller)

List the advanced therapsid apomorphies

Skull

Limbs

Short feet and toes

Loss of lumbar ribs

Shorter tail

Describe the skull apomorphy of therapsids

Size of temporal fenestra increased

Zygomatic arch bowed outward

Coronoid process of dentary is extended

Heterodont dentition (differentiation of function and roles in eating)

Bony secondary palate (allows for simultaneous eating and breathing)

Changes in skull structure allowed for increased jaw musculature

Many jaw bones that were either fused with dentary or shifted to the ear to help with hearing

Describe the limbs apomorphy of therapsids

Limbs placed more medially (resolves conflict between locomotion and breathing)

Limbs free to move anteriorly-posteriorly without bending of trunk

Gait not as much side to side movement

Supporting girdles more lightly built - weight of body supported more by limbs

Describe the short feet and toes apomorphy of therapsids

Gait not sprawling

Movement now more rapid

Describe the loss of lumbar ribs apomorphy of therapsids

Increased dorsoventral flexion

Describe the shorter tail apomorphy of therapsids

Indicates locomotion is now accomplished by limb propulsion rather than axial bending

What type of dentition do mammals have?

Mammals have diphyodont dentition, meaning they only replace their teeth once

How does diphyodont dentition differ from polyphyodont dentition?

Diphyodonts have only two sets of teeth, while polyphyodonts (most other vertebrates) continuously replace their teeth.

Which mammals are exceptions to diphyodont dentition?

Elephants and manatees continuously replace their molars from the back of the jaw

What allows mammals to efficiently chew a variety of foods?

Precise occlusion, where teeth align perfectly for efficient mastication with different diets

Why is precise occlusion difficult with only two sets of teeth?

Jaw growth could misalign teeth preventing proper occlusion

How do mammals maintain precise occlusion despite jaw growth?

Milk teeth develop when feeding on a liquid diet (where occlusion isn’t crucial) and the second set erupts when the jaw reaches full size

What glands are mammary glands similar to?

Mammary glands are similar to sebaceous glands because they secrete small amounts of organic materials

What was the likely composition of the first proto-milk?

It was produced in small quantities and contained antibacterial proteins

What was the likely function of the first proto-milk?

It helped protect thin-shelled eggs from drying out and from microorganisms

How did milk secretion evolve over time?

It became more copious and nutritive supporting the growth of young

What is a unique mammalian feature related to feeding?

Suckling

How is suckling made possible in mammals?

A fleshy seal is formed against the hard palate using the tongue and epiglottis

What is the function of the fleshy seal during suckling?

It isolates breathing and swallowing allowing both to occur simultaneously

Synapomorphies of mammals

Mammary glands

Integument (has unique features)

Skeletal System

In which male mammals are mammary glands present?

Monotremes and eutherians, but they are absent in marsupials

Which male mammal has been recently described as producing milk?

Fruit bat

In which female mammals are mammary glands present?

All species of mammals

Which mammals have nipples?

Only therian mammals (marsupials and eutherians) monotremes lack nipples

What are the unique features of mammalian integument?

Hair and glands

What are the functions of hair in mammals?

Camouflage

Communication

Sensation

Insulation

What muscle is attached midway along the hair shaft?

The arrector pili muscle

What happens when the arrector pili muscle contracts?

It raises the hair which can signal fear, anger, or cold temperature

How does hair help with insulation in cold temperatures?

The arrector pili muscle contracts making the fur stand up and trapping more air for insulation

What is the function of eccrine glands in mammals?

They produce a watery secretion that promotes adhesion

In primates they function as sweat glands for cooling

Where are eccrine glands located in most mammals?

On foot pads and prehensile tails

What is the function of sebaceous glands?

They secrete a viscous substance down the hair follicle to lubricate and maintain hair condition

What is the Harderian gland and its function?

It is a sebaceous gland associated with the eye

It secretes an oily substance that travels down the nasolacrimal duct to aid in fur preening and waterproofing

What is the function of apocrine glands?

They produce volatile secretions (mostly down the hair follicle) used in chemical communication

Where are apocrine glands found in humans?

In the armpits and pubic regions

How do ungulates use apocrine glands?

To cool their body

What type of gland are mammary glands modified from?

Apocrine glands