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Vertebrates > Amphibians > Flashcards

Amphibians Flashcards

1
Q

What are the three orders of amphibians

A

caecilians
urodela
anura

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2
Q

name some of the shared derived characters of amphibians

A

moist, permeable skin
skin - mucous skin glands that keep the skin moist
and a substantial part of the gas exchange that takes place through the skin. all also have poison glands in the skin

carnivorous
size of head determines the size of prey that can be eaten. e.g. salamanders have different head sizes

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3
Q

lissamphibian development

A

many lissamphibia have aquatic early developmental stage - the tadpole. thought to be original pattern.

eggs are laid in water by female and fertilised by attending male as they are laid
tadpole first feeds on algae, then insects
grows and develops gills
hind legs grow and then lungs develop
forelegs appear, tail regresses
froglet becomes terrestrial
grow on land then return to water to breed years later

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4
Q

lissamphibian slimy skin

A

epidermis is soft with local horny regions
dermis contains numerous glands opening to the surface :

chromatophores: expand to change skin colour
mucous glands secrete mucus to cover the skin
poison glands release alkaloids under active control
epidermal cells may contain keratin as a horny protection - moulted

there is fibrous connective tissue overlying muscle

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5
Q

skin secretions - please describe poisons

A

poisons include the deadly alkaloid - batrachotoxin 0.2mg is fatal to humans. wiped onto poison arrows

toads produce noxious irritant bufotoxin .

powerful poisons often associated with special colours and defensive behaviours

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6
Q

skin secretions - what do chromatophores do

A

chromatophores expand to change skin colour

the epidermal chromatophores are used in camouflage
(e.g. peron’s tree frog)

also for conspicuous warnings

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7
Q

gas exchange describe amphibian lungs

A

they are relatively small - may be simply sacs with a few septa maybe to increase the blood to air exchange area .
lungs of lizards are more complex

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8
Q

examples of different salamanders respiratory exchange

A

many aquatic salamanders have external gills too

plethodontid salamanders have neither lungs or gills

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9
Q

how does gas exchange work in frogs? ie.. how are the lungs filled with air

use the words

hyoid
glottis
nostrils
lung
trunk
A

frogs have low basal metabolic rate

1) nostrils open and air in, hyoid is lowered - filling the buccal cavity. glottis is shut.
2) hyoid is raised, and glottis opens, air is forced into lnun - nostrils are closed.

to get the air out,
there is no ribcage, trunk muscles contract which empties the lungs, glottis opens, nostrils open and the air is out.

additionally
frogs flutter the hyoid to purge the lungs before refilling them

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10
Q

describe cutaneous exchange

what does exchange through the lungs and skin depend on?

A

lissamphibian skin is richly vascularised - important for gas exchange

depends on temperature

at low temp, more exchange occurs via the skin than via the lungs

at high temp, the lungs become more important for O2 but skin more important for co2 exchange.

in winter, the toad relies almost completely on cutaneous exchange

amphibians show increasing reliance on lungs for o2 as temperature and activity increase

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11
Q

the amphibian heart - dual system

A

the patterns of the blood flow within hearts of adult amphibians reflect use of 2 respiratory surfaces. a description based on anuran heart

atrium of heart is divided by a septum . o2 rich blood flows into left side of the heart, o2 poor blood from systemic circulation flows into right side. o2 rich blood returning from the pulmonary veins enters the left atrium which injects it on the left side of the common ventricle . contraction of the ventricle ejects the blood in laminar streams that spiral out of the pumping chamber

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12
Q

lissanmphibian sense - vision

A

air and water have different refractive indices - the amphibian eye must accommodate both media.
lens muscle pulls the lens forward to accommodate nearer objects

the lens is rigid and high refractive index - more spherical in aquatic amphibians

retina has purple and green rods - green ones are more sensitive to movement and are unique to amphibians

distance perception relies on angle of convergence of the two eyes - they have binocular overlap in the fields of the two eyes

nicitating membrane blinks to keep the cornea moist

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13
Q

what are the three orders of lissamphibia . and where are they found.

A

urodela - newts and salamanders. 515 species. Eurasia and North America to Central America. neither africa nor Australia

Anura - frogs and toads. 4800 species. all continents, not Antarctica.

Caecilia - caecilians . 180 species. tropics around the world

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14
Q

the urodela order - newts and salamanders

A

long tails and least derived

confined to northern hemisphere. greatest diversity in southern us and tropical Northern America

range from 50mm long - plethodontid salamanders to 1.5 metres long - Japanese giant salamander

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15
Q

urodele diversity

ambystoma

megalobatrachus / andrias

amphiuma

proteus , typhmoige

A

some groups are only aquatic in the breeding season
- typical urodele lifestyle

ambystoma - can breed as either adult salamander or in the gill bearing larval axolotl form.

megalobatrachus / andrias - lives in cold mountain streams of china and Japan and grows to 1.5m in length both have highly folded large surface area skins

amphiuma has vestigial legs and siren has lost its hind legs and retains larval gills. both are wholly aquatic. the former living in swamps

proteus and typhomoige , live in caves and permanently aquatic with external gills. both colourless.

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16
Q

urodele skeletons - please describe

skull

ribs

long tail

pairs of legs

A

the bones of the skull are weak and reduced - with large open orbits

the ribs are short, extend beyond the trunk and do NOT form a ribcage

the long tail is used in both swimming and walking - only a single weak sacral vertebra

both pairs of legs are short and weak , wrist and ankle are weakly ossified - four fingers and five toes

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17
Q

urodele locomotion in swimming

A

tall long tail fin undulates but lacks fin rays - fin is reduced or absent in terrestrial phases

short legs make only a minor contribution

there are myotomes in both trunk and tail which cause lateral body undulation

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18
Q

describe walking in urodele

A

walking is accompanied by considerable bending of the body - increases the effective arc of swing of the legs

there is bending at the wrist and elbow as well as ankle and knee

so basically

body bent to the side of leg overlap, and then body straightens mid stride and body is then bent to the opposite side

body sags as newt tries to run faster

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19
Q

urodele walking motion part 2

A

body rises and falls lateral undulation in walking

and side to side body undulation

** rotation of tibia on fibula
femur swings in approx horizontal plane

20
Q

courtship in urodele repdroduction

A

elaborately patterned dorsal fin and tail enlarge and become coloured in breeding seasons

many methods of pheromone delivery from males to females described in salamanders and involves physical contact wherein the male applies secretions of special courtship glands (hedonic glands).
anterior teeth of males of many species hypertrophy during the breeding season and abrading the skin of the the female with his teeth will ensure inoculation of the female with the pheromone.

males also perform elaborate courtship displays which the male vibrates tail to create a stream of water that wafts the pheromones secreted by a gland in his cloaca towards the female.

21
Q

reproduction in urodele- salamanders

A

salamanders that breed in water mostly lay their eggs in water. eggs may be laid singly or in a mass of transparent gelatinous material. egg hatch into gilled aquatic larvae that transform into terrestrial adults except in aquatic species obvisouly.

there is a bag of sperm, and gelatinous basal attachment . fertilisation occurs in the oviduct and zygotes/embryos may be retained.

22
Q

development of urodele

A

eggs are often deposited singly on vegetation and develop as tadpoles with external gills. in European newsts, the front legs are the first to grow.

the Mexican axolotl is a neotenous salamander that retains its larval gills it lives and breeds in water.

23
Q

Anura quick facts

walking and jumping

where is the greatest diversity

what is the range in body size

A

Anura - all lack tails and are specialised for walking and jumping

greatest diversity is in the wet tropics. can be found in deserts and tundra too.

range from 10mm (frogs) to over 30cm and 3kg weight - Goliath frog .

24
Q

outline Anuran diversity

buff and Rana

hyla

pipa and xenopus

pipa alytes gastrotheca

breviceps

ascaphus

A

bufo and Rana are well known toad and frog genera of Europe

hyla - genus of tree frogs

pipa and xenopus - totally aquatic tropicsl toads. no tongues.

pipa alytes gastrotheca - interesting parental care strategies

breviceps - desert frog, specialised for burrowing.

ascaphus - “tailed” frog has internal fertilisation and extended urostyle.

25
Q

frogsicles

A

the Canadian wood frog - Rana sylvatica

26
Q

anuran skeletons

spine

hind legs

skull

shoulders, arms, and hands

A

spine is very short and the hind legs are long , there is no tail

flimsy skull with large orbits

shock absorbing shoulders, arms, and hands - because frogs jump about a lot

27
Q

anuran jumpin

longest jump records?

A

after take off, hind legs are fully extended

triple jumps totally over 10m have been recorded

many small ones can jump over 1.5m

28
Q

what is the skeletal movement during frog jumping

and draw diagram with labels

A

leg extension takes place at 4 hinges:

sacro-iliac joint
ilio-femoral joint
femoro-tibial joint
tibio-tarsal joint

29
Q

anuran landing

A

before landing, the FRONT legs are fully extended .

the kinetic energy is absorbed by bending the arms and by separation of the flexible ventral parts of the pectoral girdle

the hind legs are re-flexed after landing

30
Q

tree climbing and adhesive toe pads

A

many frogs, especially hylidae, are agile tree climbers and onto smooth surfaces/ twigs by curling their digits and/or using adhesive pads on their tips

adhesive toe pads - surfaces of toe pads have an epidermal layer with peglike projections separated by spaces/canals. mucous glands distributed over the discs secrete a viscous solution of long-chain high molecular -weight polymers in water. so wet adhesion is used to stick to smooth surfaces. watery mucus secreted forms a layer of fluid between the disc and surface. surface tension and viscosity holds the toe pad and surface together provide no air bubble enters.

frogs always orient their body upwards when sticking to vertical surfaces otherwise they will fall off due to the distribution of weight.

31
Q

anuran acoustic communication

A

all urodeles are mute and lack ear drums. anurans can make sounds and hear well.

singing

hearing
ear drum is connected by the columella or stapes to the inner ear . can hear from 50 Hz to 8kHz and locate spruces to plus minus 10 degrees.

32
Q

anuran acoustic communication

A

during the sound-making phase, the vocal sac is inflated via the larynx and produces sound as single / train of pulses. the lungs are grossly dilated and vocal sac is collapsed

then the skin of the vocal sac is elastic so the lungs are re-filled as it collapses - phase is silent. air forced from lungs and vocal sac is inflated.

33
Q

anuran songs

and what can they be used

A

are species specific and may be used in mate attraction

territorial marking, aggression, and as alarm signals

e.g. alytes, the midwife toad produces long pure tone pulses at about 1.3Hz to call females to his territory

34
Q

Anuran fertilisation

A

almost all of them have external fertilisation.

35
Q

problems of being a tiny anuran

A

froglets are only 10 to 15 mm long, vulnerable to desiccation

tropical species are tiny - only survive in rainforests, tend to live on or within wet undergrowth , hide during the heat of the day
they’re so small so they cannot lay large egg batches produced by eg.g 100mm long European toad but produce a few large eggs which develop directly into the damp leaf litter.

conventional frog strategy of laying loads of eggs are only valid when there is a rich, comparatively safe seasonal niche.

36
Q

anuran parental care

A

despite limits of external fertilisation , anurans show post oviposition parental care. eggs in dorsal pouch, and pouch opening .

brooding
sinuram toad pipa pipa females carry their eggs in pouches that form in the dorsal skin, where they develop into froglets. eggs in dorsal skin .

buccal and gastric brooders
they swallow the newly-laid eggs, which develop into froglets . e.g. rhinoderma darwinii male incubates eggs in his vocal sac where they develop into froglets .

australian gastric brooding frog - female incubates eggs in her stomach . rheabatrachus

37
Q

anuran successes

A

5000 species.
water loss is a problem. anurans are adept at gaining water and tolerating water loss, even though fertilisation is wet . anurans have evolved parental care mechanisms that emancipate from egg tadpole frog lifestyle. within the tropics, they include smallest tetrapods.

where are urodeles are relatively slow moving, anurans can hop swim and climb. widening range of habitats and ecological niches . 700 + species of tree frogs

low metabolic wrate, and water tolerant, exploit impoverished niches that cannot survive - birds and mammals. swamp dwellers

many anurans too toxic to eat. those not blessed with toxicity are cryptic and agile - land and swamp frogs.

38
Q

Anuran failures

A

in worldwide declines so something is going wrong.

human influenced climate change and intensive farming, deforestation , spread of fungal infections, increasing using of herbicides and fertilisers

39
Q

caecilians

A

all lack legs and are specialised burrowers.

inhabit soil and water in the wet topics - excluding australia.

range from 100mm to over 0.5m long many aspects of their biology remain obscure

40
Q

draw a caecilia and label their features

A

small weak eyes covered with skin (due to burrowing?)

long cylindrical trunk - with long right lung but short post anal tail

skin thrown into rings - rings of small scales to grip alls of the burrow

eyes and no ears

smooth round head for pushing through the soil

no ears but retractible chemo-sensory tentacles

41
Q

caecilia skeleton - skull

draw diagram

A

large nasal opening

small orbits and eyes

tentacle cavity

many sharp pedicellate teeth

skull robust and heavily ossified

atlas

strong lower jaw

burrows in damp soil - example skull used

42
Q

caecilian concertina burrowing

robust Pear shaped head acts as a ram

see slide

A

concertina forms an anchor - from which the body can be pushed forwards

this part of the trunk is made rigid by muscles acting on helical fibres in the skin

new concertina forms an anterior anchor allowing the rear of the body to be pulled forwards

yellow part of the trunk is drawn up passively into anterior concertina

43
Q

caecilian reproduction

A

fertilisation is internal via a male intromittent organ inflated from the cloaca

embryo with large placental gills

development is direct without metamorphosis

44
Q

why are caecilians interesting even though not enough people think so?

A

only 160 species

various archaic features such as
full set of teeth
complete ribcage with no sternum 
scales
strong skull

slimy skin - essentially lissamphibian

45
Q

what are the parallels between caecilians and snakes/lizards

A 
loss of all limbs and girdles
spade like penetrating skull
long rib bearing trunk but short tail 
concertina locomotion 
a single long R lung 
loss of ears 
vestigial eyes, with permanent covers , used mainly as light detectors

other unique sense organs

internal fertilization
viviparity in some

46
Q

conclusions

A

anurans are the big success story
two other orders play minor part in vert story unfortunately

all orders are most successful in wet, warm tropics and low energy ecosystems .

Vertebrates (3 decks)

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