amphibians

Question 1

What are shared derived features of amphibians

Answer 1

1) Smooth , moist , permeable (O2 +H2O) skin
2) papilla amphibiorum (amphibian papillal in inner ear)
3) Operculum - columella complex (ear)
4) pedicellate teeth - pedical composed of dentine and separated by connective tissue
5) levator bulbi muscle - causes eyes to bulge forward = enlarged buccal cavity

Question 2

Caecilian (legless amphibians) features

Answer 2

1) 180 species, purely tropical , blind + limbless
2) subterranean
3) internal fertilisation (sperm transferred by adapted cloaca)
4) Egg-laying or viviparous
5) energy for growth supplied by yolk then mothers uterine milk (secretion from walls of oviducts
6) foetal gill for gas exchange across oviduct walls + could also be used for exchange of metabolic waste

Question 3

Urodeles (newts + salamanders) features

Answer 3

1) 500 species, mostly internal fertilisation
2) large variation in courtship display , can be very complex with elaborate secondary sexual characters.
3) pheromone transfer by tail fanning (aquatic)
4) mostly aquatic eggs + larvae
5) Paedomorphosis / neoteny (reproduction during larval stage)

Question 4

viviparous

Answer 4

birthing of live young

Question 5

Neoteny

Answer 5

delaying or slowing of the physical development of an organism .

• can occur for just parts of the body, like heads for humans

Question 6

Anurans (frogs + toads) features

Answer 6

1) most widespread group of amphibians - 5000 sp
2) high body shape + lifestyle diversity
3) 25 sub families
4) all carnivorous
5) body specialised for jumping (urostyle)

Question 7

What 4 lifestyles can anurans lead

Answer 7

1) burrowing
2) aquatic
3) semi-aquatic
4) arboreal

Question 8

What trend is common in the life-history of amphibians

Answer 8

Evolutionary trend towards transferring as many life stages as possible to terrestrial environments.

Question 9

why do amphibians (when possible) lay eggs on land

Answer 9

predation pressure on land less than in aquatic habitats

-requires various, often convergent adaptations against desiccation .

Question 10

In amphibians what does the size of eggs/larval stage affect

Answer 10

• survival rate
• Trade-off: production of fewer , more costly eggs with longer developmental time vs. many eggs
• subsequent modes of parental care exhibit convergent evolution

Question 11

Amphibian adaptations against desiccation of eggs

Answer 11

1) foam nests - secretions from oviduct, male/females produce foam through movements of fore/hind legs. Evolved convergently within at least 6 phylogenetic lineages across all tropical continents.

2) Terrestrial eggs on water-overhanging leaves, tadpoles hatch and fall into water body
- evolved convergently in 3 groups, can involve male guarding

Question 12

what are ways in which some amphibians exhibit tadpole development on land

Answer 12

1) some members of genus Eleutheodactylus have terrestrial tadpole development, high yolk content of eggs render food intake unnecessary (tadpole matures in (egg)
2) Ovoviviparity : eggs and tadpoles develop in the female oviduct
3) Mouth-brooding and stomach-brooding

Question 13

Describe parental care in Rhinoderma dawinii - poison arrow frogs (Darwins frog)

Answer 13

1) Males (2-3cm) defend territories of up to several hundred m^2
2) Terrestrial egg clutches, when tadpoles hatch they climb on parents backs -> transported to aquatic body 3) Male or females can be responsible for parental care
4) small, ephemeral water bodies, predator free but no food.

• some species feed tadpoles with unfertilised eggs

Question 14

How do Anurans communicate for reproduction

Answer 14

• they communicate acoustically , most frogs are nocturnal or crepuscular, sex pheromones play little/no role.

Question 15

Features of anuran acoustic communication

Answer 15

1) calls are stereotyped, species have different types of calls
2) calls can be produced by in/exhaling air, on land or under water
3) only males call (there are exceptions
4) Vocal sac amplifies calls, radiates call into circular directions.

Question 16

What are the trade-offs with acoustic signalling

Answer 16

Pros - ease of signal variation, signal can circumvent obstacles , works in darkness

Cons - acoustic signals normally travel shorts distances + are temporary . can also attract predators

• acoustic signals in chorus = increased costs (mainly predation)

Question 17

Example showing the cost of singing

Answer 17

• Tungara frogs
• song = “whine” or “whine+chuck”
• females choose males that make more “chucks”
• one male = “whine” only , more males at pond more “chucks” made
• Predation increases with number of “chucks”
• as chorus size increases , predation risk decreases = advantage to complex songs

Question 18

another example of convergent evolution in anurans

Answer 18

leg waving , also known as “frog dancing”