Marine Reptiles

Question 1

How many extant reptile species have re-entered the marine realm?

Answer 1

About 100 species, including 7 sea turtles, ~80 sea snakes, the marine iguana, and species inhabiting brackish waters.

Question 2

Have all major reptile groups returned to marine habitats?

Answer 2

Yes, snakes, lizards, turtles, and crocodiles all have members that enter marine habitats, though not all are fully adapted to open-sea life.

Question 3

What are the main challenges for reptiles adapting to aquatic life?

Answer 3

Breathing: Air-breathing but subject to decompression risks.
Locomotion: Adapting to efficient movement in water.
Reproduction: Balancing large offspring and advantages of terrestrial juvenile habitats.
Osmotic balance: Managing salt ingestion despite watertight skin.

Question 4

What are the advantages of returning to aquatic life?

Answer 4

Air-breathing gives a metabolic advantage over aquatic oxygen extraction.
Moving in water is more energy efficient than on land.

Question 5

How many extant species of sea turtles are there?

Answer 5

Seven: six hard-shelled species (Cheloniidae) and the soft-shelled leatherback (Dermochelys coriacea).

Question 6

When did marine turtles first appear?

Answer 6

Marine turtles emerged in the Jurassic, evolving from freshwater turtles like the Plesiochelyidae.

Question 7

Which two marine turtle families survive today?

Answer 7

Cheloniidae and Dermochelyidae.

Question 8

What are key aspects of sea turtle nesting behavior?

Answer 8

Females excavate nests in sand and deposit up to 100 eggs.
Eggs hatch simultaneously at night, aiding survival.
Temperature-dependent sex determination influences offspring sex ratios.

Question 9

How does temperature affect sea turtle embryonic development?

Answer 9

Optimal development occurs within 25–35°C.
High temperatures shorten incubation periods and produce more females.

Question 10

What factors influence environmental sex determination?

Answer 10

Chance: E.g., marine worm larvae becoming male if landing on a female.
Temperature: E.g., turtles produce males at ~28°C and females at ~30°C.
Social dynamics: Some coral reef fish change sex based on dominance shifts.

Question 11

How has tagging advanced our understanding of sea turtle migration?

Answer 11

Electronic tagging provides data on migratory pathways, foraging areas, depth usage, and reproductive cycles.

Question 12

What threats do sea turtles face from human activity?

Answer 12

Ship strikes in nesting areas.
Pollution and fisheries bycatch.
Habitat destruction from coastal development.

Question 13

How does spatial ecology research help conservation?

Answer 13

It identifies high-risk areas (e.g., nesting beaches near boat traffic) to inform management policies.

Question 14

To which clade do marine iguanas belong?

Answer 14

Marine iguanas belong to the Amblyrhynchus clade, a monospecific lineage endemic to the Galapagos archipelago.

Question 15

How does the Galapagos archipelago influence marine iguana evolution?

Answer 15

The archipelago’s volcanic origins, distinct island ages, and strong ocean currents promote speciation and limited hybridization among islands.

Question 16

When did marine iguanas diverge from their land-based cousins?

Answer 16

Around 4 million years ago.

Question 17

What was revealed by recent genetic studies on marine iguanas?

Answer 17

High levels of island-specific genetic diversity emerged around 50,000 years ago, influenced by volcanic events, leading to the recognition of 11 sub-species.

Question 18

What are key physical adaptations of marine iguanas for marine foraging?

Answer 18

Long claws for gripping rocks.
Laterally compressed tail for swimming.
Tricuspid teeth for scraping algae.
Salt gland in nostrils for salt excretion.
Dark skin for UV protection and warming.

Question 19

How do marine iguanas regulate their body temperature?

Answer 19

They bask on land to warm up after diving in cold water and manage fluctuating conditions between the arid land and cool nights.

Question 20

What are the two main foraging strategies of marine iguanas?

Answer 20

Intertidal feeding (IF): Eating algae from exposed rocks during low tide.
Subtidal feeding (SF): Diving to graze on underwater algae.

Question 21

What types of algae do marine iguanas consume, and why are brown algae problematic?

Answer 21

They eat red and green algae, but brown algae are indigestible, leading to starvation during El Niño events.

Question 22

How does climate change affect marine iguanas?

Answer 22

El Niño events reduce red and green algae availability, causing starvation, skeletal shrinkage, breeding failure, and death.

Question 23

Why is the Galapagos ecosystem vulnerable to climate effects?

Answer 23

The islands’ location at the intersection of warm and cold currents makes them sensitive to ocean temperature anomalies.

Question 24

Why is genetic diversity important for marine iguana conservation?

Answer 24

Recognizing island-specific diversity helps design targeted management plans to protect biodiversity.

Question 25

What are major threats to marine iguanas?

Answer 25

Climate change (e.g., El Niño events).
Habitat loss.
Invasive species affecting the marine reserve ecosystem.

Question 26

What defines amniotes, and how do they differ from amphibians?

Answer 26

Amniotes possess an amniotic egg, allowing development outside water, skin covered by scales, no larval stage, and some species exhibit viviparity. Amphibians require water for reproduction, lack amniotic eggs, and often have a larval stage.

Question 27

What is the significance of the diapsid skull in reptile evolution?

Answer 27

Diapsids have two post-orbital skull openings, allowing muscle attachment for stronger jaw movement. This adaptation is seen in lizards, snakes, crocodiles, and birds.

Question 28

Why are turtles unique in reptile phylogeny?

Answer 28

Turtles have an anapsid skull (no post-orbital fenestrae), resembling early reptiles. Molecular evidence places turtles within Diapsida, suggesting a secondary loss of fenestrae rather than primitive retention.

Question 29

What are the key challenges reptiles face in marine environments?

Answer 29

Key challenges include locomotion, feeding, salt regulation, buoyancy, reproduction, and thermoregulation.

Question 30

How do marine reptiles regulate salt balance?

Answer 30

They use specialized salt glands located in their skull to excrete salt, compensating for inefficient kidneys.

Question 31

What are the two main types of locomotion in marine reptiles?

Answer 31

1. Axial Undulatory Swimming: Wave-like tail movements for propulsion (e.g., ichthyosaurs, mosasaurs). 2. Axial Oscillatory Swimming: Tail fin swiveling for propulsion, seen in advanced ichthyosaurs and some plesiosaurs.

Question 32

What is paraxial locomotion, and how does it differ?

Answer 32

Paraxial locomotion uses lift- or drag-based limbs for propulsion (e.g., plesiosaurs), contrasting with axial locomotion, which relies on body and tail movement.

Question 33

What evolutionary trends are seen in marine reptiles?

Answer 33

Trends include the transition from axial undulatory swimming to axial oscillatory swimming (e.g., ichthyosaurs, mosasaurs) and a rare transition to paraxial swimming (e.g., sauropterygians like plesiosaurs).

Question 34

Who were the sauropterygians, and what adaptations did they develop?

Answer 34

Sauropterygians were Mesozoic marine reptiles including placodonts, nothosaurs, pistosaurs, and plesiosaurs. Adaptations include euryapsid skull, retracted nostrils, closed palate, and specialized limb morphology for swimming.

Question 35

How do plesiosauromorphs differ from pliosauromorphs?

Answer 35

Plesiosauromorphs have long necks and small heads, adapted for precision feeding (e.g., elasmosaurids). Pliosauromorphs have short necks and large heads, adapted for powerful prey capture (e.g., pliosaurids).

Question 36

What defines ichthyosaurs, and why are they unique?

Answer 36

Ichthyosaurs are carnivorous marine reptiles (200–90 million years ago) with fish-like bodies, huge eyes, teeth set in grooves (not sockets), and live birth. They show an evolutionary trend toward streamlined, fish-like shapes for efficient swimming.

Question 37

Which lizard lineages entered marine environments during the Cretaceous?

Answer 37

Dolichosaurs and Aigialosaurs are small anguimorph lizards adapted to shallow marine habitats, found in Europe, the Middle East, and North America.

Question 38

What are mosasaurs, and what were their key adaptations?

Answer 38

Mosasaurs are large marine anguimorphs with flexible jaws for ratchet feeding. They evolved paddle-like limbs, retracted nostrils, and heterocercal tails for efficient swimming, becoming apex predators in Late Cretaceous marine ecosystems.

Question 39

How do climate changes like El Niño affect marine reptiles?

Answer 39

Marine Iguanas experience loss of red and green algae, leading to starvation, skeletal shrinkage, and reproductive failure. Similar events impact other marine reptiles relying on specific food sources.

Question 40

Why is understanding marine reptile phylogeny important?

Answer 40

It helps clarify evolutionary relationships, adaptations, and guides conservation efforts for both extant and extinct species.

Question 41

What are the major marine reptile groups from the Mesozoic?

Answer 41

1. Ichthyosaurs: Streamlined predators with fish-like bodies. 2. Sauropterygians: Plesiosaurs and their relatives with diverse feeding and locomotion strategies. 3. Mosasaurs: Large, agile anguimorph lizards adapted to marine life.

Question 42

What caused the extinction of Mesozoic marine reptiles?

Answer 42

The mass extinction at the end of the Cretaceous (66 million years ago), likely triggered by the Chicxulub impact and volcanic activity.