Transcript Form and Function: Fish

Marine Vertebrates: Lecture 5
Marine Reptiles
Amniote relationships
Class Reptilia: Diversity
Testudines (Turtles)
• Evolutionary relationships
uncertain
Sphenodontia (Tuataras)
Crocodilia (crocs, alligators)
• Only found on New Zealand
• Largest reptiles
• Believed to be oldest order
• Closely related to dinosaurs
Squamata (Snakes and lizards)
• Most numerous and diverse group
Reptilian Adaptations
Implications for marine existance
• Amniotic egg:
 Waterproof/breatheable
 Laid on land
• Keratinized scales
 Waterproofing
• Well-developed kidney
 Why important to marine reptiles?
• Well-developed respiratory system
 Breath-holding/oxygen conservation
• Circulatory system
 Some division into pulmonary and
systemic
• Internal fertilization
 Shell covering added post- fertilization
Indo-Pacific Crocodile
Photo: John Wattie
Indo-Pacific Crocodile
Adaptations to aquatic envirnoment
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Laterally-flattened tail (aquatic propulsion)
Able to open their mouths while underwater
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How do they keep water out of lungs and nostrils?
How do they deal with pressure change in ears?
Salt glands: modified salivary glands
Indo-Pacific (Australian) crocodile, Crocodylus
porosus, is estuarine. (= “salt water croc”)
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Largest specimens: 10 meters long
Primarily feeds on fish, may feed on mammals.
No crocodiles fully adapted to marine existence.
Marine iguana
• Galapagos
• Seven subspecies
• Close relative of land
iguana
Marine iguana, Galapagos
Photo: mongabay.com
Land iguana, Galapagos
Photo: Rod Eime
Marine iguana
Adaptations to aquatic envirnoment
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Jaw/teeth
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Secrete excess salt via
salt glands
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Short snout, three-cusp
teeth are adapted for
feeding on algae
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Beneath eyes, connect to
nostrils
“Sneezing” = salt excretion
Laterally flattened tail
Swimming posture?
Feet: webbed, long claws
Cling to rocks in surf
Submerge up to 15
meters, 30 minutes
Marine iguana
Photo: Gary Benson
Marine iguana
Other features of interest
• Huddle at night (why?)
• Body shrinkage during El Niño
 Related to shift in algal types
• Territoriality and mating behavior
• NOTE: Other iguana species are part of
marine food web
 Green iguana (Iguana iguana): Caribbean
 Why not considered “marine”?
Sea snakes
• Overview
 Family Hydrophiidae
• Cobra relatives (F. Elapidae)
 Tropical Indo-Pacific
(most)
 Evolved from land snakes
• Marine adaptations
 Laterally flattened
 Nostril valves/
enlarged mouth scales
 Enlarged left lung
• Functions?
Pelagic sea snake
Photo: Zoltan Takacs
 Salt glands (mouth)
 Lack enlarged ventral
scales
• Why relavant?
 Bear live young at sea
Sea snakes
• Other features
 Venomous
• Not aggressive
 Feeding?
 Aggregation
Pelagic sea snake
Photo: Zoltan Takacs
Sea krait (Family Lacticaudidae)
Sea krait
Photo: Nick Hope
• Less adapted to marine environment
 Enlarged belly scales
 Lay amniotic eggs on land
Coming soon to a Marine
Vertebrates class near you…
• Sea turtles!
Hawksbill turtle: Photo: Karen Haberman