Marine Reptiles BI2MBC1 2024 PDF

BI2MBC1 MARINE BIOLOGY & CONSERVATION Week 2 – Marine Reptiles Dr Brian Pickles [email protected] LEARNING OBJECTIVES LO1: Evolutionary history of marine reptiles LO2: Biodiversity of extant marine reptiles LO3: Adaptations to a marine lifestyle LO4: Oceanic migrations LO5: Con...

BI2MBC1 MARINE BIOLOGY & CONSERVATION Week 2 – Marine Reptiles Dr Brian Pickles [email protected] LEARNING OBJECTIVES LO1: Evolutionary history of marine reptiles LO2: Biodiversity of extant marine reptiles LO3: Adaptations to a marine lifestyle LO4: Oceanic migrations LO5: Conservation issues 1. EVOLUTIONARY HISTORY Lepidosauria Squamata Rhynchocephalia Lepidosauromorpha Plesiosauria Icthyosauria Saurischia Aves Diapsida Dinosauria Other saurischians Avemetatarsalia Ornithschia Archosauria Pterosauria Reptilia Crocodylia Crurotarsi Other crurotarsians Amniota Testudines Non-diapsid reptiles Synapsida Mammalia Other synapsids Paleozoic Mesozoic Mesozoic Cenozoic Carboniferous Permian Triassic Jurassic Cretaceous Tertiary Quaternary 350 Mya 300 Mya 250 Mya 200 Mya 150 Mya 100 Mya 50 Mya Present EVOLUTIONARY HISTORY Extant lineages Squamates Sea snakes – Elapines Evolved ~6-8 Mya Marine iguana – Iguanidae Diverged from land iguanas ~ 4.5 Mya Testudines Sea turtles – Cheloniidae; Dermochelyidae Common ancestor ~110 Mya Crocodylidae Salt water crocodile (semi-aquatic) Appearance 7-12 Mya  Lepidosauria Squamata Rhynchocephalia Lepidosauromorpha Plesiosauria Icthyosauria Saurischia Aves Diapsida Dinosauria Other saurischians Avemetatarsalia Ornithschia Archosauria Pterosauria Reptilia Crocodylia Crurotarsi Other crurotarsians Amniota Testudines Non-diapsid reptiles Synapsida Mammalia Other synapsids Paleozoic Mesozoic Mesozoic Cenozoic Carboniferous Permian Triassic Jurassic Cretaceous Tertiary Quaternary 350 Mya 300 Mya 250 Mya 200 Mya 150 Mya 100 Mya 50 Mya Present ICTHYOSAURIA Earliest ancestors appear ~ 248 Mya Massive Triassic diversification Eventually went extinct around 90 -100 Mya 6 Figure from Thorne et al. 2011 PLESIOSAURIA Pliosauridae Short neck Huge head 228-89 Mya Plesiosauridae Long neck Tiny head 210-66 Mya 7 MOSASAURS Closely related to Varanids (Monitor, Goana, Komodo dragon) Share some characteristics with snakes Appeared approx. 98 Mya and thrived for 32.5 Mya Extinction appears to be at K-T boundary (65.5 Mya) Species ranged from 3-15m in length Individual Mosasurus hoffmanni may have reached ~18m 8 (60ft) in length PALAEOPHEIDAE Ancient sea snake family Were found in Atlantic ocean (no modern sea snakes in Atlantic) Some apparently reached 9m in length Approx. 20 species known ~ 56-34 Mya 9 PLEUROSAURIDAE Family of marine Rhynchocephalians Known from the Jurassic (183-151 Mya) Small eel-like marine reptiles 10 TESTUDINES Two sea turtle families have gone extinct Toxochelyidae appeared 110 Mya Extinct ~50 Mya Protostegidae diverged from Dermochelyidae ~ 95 Mya Extinct ~ 35 Mya 11  CROCODYLOMORPHA Thalattosuchia Teleosauridae (180-150 Mya) Metriorhynchoidae (170-135 Mya) Tethysuchia Pholidosauridae (100-90 Mya) Dyrosauridae (70-50 Mya) Eusuchia Marine Gavialoids (70-35 12 Mya) THE PAST GIVES CONTEXT TO: 2. PRESENT DAY BIODIVERSITY Number of species Elapidae Iguanidae Cheloniidae Dermochelyidae Crocodylidae 0 10 20 30 40 50 60 13 BIODIVERSITY - SQUAMATES Main family: Elapidae Sea snakes and sea kraits Approx. 60-70 species Minor family: Iguanidae 1 species – Amblyrhynchus cristata (11 subspecies; see Aurélien et al. 2017) 14  SEA SNAKES Sea snakes are members of the Elapidae This grouping includes cobras, mambas, kraits, and “true” sea snakes Previously sub-divided into three sub-families Elapinae – terrestrial Elapids Laticaudinae – sea kraits Hydrophiinae – sea snakes Molecular evidence is not yet sufficient to resolve the phylogeny Species may be fully aquatic or semi-aquatic Even fully aquatic species will come onto land ~60-70 species 15 PRESENT DAY SEA SNAKE DISTRIBUTION 16 Figure from Lillywhite et al. 2017 SEA KRAITS Sea Kraits are Elapids in the genus Laticaudata They are semi-aquatic Adaptations for climbing as well as marine life Lay eggs on land ~8 species of sea krait 17 AMBLYRHYNCHUS CRISTATA THE GALAPAGOS MARINE IGUANA 18 Distribution of the 11 sub-species 19 Figure from Aurélien et al. 2017 BIODIVERSITY - TESTUDINES Two families: Cheloniidae - hard shells 5 genera, 6 species Dermochelyidae - osteoderms buried in leathery skin 1 genus, 1 species 20  BIODIVERSITY - CHELONIDAE Green turtle Loggerhead turtle Hawksbill (Chelonia mydas) (Caretta caretta) (Eretmochelys imbricata) Olive Ridley Kemp’s Ridley Flatback sea turtle 21 (Lepidochelys olivacea) (Lepidochelys kempii) (Natator depressus) DISTRIBUTION - CHELONIIDAE Map generated using State of the World’s Sea Turtles 22 (http://seamap.env.duke.edu/swot) NESTING BEACHES - CHELONII Map generated using State of the World’s Sea Turtles 23 (http://seamap.env.duke.edu/swot) DISTRIBUTION - DERMOCHELYI Map generated using State of the World’s Sea Turtles 24 (http://seamap.env.duke.edu/swot) NESTING BEACHES - DERMOCHELYIDAE Map generated using State of the World’s Sea Turtles 25 (http://seamap.env.duke.edu/swot) BIODIVERSITY - CROCODILIA Crocodylus porosus The “estuarine” or “salt water” crocodile Adaptations for marine lifestyle Semi-aquatic BUT can be found in the open ocean Largest one measured was 6.17m from snout to tail tip 26 DISTRIBUTION – SALT WATER CROC 27 28 3. ADAPTATIONS (Re) Adapting to a marine lifestyle presents several key challenges for terrestrial organisms Salt intake Breathing Locomotion Reproductive mode 29 ADAPTATIONS – SALT GLANDS Excretion via salt glands requires energy, why not use the kidneys to remove salt via urine? Salt glands save water Allow higher conc. (~7x > than urine) All marine reptiles excrete high conc. Na+ and Cl- ions 3 to 8x > blood plasma Salt glands have Example: Marine iguana Salt Gland 30 evolved, been lost, and SALT GLANDS – SEA SNAKE Yellow-bellied sea snake (Hydrophis platurus) 31 SALT GLANDS - MARINE IGUANA 32 SALT GLANDS – SEA TURTLE All sea turtles use Lacrymal glands in the orbit of the eyes Release salty fluid through the tear ducts Origin of the idea that sea turtles are in pain when laying eggs 33  SALT GLANDS – SALT WATER CROC Lingual glands on the tongue All crocodile species appear to have these 34 REPRODUCTION Many sea snakes are ovoviviparous i.e. Their eggs are retained in the body during development and the female then gives birth to live young (tail first) 35 REPRODUCTION Sea kraits, marine iguanas, sea turtles, and crocodiles are all oviparous i.e. They lay eggs on land 36  4. MIGRATIONS Sea turtles are well-known for their incredible migratory abilities Leatherback turtles have been satellite tracked on journeys of over 6000 miles (~9,700 km) Usually the satellite tracker falls off... 37 MIGRATIONS - LEATHERBACKS 38 MIGRATIONS – GREEN TURTLES 39 REFLECTED LIGHT 40 ORBITAL WAVE MOTION 41  ORBITAL WAVE MOTION Turtle hatchlings can detect whether they are facing into or away from waves A (into): Upwards, backwards, downwards, forwards B (away from): Upwards, forwards, downwards, backwards A B 42 Fig. modified from Lohmann et al 2008 J. Exp. Biol.  43 Lohmann et al 2008 J. Exp. Biol. SEA TURTLE NAVIGATION CUES 44 SEA TURTLE NAVIGATION CUES 45 SEA TURTLE NAVIGATION CUES 3. magnetic orientation 46 MAGNETIC FIELD DETECTION 47 Lohmann et al 2008 J. Exp. Biol.  48 Lohmann et al 2008 J. Exp. Biol.  5. CONSERVATION ISSUES OVERHARVESTING Accidental bycatch Harvested Sea snakes 49 Dynamite fishing in SE Asia Turtle egg poaching POLLUTION DISCARDED ROPES AND NETS 50 PLASTIC Much of the plastic in the ocean comes from recycling programmes All species of sea turtle have been found to contain plastic One piece of plastic can kill a turtle Leatherbacks are particularly vulnerable as jellyfish specialists 51 CHEMICAL Approx. 80% of marine pollution is in run-off from land Persistent Organic Pollutants [POPS] e.g. pesticides, herbicides, PCBs, BPA Can lead to: Feminisation or Masculinisation Birth defects, hormone and endocrine disruption, cancer Increased susceptibility to disease and/or predation 52 COASTAL DEVELOPMENT Beaches are “critical habitats” Development disrupts nesting attempts by marine reptiles Increased human activity increases pollution Can accelerate coral death etc. 53 CLIMATE CHANGE Sea level rise Nesting beach erosion Loss of low-lying islands Temperature rise + fluctuations Sex determination (turtles; croc) Changes in phenology (cold shock) Changing precipitation Access to fresh water Storm patterns Increasing acidification Coral bleaching 54 Food web disruption LEARNING OBJECTIVES LO1: Evolutionary history of marine reptiles Reptiles dominated oceans for over 182 million years >Marine turtles > 100 Ma; other extant taxa < 10 Ma LO2: Biodiversity of extant marine reptiles ~ 70-80 species; mostly snakes in the Elapidae LO3: Adaptations to a marine lifestyle Salt glands; changes in body plan; nesting or live birth LO4: Oceanic migrations All marine turtles use light, wave motion, magnetism THANKS FOR LISTENING! 56