module 3 reptiles INTRODUCTION • Carboniferous period (~325mya) à receding oceans/ h land plants/ h insects • Amphibians evolved to fill new environmental niches + escape from i water resources • Reptiles evolved from Amphibians • 1st true terrestrial vertebrates • First amniotes (shelled eggs) à didn’t float away, i predators + i reliance on water ADVANTAGES OVER AMPHIBIANS • Internal fertilisation • Stronger limbs • Impermeable skin • Shelled eggs EVOLVED 2 MAIN LINEAGES • Lepidosaurs= scaly lizards à modern day tuataras, snakes + lizards • Archosaurs= ancient lizards (incl. dinosaurs) à modern day crocs + birds TEMPORAL FENESTRAE Skulls • Temporal fenestrae= holes in skull à allows better jaw muscle attachment + potentially i skull weight for life on land • Diapsid= 2 temporal fenestrae à most reptiles (except turtles= anapsids) • Synapsid= 1 temporal fenestrae à mammals • Anapsid= no temporal fenestrae à amphibians Classification • 4 main groups= Testudines (turtles), crocodilians, tuatara + squamates (lizards/snakes) • Debate re. classification ORDERS/ SUB-CLASSES • Crocodilia= crocodiles + aligators • Lepidosauria= squamates • Rhynchocephalia= tuataras • Testudines= turtles + tortoises • Every continent Global • Hotspots= Australia, SE Asia, west + south Africa, South America distribution • Lizards= highest in Australia • Snakes= Highest in Sth America + SE Asia • Crocodilia= Nth Australia, SE Asia + Sth America • Air-breathing Basic characteristics • 3-chambered heart à except cros= 4 chambers • Bony skeleton • Skin= epidermal plates/scales/scutes • Ectothermic à don't waste energy on temp regulation • Highly variable between + within orders Anatomy + THERMOREGULATION physiology • Body temp reflects ambient/substrate temp • General preference= >28oC àdragons + goannas= 34-38oC • Cannot perspire • i metabolism, movement, growth + reproduction in non-optimal conditions • Shuttling heliotherms or basking heliotherms o Shuttling heliotherms= move b/w sun + shade as temp fluctuates o Basking heliotherms= stay in one place à e.g. crocs 3-CHAMBERED SEPTATED HEART • 2 atria= right receives deoxygenated blood + left receives oxygenated blood • 1 partially separated ventricle • Disadvantages= allows some mixing of O2 + deO2 blood + i efficient at delivering O2 to body tissues Evolution SKIN- SCALES OR SCUTES • Scales + scutes both made of structural alpha + beta proteins • Loreal scale= scales b/w eye + nostril à present in colubrids/ absent in elapids • • • • • Reproduction Scales Formed in the dermis Overlapping Help retain moisture Aid locomotion Can be shed + replaced à removed worn out skin + parasites • • • • • Scutes Formed in deep layers of dermis Individual units Help retain moisture Protection Some shed + replace à others continually produce keratin at base of scute DIGESTION • GIT= mouth à oesophagus à stomach à Intestines à cloaca • Carnivores= simple stomach + smaller intestine à protein + fat= easier to digest • Herbivores= more complex stomach + larger intestine à break down cellulose • Crocodiles= neurologically controlled heart valve à allows blood to bypass lungs + go straight to stomach= h gastric juice to allow for very large prey digestion • Turtles= o No throat= don't swallow o Excess water ingested w/ food o Oesophagus lined w/ papillae (cartilaginous + keratinised projections) pointing towards stomach to trap food while water expelled • Snakes= o elongated oesophagus w/ folds= allow for peristalsis of large prey o Venomous snakes= 1 pair of salivary glands evolved into poison glands o Environmental temp determines digestion rate COMPETITION FOR MATES • Turtles= head butt opponents + bite copulating males to dislodge them • Monitor lizards= wrestle competitors • Dragons= display frills to competing males • Garter snakes= deposit mucus plug at end of female’s cloaca after mating to prevent other males REPRODUCTION Breeding season • Year round/ multiple seasons/ single annual season Sexual/asexual • Mostly sexual • Some asexual parthenogenesis species Development • Most= inside laid egg • Some= viviparous (live birth) Clutch size • 1 to >100 eggs Sex organs • Male crocs + turtles= penis • Squamates= hemipenis à only 1 used in single event Unfavourable • Some species= Able to delay + stop development in oviduct for conditions weeks/months NESTS + INCUBATION • Egg incubation= temp dependent à cooler= longer • Some species= Temp-based sex determination à e.g. turtles (h=F) + crocs (h=M) Turtles Deposit eggs in large burrows + leave Some squamates Deposit eggs in burrow/ leaf litter + leave Geckos Deposit eggs in rock crevices/ under tree bark + leave Crocodiles • Nests from vegetation + soil • Parental care for a few months DIVERSITY Crocodilia Lepidosauria (lizards) • Only 2 species in Australia SALTWATER CROCODILE Length + • Male= 4-6m + up to 500kg weight • Female= 3-4m + up to 200kg Habitat • Saltwater • Brackish wetlands • Wet season= swamps + rivers • Dry season= estuaries + ocean Colour • Juveniles= pale yellow • Adults= greenish/brown Sexual • Male= 16yrs maturity • Female= 12-14yrs Food • Opportunistic carnivores • Drowns prey + swallows whole • Mammals/birds/reptiles/fish/sharks Behaviour • Social basking • Fight for territory (esp mammals) • 5 families • Higher abundance in arid zones (NT, WA + nth SA) AGAMIDAE (DRAGON LIZARDS) • Well-developed front + hind limbs • Claws on distal digits • No toe pads • Lower eyelid= thick, scaly + moveable • Small scales= granular or spinose (spiny) • Tongue= broad + fleshy • E.g. Bearded dragon + frilled neck lizard GEKKONIDAE (GECKOS) • Well-developed front + hind limbs • Claws on distal digits • Dilated toe pads à climbing + sticking • Some species have hooks on hindlimbs à climbing • Lower eyelid= immoveable clear scale covering eye • Scales= small + granular • Tongue= broad + fleshy • E.g. Burrow-plug gecko • • • • • FRESHWATER CROCODILE Male= 2-3m + 70-100kg Female= max 2.1m + 40kg Freshwater Wetlands, billabongs + creeks Saltwater tolerant • 15-20yrs • Birds/ fish/ amphibians/ reptiles/ small-medium mammals Shy Co-exist in small groups • • Lepidosauria (snakes) PYGOPODIDAE (PYGOD/FLAP-FOOTED LIZARDS) • No external traces of forelimbs • Hindlimbs reduced to small flattened flaps on either side of vent • Lower eyelid= immoveable clear scale covering eye • Scales= large + overlapping • Scales on ventral surface of body • Tongue= broad + fleshy • Long tail relative to body • External ear • E.g. Excitable delma SCINCIDAE (SKINKS) • Largest Lepidosauria family • Limbs vary from well-developed to externally absent • Digits= clawed + no toe pads • Lower eyelid= vary from thick, scaly + moveable to immoveable clear scale covering eye • Scales= large + overlapping à each have core of bone • Tongue= broad + fleshy • Some species= ovoviviparous (eggs hatch inside + born live) • E.g. blue tongued lizards VARANIDAE (GOANNAS/MONITOR LIZARDS) • Well-developed front + hind limbs à strong + powerful= run fast • Distal limbs= clawed + no toe pads • Some species= large claws à climbing trees + digging • Lower eyelid= thick, scaly + moveable • Scales= Granular or spinose • Tongue= long, slender + forked • E.g. lace monitor + perentie • 7 families • Australia-wide à highest abundance in north + east TYPHLOPIDAE (BLIND/WORM SNAKES) • Eyes below thickened scales= black spots only • No external traces of limbs • Ventral scales= no larger than adjacent scales • Tail= short, thick + blunt w/ thorn-like terminal scale (no tapering) • Smooth scales à allow ease of burrowing PYTHONIDAE (PYTHONS) • Obvious eyes • Pair of small spur-like vestigial hindlimbs on either side of vent • Ventral body scales= single row + distinctly wider than other scales • Tapered tail • Head scales= large symmetrical plates or small irregular scales • Non-venomous • Some arboreal= prehensile tail • E.g. carpet python ACROCHORDIDAE (FILE SNAKES) • Aquatic à freshwater/estuarine • Obvious eyes • No external traces of limbs • Scales= small + granular • Tapered tail • Non-venomous • • Testudines Loose, baggy skin à allows it to grip prey Highly developed scale sensilla= head scales sensitive to movement COLUBRIDAE (COLUBRID SNAKES) • Obvious eyes • Coloured • Loreal scales present • No traces of limbs • Ventral scales= single row + much larger than other scales • Head scales= large symmetrical plates • Enlarged teeth in some species • Tapered tail • Venomous/ non-venomous • E.g. green tree snake ELAPIDAE (ELAPID SNAKES) • Obvious eyes • No traces of limbs • No loreal scales • Ventral body scales= single row + much larger than other scales • Head scales= large symmetrical plates • Fangs at front of mouth for venom injection • Tapered tail • E.g. red bellied black snake/ eastern brown snake/ southern death adder HYDROPHIIDAE (SEA SNAKES) • Marine • Obvious eyes • No traces of limbs • Ventral body scales= variable size • Head scales= large symmetrical plates • Fangs + venom • Viviparous (live birth) • Laterally-compressed tail= paddle-like à propulsion in water • E.g. yellowbelly sea snake LATICAUDIDAE (SEA KRAITS) • Marine • Obvious eyes • No traces of limbs • Ventral body scales= single row + much larger than other scales • Head scales= large symmetrical plates • Fangs + venom • Laterally-compressed tail= paddle-like à propulsion in water • Oviparous= leave water + lay eggs on land • E.g. banded sea krait • 4 families • Carapace= top shell à diagnostic of species • Plastron= bottom shell CHELIDAE (SNAKE-NECKED TURTLES) • Freshwater • Side-neck orientation= head drawn under shell in horizontal S-bend à b/c limited space • Distinct ankle joints • Distal limbs= 4-5 claws + webbing • Basking heliotherms à either on land or water surface • Oviparous • E.g. Eastern snake-necked turtle CARETTOCHELYDIDAE (PITTED-SHELLED/ PIG-NOSED TURTLE) • Northern Aus + PNG • Freshwater à streams/ rivers/ lagoons • Distal limbs= flippers like sea turtles w/ 2 claws • Nose= pig-like • Omnivorous • Oviparous= eggs laid on river bank in dry season à don’t hatch till conditions good= h survival rate CHELONIIDAE (SEA TURTLES) • Northern Australia • Body= flat, streamlined + rounded • Large front flippers • Cannot retract head into shell • Carapace= distinct + mostly bone à pattern + scute number differentiate species • Oviparous à 2 clutches per season • Temp-dependent sex determination à h temp= h females • Late maturation • Copulate at sea + females migrate to annual breeding site to lay (where she hatched) • High hatchling + juvenile mortality Vulnerable • Carnivorous à benthic invertebrates (e.g. jellyfish) Loggerhead • Carapace= Irregular shape w/ 5-6 costal scutes • Carnivorous à soft invertebrates Flatback • Carapace= upturned edges + 4 costal scutes Endangered • Herbivorous à algae/ seagrass/ mangroves Green • Carapace= 4 costal scutes + dark pigmentation • Carnivorous à soft invertebrates Olive ridley • Carapace= wide + rounded w/ 6+ costal scutes Critically • Omnivorous à algae/ coral/ sea cucumber/ jellyfish Hawksbill endangered • Carapace= oval w/ 4 costal scutes DERMATOCHELYIDAE (LEATHERBACK TURTLE) • Marine • Largest marine turtle • Diet= jellyfish + soft invertebrates • Carapace= no scutes à leathery skin w/ osteoderms (bony deposits) to support • 7 ridges down back • Limbs= flippers w/ no claws • Oviparous= lay eggs above high tide mark in dug out nests à up to 9 clutches per year ADAPTATIONS Habitat Climbing/ gripping Swimming Desert climate • • • • • • • • • • • • Wide diversity= occur in most habitats across Australia Claws on distal forelimbs à e.g. goannas Pads on distal hindlimbs w/ hooks à e.g. geckoes Prehensile tail in some snakes= adapted for gripping à e.g. tree pythons Laterally-compressed paddle-like tails= propulsion + steering à e.g. sea snakes + kraits Powerful tails for propulsion à e.g. crocodiles Large flippers à sea turtles + leatherback turtles Webbed feet à freshwater turtles Metachromatism= adjust body/skin colour in response to temp to assist thermoregulation à light during high heat + darker in cooler periods Nocturnal activity= avoid highest heat Fringed feet= spiny scales resembling fringes à keep traction on sand Fringed ears= prevent sand entering ears while digging burrows • • • Burrows= i predation + protect from high heat Absorb water through feet from moist sand à prevent dehydration Excretion of nitrogenous waste as uric acid= minimise water loss THREATS IUCN status Habitat loss + destruction • • • • • Invasive • species Environmental • pollution Disease + parasitism Unsustainable use Climate change • • • • • • • • • • • • • • • • • 2 extinct 7 critically endangered + 77 endangered h human pop= h demand for housing + food= h encroachment on habitats Land degradation/ urbanisation/ i aquatic habitats/ i transitional habitats/ i terrestrial habitats Change ecosystems Predation/ native species naivety/ resource competition Contaminants + pollutants à metals/ herbicides/ pesticides/ PCBs/ endocrine disrupters o Bioaccumulation o Disrupt reproduction Plastic= slow degradation/ leach chemicals/ ingested + block digestion Upper respiratory tract disease caused by bacterium Shell disease in turtles Fibropapillomas virus= growths lead to vision, movement + feeding loss in Green turtles Snake fungal disease= skin lesions + blisters Novel diseases à e.g. Bellinger river snapping turtle Collection for food à e.g. turtle eggs dug up + consumed Illegal pet trade Harvesting for research Poaching for skin/shells Traded for medicinal purposes à snakes, turtles, crocodiles + lizards Once adult pops exhausted, juveniles taken next= i breeding potential in next gen. h atmospheric CO2 from fossil fuels= h greenhouse gases= h heat h ocean acidification h coral bleaching à i turtle food h drought + bushfires à cant escape Temp-dependent sex determined species= skewed sex ratios w/ h temps CASE STUDY: BELLINGER RIVER SNAPPING TURTLE Classification Species information + biology Ecology • • • • • • • • • • • • • • Order= testudines Family= chelidae (snake-necked turtles) Species name= Myuchelys georgesi Endemic to Australia Habitat= rivers w/ continuous flow, deep pools, clear water + some rock/substrate Do not like brackish waters Highly oxygenated habitat assists cloacal breathing Neck tubercles= help detect movement Omnivorous à macro-invertebrates, fruit, aquatic vegetation Hunt w/ eyesight Winter breeders à Lay oct-nov (10-15 eggs) 57km stretch of Bellingen + Kalang river systems Limited range= any impact on area can be catastrophic Prior to 2015= pop of >1500 à locally abundant • • • 2015 mortality event Initial response • Disease symptoms Identifying the cause Detecting + understanding the virus Conclusions from research Ex-situ management Face comp from Macquarie river turtle which has been introduced 14-18 Feb 2015= ~500 dead/dying found wiped out 95% of all pop in very little time (~6mths) Rapid collection of remaining healthy turtles from site • Collaborative project= many govt + independent organisations involved • Veterinary care to sick turtles à however h mortality + biosecurity risk= euthanised PROJECT AIMS • Rapid protection of turtle • Disease diagnosis • Understand ecology of virus • Assess impact in other species • Develop diagnostic test + potential vaccination • Lethargy + slow movement • Ocular inflammation • Plaque-like skin lesions • Usual process= Rule out explanations progressively before proceeding using clinical/necropsy, histology + diagnostic testing • High mortality + potential risks= all started immediately CLINICAL + HISTOLOGICAL SIGNS • Ruled out environmental causative agent • Water quality + pollutant testing= all negative • Necropsy results= indicate pathogen HISTOLOGY + BACTERIAL TESTING • Ruled out bacterial causative agent à suspected virus • All tests came back negative VIRAL TESTING • Excluded common viruses à indicates novel virus • Tested for common viruses= all negative à ranovirus/ adenovirus/ paramyxoviruses/ herpesviruses STEP 1: ISOLATE VIRUS 1. Inoculate medium w/ tissue homogenate 2. Incubate culture 3. Remove grown cells STEP 2: FIND OUT WHAT IT IS 1. Isolate viral nucleic acids 2. Nucleic acid sequencing à does it match another virus? 3. Phylogenetic analysis à most related to viruses in family Coronaviridae 4. Named Bellinger river virus STEP 3: DESIGN A DIAGNOSTIC TEST • PCR using primers to detect + amplify specific sections of the nucleic acid sequence STEP 4: TEST ON TARGET AND OTHER SPECIES • Only detected in Bellinger River Snapping Turtle • 2 cases in Murray River turtle= may have been false positives • Novel virus is pathogenic cause of mortality event • Other factors likely contributed à e.g. environment impacts on immune system • High water temps in river= good for viral growth • Off-site conservation à outside natural habitat REASONS FOR EX-SITU MANAGEMENT • Insurance colonies à quick mortality= important to remove healthy turtles immediately • Provide animals for reintroductionà high mortality= important to breed some for after disease understood • Conservation research à many unknowns= need to understand as much as possible CONSIDERATIONS • Species prioritisation • Analogue species à use similar species to develop appropriate husbandry protocols • Founder collection à genetic diversity • Biosecurity à careful hygiene, PPE, quarantine • Resource availability à funding + staff INSURANCE POPULATION • 16 individuals collected from upstream areas of river • Quarantine at WSUni until tested for virus à protect each other + other species • Early 2016= Transferred to Taronga • DNA tested to ensure wide genetic background • Jan 2017= first breeding season à 4 clutches from 4 females= 22 eggs hatched • 2018= 31 eggs hatched • Artificially incubate eggs= higher chance of success à wild= 70-80% survival rate • Raised in mesocosms= mimics natural environment under controlled conditions • Fed pet turtle cubes= contain all essential nutrients à couldn't be fed natural diets b/c unknown whether disease caused by food/environment REINTRODUCTION • Nov 2018= 10 captive-bred turtles released to upper Bellinger river • Only release juveniles • Health assessment prior to release • Radio transmitters attached to shellà tracking survival + monitoring • 9 still alive 6 months later