2 Introduction from Chapter 11 Early division of amniotes produced 2 evolutionary lineages that include the vast majority of extant terrestrial vertebratesSynapsidsInclude mammalsSuaropsids
3 IntroductionFrom classification based on temporal fenestration two groups of Sauropsida emergeAnapsidaThis group include turtlesDiapsidaDinosaurs, tuataras, lizards,snakes, crocodiles and birds
4 Introduction Sauropsids are the bulk of the reptiles plus birds while Synapsids are the mammal-like reptiles and mammals
5 Turtles Earliest fossil date to late Triassic Very little morphological change has taken place since that timeShell has been their key to successShell has also limited group diversityHave Anapsid skulls
6 TurtlesSystematic relationships with other amniotes poorly understood.Their combination of ancestral and highly derived traits makes determining relationships difficultTwo hypotheses currently being debatedTurtles are sister group to reptilesTurtles are Diapsids
8 Distribution Worldwide distribution and a variety of habitats Turtles and tortoises can be found in all continents except AntarcticaCan also be found in all warm and temperate oceansOccupy a wide diversity of both terrestrial and aquatic habitats
9 Turtles 13 families Two major grps (suborders) of turtles are 1. Cryptodires (hidden necked)Retract head into shell by bending the neck in a vertical s-shapecan pull their heads, legs, and feet inside their shells. In order to make room inside the shell, they sometimes have to exhale air out of their lungs, which makes a hissing sound.Both aquatic & terrestrialOnly type found in Northern HemisphereMarine turtles are cryptodires
10 Turtles; Pleurodires Pleurodires (side necked turtles) Other turtles can’t pull their legs or heads into their shells. Some of these have long necks and protect their heads by tucking them sideways up against the shell.Found only in the southern hemisphereSemi-aquaticMost terrestrial ones in Africa for example the the African Pond turtle. Moves on land from pond to pondSnake-necked pleurodiran turtles are found in S AmericaHave long slender necksFeed on fishes, mollusksHave large palatal surfaces used to crush shells
11 Characteristics of turtles Horny beaksNo teethLimb girdles are inside the ribsUnique in turtlesShell composed of 2 partsCarapace- upper shellPlastron- lower shell
12 Turtle Shell: Carapace Composed of dermal boneBone grow form 59 centers of ossificationThere about bonesCenters of ossification give rise to several series of dermal bones in the carapacePeripherals: 11 pairs, form marginsCostals: fused to ribsNeural: formed by 8 plates along the dorsal mid-line. Fused to the vertebrae
13 Turtle Shell: Carapace Carapace covered by epidermal scutes (keratin scales)Epidermal scutes do not correspond in number & position to the underlying dermal bones of shellRow of 5 central scutesFour lateral scutes form borders11 marginal scutes on each side turn under edge of carapaseSee figure 12.5
14 Turtle Shell: Plastron Formed also from the dermal boneInterior of plastron (entoplastron) is formed from clavicles and interclavicleCovered by a series of 6-paired scutesSee page 309.
15 Turtle shell: HingesSome shells have one or two hinges in the plastron; these are flexible areasFront and rear lobes can be pulled upward to close openingsAllows turtles to draw into its shell and then close the shell as protection against predationSeen on N American Box turtlesCalled kinetic shellsExact number & position variesIn others, plastron is reduced in size allowing greater mobility. One spp (musk turtle) can even climb several feet into trees.
17 Variation in shell morphology Soft shelled turtlesLack peripheral ossificationNo epidermal scales (scutes)Carapace and plastron covered with skinSoft shelled turtles IINew Guinea river turtleCovered by skin, no scutesPeripheral bones presentIn general soft shelled turtles are aquatic, have webbed feet for swimming
18 Variation in shell morphology Leatherback sea turtleCarapase formed of cartilage supported by tiny bones. Skin is leathery..Plastral bones form a very thin edgeGreatly reduced ossificationThis adaptation allows the turtle to dive up to 3,000 feet (900 meters) below the ocean surface. At this depth, the incredible water pressure would crush a turtle with a heavy shell and less flexible body.
19 Variation in shell morphology Terrestrial species tend to haveHigh domesBroad feetE.g. box turtles.
20 Turtle Vertebral column The Turtle vertebral column has 8 cervical, 10 trunk, 2 sacral and 16 to 30 caudal vertebrae.Cervical vertebra allow the S-shaped bend used to retract the head into the shellThe first caudal as well as all the sacral and trunk vertebrae are fused with dermal bone to form the carapace.The ribs are expanded and fused to the inner surface of the costal plates of the carapace.
21 Circulatory System Double circuit Systemic circulation carries blood throughout body (head, trunk & appendages)Pulmonary circuit: carries blood to lungs
22 Heart3 chamberedCompletely divided atriaIncompletely divided 3- region ventriclesAllow complete separation of oxygen rich and oxygen poor bloodHigh pressure systemic and low pressure pulmonaryAllows shunting of blood between systemic and pulmonary circuitOccurs when lungs are not used for respiration (during diving or hibernation)
23 Heart: Structure of ventricles Cavum PulmonaleOpens into pulmonary artery (RHS)Cavum VenosumOpens into the right and left aortic archesReceives blood from body veins and also from the CA.Cavum arteriosus3rd regionDorsal to the CV and CP.Receives blood from left atrium
24 Heart: ventricle structures Muscular ridge partially divides the CV and the CPIntraventricular canal (IVC)Connects the CV with the CA.
25 Blood flowRight atrium receives poor oxygen blood from the systemic circuit via the sinus venosusPasses it to the Cavum venosum thru the atrioventricular valve (AVV)AVV prevent backflowAlso prevents blood flow into the intraventricular canal, hence cannot go the , thus cannot go the Cavum Arteriosus
26 Blood flowCavum venosum passes blood to the cavum pulmonale which then passes blood to the to the pulmonary artery to to the lungs
27 Blood Flow The left atrium receives oxygen rich blood from lungs Passes thru the AVV into the Cavum arteriosus (CA)Ventricle contracts, blood flows from CV to CP. As pressure builds up, muscular ridges closes passages between the CV and CP, then allows blood to flow from the CA to CV and then to aortic archesThus the CV handles both Oxygen poor and oxygen rich blood, but separately..
28 Blood Flow O2 Poor blood O2 rich blood Body – RA----av---CV-----CP----Pa---lungsAv also closes the IVC.. No blood to CA at this pointO2 rich bloodLA ----av-----CA CV---aortic arches---arteries.High pressure cause IVC to open to allow blood flow into CV from CA
29 Blood FlowTiming of blood flow thru the heart prevents the mixing of Oxygen rich blood coming from the pulmonary circulation with deoxygenated blood from the systemic circulation
30 Respiration Ribs fused to carapace; are immovable Ventilation by moving rib-cage is impossibleLungs are large and are also attached to carapace dorsally and ventrallyThus turtles cannot ventilate by expanding or contracting the rib cage/thoracic cavity because its rigid.
31 Respiration: Use of visceral cavity Lungs are attached to visceral cavity ventrally by a rigid sheet of connective tissue: Diaphragmatic tissueNon-muscle tissue that connects ventral side of lungs to the visceral organWt of viscera keeps diaphragmatic sheet pulledVentilation is by visceral pumpViscera push against the pleural cavity to force air out of the lungs (exhalation)Viscera pull down on diaphragmatic sheet, this expands the lungs. Air comes in..
32 Respiration: Other Muscles ExhalationTransverse abdominus muscles: contract to pull viscera upward against lungsPectoralis draws pectoral girdles back into the shell. They reduce volume of VCInhalationAbdominal obliquePectoral serratus
33 Respiration: other structures used by aquatic spp Pharynx in soft shelled turtlesCloaca in diving shellsIn both cases, turtles pump water in and out of the pharynx or cloaca and can exchange O2 and CO2 across membranes of the structures
34 Intracardiac ShuntsTurtles are able to shunt blood from the pulmonary circulation to the systemic circulation (by pass lungs)Occurs during prds of apnea (no breathing)When lungs are not being ventilated and there would be no oxygen to be taken up into the bloodDiving is the most common reason for thisRight to left intracardiac shuntBlood shunted directly from the right side to the systemic circulation.
35 Reproduction All Oviparous Eggs covered in a leathery membrane to prevent sperm from reaching the fertilized eggFertilization is internal before shell is produced to coat egg
36 Reproduction: Courtship Courtship signals and other spp recognition signals are usedEmploy visual, olfactory, tactile and olfactory cues during courtshipMany pond turtles have distinct series of lines on their heads, necks, and forelimbs and on their hind limbs and tailUsed for spp recognition
37 Reproduction: Courtship Several spp have glands in the male that enlarge during breeding and produce pheromones that are used to mark substrates within a territoryTortoises vocalize during courtship. Produce grunts, moans, bellows.Tactile signals entails that males engage in combat that involves biting the head of an opponent or ramming him and trying to overturn him
38 Reproduction: Courtship Large tortoise often live in herds and a large male is often dominant. Fighting among individuals serves to establish the dominancy hierarchy- elevating headSee figure 12-9
39 Reproduction: Nesting Eggs laid in a nest dug by the femaleAfter this no parental careClutch of eggs laid: 4-5 eggs for small spp to 100 eggs for large sppEmbryonic development is daysEggs have a diapause prd during the winter. Resume development when temperature rises in spring
40 Reproduction: Nesting Nesting TemperatureDetermines sex of offspringHigh temp---- development of larger sex (females)Low temp---development of smaller sex (males)Range in temp for sex change is very narrow (3-4o C)
41 Reproduction: Nesting Wet incubation produces larger hatchlings than dry conditionsIn dry conditions turtles hatched are small, hatch early, contain more of unmetabolized egg yolkCannot run or swim fast as does the wet hatchlings- not very successful at escaping predation
42 Hatching Behavior Turtles show self sufficiency at hatching Hatchling behavior studied in marine turtlesClutch of eggs in a nest hatch simultaneouslyVocalizations used to get all the nest mates synchronized for hatchingEnmass dig their way to the surfaceAt night when temperatures are low, all baby turtles emerge from nest at once and then race to the ocean
43 Hatching BehaviorAlong the stretch of beach, there will be many other nests of turtles emerging at same timeSusceptible to heavy predation simultaneously, saturate predatorsCrabs, foxes, raccoons, sharks, bony fishes
44 Temperature regulation Turtles are ectothermsBody temp determined by environmentRegulation of body temperature is behavioralBask in sun to increase body temperatureIncreases rate of metabolic reactionsHelps to kill and rid themselves of leeches in case of aquatic turtlesRate of heating & cooling easier with small turtlesOverheating a problem with giant turtles in an open sunny habitat
45 Temperature regulation Some are endothermicMarine turtles are very large and endothermicLeatherbacks are the largest living turtles ----~ 1000 kgsFound in Temps of 8, 15 or 20 degrees Celsius but with body temps >= 18 degrees above that of waterUse countercurrent exchange system of blood vessels in the flippers to conserve heat
46 Temperature regulation: countercurrent exchange Venous blood returning from the flipper is coldReturns through veins closely associated with the arteries that carry blood from the body to the flippersCold venous blood is heated by warm arterial blood flowing out of the core of body. By the time venous blood reaches core of boy it is back to body temperature.
47 Feeding: Mostly carnivorous– as seen in sea turtles Leatherbacks eat jellyfishOthers are vegetarianfeed on turtle grass that grows in shallow or protected shorelines in the tropics.
48 Threats to Survival Low reproductive rates Lack of parental care Habitat loss and degradationOverexploitation for food and pet tradeAsians markets for turtle meatLack of basic natural history information on many species(Read text for more details)