鲨鱼-软骨鱼类

Elasmobranch BiologyElasmobranch:Any of numerous fishes of the class Elasmobranch:Any of numerous fishes of the class Chondrichthyes,characterized by a cartilaginous skeleton and Chondrichthyes,characterized by a cartilaginous skeleton and placoid scales and including the sharks,rays,and skates.placoid scales and including the sharks,rays,and skates.FLORIDA PROGRAM FOR SHARK RESEARCHFlorida Museum of Natural History鲨鱼鲨鱼-软骨鱼类生物软骨鱼类生物TopicsBasic MorphologyBasic MorphologySensesSensesDigestion systemDigestion systemCirculatory systemCirculatory systemOsmoregulationOsmoregulationReproduction systemReproduction systemEvolutionary adaptationsEvolutionary adaptations There are approximately 400 described species of sharks.There are approximately 400 described species of sharks.Additionally,there are around 400 species of batoids Additionally,there are around 400 species of batoids (rays and skates).(rays and skates).When did sharks first appear?Sharks and their ancestors first appeared in the late Sharks and their ancestors first appeared in the late Silurian/early Devonian,or around 400 million years ago.Silurian/early Devonian,or around 400 million years ago.Sharks predate dinosaurs by 200 million years.Sharks predate dinosaurs by 200 million years.Body PlanElasmobranch SensesElasmobranch Senses Olfactory(Smell):Olfactory(Smell):Highly acute sense of smellHighly acute sense of smell Used to locate food or potential matesUsed to locate food or potential mates Paired openings with or without a Paired openings with or without a connection to the mouthconnection to the mouth Not used for respirationNot used for respiration Lack external ears Lack external ears Good sense of hearing especially in the Good sense of hearing especially in the lower frequency range lower frequency range Often first sense to detect prey from Often first sense to detect prey from a distance a distanceElasmobranch SensesSound:Sound:Elasmobranch SensesPressure:Pressure:Sharks,like other fish,Sharks,like other fish,have a lateral line system have a lateral line system that can detect pressure that can detect pressure waves in the water.waves in the water.Sense struggling preySense struggling prey Shark eyesight will vary by species but Shark eyesight will vary by species but most have good visual acuity most have good visual acuity Sharks have both rods(light/dark)and Sharks have both rods(light/dark)and cones(color)cones(color)Retina posses a“Retina posses a“tapetum lucidumtapetum lucidum”Elasmobranch SensesVision:Vision:Elasmobranch SensesElectric:Electric:Electrosensory system:“Ampullae of Lorenzini”Electrosensory system:“Ampullae of Lorenzini”Allows for detection of weak electric fields given off by Allows for detection of weak electric fields given off by prey organisms or potential matesprey organisms or potential matesDigestionShark Digestion Large Liver Large Liver up to 25%of body weight.up to 25%of body weight.Short Gut Short Gut long passage ratelong passage rate Spiral Valve intestine Spiral Valve intestine increase surface areaincrease surface areaCirculatory System Four chamber heart:Four chamber heart:sinus venosus,atrium,ventricle,and sinus venosus,atrium,ventricle,and conus arteriosus.conus arteriosus.One direction of flow:HeartOne direction of flow:HeartGillsGills Body Body Ectotherms/EndothermsEctotherms/EndothermsOsmoregulation Sharks are slightly hyperosmotic to sea waterSharks are slightly hyperosmotic to sea water Retain urea and TMAORetain urea and TMAO Results in slight but continuous influx of waterResults in slight but continuous influx of water Excess water is excreted by the kidneyExcess water is excreted by the kidney Most sharks are stenohalineMost sharks are stenohalineReproductionMale SharksMale Reproductive System Both testes functionalBoth testes functional Seasonal reproduction cycle Seasonal reproduction cycle Sperm stored in seminal vesicles Sperm stored in seminal vesicles Both Both claspers claspers functionalfunctionalWarning!Graphic images ahead.Viewer discretion is advised.Female SharksModes of ReproductionOviparous:Oviparous:Oviparous species,eggs are released into the environmentOviparous species,eggs are released into the environment Females select sites to deposit eggsFemales select sites to deposit eggs 40%of all Shark species and all skates are oviparous40%of all Shark species and all skates are oviparousModes of ReproductionAplacental viviparity:Aplacental viviparity:Females retain developing embryos Females retain developing embryos in uteroin utero Embryos nourished with yolk and then“histotroph”,or Embryos nourished with yolk and then“histotroph”,or ovulated eggs(oophagy)or siblings(embryophagy)ovulated eggs(oophagy)or siblings(embryophagy)All rays are aplacental viviparous with histotrophAll rays are aplacental viviparous with histotrophModes of ReproductionPlacental viviparity:Placental viviparity:Females retain embryos Females retain embryos in uteroin utero Embryos nourished through yolk and then through a Embryos nourished through yolk and then through a placental connectionplacental connection 10%of shark species are placental viviparous10%of shark species are placental viviparous AppendiculaeAppendiculaeFemale Reproductive System One functional ovary in most One functional ovary in most viviparous species viviparous species Seasonal reproductive cycle Seasonal reproductive cycle Fertilization in Fertilization in nidamental nidamental glandglandNidamentalNidamentalStomachStomachOvaryOvaryFemale AnatomyFemale AnatomyOvaryOvaryNidamentalNidamental GlandsGlandsUteriUteriLiverLiverUteriUteriPregnant Sandbar Shark Carcharhinus plumbeusPlacental EmbryosParturitionShark MatingShark Mating One clasper will rotate 90One clasper will rotate 90 and will be inserted into and will be inserted into the females the females cloacacloaca Clasper will expand Clasper will expand cartilaginous spurs to cartilaginous spurs to anchor in the female anchor in the femaleShark MatingMating ScarsEvolutionary AdaptationsEvolutionary Adaptations Placoid Scales=decrease dragPlacoid Scales=decrease dragEvolutionary Adaptations:Teeth Large Liver and cartilaginous skeleton helps with buoyancyLarge Liver and cartilaginous skeleton helps with buoyancyEvolutionary AdaptationsHammerhead Sharks The unique head(cephalophoil)provides several advantagesThe unique head(cephalophoil)provides several advantages Increase lift,Increase lift,maneuvering maneuvering ElectrosensoryElectrosensory OlfactoryOlfactory Feeding FeedingQuestions?