鯊魚-軟骨魚類

1、Elasmobranch BiologyElasmobranch: Any of numerous fishes of the class Chondrichthyes, characterized by a cartilaginous skeleton and placoid scales and including the sharks, rays, and skates.FLORIDA PROGRAM FOR SHARK RESEARCHFlorida Museum of Natural History鯊魚-軟骨魚類生物TopicsBasic MorphologySensesDigest

2、ion systemCirculatory systemOsmoregulationReproduction systemEvolutionary adaptations There are approximately 400 described species of sharks. Additionally, there are around 400 species of batoids (rays and skates). When did sharks first appear?Sharks and their ancestors first appeared in the late S

3、ilurian/early Devonian, or around 400 million years ago.Sharks predate dinosaurs by 200 million years.Body PlanStingrays vs. SkatesWhats the difference?Stingray FinsSkate FinsPectoralPelvicPectoralPelvicDorsalCaudalSpiracleSpiracleStingray vs. SkateMost have venomous spineNo spine presentStingray Ta

4、ilSpineDorsal fin-foldAnal fin-foldReproduction: Aplacental viviparity (live birth).Reproduction: Oviparous (lay eggs).Stingray vs. SkateCan be very large in size.Usually smaller in size.Stingray vs. SkateStingray vs. SkateIn general have thinner tailsCan have very thick tailsElasmobranch SensesElas

5、mobranch Senses Olfactory (Smell): Highly acute sense of smellUsed to locate food or potential matesPaired openings with or without a connection to the mouthNot used for respiration Lack external ears Good sense of hearing especially in the lower frequency range Often first sense to detect prey from

6、 a distanceElasmobranch SensesSound:Elasmobranch SensesPressure:Sharks, like other fish, have a lateral line system that can detect pressure waves in the water.Sense struggling prey Shark eyesight will vary by species but most have good visual acuity Sharks have both rods (light/dark) and cones (col

7、or) Retina posses a “tapetum lucidum” Elasmobranch SensesVision:Elasmobranch SensesElectric:Electrosensory system: “Ampullae of Lorenzini” Allows for detection of weak electric fields given off by prey organisms or potential matesDigestionShark Digestion Large Liver up to 25% of body weight. Short G

8、ut long passage rate Spiral Valve intestine increase surface areaCirculatory SystemFour chamber heart: sinus venosus, atrium, ventricle, and conus arteriosus.One direction of flow: HeartGills BodyEctotherms/EndothermsOsmoregulationSharks are slightly hyperosmotic to sea waterRetain urea and TMAOResu

9、lts in slight but continuous influx of waterExcess water is excreted by the kidneyMost sharks are stenohalineReproductionMale SharksMale Reproductive System Both testes functional Seasonal reproduction cycle Sperm stored in seminal vesicles Both claspers functionalWarning! Graphic images ahead. View

10、er discretion is advised.Female SharksModes of ReproductionOviparous:Oviparous species, eggs are released into the environmentFemales select sites to deposit eggs40% of all Shark species and all skates are oviparousModes of ReproductionAplacental viviparity:Females retain developing embryos in utero

11、Embryos nourished with yolk and then “histotroph”, or ovulated eggs (oophagy) or siblings (embryophagy)All rays are aplacental viviparous with histotrophModes of ReproductionPlacental viviparity:Females retain embryos in uteroEmbryos nourished through yolk and then through a placental connection10%

12、of shark species are placental viviparousAppendiculaeFemale Reproductive System One functional ovary in most viviparous species Seasonal reproductive cycle Fertilization in nidamental glandNidamentalStomachOvaryFemale AnatomyFemale AnatomyOvaryNidamental GlandsUteriLiverUteriPregnant Sandbar Shark C

13、archarhinus plumbeusPlacental EmbryosParturitionShark MatingShark Mating One clasper will rotate 90 and will be inserted into the females cloaca Clasper will expand cartilaginous spurs to anchor in the femaleShark MatingMating ScarsEvolutionary AdaptationsEvolutionary AdaptationsPlacoid Scales = decrease dragEvolutionary Adaptations: Teeth Large Liver and cartilaginous skeleton helps wit