鲨鱼软骨鱼类.ppt

Elasmobranch Biology
Elasmobranch: Any of numerous fishes of the class Chondrichthyes, characterized by a cartilaginouserms
Osmoregulation
Sharks are slightly hyperosmotic to sea water
Retain urea and TMAO
Results in slight but continuous influx of water
Excess water is excreted by the kidney
Most sharks are stenohaline
Reproduction
Male Sharks
Male Reproductive System
Both testes functional
Seasonal reproduction cycle
Sperm stored in seminal vesicles
Both claspers functional
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Graphic images ahead.
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Female Sharks
Modes of ReproductionOviparous:
Oviparous species, eggs are released into the environment
Females select sites to deposit eggs
40% of all Shark species and all skates are oviparous
Modes of ReproductionAplacental viviparity:
Females retain developing embryos in utero
Embryos nourished with yolk and then “histotroph”, or ovulated eggs (oophagy) or siblings (embryophagy)
All rays are aplacental viviparous with histotroph
Modes of ReproductionPlacental viviparity:
Females retain embryos in utero
Embryos nourished through yolk and then through a placental connection
10% of shark species are placental viviparous
Appendiculae
Female Reproductive System
One functional ovary in most
viviparous species
Seasonal reproductive cycle
Fertilization in nidamental
gland
Nidamental
Stomach
Ovary
Female Anatomy
Female Anatomy
Ovary
Nidamental Glands
Uteri
Liver
Uteri
Pregnant Sandbar Shark
Carcharhinus plumbeus
Placental Embryos
Parturition
Shark Mating
Shark Mating
One clasper will rotate 90º
and will be inserted into
the female’s cloaca
Clasper will expand
cartilaginous spurs to
anchor in the female
Shark Mating
Mating Scars
Evolutionary Adaptations
Evolutionary Adaptations
Placoid Scales = decrease drag
Evolutionary Adaptations: Teeth
Large Liver and cartilaginous skeleton helps with buoya