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Shark Mating

Shark Mating. Claspers: grooved organs that are used to deposit sperm into the genital duct of sexually receptive female sharks developed along the inner margin of each pelvic fin (the paired fins located behind a shark’s belly) because the pelvic fins are paired, so are the claspers

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Shark Mating

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  1. Shark Mating • Claspers: • grooved organs that are used to deposit sperm into the genital duct of sexually receptive female sharks • developed along the inner margin of each pelvic fin (the paired fins located behind a shark’s belly) • because the pelvic fins are paired, so are the claspers • when not in use, both claspers lie flat against the undersurface of the body

  2. Shark Mating • The male shark communicates his amorous intentions to a sexually receptive female through ritualized swimming and not-so-gentle love nips • male grasps one of her pectoral fins in his mouth and arches his body so that his pelvic fins are brought close to hers. • If the amorous male happened to ‘dock’ along the left side of the female, he flexes his right clasper in place • its tip unfolds in complex, species specific ways-often anchoring by way of one or more spike-like clasper spurs (ouch!). • Often, shark mating occurs on the ocean floor, with the larger female on the bottom • Some species need to stay moving to get oxygen over their gills. These species (Great White, Gray Reef, etc.) mate at or near the surface or in channels with strong currents at the ocean floor

  3. Virgin Births • Recently there have been a few examples of sharks that appear to be able to give birth to offspring without conception from a male. • In 2001, a bonnethead shark gave birth without having any contact with any males for three years. • In 2002, a white spotted bamboo shark also gave birth and had no contact with any males for six years. • The reason is not clear yet, but one hypothesis is that they are reproducing through parthenogenesis, which has been found in birds, snakes and reptiles. First witnessed virgin birth

  4. Reproduction Example of hammerhead shark and viviparity. There are three modes of reproduction within sharks. Viviparity- the female provides nourishment for embryos as they develop inside her. The nourishment is delivered as a secretion called uterine milk or through placental connection. (i.e. Hammerhead, Bull, Blue, and Whale sharks) Ovoviviparity- the eggs are fertilized, hatched, and developed within the female. No direct nourishment is given after egg production. The offspring eat either newly ovulated eggs, less developed embryos, or siblings, called oophagy. (i.e. Great white, Tiger, and Nurse sharks) Oviparity- the females lay egg cases and after the eggs are secured, there is no longer any protection for them. (i.e. Port Jackson, Zebra, and Swell sharks) Hammerheads have set the world record for the most pups with one being pregnant with 55! (only 52 would have made it)

  5. Shark Eggs • There are a wide variety of shark eggs • Each egg is suited for its individual environment • Most often the egg is see through for the beginning portion and then gradually darkens • None-the-less, you can always see the shark inside if you hold it up to the light

  6. Shark Parental Care Or Lack Thereof

  7. There has been little evidence of shark parental care • The most definitive proof of shark parental care is seen in Port Jackson Sharks • They carry their egg cases in their mouths and bury them in a suitable environment • Until recently this was believed to be the only parental care sharks exhibit

  8. New Cases of Parental Care? • Scalloped hammerheads • In the Red Sea, adults have been seen forming protective rings around pups • Whale Sharks • In 2001 Krishna Pillai reported an adult female whale shark swimming with 16 neonates • May indicate that the young sometimes remain with their mother for an indeterminate period • conserving energy stores by echelon swimming with her? • using her body as a kind of moving hide to provide some protection against predators. • (A review of behavioural ecology of whale sharks (Rhincodon typus). By R. Aidan Martin)

  9. Classic ecological theory • suggests that by producing such large, well-formed young, K-selected mothers greatly increase the survival odds of their young—and thereby, greatly increase their chances of genetic immortality. • But maybe there’s a simpler explanation: • Giving birth to kids that are already big enough to pack off to college may get them out of the mother’s face a little sooner. • (http://www.elasmo-research.org/education/topics/lh_maternity.htm)

  10. Deep Questions • Developmental • Does learning to hunt in the womb (intrauterine cannibalism) give sharks a better ability to hunt after birth than sharks hatched from eggs? • What advantage does the limited adult care of some sharks (Scalloped Hammerheads & Whale Sharks) give to the pups? • Ecological • What changes in the environment trigger the sharks to start mating? • What factors in the environment lead to different types of eggs to form and or internal development to be favored? • Evolutionary • Why did certain species of sharks evolve to show intrauterine cannibalism? • Why did female’s develop skin twice as thick as the male’s skin and the ability to self fertilize? • Physiological • When the males bite the females during mating, are there signals sent to the brain of the females which then cause them to start ovulating? • What structures or chemicals are in the body of the females that can help start and then create the self-fertilized eggs?

  11. What Started This Whole Idea? • Developmental question regarding that… • How does the oviparous species (“egg birth”) embryonic development verses viviparous (“live birth”) embryonic development contribute to the prenatal care of sharks? • Based on research conducted, there is evidence that viviparous species, like whale and hammerhead sharks, may give parental care to their young because of the way in which they receive nutrients from the mother’s placenta. This is an intense connection between mother and her young. Scalloped hammerheads in the Red Sea have been observed forming protective rings around their young and 14 pup whale sharks were observed surrounding an adult female in the Ningaloo Reef in Western Australia. Viviparous species are not as large and strong as oviparous species, indicating why viviparous species may care for their young to increase their success.

  12. Scientists in Germany Have Recently Discovered the 5 Best Songs to Get Sharks "In The Mood"

  13. 5th Place Bob Marley’s No Woman No Cry 2nd Place 4th Place 3rd Place Justin Timberlake’s Rock Your Body Joe Cocker’s You Can Leave Your Hat On James Last’s Traumschiff (German version of the Loveboat theme song)

  14. And Now, The Moment You've All Been Waiting For..... The #1 Song To Get Sharks In The Mood..... IS

  15. Salt-N-Pepa's Push It

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