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Sex and the sea!

Sex and the sea!. Reproduction beneath the waves. X – RATED!. Session outline. Reproduction: the basics Sex underwater Internal vs. external fertilisation. Reproduction: the basics. Why reproduce?

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Sex and the sea!

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  1. Sex and the sea! Reproduction beneath the waves X – RATED!

  2. Session outline • Reproduction: the basics • Sex underwater • Internal vs. external fertilisation

  3. . . . . . . . . . . . . . . . . Reproduction: the basics • Why reproduce? • Every living thing eventually dies. Organisms need to make more of themselves otherwise there would be no life on Earth at all! • How do organisms reproduce? • Usually sexually, but sometimes asexually • Involves the fusing (bringing together) of a male sex cell (SPERM) and a female sex cell (EGG). This is the process of FERTILISATION • This grows and develops into an EMBRYO which goes on to develop into an adult version of its parents after a larval / juvenile life stage Egg cell Fertilisation Embryo

  4. Periwinkle Edible Crab Starfish Barnacle Break Time game… Guess the adult phase

  5. 1. Nauplius 3. Megalopa Edible Crab 2. Zoea Can you guess what these marine animal larvae develop into?

  6. 1. Nauplius 3. Settling Cypris Barnacle 2. Cypris Can you guess what these marine animal larvae develop into?

  7. 1. Trochophore 3. Spat Periwinkle 2. Veliger Can you guess what these marine animal larvae develop into?

  8. 1. Dipleurula 3. Brachiolaria Starfish 2. Bipinnaria Can you guess what these marine animal larvae develop into?

  9. Reproduction: the basics • Fertilisation can be internal and external • INTERNAL FERTILISATION - The male deposits sperm cells inside the female – Usually on land • EXTERNAL FERTILISATION – The male deposits sperm cells onto the egg cells as the female lays them – Usually in water Why do you think organisms living in water usually reproduce using external fertilisation? ? ?

  10. Sex underwater: 1 - A vast environmentDifficult to find mates 2 - Currents, tides and wavesDifficult to have sexual intercourse (copulate) 3 - Risk of predationreduce the risk of being eaten 4 - Availability of resourcesIf in short supply, external fertilisation allows young to spread far and wide 5 - Inability to move Marine organisms have adapted to overcome these difficulties. Let’s look at some examples…

  11. Sex underwater: Finding mates Sperm storage Nautilus Anglerfish • Deep / open sea organisms may encounter potential mates very rarely • Nautilus • Shelled organism related to octopus/squid • Smaller males detach their penis’ which swims off by itself to join to a passing female! She can use the sperm ball attached to the penis whenever she likes • Anglerfish • Males tiny and born without a digestive system • Races to find a female • Bites the female and releases a chemical to fuse the two together

  12. Sex underwater: Sexual intercourse Hammerhead shark Self-fertilisation – ASEXUAL REPRODUCTION Giant clam One big effort – BROADCAST SPAWNING Coral reefs Grunion

  13. Some more reproductive strategies: Sex changing fish! Sneaky spawners! Male pregnancy!

  14. Did you know? The acorn barnacle has the largest penis to body size ratio in the entire animal kingdom! Internal fertilisation still occurs: Inability to move

  15. Did you know? Dolphins are the only organism to have sexual intercourse for pleasure other than humans! Internal fertilisation still occurs:

  16. External vs. Internal fertilisation External Many offspring e.g. broadcast spawning Poor parental care and protection Offspring have a low chance of survival to adulthood Offspring have low chance of survival to adulthood Internal Few offspring Sexual reproduction (copulation) Good parental care and protection Offspring have a high chance of survival to adulthood Offspring have high chance of survival to adulthood

  17. Take home messages • Many marine organisms live in an environment where mates can be hard to find and predators hard to avoid • They have developed some bizarre reproductive strategies to reproduce and avoid being eaten at the same time • Marine organisms tend to use external fertilisation to get around problems such as finding mates, avoiding predation etc… but some use internal fertilisation such as barnacles and dolphins • There are both advantages and disadvantages to external fertilisation

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