Eve s Testicle: Examples & Lessons. Jack-Attack & Gin-4-the-WIN

Transcription

1 Eve s Testicle: Examples & Lessons Jack-Attack & Gin-4-the-WIN

2 Slime Mold Sex determined by 3 genes (A1-13, B1-13, C1-3) Each slime can produce 8 different sex cells (2*2*2) 507+ combinations (aka sexes) Reproduces by releasing spores from cytoplasm

3 Number of Sexes Purpose of sex cell: Find, recognize, fuse with suitable sex cell Why is a new sex advantageous? A 3rd can fuse with 1 and 2 (more than an old sex), genes spread until equal representation Exoticism - it is new and exciting (favorable for mating) A large number of sexes simultaneously increases the probability of finding a mate while reducing the risk of inbreeding

4 Challenges of Multiple Sexes Endosymbiotic theory of mitochondria and chloroplasts - only one parent should pass down DNA or the DNA in the organelles may not be compatible But what about the slime mold? Internal mechanism to destroy one of the mata genes Another exception: Mushrooms and ciliates swap half a nucleus to become identical twins Able to produce thousands of different sexes because they don t need to regulate mitochondrial inheritance

5 Green Alga Isogamous Reproduction through fusion of gametes that are similar in size/structure

6 Sex Cells of Different Sizes Having two bigger sized gametes fuse is advantageous because the zygote will be larger and more viable, so why have two different sizes? Big sex cells are easier to find Different sized sex cells can only arise if one gets smaller while the other gets bigger Take up more space Release more attractants Little sex cells are produced in larger quantities There s no evidence that the evolution of big / small has to do with mitochondrial inheritance

7 Sea Hares Hermaphrodites: Having both sex organs

8 Types of Hermaphrodites Orgies: everybody plays both parts Taking turns (swapping genders) Permanently fusing genitalia Slugs hanging off trees

9 Why Hermaphrodites? Only theories - there are no clear ecological associations that reliably occur with the trait Self-fertilization is good in low densities Could be worth it when there s no pushing force to have two sexes (beautiful flowers need to be pollinated) Compare to wind-pollinated plants: doesn t matter if they are beautiful; in fact it might be better to have fruit so animals carry seeds Costly to evolve a second reproductive system, not always advantageous Side note: populations can combine hermaphrodites with males, females, or both

10 Green Spoon Worm Androecium Small man room Male 200,000 times smaller than female Faster maturation reproduce sooner, able to spend more energy finding females (who are spread out and sedentary)

11 Environmental Sex Determination Green spoon worm: worm larva is sexless at first - if it meets a female, it becomes male After 3 weeks without a female, it becomes a female Reptiles: temperature of egg incubation Tropical insect (S. sjoestedtı): infection of a fungus makes eggs female

12 Social Sex Determination Flexible gender when reproductive success depends greatly on circumstances C. fornıcata change sex during stacked orgies O. puerılıs: 2 mates go back and forth, depending on size (the smaller one always becomes the male)

13 Spotted Hyena Female dominant Sex: retract clitoris (fold it up) so male can enter Birth canal is a crazy shape Birth: clitoris ruptures >10% lethality siblicide

14 Why and How? Not sure on either! Maybe Greeting ceremonies a. b. Inspect each other s members Exert dominance 2. Resist unwanted advances a. b. Sex requires full cooperation Not likely - little evidence of rape in this species Androgen exposure: linked to aggression, causes genital abnormalities With more aggression, females are higher ranking become pregnant younger and more frequently, offspring survival rate is 2x as high Stronger argument than the idea that more aggression promotes siblicide

15 Sex Organs Internal fertilization - often accompanied with evolution of a penis Crazy varieties! S. amıcorum - male genitalia inside mouth: extraspecial kiss P. nautılus - male, never seen, fires off his penis and it takes independent life inside female

16 Child Care - Not Just for Mothers Leeches: hermaphrodites guard egg; some species carry it in a pouch, some even catch worms to feed it Green poison arrow frogs: male keeps eggs wet in a puddle and sits on them, drops off tadpoles into pools Spraying characid: lays eggs out of water by jumping near a blade of grass or the underside of a leaf Male stays to splash eggs with tail Dayak fruit bat: males and females nurse

17 Review of Themes - You Won t Find Any Rules The positives and negatives of having more than 2 sexes in a species Why different sized sex cells arise instead of isogamy The theoretical advantages and disadvantages of hermaphrodites The difference between environmental and social sex determination Why flexible gender is advantageous The definition of internal fertilization and why it drives evolution of a penis The diversity of child care across species

18 When you gaze at a couple and wonder What trait makes him him and her her, Beware, for it s easy to blunder And be false in what you aver. Some creatures change sex before teatime, Some others find two sexes dull, And that virile male fish has no free time He s got all his kiddies to lull. When it comes to the topic of gender, Mother Nature s been having some fun. Take nothing for granted! Remember, You won t find any rules - not one!