Sperm Competition

1
Sperm Competition
2
Male-Male Competition

• Andersson, 1994 Sexual Selection
• 5 fundamental areas of male-male competition
• Scrambles
• Endurance Rivalry
• Contests
• Sperm competition
• Mate choice (Female choice)

3
Sperm Competition

• Competition between the sperm of 2 or more males
  within the reproductive tract of the female
• Typically Post copulatory sperm competition
• Competition between males after copulation
• With few ova huge battle
• promiscuity go for broke
• Involves
• Physiological events that occur after
  insemination
• Behaviors before after copulation
• Morphology

4
The Father of Sperm Competition

• Geoff Parker, 1970
• Studied sexual selection in Yellow Dungfly
• Looked at patterns of male-male competition

5
Yellow Dungfly
6
Whats poo got to do with it

• Female arrives at dung patty ready to mate
• After copulation lays eggs on dung
• Males mount copulate with female as soon as she
  arrives
• Larger males removes male from female copulates
  with her
• Females mate with multiple males throughout day

7
Cow Patties
8
Yellow Dungfly
9
Parkers Observations

• Under such extreme male male competition Parker
  realized competition between males continues
  through action of their sperm
• Copulation is not enough, sperm must make it to
  the egg
• Defined sperm competition
• The competition between ejaculates of different
  males for the fertilization of a females eggs

10
(No Transcript)
11
Parkers Observations

• Sexual selection occurs in the reproductive tract
• Fertilization not copulation is the driving force
• Males win by
• Inseminating more sperm per ejaculate
• Faster swimming sperm
• Inseminate moderate amounts of sperm remove
  sperm from the last guy
• Disabling rival sperm
• Sperm competition results in opposing selection
  forces in males

12
The Trade-off

• Selection favors BOTH
• Males that fertilize females that have been
  inseminated by other males
• Males who prevent females they have inseminated
  from being fertilized by another male
• Results in counter adaptations among competing
  male strategies
• Ex producing larger ejaculates vs better mate
  guarding strategies
• What?
• Males want to go around fertilize as many
  females as possible, but this is hard to do while
  they are mate guarding

13
Darwin Sperm Competition
14
2 General categories of Sperm Competition

• Adaptations that preventing rival sperm from
  copulating with the mate
• Mate guarding, sequestering, frequent copulation,
  production of mating plug, displacing rival sperm
• Adaptations that increase the Ability of one
  males sperm to outcompete the sperm of another
  male
• production of abundant sperm, fast sperm

15
Cuckoldry

• Female infidelity
• Derived from cuckoo
• Male loses some of his reproductive fitness to
  another male

16
(No Transcript)
17
Sperm Precedence

• The sperm that fertilizes the egg effected by
  the order of fertilization

18
Sperm Precedence

• X rayed hapless insects to render them sterile
  without killing the sperm
• Allows egg to be fertilized but not develop
• Alternate mating with sterile fertile males to

19
Sperm Precedence

• First male precedence
• First male fertilizes the majority of eggs
• Last male precedence
• Last male fertilizes the majority of eggs
• Ch 6 promiscuity

20
Sperm Competition

• Adaptations that preventing rival males from
  copulating with the mate
• Mate Guarding

21
Mate Guarding

• Male increases the amount of time he spends in
  close association with a fertile female
• Male guards female partners from mating with
  other males
• Tactic for reducing or preventing sperm
  competition
• Typically occurs when female is receptive for a
  short time period
• Costs of mate guarding
• Interferes with male foraging
• Vulnerable to predators

22
Sand Martin
23
Sand Martin

• Male guards female 7-8 days
• Begins few days before she lays first egg
• Male remains next to female during her fertile
  period
• Male presence reduces risk other males copulating
  with female

24
Red-winged Blackbird

• David Westneat
• Male guards females
• Male experimentally removed from territory
• Female copulations with other males increased
  100X
• Males Compromise guarding for foraging time
• When males given food paternity went up

25
Mate guarding strategies

• Mate grasping
• Prolonged copulations
• Frequent Copulations
• Mate sequestering
• Mating plugs

26
Yellow DungflyMate Grasping
Male remains on females back as she lays eggs
27
Pre-copulatory Guarding

• Occurs in species where the first male has the
  best chance fertilizing the females egg

28
Freshwater Shrimp

• Males use specialized legs to carry females
  around
• Males attach to female 9 days before she is
  receptive

29
Mate Guarding- Amplexus

• Salamanders Frogs

30
Mate Guarding- Prolonged Copulation

• Male females remain in copulation
• May last hours to days
• Male prevents other males by staying attached

31
Yellow Dungfly
Prolonged copulationmale remains with female
40min
32
Prolonged Copulation
33
Frequent Copulations

• Male who increases copulation events with female
  prevents mating with other males
• Animals frequently mate more often than necessary
  for fertilization
• Lions, sea birds, birds of prey
• 10-100x

34
Mate Guarding- Frequent Copulation

• Giant water bug aka toe biter
• Male fertilizes females eggs
• As female lays eggs she sticks them to the males
  back
• Lays 1-2 eggs at a time
• Cycle can last up to 36 hours (144 eggs)
• Male fertilizes over 99 of eggs

35
Giant Water Bug
36
Days.
37
Finding food takes precedence
38
Frequent Copulations

• Mountain Lion
• Ave 9 copulations per hour

39
Mate Sequestering

• Male limits female contact with other males by
  isolating her
• Physical isolation
• Chemical isolation

40
Mate Sequestering Physical Isolation
41
Mate Sequestering Physical Isolation

• Douglas Fir Bark Beetle
• Male sequesters female in gallery

42
Mate Sequestering Chemical isolation

• Reducing Attractiveness of mates
• Anti-aphrodisiac
• Substances that reduce the females attractiveness
• Ex. Make her smell like a male
• Reduce her pheromonal output

43
Chemical Mate Guarding

• Green veined white butterfly
• Males inject methyl salicylate along with sperm
• Chemical compound derived from host plant
• Smell repels other males

44
Green veined white butterfly
45
Spider- Linyphia litigiosa

• Male disrupts females chemical signals
• Male that finds virgin female will reduce
  evaporation of attractive pheromones from her web
  by packing it into a tight mass

46
Central American Bee

• Centris adani
• Mandibular gland rubs secretions onto female
  makes her smell like a male
• Conceals female

47
Darkling Beetle

• Male rubs anti-aphrodisiac pheromone with
  genitals
• Makes female less attractive to other males

48
Mating Plugs

• Aka copulatory plugs
• Male produced substances or structures which are
  transferred to the female after copulation
• Seal genital opening
• Ex guinea pig, chimpanzee, lemur, masked palm
  civet,

49
Red-sided Garter Snake
50
Red-sided Garter Snake

• Intense male competition
• Male produces gelatinous secretion in ejaculate
• Secretion hardens in the female oviduct

51
(No Transcript)
52
Ground Squirrels

• Intense competition for females
• Male emerges from hibernation first
• Testes grow
• Females emerge within 4 days are receptive
• 1-2 hours

53
Mating Plugs
54
Mating Plugs
55
Orb Spider Argiope bruennichi
56
Orb Spider Argiope bruennichi

• Male transfers sperm packet to female
  reproductive tract using pedipalp
• Pedipalp breaks off in female created mating
  plug

57
Orb Spider Argiope bruennichi
58
Honey Bee

• Uses own body as a copulatory plug
• Male dies after reproduction
• Harvester ant

59
Fly with no common name

• Ceratopogonid Johannseniella nitida
• Tiny male crawls into female genital opening to
  create mating plug

60
Ring-tailed Lemur
61
(No Transcript)
62
Other Functions of Mating Plugs

• Sperm storage reservoir
• Reduce leakage
• Humans?

63
Displace Rival Sperm

• displace a previous males sperm
• Mechanism for last male precedence
• Last male fertilizes the majority of the
  offspring by removing previos males sperm
• Adaptations
• Physical
• Chemical

64
Black-winged Damselfly

• Females mate with multiple males within a few
  hours of each other
• Sperm storage in spermotheca
• Male penis shaped like scrub brush
• During copulation male abdomen pumps up down
  scrubbing out the sperm of other males
• 90-100 of sperm removed

65
Whats a Spermatheca?
66
Black-winged Damselfly
67
Cloaca Pecking

• Dunnocks
• Female mates with multiple males
• Female exposes cloaca to male
• Male pecks at female cloaka 30 times

68
http//jenniferleah.blogspot.com/2006/04/sperm-com
petition-in-dunnocks.html