life history patterns. life history patterns: is a genetically inherited pattern of resource...
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LIFE HISTORY PATTERNS
LIFE HISTORY PATTERNS:
is a genetically inherited pattern of resource allocation (= investment) to that optimizes the passing of genes to the next generation
Different investmentpatterns
FOR REST OF TERM – LIFE HISTORY PATTERNS:
EGG AND SPERM PRODUCTION
SPERM COMPETITION
FERTILIZATION PATTERNS
TYPES OF DEVELOPMENT
LARVAL DISPERSAL STRATEGIES
SETTLEMENT PATTERNS
is a genetically inherited pattern of resource allocation to that optimizes the passing of genes to the next generation
Spawing and
Fertilization
Evolution of Anisogamy
Imagine some Precambrian creature
Produces undifferentiated gametes
Fertilization
G. Parker
Gametes produced come in a variety of sizes
Large Medium Small
Number produced
Mitotic competence
Gamete size
Number produced
Size distribution of gametes produced
External fertilization
Which ones are the most likely to produce offspring?
Combinations
Competence Frequency of contact
Very high Very high Very high
Moderate Low
Very low
Very low Moderate Very high
Low High
Very high
Gamete size
Number produced
After several generations
Selected against
Anisogamy
Spermiogenesis is the final stage of spermatogenesis in which spermatids add tails and become motile
Spermatogenesis is the process by which spearmtids are produced from male germ cells via mitosis and meiosis
FERTILIZATION
TYPES OF SPERM AND EGG RELEASE AND FERTILIZATION
1. Broadcast spawners (= free spawners)
-eggs and sperm are released into the water column - fertilization is external
2. Spermcast spawners
-sperm are released into the water column and taken in by the female-fertilization is internal
3. Copulators
-sperm placed in the body of the female usually with some intromittent orgtan-fertilization is internal
SPAWNING
1. BROADCAST SPAWNING
SPAWNING
1. BROADCAST SPAWNING
Problems for broadcast spawners
How does an animal ensure fertilization by dumping eggs and sperm in the open ocean?
1. Proximity
2. Timing
3. Currents
4. Sperm/egg contact
Boradcast spawners suffer a dilution effect
Quinn and Ackerman. 2011. Limnol Oceanogr. 2011: 176
Boradcast spawners suffer a dilution effect
1. Proximity
How to get around this problem
mussels oysters
2. Timing and synchrony
How to get around this problem
Haliotis asinina
Counihan et al. 2001. Mar.Ecol.Prog.Ser.213:193
2. Timing and synchrony
How to get around this problem
Haliotis asinina
Counihan et al. 2001. Mar.Ecol.Prog.Ser.213:193
2. Timing and synchrony
How to get around this problem
Haliotis asinina
Counihan et al. 2001. Mar.Ecol.Prog.Ser.213:193
2. Timing and synchrony
How to get around this problem
Haliotis asinina
Counihan et al. 2001. Mar.Ecol.Prog.Ser.213:193
2. Timing and synchrony
How to get around this problem
Haliotis asinina
Counihan et al. 2001. Mar.Ecol.Prog.Ser.213:193
Conclusions (Counihan et al. 2001)
1. Spawning season is determined by water temperature
2. Precise time of spawning is influenced by tidal regime
3. Both sexes spawn in response to an evening high tide
4. Males spawn 19 mins before high tide: females 11 mins after
5. More animals spawn in presence of opposite sex.
3. Currents
3. Currents
Patterns of flow – move gametes unpredictably
Advection – mean direction and velocity of a gamete cloud
Diffusion –rate of gamete spreading
Main problem – production of eddies (vortices) – unpredictable and ephemeral
3. Currents
4. Sperm-egg contact
a. Dilution
-is it sperm concentration or egg:sperm ratio?
If sperm and egg are at similar concentrations-sperm :egg ratio is important
Sperm:egg ratio importantSperm concentration
is imporant
Sperm concentration and fertilization
1) Fertilization success more sensitive to sperm concentration
Reduction in egg concentration
Reduction in sperm concentration
Same reduction in fertilization success
Reduction in egg concentration
Reduction in sperm concentration
Final problem
Egg and sperm longevity
Sperm live less than a few hours
Horseshoe crabsSea urchins
Sea starsAscidianshydroids
Eggs live about 3x longer than spermSea urchins
Sea starsAscidians
How can sperm and egg increase the chances of contact?
a) Chemical attractants
How can sperm and egg increase the chances of contact?
a) Chemical attractants
L- Tryptophan in abalone
Tryptophan ‘cloud’
How can sperm and egg increase the chances of contact?
b) Jelly coat
Jelly coat increases the size of the egg and acts as a sperm‘trap’
Fertilization
Spermcast spawning
-mating “by releasing unpackaged spermatozoa to be dispersed to conspecifics where they fertilize eggs that have been retained by their originator.”
Bishop and Pemberton.2006. Integr.Comp.Biol. 46:398
Fertilization
Spermcast spawning
most spongesmany hydroids some corals (Cnidaria)some polychaetes (Annelida),some bivalve Mollusca,Entoprocta, some articulate Brachiopoda, all Ectoprocta, most or all pterobranchs(Hemichordata), most ascidians (Chordata: Tunicata)
Fertilization
Spermcast spawning
In most spermcasters -
Sperm release
Intake by female
Storage of sperm
Fertilization and brooding
Release of competent larvae
Fertilization
Spermcast spawning
Factors influencing spermcasters
1. Longevity of sperm
Species Temperature Half life (h)
Tunicate A 16.5 8
Ectoproct 12, 16, 18 1.2
Tunicate B 15 26.3
22 16.1
Retain ability to fertilize longer than free spawners
Fertilization
Spermcast spawning
Factors influencing spermcasters
2. Conservation of energy
Sperm release
Sperm are inactive or periodically active
Intake by ‘female’
Sperm consistently activeConsequence: Fertilization can happen with fewer sperm at greater distance
Fertilization
Spermcast spawning
Factors influencing spermcasters
3. Sperm storage
-allows accumulation of a number of allosperm
Celleporella hyalina - Several weeks Diplosoma listerianum - 7 weeks
Fertilization
Spermcast spawning
Factors influencing spermcasters
4. Egg development
Celleporella hyalina
Diplosoma listerianum
Sperm release
Intake by ‘female’
Triggering of vitellogenesis
Consequence: Investment in eggs is not wasted.
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