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

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.

Next time : Sperm Competition