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LIFE HISTORY PATTERNS. Spawning and Fertilization. Evolution of Anisogamy. Imagine some Precambrian creature. G. Parker. Produces undifferentiated gametes. Fertilization. Gametes produced come in a variety of sizes. Large. Medium . Small . Number produced. Mitotic competence.
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Evolution of Anisogamy Imagine some Precambrian creature G. Parker Produces undifferentiated gametes Fertilization
Gametes produced come in a variety of sizes Large Medium Small Number produced Mitotic competence
Size distribution of gametes produced Gamete size Number produced
External fertilization Which ones are the most likely to produce offspring?
Combinations Very high Very high Very high Moderate Very high Very low Moderate Low Low High Very low Very high Competence Frequency of contact
After several generations Selected against Gamete size Number produced
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. Spermcastspawners -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 intromittentorgtan -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
Boradcastspawners suffer a dilution effect Quinn and Ackerman. 2011. LimnolOceanogr. 2011: 176
How to get around this problem 1. Proximity oysters mussels
How to get around this problem 2. Timing and synchrony Haliotisasinina Counihan et al. 2001. Mar.Ecol.Prog.Ser.213:193
How to get around this problem 2. Timing and synchrony Haliotisasinina Counihan et al. 2001. Mar.Ecol.Prog.Ser.213:193
How to get around this problem 2. Timing and synchrony Haliotisasinina Counihan et al. 2001. Mar.Ecol.Prog.Ser.213:193
How to get around this problem 2. Timing and synchrony Haliotisasinina Counihan et al. 2001. Mar.Ecol.Prog.Ser.213:193
How to get around this problem 2. Timing and synchrony Haliotisasinina Conclusions (Counihanet 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. Counihan et al. 2001. Mar.Ecol.Prog.Ser.213:193
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
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 concentration is imporant Sperm:egg ratio important
Final problem Egg and sperm longevity Horseshoe crabs Sea urchins Sea stars Ascidians hydroids Sperm live less than a few hours Sea urchins Sea stars Ascidians Eggs live about 3x longer than sperm
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 In most spermcasters- Sperm release Intake by female Fertilization and brooding Storage of sperm Release of competent larvae
Fertilization Spermcast spawning Factors influencing spermcasters 2. Conservation of energy Sperm release Sperm are inactive or periodically active Intake by ‘female’ Consequence: Fertilization can happen with fewer sperm at greater distance Sperm consistently active
Fertilization Spermcast spawning Factors influencing spermcasters 3. Sperm storage -allows accumulation of a number of allosperm Diplosomalisterianum- 7 weeks Celleporellahyalina- Several weeks
Fertilization Spermcast spawning Factors influencing spermcasters Diplosomalisterianum 4. Egg development Sperm release Intake by ‘female’ Celleporellahyalina Triggering of vitellogenesis Consequence: Investment in eggs is not wasted.
Patterns of Development Nutritional mode 1) Planktotrophy - larval stage feeds This separates marine invertebrates from all others – can feed in dispersing medium - Probably most primitive
Patterns of Development Nutritional mode 2) Maternally derived nutrition a) Lecithotrophy - yolk b) Adelphophagy – feed on eggs or siblings c) Translocation – nutrient directly from parent
Patterns of Development Nutritional mode 3) Osmotrophy - Take DOM directly from sea water
Patterns of Development Nutritional mode 4) Autotrophy - by larvae or photosynthetic symbionts - In corals, C14 taken up by planulae - In Porites, symbiotic algae to egg
Patterns of Development Site of Development 1) Planktonic development - Demersal – close to seafloor - Planktonic – in water column 2) Benthic development - Aparental – independent of parent – encapsulation of embryo - Parental – brooding – can be internal or external
Patterns of Development Dispersal Potential of Larvae 1) Teleplanic - Larval period – 2 months to 1 year + 2) Achaeoplanic – coastal larvae -1 week to < 2 months (70% of littoral species) 3) Anchioplanic - larval period – hours to a few days
1) Fertilization patterns 2) Development patterns Developmental Patterns -Kinds of eggs 3) Dispersal patterns 4) Settlement patterns Holoblastic Isolecithal • • • • • • • • • • • • • • • • • • • • • • Cleavage through entire egg • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Telolecithal Meroblastic • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Cleavage not through entire egg • • • • • • • • • •
1) Fertilization patterns 2) Development patterns Developmental Patterns -Kinds of eggs 3) Dispersal patterns 4) Settlement patterns Isolecithal - Holoblastic Telolecithal - Meroblastic
1) Fertilization patterns 2) Development patterns Developmental Patterns -Kinds of eggs 3) Dispersal patterns 4) Settlement patterns Holoblastic Isolecithal • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Planktotrophic larvae Telolecithal Meroblastic • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Lecithotrophic larvae
LIFE HISTORY TRAITS Fecundity - Total number of offspring (expressed as a number of offspring over a period of time) Three categories of fecundity 1) Potential – number of oocytes in ovary 2) Realized – number of eggs produced 3) Actual – number of hatched larvae CENTRAL TO THIS – FECUNDITY – EXPENSIVE AND DIRECTLY LINKED TO FITNESS
Relationship of fecundity to other traits • Egg size • - Generally egg size 1/fecundity Look at poeciliogonous species Produce both lecithotrophic and planktotrophic larvae Lecithotrophic – egg 6X larger Planktotrophic –6X as many eggs Streblospiobenedicti Same reproductive investment
OFFSPRING SIZE -volume of a propagule once it has become independent of maternal nutrition Egg size – most important attribute in: 1) Reproductive energetics 2) Patterns of development and larval biology 3) Dispersal potential
Effects of Offspring Size 1) Fertilization -some controversy about evolution of egg size Either a) influenced by prezygotic selection for fertilization OR b) post-zygotic selection
Effects of Offspring Size 1) Fertilization One consequence of size-dependent fertilization Low sperm concentration larger zygotes High sperm concentration smaller zygotes (effects of polyspermy) Size distribution of zygotes - function of both maternal investment and of local sperm concentration
Effects of Offspring Size 2) Development Prefeeding period increases with offspring size Feeding period decreases with offspring size
Effects of Offspring Size 2) Development Prefeeding period increases with offspring size Feeding period decreases with offspring size Evidence? Planktotrophs • pre-feeding period • -larger eggs take longer to hatch • in copepods • - in nudibranchs – no effect
2) Entire planktonic period -review of 50+ echinoids – feeding 5 echinoids – non feeding Larval period decreases with increase in egg size But for polychaetes and nudibranchs Nudibranchs Polychaetes Planktotrophic • • • Lecithototrophic • Dev. time • • • • • • • • • • • • • • • • • • • • • • • • Egg size (mm) Egg size (mm)