LIFE HISTORY PATTERNS

Spawning and Fertilization

Evolution of Anisogamy Imagine some Precambrian creature Produces undifferentiated gametes Fertilization G. Parker

Gametes produced come in a variety of sizes LargeMediumSmall 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 Moderate Low Very low Moderate Very high Low High Very high

Gamete size Number produced After several generations Selected against

Anisogamy

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 Limnol Oceanogr. 2011: 176

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 Mar.Ecol.Prog.Ser.213:193

2. Timing and synchrony How to get around this problem Haliotis asinina Counihan et al Mar.Ecol.Prog.Ser.213:193

2. Timing and synchrony How to get around this problem Haliotis asinina Counihan et al Mar.Ecol.Prog.Ser.213:193

2. Timing and synchrony How to get around this problem Haliotis asinina Counihan et al Mar.Ecol.Prog.Ser.213:193

2. Timing and synchrony How to get around this problem Haliotis asinina Counihan et al 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

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 important Sperm concentration is imporant

Final problem Egg and sperm longevity Sperm live less than a few hours Horseshoe crabs Sea urchins Sea stars Ascidians hydroids Eggs live about 3x longer than sperm Sea urchins Sea stars Ascidians

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 Integr.Comp.Biol. 46:398

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 2. Conservation of energy Sperm release Sperm are inactive or periodically active Intake by ‘female’ Sperm consistently active Consequence: 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.

PROPAGULES AND OFFSPRING

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, C 14 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 + 3) Anchioplanic - larval period – hours to a few days 2) Achaeoplanic – coastal larvae -1 week to < 2 months (70% of littoral species)

Developmental Patterns -Kinds of eggs Isolecithal Telolecithal Cleavage through entire egg Cleavage not through entire egg Holoblastic Meroblastic 1) Fertilization patterns 2) Development patterns 3) Dispersal patterns 4) Settlement patterns

Developmental Patterns -Kinds of eggs Isolecithal - HoloblasticTelolecithal - Meroblastic 1) Fertilization patterns 2) Development patterns 3) Dispersal patterns 4) Settlement patterns

Developmental Patterns -Kinds of eggs Isolecithal Telolecithal Holoblastic Meroblastic Planktotrophic larvae Lecithotrophic larvae 1) Fertilization patterns 2) Development patterns 3) Dispersal patterns 4) Settlement patterns

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 1)Egg size - Generally egg size  1/fecundity Look at poeciliogonous species Streblospio benedicti Produce both lecithotrophic and planktotrophic larvae Lecithotrophic – egg 6X larger Planktotrophic –6X as many eggs 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 1)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 Dev. time Egg size (  m) NudibranchsPolychaetes Planktotrophic Lecithototrophic

Intraspecific comparisons Larger larvae result in longer lifetimes e. Ascidians and urchins Dev. time Egg size (  m)

POST -METAMORPHOSIS Does egg size affect juvenile size? Echinoids Nudibranchs Conus a.Planktotrophs Size at metamorphosis is independent of egg size b. Non-feeding larvae H. erythrogramma -used for post-metamorphic survival -most maternal investment (lipid) -not necessary for larval development

POST -METAMORPHOSIS Does egg size affect juvenile size? b. Non-feeding larvae Bugula -larval size affects - post settlement mortality - growth -reproduction -offspring quality -need energy to develop feeding structures – 10 – 60% of reserves

Summary of Offspring Size Predictions -closer to metabolic minimum 1)Species with non-feeding larvae -greatest effect is on post-metamorphic survival 2) Sources of mortality - physical, disturbance, stress – size independent - biological sources – size dependent 3) Offspring size - very different effects among populations

SOURCES OF VARIATION IN OFFSPRING SIZE 1) Offspring size varies a) within broods b) among mothers c) among populatioins 2) Within populations a) stress – salinity, temperature, food availability, pollution b) maternal size - +ve correlation

3) Among populations a) habitat quality – poorer habitat results in smaller offspring b) latitudinal variation Bouchard & Aiken 2012

3) Among populations a) habitat quality – poorer habitat results in smaller offspring b) latitudinal variation Bouchard & Aiken 2012

OFFSPRING SIZE MODELS Same basic features 1) Trade off in size and number of offspring 2) Offspring size-fitness function 1) Trade off in size and number of offspring N =c/S c = resources N = number S = Size Refers to energetic costs to mother not energy content of eggs Size:energy content more variable

OFFSPRING SIZE MODELS Same basic features 1) Trade off in size and number of offspring 2) Offspring size-fitness function 1) Trade off in size and number of offspring -other costs may be involved e.g. packaging of embryos e.g. brood capacity of the mother

OFFSPRING SIZE MODELS Same basic features 1) Trade off in size and number of offspring 2) Offspring size-fitness function - Focused on planktonic survival Decrease in size Longer planktonic period Higher mortality

OFFSPRING SIZE MODELS Same basic features 1) Trade off in size and number of offspring 2) Offspring size-fitness function Other effects- fertilization rates - facultative feeding - generation time - post metamorphic effects VARIATION IN OFFSPRING SIZE AFFECTS EVERY LIFE HISTORY STAGE

SUMMARY OF EFFECTS Planktotrophs - Strong effects of offspring size on life history stages 1) Fertilization in free (broadcast) spawners 2) Larger eggs result in larvae that spend less time in the plankton 3) Larger larvae feed better

VARIATION IN OFFSPRING SIZE AFFECTS EVERY LIFE HISTORY STAGE SUMMARY OF EFFECTS 2. Non-feeders - Strong effects of offspring size on life history stages 1) Fertilization success 2) Developmental time 3) Maximize larval lifespan 4) Postmetamorphic performance 5) Subsequent reproduction and offspring size

VARIATION IN OFFSPRING SIZE AFFECTS EVERY LIFE HISTORY STAGE SUMMARY OF EFFECTS 3. Direct developers - Strongest effects of offspring size on life history stages - Mothers may be able to adjust provisioning to local conditions