Spawning and Fertilization

Report
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
Growth
Reproduction
Respiration
Feeding
Mate Seeking
Defense
Growth
Reproduction
Respiration
Feeding
Mate Seeking
Defense
Different investment
patterns
FOR REST OF TERM – LIFE HISTORY PATTERNS:
is a genetically inherited pattern of resource allocation to that optimizes the
passing of genes to the next generation
EGG AND SPERM PRODUCTION
FERTILIZATION PATTERNS
SPERM COMPETITION
TYPES OF DEVELOPMENT
LARVAL DISPERSAL STRATEGIES
SETTLEMENT PATTERNS
Spawing
and
Fertilization
Evolution of Anisogamy
Imagine some Precambrian creature
G. Parker
Produces undifferentiated gametes
Fertilization
Gametes produced come in a variety of sizes
Large
Number
produced
Medium
Small
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
Very low
Moderate
Very high
Moderate
Low
Low
High
Very low
Very high
Competence
Frequency of contact
After several generations
Selected against
Gamete size
Number produced
Anisogamy
Spermatogenesis is the process by which spearmtids are produced from male
germ cells via mitosis and meiosis
Spermiogenesis is the final stage of spermatogenesis in which spermatids add
tails and become motile
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
How to get around this problem
1. Proximity
mussels
oysters
How to get around this problem
2. Timing and synchrony
Haliotis asinina
Counihan et al. 2001. Mar.Ecol.Prog.Ser.213:193
How to get around this problem
2. Timing and synchrony
Haliotis asinina
Counihan et al. 2001. Mar.Ecol.Prog.Ser.213:193
How to get around this problem
2. Timing and synchrony
Haliotis asinina
Counihan et al. 2001. Mar.Ecol.Prog.Ser.213:193
How to get around this problem
2. Timing and synchrony
Haliotis asinina
Counihan et al. 2001. Mar.Ecol.Prog.Ser.213:193
How to get around this problem
2. Timing and synchrony
Haliotis asinina
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.
Counihan et al. 2001. Mar.Ecol.Prog.Ser.213:193
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
2
é
æ y2u2
z-h) u 2 ö
Qu
(
êexp- ç
÷ + exp c(x,y,z) =
+
2 2
2 2 2
2 2 2 ÷
ç
2pa ya z u x êë
2a z u x ø
è 2a y u x
2
æ y2u2
z-h) u 2 öù
(
ç 2 2 2 +
÷ú
2 2 2 ÷
ç 2a u x
2a z u x øúû
è y
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
Horseshoe crabs
Sea urchins
Sea stars
Ascidians
hydroids
Sea urchins
Sea stars
Ascidians
Sperm live less than a few hours
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
most sponges
many 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
Fertilization and brooding
Storage of sperm
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’
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
Celleporella hyalina - Several weeks
Diplosoma listerianum - 7 weeks
Fertilization
Spermcast spawning
Factors influencing spermcasters
Diplosoma listerianum
4. Egg development
Sperm release
Intake by ‘female’
Celleporella hyalina
Triggering of vitellogenesis
Consequence: Investment in eggs is not
wasted.
Next time : Sperm Competition

similar documents