Reproductive Strategies

What is fitness?

The reproductive capabilities of a female.

Reproduction in Hagfish

Females lay 20-30 large leathery eggs

Low fecundity, low reproductive success

What are the two life cycle types in lamprey?

Migratory feeding adult

Larvae with non-feeding adult

Reproduction in chimeras

Lay small numbers of benthic eggs with leathery covering

Reproduction in squalomorph sharks?

Produce benthic eggs

Reproduction in mackerel sharks

Placental nutrition, long gestation with low output

What are the trades off for reproduction?

Continued growth vs reproduction

Quality of offspring vs quantity of offspring

Risk of predation vs chance of finding quality food

How does fecundity change over growth?

Increases geometrically with body size

How does fecundity and risks change with age?

Early growth & deferred reproduction lead to higher fecundity, higher chance of mortality

How does probability of offspring survival change with size?

Increases with the size of offspring

Why does offspring survival increase with size?

Larger supply of reserves

Fewer potential predators

Greater feeding efficiency

How does age of mother affect offspring survival in Black Rockfish?

Rockfish produce eggs with a yolk, developing fish use up the yolk until it becomes an oil globule as juveniles

Scale of the oil globule corresponds to age of mother, larger females (older) produce more offspring that are larger and more likely to survive

Productivity impacts in reproduction

Large variability in the availability of nutrients due to seasonal variations, the amount of energy some fish put into their offspring corresponds with the primary productivity

What are the 4 mating system types?

Promiscuous - both sexes mate with multiple partners

Polygynous - males have multiple mates (harem systems)

Polyandry - females with multiple mates (anglerfish)

Monogamy - mating pair remains together over time

Semelparous reproduction frequency?

Single spawning effort

Iteroparous reproduction frequency?

Repeated spawning efforts

What is the cost of parental care?

High energetic costs (reducing fecundity)

What is the benefit of parental care?

Increases probability of offspring survival (reduced predation, increased food access)

What are parental care examples?

Brood hiding

Nest guarding

Internal gestation

Oviparous maternal care?

Egg laying with behavioural care, generally lecithotrophic, external development

Viviparous maternal care?

live birth internal development or placental

What are allee effects?

When reproduction goes to zero before the population size goes to zero - failure of reproduction at low density

What may cause allee effects?

Failure of fertilisation

Inability to find mates

Inbreeding depression

Demographic stochasticity in mate choice

How do deepsea anglerfish solve the low density of mates?

Males attach to females (pump semen into females) and functions to guarantee fertilisation

What are the 4 main methods of fertilisation?

External fertilisation

Internal fertilisation

Surfperches

Buccal fertilisation

What are the sex systems in fish?

Gonochoristic

Hermaphroditic (Simultaneous or sequential)

Protogynous

Sequential hermaphrodism in clownfish

Clowfish pair-bond, form benthic egg masses that they guard. If female is killed then the male becomes a females to pair-bond with another male

Sequential hermaphrodism in Wrasses

presence of a dominant male prevents the largest females from transitioning. If the male is removed then the largest females becomes the male

Gynogenetic reproduction in parthenogenic fish?

Sperm is required for egg development but no fertilisation occurs, daughters are genetic clones of mother

Triploid → diploid

Hybridogenetic reproduction in parthenogenetic fish?

Egg development with fertlisation by male of another species, but male genes are discarded in next generation (diploid eggs)

What are the different types of dimorphism/polymorphism?

Monomorphic

Permanently dimorphic (mature sexes distinguishable)

Seasonally dimorphic (mature sexes distinguishable only during breeding)

Polymorphic