Reproductive Strategies Flashcards
(24 cards)
How do Hagfish reproduce?
Females lay 20-30 (3cm) leathery eggs (oviparous)
How do chimeras (Chondrichthyes) reproduce?
Lay small number of benthic eggs with leathery covering
What does reproduction look like in requiem and mackerel sharks?
Viviparous
Low gestation (1-2 years)
Low number of offspring
Internal fertilisation
How do rays and squalomorph sharks reproduce?
Lay benthic eggs encased in a leathery covering
How has reproduction in teleosts led to speciation?
Sympatric speciation through diversity of habitat use and mating systems
What are the trade offs in reproduction and development in teleosts?
Risks and benefits of continued growth vs. reproduction.
Quantity of offspring vs. quality of offspring.
Risk of predation vs. chance of finding food.
What factors influence fecundity in teleosts?
Increases geometrically with size.
Early growth and deferred reproduction lead to higher fecundity, higher chance of mortality.
What influences the probability of offspring surviving in teleosts?
Larger supply of reserves.
Fewer potential predators.
Greater feeding efficiency.
What are the different types of mating systems in teleosts?
Promiscuous.
Polygamous.
Polyandry.
Monogamy.
What is a promiscuous mating system and what species is it found in?
Both sexes with multiple partners.
Example: Grouper
What is a polygynous mating system and what species is it found in?
Males with multiple mates.
Example: Cichlids
What is a polyandry mating system and what species is it found in?
Females with multiple mates.
Example: anglerfish
What is a monogamy mating system and what species is it found in?
Mating pair remains together over time, long gestation of young.
Examples: Seahorses, pipefish
What is the name of single spawning effort and what are the characteristics of it?
Semelparous:
- Metabolic efficiency
- Max. Fecundity
- Match offspring to ideal growing conditions
- Risk of waiting
What is the name of repeated spawning efforts and what are the characteristics of it?
Iteroparous:
- Spawn before death
- Spread offspring over multiple entry times
- Reduce fecundity to ensure some reproduction
What is the reproductive strategies of oncorhynchys?
Stream form iteroparous and diadrmous form iteroparous (brown trout).
Diadromous semelparous (King salmon).
How much time and energy to invest in young?
Parental care:
- Increases probability of offspring survival:
- Due to reduced predation risk
- Due to increased access to food
- Costs energy - reduced fecundity
- Takes many forms:
- Brood hiding (behavioural)
- Nest guarding (behavioural)
- Internal gestation (physiological)
What is viviparous and oviparous?
Oviparous: (egg laying) with behavioural care - generally yolk fed (lecithotrophic), external development
Viviparous: live birth yolk supplement (matrotraphy), internal development.
- Placental (Some sharks and rays) aplace (oophagy)
What is the allele effect?
When reproduction goes to zero before the population size goes to zero, due failure of reproduction at low density:
- Failure of fertilisation
- Inability to find mates
- Inbreeding depression
- Demographic stochasticity in mate choice
What are the methods of fertilisation in fish?
- Most fishes use external fertilisation:
- Less time and energy in courtship
- Increases number of potential mates
- Greater fecundity
- Internal fertilisation in few groups: lengthy courtship, preparation: sharks, rays, skates, rat fishes (Chondrichthyes); guppies, mollies
What sex determination is found in fish?
- Most a gonochoristic (single sex, fixed at maturity)
- some are hermaphroditic: simultaneous hermaphrodites; sequential hermaphrodites
What are simultaneous hermaprhodites? Give an example:
Function as female and male at the same time.
Example: Anguilliformes (eels)
What are sequential hermaphrodites? Give an example:
Start life as one sex, change sex after maturity:
- Protoandrous: male first, female later (clown fish)
- Protogynou: female first, male later (most common, wrasses)
- Parthenogenic (female only)
What are parthenogenetic fish?
Gynogenetic: Sperm needed to stimulate egg development, but mating without fertilisation - females are genetic clones of mothers
Hybridogenetic: egg development with fertilisation by males of other species, but males genes are discarded at the next generation
