fish reproduction and development coevolved traits for producing another generation that will...

Fish Reproduction and Fish Reproduction and DevelopmentDevelopment

Coevolved traits for producing Coevolved traits for producing another generation that will produce another generation that will produce

another generation...another generation...and anotherand another......and and another...another...

Coevolution of reproduction and Coevolution of reproduction and developmentdevelopment

Bioenergetic equation:Bioenergetic equation:

I = M + I = M + G + RG + R + E+ E

Surplus energy can be spent on Surplus energy can be spent on

GGrowth, rowth,

RReproduction, eproduction,

or some combination of or some combination of GG & & RR

Coevolution of reproduction and Coevolution of reproduction and developmentdevelopment

• Linkage between reproductive traits and development Linkage between reproductive traits and development patternspatterns

• Represent tradeoffs between:Represent tradeoffs between:

– risks risks & & benefitsbenefits of continued of continued growthgrowth vs. vs. reproductionreproduction

– quantityquantity of offspring vs. of offspring vs. qualityquality of offspring of offspring

– risk of predation vs. chance of finding quality foodrisk of predation vs. chance of finding quality food

Octopus larvaeOctopus larvae

Reproductive traits that vary with Reproductive traits that vary with life-history patternslife-history patterns

• Fecundity (no. eggs):Fecundity (no. eggs):– increases geometrically with body sizeincreases geometrically with body size– early growth and deferred reproduction lead to early growth and deferred reproduction lead to

higher fecundityhigher fecundity– early growth and deferred reproduction increase early growth and deferred reproduction increase

probability of dying before reproducingprobability of dying before reproducing


• Size of offspring:Size of offspring:– probability of survival increases with size of probability of survival increases with size of

offspringoffspring• larger supply of reserveslarger supply of reserves

• fewer potential predatorsfewer potential predators

• greater feeding efficiencygreater feeding efficiency

– cost of producing offspring increases with sizecost of producing offspring increases with size– fecundity is reduced as offspring size increasesfecundity is reduced as offspring size increases


• Mating system:Mating system:– Promiscuous Promiscuous - both sexes with multiple partners - - both sexes with multiple partners -

most (common)most (common)– PolygynousPolygynous - males with multiple mates (cichlids) - males with multiple mates (cichlids)– PolyandryPolyandry - females with multiple mates – few - females with multiple mates – few

(Anglerfish, males “parasitize” females(Anglerfish, males “parasitize” females– MonogamyMonogamy - mating pair remains together over - mating pair remains together over

time, long gestation of young (some cichlids, time, long gestation of young (some cichlids, seahorses, pipefish)seahorses, pipefish)

Reproductive frequencyReproductive frequency

• Single spawning effort in Single spawning effort in life (life (semelparoussemelparous), ), – metabolic efficiencymetabolic efficiency

– max. fecunditymax. fecundity

– match offspring to ideal match offspring to ideal growing conditionsgrowing conditions

– overwhelm predatorsoverwhelm predators

– risk of waiting (death)risk of waiting (death)

• Repeated spawning Repeated spawning efforts (efforts (iteroparousiteroparous))– spawn before deathspawn before death

– spread offspring over spread offspring over multiple entry timesmultiple entry times

– reduce fecundity to ensure reduce fecundity to ensure SOME reproductionSOME reproduction

“ “ To love’em and leave ‘em, or not..”To love’em and leave ‘em, or not..”

• Parental careParental care– increases probability of offspringincreases probability of offspring

survivalsurvival• due to reduced predation riskdue to reduced predation risk

• due to increased access to fooddue to increased access to food

– costs energy - reduces fecunditycosts energy - reduces fecundity– takes many formstakes many forms

• brood hiding (behavioral)brood hiding (behavioral)

• nest guarding (behavioral)nest guarding (behavioral)

• internal gestation (physiological)internal gestation (physiological)

Reproductive traits (cont.)Reproductive traits (cont.)

• Parental care, cont.Parental care, cont.– male care givers - mostly behavioral (advantage)male care givers - mostly behavioral (advantage)– female care givers - mostly physiologicalfemale care givers - mostly physiological

• oviparousoviparous – (egg laying) with behavioral care - yolk fed – (egg laying) with behavioral care - yolk fed (lecithotrophy), external development(lecithotrophy), external development

• ovoviviparousovoviviparous – embryo within female, – embryo within female,

yolk-fed, internal devel.yolk-fed, internal devel.• viviparousviviparous – live birth yolk supplemented – live birth yolk supplemented

(matrotrophy), internal development(matrotrophy), internal development

– biparental carebiparental care


• Method of fertilization:Method of fertilization:– most fishes use most fishes use externalexternal fertilization fertilization

• less time and energy in courtship, pair bondingless time and energy in courtship, pair bonding

• increases number of potential matesincreases number of potential mates

• greater fecunditygreater fecundity

– internalinternal fertilization in few groups: fertilization in few groups:• sharks, rays, skates, ratfishes (Chondrichthyes)sharks, rays, skates, ratfishes (Chondrichthyes)

• guppies, mollies, etc. - Poeciliidae, Goodeidaeguppies, mollies, etc. - Poeciliidae, Goodeidae

• surfperches - Embiotocidaesurfperches - Embiotocidae


• Method of fertilization, Method of fertilization, cont.cont. : :– internal fertilization requiresinternal fertilization requires

• lengthy courtship, preparation for matinglengthy courtship, preparation for mating• intromittent organintromittent organ

– claspers (pelvic fins) in Chondrichthyesclaspers (pelvic fins) in Chondrichthyes– modified anal fin in poeciliids, goodeidsmodified anal fin in poeciliids, goodeids– modified genital papilla in embiotocidsmodified genital papilla in embiotocids

• male structure for storing sperm (seminal vesicle)male structure for storing sperm (seminal vesicle)

– buccalbuccal fertilization—sperm swallowing?? Yep! fertilization—sperm swallowing?? Yep!

Callichthyid catfish (Callichthyid catfish (CorydorasCorydoras) Why, why...?) Why, why...?


• Gender system:Gender system:– most are most are gonochoristicgonochoristic (single sex, fixed at maturity) (single sex, fixed at maturity)– some are some are hermaphroditichermaphroditic

• simultaneoussimultaneous hermaphrodites function as male and female hermaphrodites function as male and female at same time (23 families; ex. Anguilliformes, eels; at same time (23 families; ex. Anguilliformes, eels; Atheriniformes, killifish)Atheriniformes, killifish)

• sequential sequential hermaphrodites start life as one sex, change sex hermaphrodites start life as one sex, change sex after maturity (after maturity (

– protandrous: male first, female later protandrous: male first, female later – protogynous: female first, male later (most common, Wrasses)protogynous: female first, male later (most common, Wrasses)


• Gender system (Gender system (contcont.):.):– Parthenogenetic:Parthenogenetic:

• gynogeneticgynogenetic – sperm needed for egg development, – sperm needed for egg development, but mating without fertilization (triploid - triploid but mating without fertilization (triploid - triploid eggs), result is daughters are genetic clones of eggs), result is daughters are genetic clones of mothers (Amazon molly, mothers (Amazon molly, Poecilia formosaPoecilia formosa))

• hybridogenetichybridogenetic - egg development with fertilization - egg development with fertilization by males of by males of otherother species, but male genes discarded species, but male genes discarded at next generation (diploid - haploid eggs)at next generation (diploid - haploid eggs)


• Secondary sexual characteristicsSecondary sexual characteristics– monomorphicmonomorphic (males and females alike) (males and females alike)– permanently permanently dimorphicdimorphic (mature sexes (mature sexes

distinguishable)distinguishable)– seasonally dimorphic (mature sexes seasonally dimorphic (mature sexes

distinguishable only at spawning time)distinguishable only at spawning time)– polymorphicpolymorphic

Reproductive traitsReproductive traits

• Reproductive morphology, bony fishes:Reproductive morphology, bony fishes:– male: testes -> vas deferens -> urogenital poremale: testes -> vas deferens -> urogenital pore– female: ovary -> oviduct -> urogenital porefemale: ovary -> oviduct -> urogenital pore


• Reproductive morphology, cartilaginous Reproductive morphology, cartilaginous fishes:fishes:– male: testes -> Leydig’s gland -> seminal male: testes -> Leydig’s gland -> seminal

vesicle -> cloaca -> claspersvesicle -> cloaca -> claspers

– female: ovary -> ostium tubae -> oviduct -> female: ovary -> ostium tubae -> oviduct -> shell gland -> [uterus] -> cloacashell gland -> [uterus] -> cloaca

FemaleFemaleMaleMale

Behavioral adaptations for Behavioral adaptations for reproductionreproduction

• Courtship - color, size, movements importantCourtship - color, size, movements important

• Spawning site selectionSpawning site selection– substrate spawners - broadcastsubstrate spawners - broadcast– water-column spawners - broadcastwater-column spawners - broadcast– site preparerssite preparers– internal fertilization - also may be habitat-internal fertilization - also may be habitat-

specificspecific


• Care-giving behavior - Balon’s classification:Care-giving behavior - Balon’s classification:– Non guardersNon guarders– GuardersGuarders– BearersBearers

See handout! Much diversity here!See handout! Much diversity here!


• Care-giving behavior - Balon’s classification:Care-giving behavior - Balon’s classification:– Non guardersNon guarders

• open substrate spawnersopen substrate spawners

• brood hidersbrood hiders

– GuardersGuarders– BearersBearers


• Care-giving behavior - Balon’s classification:Care-giving behavior - Balon’s classification:– Non guardersNon guarders– GuardersGuarders

• substratum chooserssubstratum choosers

• nest spawnersnest spawners

– BearersBearers


• Care-giving behavior - Balon’s classification:Care-giving behavior - Balon’s classification:– Non guardersNon guarders– GuardersGuarders– BearersBearers

• GuardersGuarders

• BearersBearers– externalexternal

– internalinternal

FishFishDevelopmentDevelopment

• Balon’s theory of Balon’s theory of

saltatorysaltatory development:development:– Development occurs as a Development occurs as a

series of discrete transitions series of discrete transitions in form and function in form and function ((thresholds thresholds or or metamorphoses), with metamorphoses), with periods of change in size periods of change in size ((periodsperiods) between thresholds) between thresholds

Developmental stages in fishesDevelopmental stages in fishes

PERIODSPERIODS

EMBRYOEMBRYO

LARVALARVA

JUVENILEJUVENILE

ADULTADULT

SENESCENTSENESCENT

THRESHOLDSTHRESHOLDS

fertilizationfertilization

exogenous feedingexogenous feeding

full fin development, full fin development, body shape of adultbody shape of adult

reproductionreproduction

cessation of growthcessation of growth, , fertilityfertility

Developmental stages in fishesDevelopmental stages in fishes

• Advantages of Advantages of saltatorysaltatory (unique stages) (unique stages) development?development?– separation of life stagesseparation of life stages– niche specificity adapted to sizeniche specificity adapted to size

• food acquisitionfood acquisition

• predator avoidancepredator avoidance

• temperature optimizationtemperature optimization

• others...others...

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