Reproduction in fishes. Reproduction what defines male vs. female?

Reproduction in fishes

Reproduction

what defines ‘male’ vs. ‘female’?

Reproduction

what defines ‘male’ vs. ‘female’? – reproductive investment

sexual strategies:females must be ‘careful’ in mate selection due to cost

Reproduction

what defines ‘male’ vs. ‘female’?

sexual strategies:females must be ‘careful’ in mate selection due to costmale investments in reproduction :

advertisement, colors, tubercules, kypes, displaysnest building, territorial defenseparental care, brood guarding

Reproduction

bioenergetics: C = E + M + G + S + R

C – consumptionE – excretionM – metabolismG – growthS – storageR – reproduction

Reproduction

sexual strategies: females must be ‘careful’ in mate selection due to cost

- energy investment in eggs- migration, brooding

male investments in reproduction :- advertisement, colors, tubercules, kypes, displays- mate competition- nest building, territorial defense, migration- parental care, brood guarding

Anatomy

hagfish, lamprey: single gonadsno ducts; release gametes into body cavity

Anatomy

hagfish, lamprey: single gonadsno ducts; release gametes into body cavity

sharks: paired gonadsinternal fertilizationsperm emitted through cloaca, along grooves in claspers

Anatomy

hagfish, lamprey: single gonadsno ducts; release gametes into body cavity

sharks: paired gonadsinternal fertilizationsperm emitted through cloaca, along grooves in claspers

chimaeras, bony fishes: paired gonadsexternal and internal fertilizationsperm released through separate opening

Anatomy

hagfish, lamprey: single gonadsno ducts; release gametes into body cavity

sharks: paired gonadsinternal fertilizationsperm emitted through cloaca, along grooves in claspers

chimaeras, bony fishes: paired gonadsexternal and internal fertilizationsperm released through separate opening

most teleosts: ova maintained in continuous sac from ovary to oviductexceptions: Salmonidae, Anguillidae, Galaxidae, non-

teleosts - these release eggs into body cavity when ripe

Anatomy

in general: gametes produced only during spawning seasongonads reduced during non-reproductive season

Timing and location of spawning

strategy: avoid competition for spawning habitatmaximize access to food for offspring minimize access to offspring by predators

Timing and location of spawning

strategy: avoid competition for spawning habitatmaximize access to food for offspring minimize access to offspring by predators

example: Lake Champlainanadromous – salmoncatadromous – eelsfall spawners – lake trout, whitefishspring spawners – smeltlittoral spawners – sculpins, sunfishes, bassesstream spawners – suckers, darters, minnows, sturgeonpelagic eggs – burbot

Reproduction

fecundityegg size and number inversely relatedegg number directly related to female size (within species)

related to food supply, competition= population-regulating mechanism

Reproduction

fecundityfractional spawners – produce eggs continuously,

spawn frequentlybatch spawners – single reproductive season

release all eggs in a short period

Reproduction

onset of reproductionmales typically mature earlier and smaller than femalesmature earlier if survival and growth are lowstable environment – delayed reproduction

Reproduction

onset of reproductionmales typically mature earlier and smaller than femalesmature earlier if survival and growth are lowstable environment – delayed reproduction

survivorshiphigh if egg production is low, and vice versahigh fecundity fish respond more rapidly to change

Reproduction

frequency of reproductionsemelparity - spawn and then die

- huge investment in egg production

iteroparity - repeated reproduction allows compensation for a “bad” yearmore common in more unstable environments may not spawn every year (sturgeon)

Reproductive strategies

fertilization external except livebearers (elasmobranches, Poecilidae, etc)

mass spawning events (Clupeiformes, smelt, etc.)

several males to each female (Salmoniformes, lampreys)

several females to each male (Gobiidae)

single-pair matings (guppies)

Reproductive strategies

non-guarders - pelagic (broadcast) spawners

semi-buoyant eggshigh fecundityegg and larval ‘migrations’

Reproductive strategies

non-guarders - pelagic (broadcast) spawners- benthic spawners

on coarse substrates (lake trout)on vegetation (carp, perch)on fine substrates (smelt)

Reproductive strategies

non-guarders - pelagic (broadcast) spawners- benthic spawners- brood hiders

build redd on coarse substrates (salmon, lamprey)

credit: Thomas B. Dunklin

Reproductive strategies

non-guarders - pelagic (broadcast) spawners- benthic spawners- brood hiders

build redd on coarse substrates (salmon, lamprey)beach spawners (grunion)use another species (bitterling)

Reproductive strategies

guarders - nest builders (largemouth bass)

Reproductive strategies

guarders - nest builders (largemouth bass)

rock and gravel (like a lentic redd - sunfishes)plant material (sticklebacks)holes, crevices, cavities (gobies, sculpin, blennies)froth (bettas)anemones (clown fish)

Reproductive strategies

Bearers - carry eggs and/or fry with them

Reproductive strategies

Bearers - external bearers

transfer: Gasterosteidae, Sygnathidae (pipefishes, seahorses)

grade from attachment to skin, to open pouch, to closed pouchgill chambers, forehead

obstetrical catfish carry eggs on ventral surface

Reproductive strategies

Bearers - external bearers

mouth: males or females some cichlids and bonytongues

Reproductive strategies

Bearers - external bearers

- internal bearers (viviparity)facultative - killifishes

obligate - Lake Baikal sculpins, marine rockfishes (Scorpaenidae)

livebearers - Poeciliids, many sharksgradient of nutrient supply from mother

superfetation

placental viviparity - sharks

Reproductive strategies

the other extreme: minimal male investmentLophiiformes: deepsea anglerfishes

Alternative reproductive strategies

sexual vs asexual – pros and cons

Alternative reproductive strategies

Hermaphroditismsynchronous (or simultaneous) hermaphrodites

Myctophiformes: (laternfishes) - several familiesAtheriniformes: Aplocheilidae, PoeciliidaePerciformes: Serranidae (sea basses, hamlets),

Labridae (wrasses), and others

"Egg-trading" in black hamlets Hypoplectrus nigricans (serranid)

Alternative reproductive strategies

Hermaphroditismconsecutive (sequential) hermaphrodites

first male (protandrous) – less commonStomiiformes (lightfish, dragonfish)Scorpaeniformes: PlatycephalidaePerciformes: Serranidae, Labridae, and others

blue-headed wrasse

Alternative reproductive strategies

Hermaphroditismconsecutive (sequential) hermaphrodites

first male (protandrous) – less common

first female (protogynous)Synbranchiformes (swamp eels – only freshwater example)Perciformes: Serranidae, Maenidae, Labridae

from 100% female -> 100% malefrom 100% female -> 50% male / 50% femalesome do not pass thru a female stage ("primary males")

Alternative reproductive strategies

Unisexual species

processes of DNA re-assortment in sexual species:

1. crossing-over during first meiotic division 2. random segregation of chromosomes in second meiotic division 3. addition of male and female chromosomes after fertilization

Alternative reproductive strategies

parthenogenesis: females produce diploid eggs, no sperm used

premeiotic endomitosis - mitotic division without cytokinesis

Alternative reproductive strategies

parthenogenesis: females produce diploid eggs, no sperm used

premeiotic endomitosis - mitotic division without cytokinesis

gynogenesis: females produce diploid eggs, use sperm to stimulate development

male genome not usedcongeneric species are used for spermexample: Poecilia formosa (Amazon molly)

Alternative reproductive strategies

parthenogenesis: females produce diploid eggs, no sperm used

premeiotic endomitosis - mitotic division without cytokinesis

gynogenesis: females produce diploid eggs, use sperm to stimulate development

male genome not usedcongeneric species are used for sperm

androgenesis – does not exist (why?)

Alternative reproductive strategies

parthenogenesis: females produce diploid eggs, no sperm used

premeiotic endomitosis - mitotic division without cytokinesis

gynogenesis: females produce diploid eggs, use sperm to stimulate development

male genome not usedcongeneric species are used for sperm

hybridogenesis: one genome from female in egg, male genome discarded - then uses sperm to restore ploidy - no crossing over example: Poeciliopsis monacha-lucida

Alternative reproductive strategies

Alternative male strategies

- jacks (salmon and trout)

Alternative reproductive strategies

Alternative male strategies

- jacks (salmon and trout)

- sneakers (“SF”s) in bluegills, wrasses, sunfishesevolutionarily stable strategy - if small, become SF, avoid stress of being parental male

Alternative reproductive strategies

Alternative male strategies

- jacks (salmon and trout)

- sneakers (“SF”s) in bluegills, wrasses, sunfishesevolutionarily stable strategy - if small, become SF, avoid stress of being parental male

- satellite males (mimic females) in bluegills, hover near nest

DEVELOPMENT

Developmental stages

egg <0.5 mm - 10 cmvariable shape, attachmentsvariable buoyancywater hardening

yellow perch egg mass

round goby (0.5 mm)

lake trout (5 mm)

skate (5 cm)

Developmental stages

eggembryo - dependent on mother or yolk sac for food (free embryo)

Credit: Fly Anglers online

Susan Middleton & David Liittschwager

Developmental stages

eggembryo - dependent on mother or yolk sac for food (free embryo)larvae - not fully functional, may look totally unlike adult

ends when axial skeleton is formed

Developmental stages

eggembryo - dependent on mother or yolk sac for food (free embryo)larvae - not fully functional, may look totally unlike adult

ends when axial skeleton is formedjuvenile - small functional individual, immatureadult - reproductively mature

Developmental stages

eggembryo - dependent on mother or yolk sac for food (free embryo)larvae - not fully functional, may look totally unlike adult

ends when axial skeleton is formedjuvenile - small functional individual, immatureadult - reproductively mature

Credit: USFWS, GLFC

indirect development (perch) - larval stages go through trophic phases different from adults

intermediate (salmonids) - embryonic stage with yolk; virtually no larval stage

direct development (gobies) - juvenile is fully functional miniature of adults (no larval stage)

Genetics

Sex determinationheterogametic sex can be male or female

Genetics

Sex determinationheterogametic sex can be male or female

Polyploidy - more than two sets of chromosomes critical difference between odd and even sets

Genetics

Sex determinationheterogametic sex can be male or female

Polyploidy - more than two sets of chromosomes critical difference between odd and even sets - use of triploid grass carp

Genetics

http://www.bajthomas.btinternet.co.uk

Natural polyploidstriploids - Cyprinidontiformes: Poeciliid triploids- different solutions to the problem of triploid gametes….

Genetics

Natural polyploidstriploids - Cyprinidontiformes: Poeciliid triploids

tetraploids (autotetraploids vs. allotetraploids)Acipenseriformes (sturgeons and paddlefish)Salmonidae (all trouts - autotetraploid)

ancestral chromosome doubling eventCypriniformes

some cyprinidsall catostomids are allotetraploid

SiluriformesCorydoras catfishes

PerciformesOnly Lucioperca sandra: 2n = 24 in Sweden

but 2n = 48 in Finland

Genetics

Natural polyploidstriploids - Cyprinidontiformes: Poeciliid triploids

tetraploids (autotetraploids vs. allotetraploids)

hexaploids and octaploids (rare in carp)

Genetics

Natural hybrids

salmonids

centrarchids

Genetics