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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