Fish Reproduction and Development by malj

VIEWS: 0 PAGES: 30

									  Fish Reproduction and
       Development
  Coevolved traits for producing
another generation that will produce
 another generation...and another...and
                another...
Coevolution of reproduction and
         development
Bioenergetic equation:

             I=M+G+R+E
Surplus energy can be spent on
  Growth,
  Reproduction,
  or some combination of G & R
  Coevolution of reproduction and
           development
 • Linkage between reproductive traits and development
   patterns
 • Represent tradeoffs between:
    – risks & benefits of continued growth vs.
      reproduction
    – quantity of offspring vs. quality of offspring
    – risk of predation vs. chance of finding quality food




Octopus larvae
Reproductive traits that vary with
      life-history patterns
• Fecundity (number of eggs):
  – increases geometrically with body size
  – early growth and deferred reproduction lead to
    higher fecundity
  – early growth and deferred
    reproduction increase
    probability of dying before
    reproducing!
Reproductive traits that vary with
      life-history patterns
• Size of offspring:
   – chance of survival increases with increasing size of
     offspring
      • larger supply of reserves
      • fewer potential predators
      • greater feeding efficiency
   – cost of producing offspring
     increases with size
   – fecundity is reduced as
        offspring size increases
 Reproductive traits that vary with
       life-history patterns
• Mating system:
  – Promiscuous - both sexes with multiple partners -
    most (common)
  – Polygynous - males with multiple mates (cichlids)
  – Polyandry - females with multiple mates – few
    (Anglerfish, males “parasitize” females,
    clownfish)
  – Monogamy - mating pair remains together over
    time, long gestation of young (some cichlids,
    seahorses, pipefish)
What if this was your lot in life??
Who’s your daddy??
           Reproductive frequency
• Single spawning effort in     • Repeated spawning
  life (semelparous),             efforts (iteroparous)
   – metabolic efficiency          – spawn before death
   – max. fecundity                – spread offspring over
   – match offspring to ideal        multiple entry times
     growing conditions            – reduce fecundity to ensure
   – overwhelm predators             SOME reproduction
   – risk of waiting (death)
  “ To love’em and leave ‘em, or not..”
• Parental care
  – increases probability of offspring
      survival
     • due to reduced predation risk
     • due to increased access to food
  – costs energy - reduces fecundity
  – takes many forms
     •   brood hiding (behavioral)
     •   nest guarding (behavioral)
     •   internal gestation (physiological)
       Reproductive traits (cont.)
• Parental care, cont.
  – male care givers - mostly behavioral (advantage?)
  – female care givers - mostly physiological
     • oviparous – (egg laying) with behavioral care - yolk
       fed (lecithotrophy), external development
     • ovoviviparous – embryo within female,
        yolk-fed, internal devel.
     • viviparous – live birth yolk supplemented
       (matrotrophy), internal development
  – biparental care
     Reproductive traits (cont.)
• Method of fertilization:
  – external fertilization (most fish)
     •   less time and energy in courtship, pair bonding
     •   increases number of potential mates
     •   greater fecundity
  – internal fertilization in few groups:
     •   sharks, rays, skates, ratfishes (Chondrichthyes)
     •   guppies, mollies, etc. - Poeciliidae, Goodeidae
     •   surfperches - Embiotocidae
  Is internal fertilization better?
– internal fertilization requires
   • lengthy courtship, preparation for mating
   • intromittent organ
      –   claspers (pelvic fins) in Chondrichthyes
      –   modified anal fin in poeciliids, goodeids
      –   modified genital papilla in embiotocids
   • male structure for storing sperm (seminal vesicle)
– buccal fertilization—sperm swallowing?? Yep!
   Callichthyids (“Corydoras”) Why, why, why?
  Reproductive traits that vary with
        life-history patterns
• Gender system:
  – most are gonochoristic (single sex, fixed at maturity)
  – some are hermaphroditic
     • simultaneous hermaphrodites function as male and female
       at same time (23 families; ex. Anguilliformes, eels;
       Atheriniformes, killifish)
     • sequential hermaphrodites start life as one sex, change
       sex after maturity
        – protandrous: male first, female later (clownfish)
        – protogynous: female first, male later (most common, Wrasses)
Reproductive traits that vary with
      life-history patterns
• Gender system (cont.):
  – Parthenogenetic:
     • gynogenetic – sperm needed for egg development,
       but mating without fertilization (triploid - triploid
       eggs), result is daughters are genetic clones of
       mothers (Amazon molly, Poecilia formosa)
     • hybridogenetic - egg development with fertilization
       by males of other species, but male genes discarded
       at next generation (diploid - haploid eggs)
Reproductive traits that vary with
      life-history patterns
• Secondary sexual characteristics
  – monomorphic (males and females alike)
  – permanently dimorphic (mature sexes
    distinguishable)
  – seasonally dimorphic (mature sexes
    distinguishable only at spawning time)
  – polymorphic
        Reproductive traits




• Reproductive morphology, bony fishes:
  – male: testes -> vas deferens -> urogenital pore
  – female: ovary -> oviduct -> urogenital pore
Reproductive traits that vary with
      life-history patterns
• Reproductive morphology, cartilaginous
  fishes:
  – male: testes -> Leydig’s gland -> seminal
    vesicle -> cloaca -> claspers

  – female: ovary -> ostium tubae -> oviduct ->
    shell gland -> [uterus] -> cloaca
Male   Female
    Behavioral adaptations for
          reproduction
• Courtship - color, size, movements important
• Spawning site selection
  – substrate spawners - broadcast
  – water-column spawners - broadcast
  – site preparers
  – internal fertilization - also may be habitat-
    specific
     Behavioral adaptations for
           reproduction
• Care-giving behavior - Balon’s classification:
  – Non guarders
  – Guarders
  – Bearers
     Behavioral adaptations for
           reproduction
• Care-giving behavior - Balon’s classification:
  – Non guarders
     • open substrate spawners
     • brood hiders
  – Guarders
  – Bearers
     Behavioral adaptations for
           reproduction
• Care-giving behavior - Balon’s classification:
  – Non guarders
  – Guarders
     • substratum choosers
     • nest spawners
  – Bearers
     Behavioral adaptations for
           reproduction
• Care-giving behavior - Balon’s classification:
  – Non guarders
  – Guarders
  – Bearers
     • Guarders
     • Bearers
        – external
        – internal
  Fish
  Development
• Balon’s theory of
   saltatory development:
  – Development in discrete
    transitions in form and
    function (thresholds or
    metamorphoses), with
    periods of change in size
    (periods) between thresholds
 Developmental stages in fishes
PERIODS         THRESHOLDS
  EMBRYO          fertilization
                  exogenous feeding
 LARVA
                  full fin development,
 JUVENILE           body shape of adult
                  reproduction
 ADULT
                  cessation of growth,
 SENESCENT          fertility
 Developmental stages in fishes
• Advantages of saltatory (unique stages)
  development?
  – separation of life stages
  – niche specificity adapted to size
     •   food acquisition
     •   predator avoidance
     •   temperature optimization
     •   others...

								
To top