1. Fish Reproduction and Development Coevolved traits for producing another generation that will produce another generation... and another... and another...

2. 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

3. Coevolution of reproduction and development Linkage between reproductive traits and development patternsLinkage between reproductive traits and development patterns Represent tradeoffs between: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

4. Reproductive traits that vary with life-history patterns Fecundity (no. eggs):Fecundity (no. 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

5. Reproductive traits that vary with life-history patterns Size of offspring:Size of offspring: –probability of survival increases with size of offspring larger supply of reserveslarger supply of reserves fewer potential predatorsfewer potential predators greater feeding efficiencygreater feeding efficiency –cost of producing offspring increases with size –fecundity is reduced as offspring size increases

6. Reproductive traits that vary with life-history patterns Mating system: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 –Monogamy - mating pair remains together over time, long gestation of young (some cichlids, seahorses, pipefish)

7. Reproductive frequency Single spawning effort in life (semelparous),Single spawning effort in life (semelparous), –metabolic efficiency –max. fecundity –match offspring to ideal growing conditions –overwhelm predators –risk of waiting (death) Repeated spawning efforts (iteroparous) –spawn before death –spread offspring over multiple entry times –reduce fecundity to ensure SOME reproduction

8. “ To love’em and leave ‘em, or not..” “ To love’em and leave ‘em, or not..” Parental careParental care –increases probability of offspring survival survival due to reduced predation riskdue to reduced predation risk due to increased access to fooddue to increased access to food –costs energy - reduces fecundity –takes many forms brood hiding (behavioral)brood hiding (behavioral) nest guarding (behavioral)nest guarding (behavioral) internal gestation (physiological)internal gestation (physiological)

9. Reproductive traits (cont.) Parental care, 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 developmentoviparous – (egg laying) with behavioral care - yolk fed (lecithotrophy), external development ovoviviparous – embryo within female,ovoviviparous – embryo within female, yolk-fed, internal devel. yolk-fed, internal devel. viviparous – live birth yolk supplementedviviparous – live birth yolk supplemented (matrotrophy), internal development –biparental care

10. Reproductive traits (cont.) Method of fertilization:Method of fertilization: –most fishes use external 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 –internal 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

11. Reproductive traits (cont.) Method of fertilization, cont. :Method of fertilization, cont. : –internal fertilization requires lengthy courtship, preparation for matinglengthy courtship, preparation for mating intromittent organintromittent organ –claspers (pelvic fins) in Chondrichthyes –modified anal fin in poeciliids, goodeids –modified genital papilla in embiotocids male structure for storing sperm (seminal vesicle)male structure for storing sperm (seminal vesicle) –buccal fertilization—sperm swallowing?? Yep! Callichthyid catfish (Corydoras) Why, why...? Callichthyid catfish (Corydoras) Why, why...?

12. Reproductive traits that vary with life-history patterns Gender system: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)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 (sequential hermaphrodites start life as one sex, change sex after maturity ( –protandrous: male first, female later –protogynous: female first, male later (most common, Wrasses)

13. Reproductive traits that vary with life-history patterns Gender system (cont.):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)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)hybridogenetic - egg development with fertilization by males of other species, but male genes discarded at next generation (diploid - haploid eggs)

14. Reproductive traits that vary with life-history patterns Secondary sexual characteristicsSecondary sexual characteristics –monomorphic (males and females alike) –permanently dimorphic (mature sexes distinguishable) –seasonally dimorphic (mature sexes distinguishable only at spawning time) –polymorphic

15. Reproductive traits Reproductive morphology, bony fishes:Reproductive morphology, bony fishes: –male: testes -> vas deferens -> urogenital pore –female: ovary -> oviduct -> urogenital pore

18. Reproductive traits that vary with life-history patterns Reproductive morphology, cartilaginous fishes:Reproductive morphology, cartilaginous fishes: –male: testes -> Leydig’s gland -> seminal vesicle -> cloaca -> claspers –female: ovary -> ostium tubae -> oviduct -> shell gland -> [uterus] -> cloaca

19. Female Male

20. Behavioral adaptations for reproduction Courtship - color, size, movements importantCourtship - color, size, movements important Spawning site selectionSpawning site selection –substrate spawners - broadcast –water-column spawners - broadcast –site preparers –internal fertilization - also may be habitat- specific

21. Behavioral adaptations for reproduction Care-giving behavior - Balon’s classification:Care-giving behavior - Balon’s classification: –Non guarders –Guarders –Bearers See handout! Much diversity here!

22. Behavioral adaptations for reproduction Care-giving behavior - Balon’s classification:Care-giving behavior - Balon’s classification: –Non guarders open substrate spawnersopen substrate spawners brood hidersbrood hiders –Guarders –Bearers

23. Behavioral adaptations for reproduction Care-giving behavior - Balon’s classification:Care-giving behavior - Balon’s classification: –Non guarders –Guarders substratum chooserssubstratum choosers nest spawnersnest spawners –Bearers

24. Behavioral adaptations for reproduction Care-giving behavior - Balon’s classification:Care-giving behavior - Balon’s classification: –Non guarders –Guarders –Bearers GuardersGuarders BearersBearers –external –internal

25. Fish Development Balon’s theory ofBalon’s theory of saltatory development: saltatory development: –Development occurs as a series of discrete transitions in form and function (thresholds or metamorphoses), with periods of change in size (periods) between thresholds

26. Developmental stages in fishes PERIODSEMBRYOLARVAJUVENILEADULTSENESCENT THRESHOLDS fertilization exogenous feeding full fin development, body shape of adult reproduction cessation of growth, fertility

27. Developmental stages in fishes Advantages of saltatory (unique stages) development?Advantages of saltatory (unique stages) development? –separation of life stages –niche specificity adapted to size food acquisitionfood acquisition predator avoidancepredator avoidance temperature optimizationtemperature optimization others...others...