1Fish Reproduction – Anything Goes! Chap 20• Male vs. female reproductive effort:• Female gametes costly - female reproductive success limited by # gametes she produces• Male reproductive success - limited by number of available mates• When is it better to be male or female?• What type of males are likely to be monogamous?• When are males likely to give parental care? • Why do female fishes give less parental care?Fish Reproduction – Breeding Opportunities• Lifetime Reproductive Opportunities• Iteroparous - most fish • Semelparous – salmon (Oncorrhynchus), lampreys, anguillid eels, galixiids, etc. • American shad - semelparous (30-33 N) and iterioparous (41-47 and variable inbetween2Case Study• Anguilla anguilla- Males mature 3-6 years - restricted distribution. Females - mature quickly at low latitudes 4-13 years & slowly at high latitudes 6-43 years but produce more eggs females have a wider distribution• All go to Sargasso sea to mate and die• Young eels return to the correct continentGender Roles in Fishes• 1) Most Fish = Gonorchoristic (sex fixed at maturation) – elasmobranchs, lungfish, sturgeons, clupeiforms, cyprinids, salmonids3Mating Systems• Promiscuous – herring, damselfish, wrasses, surgeonfish, sticklebacks – no mate choiceMating Systems• Polygamous – 3 types • A) Polygyny – sculpins, sunfish, darters, cichlids, anglefish, damselfish, wrasses, etc. – 1) males defend territories/nests damselfishes, some cichlids– 2) males have harem of females- bluehead wrasse– 3) leks- display areas Cyrtocara eucinostomus4Mating Systems• Polygamous – 3 types – B) Polyandry – anemone fish (sometimes) – C) Monogamy – bullheads, pipefish, jawfishes, damselfishes, butterflyfishes, blennies, etc.Gender Roles in Fishes• 2) Hermaphroditic – Simultaneous – Rivulus, Serranus, hamlets5Gender Roles in Fishes• 2) Hermaphroditic – Sequential • Protandrous – male-female – anemonefish, Lates, moray eels• Protogynous – female-male – Anthias, wrassesGender Roles in FishesWhy Sequential hermaphrodites: Protandrous- size advantage hypothesis -indeterminate growth, greater fecundity with size therefore females should be larger• Example = anemonefish- small males which are psycho-physiologically castratedProtogynous - more common, competition gives a size advantage: expect large territorial males6CASE STUDY: Caribbean bluehead wrasse Thalassoma bifasciatum• Initial phase coloration -mostly yellow female• Terminal males = distinct coloration, territorial, get 40-100 spawns/day • Sneaker males rush females in group aggregations typically get 1-2 dilute matings/day; • Small vs large reefsGender Roles in Fishes• 3) Parthenogenic-Mexican livebearers, Poeciliopis spp. need sperm to activate fertilization, some sperm incorporated, others the male genes are lost in the next generation7Gender Roles in Fishes• 3) Parthenogenic - Mexican livebearers, Poeciliopisspp.- P. monacha and lucida• Gynogenesis = Triplod female (MLL) – sperm from L -activates – offspring = MLL• Hybridogenesis – Diploid ML produes only haploid M eggs (with maternal only) BUT sperm from L produces ML offspringSecondary Sexual Characteristics• Monomorphic• Sexually Dimorphic• Permanent• Seasonal• Polymorphic8SPAWNING Site • Water column- often in large groups, many eggs released• Substrate- males territorial• Sperm released immediately-paternity assured• Lots of sites for nests: hard substrate, algae, shells, grunion, spraying characinParental Care • Parental care in 90 of 420 bony fish families -includes: making a nest, burying eggs, chasing predators, oxygenating, cleaning, carrying eggs inc. live birth and oral brooding, trophicprovisioning (some catfishes and cichlids)• Males are often primary caregivers• No paternal care when internal fertilization• How does external fertilization promote paternal care? Paternity assurance, males can get multiple mates, females prefer males with eggs, caring is costly-less foraging, predatory attacks, fewer eggs9Alternative Tactics• CASE STUDY- male reproductive strategy in bluegill sunfish Lepomis macrochirus• Large old males make nests, guard eggs• Sneaker males - small dart though nest depositing sperm, become satellite males which are female mimics;Alternative Tactics• CASE STUDY- similar pattern in Coho salmon Oncorhynchus kisutch with conservation