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IB 362 lecture 6. Reproduction, Dispersal and Migration in Marine Organisms. Reproduction. Behavior Regulation/effect of hormones Allocation of resources i.e. somatic vs. non-somatic tissue growth Method/frequency of fertilization Parental Care.
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IB 362 lecture 6 Reproduction, Dispersal and Migration in Marine Organisms
Reproduction Behavior Regulation/effect of hormones Allocation of resources i.e. somatic vs. non-somatic tissue growth Method/frequency of fertilization Parental Care
dominant/large males select best shelters • females select dominate male’s shelter and moves in • female will molt and then mate • after mating, female waits for shell to harden then moves out • other females in waiting move into shelter with olfactory cues Reproduction Behavior North Atlantic Lobster – Homarus americanus
Reproduction • no active searching for mates or pre-spawning behavior • females secrete pheromone after molting and any nearby male is attracted Behavior Opossum Shrimp
Reproduction Behavior Regulation/effect of hormones Allocation of resources i.e. somatic vs. non-somatic tissue growth Method/frequency of fertilization Parental Care
Lifetime Reproduction-two basic strategies • Iteroparous: • spawning possible more than once • most fishes and invertebrates • Semelparous: • spawning only once, followed by death • pacific salmon, some eels, lampreys
Lifetime Reproduction-two basic strategies • Iteroparous: • spawning possible more than once • most fishes and invertebrates • Semelparous: • spawning only once, followed by death • pacific salmon, some eels, lampreys
Lifetime Reproduction What are benefits and potential risks of each strategy? • Iteroparous • Semelparous
Advantages / Disadvantages • Iteroparous: +several opportunities + environment unpredictable - longevity expected • Semelparous: + maximum investment - unfavorable conditions
Mating Systems number of mating partners an individual has during a breeding season • Promiscuous: little or no mate choice • Polygamous: one sex has multiple partners • Polyandry: one female, several males - rare • Polygyny: one male, several females - common • Monogamous: mates stay together, exclusively
Mating Systems • Promiscuous • organisms that live in large groups • organisms with high fecundity • sedentary organisms
Mating Systems • Polygamous – Polyandry / Polygyny • none to some parental care • nest guarding • relatively rare in marine organisms, especially beyond egg stage
Mating Systems • Monogamous • defense of territory / resource • parental care by both parents • relatively rare in marine organisms
Extreme/Atypical Mating Systems • Monogamous Males rely on females for nutrition - internal organs degenerate with exception of testes
Gender Roles • Gonochoristic:gender fixed, determined early • Hermaphrodites:either both, or sex change • Simultaneous: eggs & sperm at same time Hamlets
Gender Roles • Gonochoristic:gender fixed, determined early • Hermaphrodites:either both, or sex change • Simultaneous: eggs & sperm at same time • Sequential : sex change during life
Sequential – common in several marine fishes (most common in wrasse family – Labridae) Lyretail Coralfish: • Large aggregations • Sex-ratio 36F:1M • If x M removed, x F change sex
Sex Change Clownfish – 30 species • Two large and several small fish • largest = female • 2nd largest = male • rest = immature(even if same age as mature fish) but hiearchal by size • Body size maintained until change
Parental Care very diverse across fishes Trade-off in resource allocation: • few, but high-quality • many, but low-quality ? 7 300,000,000
Fertilization InternalExternal Transfer of sperm in many invertebrates is via a spermatophore • Can be stored internally or attached externally • May provide nutrients to female • May prevent subsequent matings by other males • Decreased surface area
Fertilization Transfer of sperm in many invertebrates is via a spermatophore • Successful system, why not more common?
Fertilization Transfer of sperm in many invertebrates is via a spermatophore • Successful system, why not more common? Metamerism – serial repetition of body regions = more opportunity for appendage specialization
Fertilization • Rare in invertebrates • Becomes more common in “higher” vertebrates Internal (in body cavity)External
Open spawners Brooders External pelagic benthic • More common in marine fishes • Also known as broadcast spawners • Some benthic fishes will do it • high fecundity
Open spawners Brooders External benthic pelagic • gametes released into current • settle to substrate after fert.
Open spawners Brooders • gametes can be stored internally • fertilization is external • fert. eggs carried (usually by females) • until hatching • more common in invertebrates External
Open spawners Brooders External • parental care of juveniles after hatching • does occur but is rare, mostly in fishes Cardinal Fish
Occurs via splitting, budding or fragmentation • Generally rare, but more common in colonial organism at • the cellular level of organization Asexual Reproduction
Dispersal egg >> larvae >> juveniles >> adults • Most marine organisms have a larval stage
Dispersal egg >> larvae >> juveniles >> adults • Most marine organisms have a larval stage • Most freshwater organisms do not • Why the difference?
Hatch – egg to larvae • not tied to specific developmental stage • water temp and oxygen content • tide conditions, time of day, seasonal current changes Hatching occurs at sunset of night of strongest ebb tide Coral Reef Flat Damselfish
Larval stage Duration of larval stage dependant on resource needs in relation to currents • Food, habitat • 1 week to 18 months
Two main types • Lecithotrophic –with yolk sac, no digestion • Planktotrophic – feed while larvae, digestion Larval stage • Name different across taxonomic groups Zoea – Crustaceans Amphiblastula - sponges Veliger – some molluscs Leptocephalus – some fishes Hard corals - planula
