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REPRODUCTION IN CORALS Life history -sequence of developmental stages from birth to death Growth, Reproduction, Senescence, Mortality All of this activity takes energy - must be apportioned Growth Reproduction Respiration Feeding Mate Seeking Defense Growth Reproduction Respiration Feeding Mate Seeking Defense Different investment patterns Aclonal Life History recruitment Sexual reproduction Death Clonal Life History Sexual reproduction recruitment Fission Fission Fission Death Concept of the Individual in Corals 1. Morphological - Polyp (= ramet) Concept of the Individual in Corals 2. Physiological - Groups of connected polyps Concept of the Individual in Corals 3. Genetic - All polyps and colonies derived from the same zygote (Genet) Asexual reproduction in corals - Budding Intratentacular Extratentacular Asexual reproduction in corals - Budding Intratentacular Can stay in place = growth Extratentacular Can detach and grow elsewhere = asexual reproduction Asexual reproduction in corals - Budding Asexual reproduction in corals - Fragmentation Three colonies but one genetic individual Partial colony mortality Dead areas Costs and Benefits of Fragmentation Benefit - risk of genet mortality -spread over several colonies Costs -disrupt physiological function - possible decrease in fecundity - possible postponement of sexual reproduction Asexual reproduction in corals - Polyp Bailout Coral Budding Sexual Patterns 1. Gonochoristic (dioecious) 2. Hermaphroditic (monecious) Development Patterns 1. Brooders -retain embryo 2. Spawners -free-spawning Development Patterns Can these patterns be related to life history/structure/habitat? 1. Related to whether species is r- or K- selected? X 2. Related to depth? -shallow should brood, deeper should spawn X 3. Related to the size and structure of the coral? -small, branched corals should brood, larger massive corals should spawn X 4. Related to habitat stability? -corals in predictable habitats should brood ? Strategies Revisited All life functions can be seen as competing with each other for energy 1. Growth rate and reproduction Growth rate Size Strategies Revisited All life functions can be seen as competing with each other for energy 1. Growth rate and reproduction Growth rate or calcification rate Pavona Breeding season Time of year Strategies Revisited All life functions can be seen as competing with each other for energy 2. Polyp size Strategies Revisited All life functions can be seen as competing with each other for energy 3. Allocation of energy (within reproduction) Pavona 25-50% of colony biomass as planulae 50 – 180% of colony biomass as planulae Strategies Revisited All life functions can be seen as competing with each other for energy 3. Allocation of energy (within reproduction) Across species planulae eggs Mean diameter (µm) Fecundity / year Strategies Revisited All life functions can be seen as competing with each other for energy 4. Temporal variation in fecundity Brooders Size Spawners Time Strategies Revisited All life functions can be seen as competing with each other for energy 4. Temporal variation in fecundity Age or size? Goniastrea -complex interaction Montastrea Gametogenic cycles gametogenesis ovogenesis spermatogenesis spawn quiescence gametogenesis Correlated with a. Change in sea temperature b. Lunar/tidal cycles c. Photoperiod Time Gametogenesis Gametogenesis Release of sperm and egg packets Release of sperm and egg packets Coral Spawning Release of sperm and egg packets Release of sperm and egg packets Free spawning coral Synchrony in spawning Sea temperature Tidal cycle Photoperiod Synchrony in spawning - Low tide, late afternoon Goniastrea - Low tide, evening Synchrony in spawning -grind up male polyps -expose female polyps to extract Caryophyllia -egg release by exposed females Development Patterns -effects on planula larva 1. Brooders 2. Spawners - immediately competent - lag time until competence - larger - smaller - have all zooxanthellae - must acquire zooxanthellae Predation on spawned gametes Predation on spawned gametes Acanthochromis polyacanthus Abudefduf bengalensis Caesio cuning Westneat & Resing. 1988. Coral Reefs 7:89 Larval Settlement -success depends on ability to identify site for settlement and metamorphosis Substrate type Salinity (>32 ppt) Illumination Water motion Sediment level Chemical signals from algae, biofilms, conspecifics Settlement & metamorphosis Larval Settlement -success depends on ability to identify site for settlement and metamorphosis Acropora millepora Neogoniolithon fosliei Harrington et al 2004. Ecology 85: 3428 Larval Settlement -success depends on ability to identify site for settlement and metamorphosis Corraline algae Harrington et al 2004. Ecology 85: 3428 Summary Planulae Sample and assess subtrate: prepare to settle Young primary polyp Planulae released from individual polyps Zygote Brooders internal fertilization Asexual colony growth Broadcasters external fertilization
