BIO 475 Lecture Notes - Lecture 12: Stolon, Parthenogenesis, Sexual Reproduction
● Reproduction
○ Process by which new individuals are formed
● Settlement: change from a planktonic existence to a benthic lifestyle
● Metamorphosis: series of morphological and biochemical changes to the benthic juvenile
stage
● Recruitment: process by which newly formed individuals become a part of the reef
community
● Post-settlement mortality
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● Critical process
● Replenishment of reefs from disturbance
● Important to coral reef management and preservation
Asexual reproduction
● Must distinguish between colony growth and formation of new colonies
● Intratentacular budding: new polyps formed from the division of already existing polyp
○ Fission
○ Two separate polyps of equal size
● Extratentacular budding: new mouth and tentacles form in the space between polyps
○ Secondary smaller polyp that is smaller than the original
● In either case the new polyp becomes detached from the parent colony then have
asexual reproduction
● If new polyp remains part of the parent colony than this is colony growth
● Modes
○ Fragmentation
■ Branching corals
● Broken up by wave action, being carried away, will get logged
back into reef. New colony identical to the colony it broke off from
○ Stolon formation
■ Sends out a runner; stolon, and it was translocate material along stolon,
and will eventually form a new colony. The stolon will break off and reform
back to the colony
○ Polyp Bail out
■ Adult coral colony experiencing some sort of stress, to avoid stress, the
polyp itself reverts to larval form, swims away, attaches somewhere else,
metamorphosis back and forms a new colony
○ Parthenogenesis
■ Process of an egg undergoing replication and maturation without input of
sperm. Egg, no genetic input, but still develops properly all on its own.
● Advantages
○ Fragments are generally larger than sexual recruit (new colony); lower rates of
mortality; higher competitive ability
○ Recruitment to space creation can be rapid
● Disadvantage
○ Offspring genetically identical to parent, results in low genetic variation
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■ Under stable conditions, offspring have the same level of success as
parent, but conditions are rarely stable
○ Low dispersal abilities
■ Can only go so far away from parent ( branching pieces)
○ Results in patchy distribution of colonies
Sexual reproduction
● Compromises the process of gametogenesis s followed by the successful fusion of eggs
and sperm and the formation of a planula(larva singular, larvae plural)
● Brooders (Internal fertilization)
○ Release sperm into water column, sucked into neighboring colony with eggs
developing internally. Zygote is formed inside parent polyp, and mature planula
larva is released. Time spent in the water column is shorter
○ 2-5 days
○ 0-3 days to settle
● Broadcast spawning (External fertilization)
○ Release egg and sperm into water column, fuse to form zygote, which then has
to form in the water column.
○ Could take up until 2 weeks for the larvae to settle
○ 0-3 days to settle
Gamete and formation and location
● No specific gonad structures
● Primordial germ cells develop from endodermis and then migrate to the mesoglea where
they develop
● Developing gametes can be seen as “bulges” in the mesenteries (inside gastrodermis ,
there are folds, gametes migrate into these folds and develop there) or on stalks
attached to the mesenteries
● Mesenteries can be hermaphroditic or gonochoric
Sexuality
● Gonochoric: individual colonies produce only one type of gamete (colonies have a sex)
● Hermaphroditic: individual colonies have both male and female gametes
○ Simultaneously (primarily this)
■ Both sets of gonads ripe at the same time
○ Sequential
● Species either one or the other
Adv. Disadv.
Hermaphroditism
Gonochorism
High rate of fertilization
Increased outcrossing and rate of
recombination
Problems with self-fertilization
● Adaptation
● Broadcasters: egg/sperm bundles
break at surface to mix
● Risky and may lead to low/no
fertilization
○ Adaptation:
○ Broadcaster
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Document Summary
Process by which new individuals are formed. Settlement: change from a planktonic existence to a benthic lifestyle. Metamorphosis: series of morphological and biochemical changes to the benthic juvenile stage. Recruitment: process by which newly formed individuals become a part of the reef community. Must distinguish between colony growth and formation of new colonies. Intratentacular budding: new polyps formed from the division of already existing polyp. Extratentacular budding: new mouth and tentacles form in the space between polyps. Secondary smaller polyp that is smaller than the original. In either case the new polyp becomes detached from the parent colony then have asexual reproduction. If new polyp remains part of the parent colony than this is colony growth. Broken up by wave action, being carried away, will get logged back into reef. New colony identical to the colony it broke off from. Sends out a runner; stolon, and it was translocate material along stolon, and will eventually form a new colony.
