Marine Ecology Study Guide

Topics: Coral reef, Species, Coral Pages: 28 (6300 words) Published: March 18, 2013
Marine Ecology Final Exam Review

Difference between broadcast spawners, brooders, direct developers, lecithotrophic and planktotrophic larvae

* Many marine organisms have a dispersal phase in their life history * Dispersal can occur as eggs, sperms, fertilized eggs, larvae, juveniles or adults * Many species only disperse as juveniles or adults

* Other species take advantage of high density of water to disperse during very early life stages: eggs/sperm/fertilized eggs/larvae
1. Broadcast spawners: parent release eggs/sperm/young fertilized eggs into water; developing young is on its own in the water column long time

2. Brooders: parent retains fertilized egg in body and releases young at a more developed stage; developing young spends less time in water column

3. Direct developers: parent retains fertilized egg in its body or in a large egg case until it hatches as a small version of an adult

* Larvae: independent, morphologically different stages developing from fertilized eggs and going through metamorphosis before reaching final adult stage.

* Are usually fundamentally unlike the adult stage morphologically, behaviorally, Physiologically

* Two basic types of larval production strategies:

1. Produce huge number of small eggs with little to no yolk that hatch quickly into feeding, free-swimming larvae: planktotrophic larvae 2. Produce smaller number of larger eggs with some yolk that hatch into non-feeding, free-swimming larvae: lecithotrophic larvae 3. In general, time in spent in plankton decreases as egg size increases

Pros and cons of different larval dispersal strategies; why all of them persist over time

* Planktotrophs:

1. Can produce more offspring with less parental investment (yolk) 2. Greater dispersal (longer time in water column)

1. Larvae might not find enough food in plankton
2. Long time in water column increase chances of predation

* Lecithotrophs

1. Less time in plankton reduces chances of predation
2. Get all nutrition from yolk: guaranteed food source

1. Fewer offspring produced per unit of parental energy
2. Larger eggs more of a target for visual predators
3. Shorter time in plankton = less dispersal

* Direct developers

1. Higher survivorship per capita

1. Only very few offspring produced per unit of parental energy 2. Zero dispersal in early life stage

* Nonpelagic development most common in polar waters, lecithotrophs in temperate waters, planktotrophy in tropics:

* Precise timing of planktonic larval release that’s necessary in polar waters too risky given very short time period of primary productivity; slow development b/c of cold water means larvae would be in water having to feed for a long time. * Where blooms last longer and water slightly warmer in temperate waters, lecithotrophy allows for dispersal and safe source of food. * Having feeding larvae in water for long periods is safer in tropics where there is a predictable, year-round supply of planktonic food; development also occurs faster b/c of warm water so don’t stay in water for too long.

* Small invertebrates are brooders (direct developers) more frequently than large ones:

* Small animals don’t have body space to produce huge numbers of eggs, so invest more in each fertilized embryo instead * Large animals can produce more eggs, but need to space them out to aerate them properly: selects for planktonic eggs/larvae to prevent suffocation

* Abundance of suitable habitat for next generation affects selection for dispersal:

* If suitable habitat is sparse and patchy, better to produce large numbers of widely dispersed larvae (planktotrophy) * Is suitable habitat is extremely common, dispersal is not as important...
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