Marine Zoology & Ecosystems: Larval Ecology

Larva definition

post embryonic stage, ends with metamorphosis to adult body plan

Metamorphosis

transformation from larval body plan to adult

Shore crab: life cycle stages

Hatch-Zoea-Megalopa-Metamorphosis

Invertebrates: Pelagic life cycle: Copepods

Indirect development

Egg-larva-juvenile-adult

spawn eggs in water or carry in sacks

Invertebrates: Pelagic life cycle: Arrow worms

Direct development

Egg-juvenile-adult

Invertebrates: Fully benthic life cycle

crawling larvae or follow direct development

egg-juvenile-adult

no larvae

Invertebrates: larvae=Benthic, adult=Pelagic life cycle

jellyfish

Invertebrates: Adult=Benthic, Larvae=Pelagic life cycle

sponges, corals, polychaetes, molluscs, echinoderms

Brooders: Gastropods

females carry eggs or deposit egg capsules

look after young before depart from parent

release larva directly in water column after fertilisation

grow in polyp corals

Broadcast spawners

release gametes into water column

fertilisation takes place in water

Types of Larvae: Planktonic

small at hatching

pelagic larvae- feed on plankton

long development times (>6 weeks)

high dispersal potential

Types of larvae: Lecithotrophic

large, lose reserves over time

pelagic or benthic

short development times

low dispersal potential

Is Lecithotrophic or Planktotrophic larvae more common

Planktotrophic

Advantage of having larvae

dispersal

escape poor conditions

new habitat colonisation

reduced competition for adults

Disadvantages of having larvae

High mortality

uncertain settlement

energetic cost

risk of being transported away from suitable habitat

What determines larval connectivity

Currents, wind, larval behaviour, vertical migration

What is marine metopopulation

system of local populations connected by larval dispersal

Retention vs dispersal

retention keeps larvae near natal population

dispersal connects population