APSC Legal Metrology: Copepods (Paper 1)

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Section:

Science

Definition:

• Tiny aquatic crustaceans; among the most abundant multicellular organisms in marine and freshwater ecosystems.
• Act as crucial links in food webs between phytoplankton and higher predators (fish, whales, etc.).

Habitat:

• Found globally: from polar ice caps to deep-sea trenches and hydrothermal vents.
• Also inhabit freshwater bodies, underground caves, leaf litter, and moist soil.

Characteristics:

• Physical:
  • Size: Typically 1–2 mm; parasitic species may grow up to 20 cm.
  • Appearance: Transparent, teardrop-shaped body, long antennae, single red eye.
• Biological:
  • Lack heart and blood vessels (except in Calanoida order).
  • Respire through body surface (diffusion).
  • Some species exhibit bioluminescence to evade predators.
• Behavioural:
  • Movement: Quick “jumps” using oar-like antennae.
  • Reproduction: Follow pheromone trails to locate mates.
  • Feeding: Highly efficient filter feeders—can filter water volume a million times their body size daily; primarily consume phytoplankton.