Image Key > Cladocera

Select from one of the following Genus:

Evadne sp.	Penilia sp.	Podon sp.

• Approximately 1 mm long.

• Commonly called water fleas.

• The thoracic appendages (pereiopods) are typically leaf-like, lobed and densely setose.
• These appendages also bear gills and explain the derivation of the name Branchiopoda (gill-feet).
• The carapace of cladocerans is folded along the back, giving a bivalve appearance, but there is neither a dorsal hinge nor an adductor as seen in scallops, mussels and ostracods.
• The carapace terminates posteriorly with an apical spine.
• The first antenna is uniramous and short.
• The second antenna is biramous and used for swimming.
• Cladocerans are generally transparent with little pigmentation except for the single black compound eye.

• Widely distributed throughout the world.
• Common in coastal waters and can also be found in open ocean systems.

• Marine cladocerans are usually herbivorous filter feeders that sieve phytoplankton from the water using setae on the pereiopods. However, they also graze on bacteria and microzooplankton including protozoans.
• Quite selective in their feeding, preferring certain species of phytoplankton to others.
• Asexual reproductive strategies allow cladocerans to exploit favourable food conditions.
• Environmental stress may induce females to produce male offspring, thus leading to bisexual reproduction.
• After copulation and internal fertilization, the eggs are brooded in a pouch within the carapace of the female until they are ready to hatch as miniature adults.
• Cladocerans can also reproduce asexually through a process called parthenogenesis, which results in females dominating the population before reverting to sexual reproduction.
• In some cases, paedomorphosis has been observed where developing embryos in the mother’s brood pouch become sexually mature and can themselves carry eggs.

• Most cladocerans are freshwater, but three genera commonly occur in coastal plankton samples.
  • Penilia sp.
  • Evadne sp.
  • Podon sp.
• In south-east Tasmanian waters Evadne and Podon can be common, whilst Penilia is usually less common.