Is it a mite?

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Common names

water fleas, daphnia

Probability of encounter

High if intercept has standing water and from some soils if appropriate extraction techniques used (i.e., wet funnel, flotation).

Quarantine importance

Unknown. Most species are suspension feeders on detritus and microbes.

Similarity to mites

Small size, lack of clear segmentation.

Morphology

Normal adult length: mostly 0.25–2 mm
Body tagmata: head (1 pair of antennae), trunk, postabdomen
Eyes: median fused compound eye, naupliar eye
Antennae: biramous, swimming
Mouthparts: mandibles without palps; one pair of maxillae
Legs: 5–6 pairs of swimming/ grasping/ filtering legs
Respiration: cutaneous and coxal epipodites of trunk limbs
Gonopore: various on trunk
Distinguishing features: Minute swimming crustaceans with head shield and shell-like carapace, swimming 2nd antennae, dorsal brood chamber

Comments: Water fleas are normally considered aquatic organisms and would be expected primarily in moist intercepts (e.g., bromeliads); however, they also can be extracted with wet funnels from some soils. Eggs are brooded under the carapace which sometimes forms a protective capsule (ephippium) that allows aerial dispersal by wind.

Diversity

4 suborders, 11 families, 80+ genera, >400 species

References

• University of Guelph Arboretum n.d.University of Guelph Arboretum n.d.:
  University of Guelph Arboretum. n.d. Water Flea. Accessed 2024.