Among the listed Daphniidae genera, Ceriodaphnia (and to a similar extent Scapholeberis) tends to include the smallest species overall, while Daphnia includes the largest.
Megafenestra, Daphniopsis, and Simocephalus generally fall in the intermediate range (mostly 1–3 mm adults).
Sizes vary by species, environment, food, and temperature, so these are typical/approximate ranges from literature.
Among the listed Daphniidae genera:
Ceriodaphnia (and Scapholeberis) are generally the smallest.
Daphnia includes the largest species.
Megafenestra, Daphniopsis, and Simocephalus are intermediate.
SMALLEST: Ceriodaphnia (e.g. C. dubia, C. reticulata) Freshly born neonates: ~0.3 – 0.4 mm Largest adults: 0.5 – 1.4 mm (usually under 1.2 mm)
Also very small: Scapholeberis Neonates: ~0.28 – 0.4 mm Adults: 0.4 – 1.35 mm
LARGEST: Daphnia (e.g. D. magna, D. carinata) Freshly born neonates: ~0.5 – 0.8 mm Largest adults: up to 3 – 7 mm (D. magna often 4–6 mm, some species reach 7 mm)
Intermediate: Simocephalus: neonates ~0.5–0.7 mm, adults 1–3+ mm Daphniopsis: adults usually 1–3 mm Megafenestra: adults ~0.8–1.5 mm
Note: Sizes are approximate and can vary with food, temperature, and species. Cladocerans are born as miniature adults (no nauplii stage).
For Reference
Freshly hatched nauplii (Instar I) of San Francisco Bay brine shrimp (Artemia franciscana) are typically around 428–435 µm (0.43 mm) in length.
Average length: ~428 µm (San Francisco Bay strain)
Common range: 400–450 µm (often cited as ~430 µm)
Comparison: Smaller than Great Salt Lake (GSL) strain, which is ~480–490 µm.
