Calculation of the Blood Volume that Moves through the Dorsal Blood Vessel
in Lumbriculus variegatus (Oligochaeta, California blackworm)
           - - - -


1) Use a microruler to estimate the diameter of the dorsal blood vessel. Use a whole worm (or a worm fragment) that is confined to a narrow space to restrict its movements. NOTE: Worm confinement options include:

2) Use a microruler to estimate velocity of the pulse wave. Do this my determining the number of seconds it takes for the pulse to travel 1 mm.

- - - -

Measurement or Calculation                                                         Sample Values

Estimated diameter (D) of dorsal blood vessel in mm

D =  0.2 mm

Calculate radius (r) of dorsal blood vessel [r = 1/2 D]

r =  0.1 mm

Estimated velocity (c) of pulse wave

c =  1 mm in 5 sec

   =  0.2 mm/sec

Calculate cross-sectional area of dorsal blood vessel

A = π x r2  or A = 3.14 x (0.1) 2

A = 0.0314 mm2

Calculate volume (V) of blood moved per second

V = c x(same formula as volume of a cylinder = area x length)

V = 0.2 mm/sec x 0.0314 mm2

V = 0.00628 mm3/sec

Convert V/sec to V/day

(multiple by 60 sec/min, 60 min/hr, 24 hr/day)

V = 542 mm3/day

Convert mm3/day to ml/day (1000 mm3 = 1 cm3 = 1 ml)

V = 0.542 ml/day


By comparison, 1 ml water = 1 gram (about 20 drops). So, the worm pumps about 0.5 ml, or 0.5 gram of blood, through its dorsal blood vessel per day. If a normal-size worm weighs 0.010-0.015 grams (= 10-15 mg), then the worm pumps about 50 times its body weight in blood per day.

[Q: How does this compare to the human circulatory system? A: An average human heart pumps about 5 liters blood/min, or 7,200 kg/day. If a human weighs 72 kg (= 160 pounds), then the amount of blood pumped per day is about 100 times the body weight of a human.]