First published online August 4, 2005
Journal of Experimental Biology 208, 3211-3218 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01756
A chemotactic response facilitates mosquito salivary gland infection by malaria sporozoites
Mayumi Akaki and
James A. Dvorak*
Biochemical and Biophysical Parasitology Section, Laboratory of
Malaria and Vector Research, National Institute of Allergy and Infectious
Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Bethesda, MD
20892-8132, USA
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Fig. 1. (A) Schematic diagram of the custom-built chamber used for studies of
sporozoite chemotaxis. a, 18 mmx18 mm coverglass; b, 9 mmx18 mm
coverglass. (B) Diagram of the mathematical procedure used to analyze the
direction of sporozoite movement calculated as tangency angle  .
Movement directed to the bottom of the figure is defined as 90°.
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Fig. 2. Sporozoite transport through the hemolymph in mosquito wing veins. Arrows
show the progress of a sporozoite (green) floating passively through a
peripheral vein (upper images, 0–2 s) and subsequently through a larger
central vein (bottom images, 2.64–4.64 s). Asterisks indicate a
sporozoite apparently caught in a wing vein constriction. The number at the
lower left in each frame is the time (s) at which the image was recorded.
Scale bar, 100 µm.
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Fig. 3. Representative examples of sporozoite motility in assay medium. (A)
Circular gliding motion. X–Y maximum projection of five
time-lapse images acquired over a period 21 s, artificially colored as green
(the first four frames) and yellow (the last frame). The white arrows indicate
the direction of rotation of the two sporozoites. (B) Attached waving motion.
X–Y maximum projection of four time-lapse images acquired over
a 32 s period, artificially colored as red, cyan, green and yellow,
respectively. Scale bars, 5 µm.
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Fig. 4. Representative examples of the effects of salivary gland homogenate on
sporozoite motility. (A) Random sporozoite motility in Matrigel. (B) Directed
sporozoite motility in the presence of salivary gland homogenate.
X–Y (upper left), X-time (bottom), and Y-time
(upper right) maximum projections of 60 time-lapse images acquired over a 318
s period. The yellow outlined arrows show the directions of sporozoite
movement (green). To highlight the influence of time on sporozoite direction,
the yellow broken lines indicating the starting and ending points of a
sporozoite moving in X–Y space were projected into both
X- and Y-time space to demonstrate the influence of time on
motility. The solid yellow arrow in B indicates the relative position of the
salivary gland homogenate.
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Fig. 5. Effects of sample preparation temperature on sporozoite motility.
Sporozoites in Matrigel were exposed at 4°C for  40 min and transferred
to the chamber at 20°C at time 0. The graph is a summary of 240 time-lapse
images acquired over a 21 min period. Migration area of sporozoites in each
image was normalized to sporozoite number.
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Fig. 6. Sporozoite motility in the absence of salivary gland homogenate. (A)
Salivary gland-derived sporozoites. (B) Oocyst- and hemolymph-derived
sporozoites. The images represent X–Y maximum projections of 50
time-lapse images acquired over a 265 s period. The yellow outlined arrows
show the direction of sporozotie movement (green). Scale bars, 50 µm.
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Fig. 7. The effects of salivary gland treatment on sporozoite motility. Sporozoite
motility in the presence of (A) unheated or (B) heated salivary gland
homogenate. X–Y maximum projections of 106 time-lapse images
acquired over a 561 s period. The yellow outlined arrows show the direction of
sporozoite movement (green). The yellow solid arrows points to the relative
position of the unheated or heated salivary gland homogenate. The white arrows
point to fluorescent beads (b). Scale bars, 50 µm.
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Fig. 8. The effects of the site of origin of sporozoites on motility in the
presence of salivary gland homogenate. (A) Salivary gland-derived sporozoites.
(B) Oocyst- and hemolymph-derived sporozoites. The images represent
X–Y maximum projections of 140 time-lapse images acquired over
a 742 s period. The yellow outlined arrows show the direction of sporozotie
movement (green). The yellow solid arrows indicate the relative position of
the salivary gland homogenate. The white arrows indicate fluorescent beads
(b). Scale bars, 50 µm.
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© The Company of Biologists Ltd 2005
