Figure 1.
Mosquito body plan and positioning system.
A. Mosquito body plan, illustrating the position of the dorsal vessel (divided into an abdominal heart and a thoracic aorta), the ostia (valves), and the excurrent openings. B–D. In this study, mosquitoes were restrained in lateral (B), ventral (C) and dorsal (D) orientations using non-invasive methods.
Table 1.
Quantitative analyses of ventral abdominal contractions.*
Table 2.
Quantitative analyses of heart and abdominal contractions.*
Figure 2.
The ventral abdomen contracts in a retrograde direction during periods of anterograde heart contractions.
Quantitative analysis of video S1 showing percent area changes in a section of the anterior heart (top graph) and a section of the posterior ventral abdomen (bottom graph) showing the temporal correlation of heart and abdominal contractions (peaks) during the three principal contraction periods: anterograde heart contractions and abdominal rest, anterograde heart contractions and ventral abdominal contractions, and retrograde heart contractions and abdominal rest (bottom diagram). Overall, ventral abdominal contractions (asterisks) correlate with anterograde heart contractions. Shaded boxes depict the direction of heart contraction periods (AG, anterograde; RG, retrograde).
Figure 3.
Hemolymph flow in the lateral and ventral mosquito abdomen.
Intrathoracically-injected fluorescent microspheres were tracked as they flowed in the lateral (A) and ventral (B) abdomen during periods of anterograde heart contractions and abdominal rest, and during periods of anterograde heart contractions and ventral abdominal contractions (0.55 seconds of tracking data are shown per microsphere). In both the lateral and ventral abdomen, microspheres flowed in retrograde and dorsal directions, and achieved higher net displacement during periods of ventral abdominal contractions. Roman numerals denote abdominal segment number. D, dorsal; V, ventral; A, anterior; P, posterior; L, lateral.
Figure 4.
Hemolymph flow velocity and acceleration in the lateral and ventral mosquito abdomen.
A. Diagrammatic representation of the general path of microspheres in the lateral and ventral abdomen during periods of anterograde heart contractions (black dotted arrows), illustrating the location where microspheres were tracked for velocity and acceleration calculations (panels C–H). B. In panels C–H, velocity represents the actual distance traveled (gross displacement; d, solid line) divided by time (T), velocity from origin represents the net displacement (d, dotted line) divided by time (T), and maximum acceleration represents the highest acceleration measured for a given microsphere. C–H. Velocity (C, F), velocity from origin (D, G), and maximum acceleration (E, H) of 2 µm fluorescent microspheres flowing through major lateral (C–E) and ventral (F–H) hemolymph flow lines. During periods of anterograde heart flow, hemolymph flows through the lateral and ventral abdomen at higher velocities and greater acceleration during periods of ventral abdominal contractions as compared to periods of abdominal rest (Mann-Whitney). Median, center line; 50% of the data, box; 90% of the data, whiskers; mean, solid square.
Figure 5.
A. Dissected whole mount showing that the abdominal musculature in the dorsal tergum is composed of (1) six complete pairs (red arrows) and two incomplete pairs (blue arrows) of alary muscle pairs (e.g., dotted circle) that support a muscular heart (yellow arrows), (2) paired intersegmental muscle bands (e.g., dotted rectangles) that connect adjoining tergites, and (3) intrasegmental lateral muscle fibers (e.g., hexagon) that extend from the lateral tergum to the lateral sternum. B. Dissected whole mount showing that the abdominal musculature in the ventral sternum is composed of (1) five complete pairs (red arrows) and two incomplete pairs (blue arrows) of ventral transverse body muscles (e.g., dotted circle) that laterally extend across sternites and form the ventral diaphragm, (2) paired intersegmental muscle bands (e.g., dotted rectangles) that connect adjoining sternites, and (3) intrasegmental lateral muscle fibers (e.g., hexagon) that extend from the lateral sternum to the lateral tergum. The underlined areas of this specimen, or an analogous specimen, are magnified in figure 6A–C. C. Whole mount imaging through the sternum showing the ventral diaphragm (vd; one ventral transverse muscle pair is circled) and the lateral intrasegmental muscles (e.g., hexagon). D. Whole mount of a specimen dissected along a sagittal plane showing the heart (h), three alary muscle pairs (am), three ventral transverse body muscle pairs (vd), intersegmental muscles, and intrasegmental lateral muscles (asterisk). Note that the alary and transverse muscles are attached to the lateral edges of the tergum and sternum (yellow arrows), respectively, and overlap with the intrasegmental lateral muscles that span the pleuron. E. Whole mount imaging through the pleuron and sternum showing the origin of ventral transverse muscle pairs (yellow arrows). Bars: A–C = 500 µm; D = 200 µm; E = 100 µm. White arrows point toward the anterior of the mosquito.
Figure 6.
A–C. Imaging of anterior (A), middle (B), and posterior (C) segments of the ventral diaphragm. Note that the intersegmental muscle bands (e.g., yellow arrows) are considerably more robust in abdominal segments 1 and 2 (A). Furthermore, the terminal incomplete transverse body muscle pair is located in the anterior portion of abdominal segment 7 (C; red arrows), but extends bilaterally symmetrical myofibers that anchor on the 8th sternite (C; blue arrows). Bar = 150 µm. White arrow points toward the anterior of the mosquito.