Use of the continuity principle to evaluate water processing rate of suspension-feeding mosquito larvae

Water processing rates of active suspension-feeding larvae of Culiseta mors itans and Cities quinquefasciatus 2nd and 4th instars were estimated throug h video image analysis of the conical jet flow driving the large recirculat ion patterns surrounding the organisms. In accordance with the principle of continuity, individual processing rates (PRs) were assessed by averaging a series of consecutive flow rates (Q(x)) defined as the product of the wate r velocity (U-x) and the associated cross-sectional area (A(x)) along a tra nsect passing through the center of the delineated jet flow. Results clearl y show very tight adherence to the principle of continuity. They also demon strate that, although extreme care must be taken when streamtube delineatio n is performed, the methodology used can generate reliable assessment of in dividual processing rates regardless of the instars or species studied. The small coefficient of variation observed in assessing PR at the larval leve l further underlines the consistency of the method. Significant differences in water processing rates were observed for different species and instars. These could partially be related to body size, head width, and the length of the lateral palatal brushes (LPBs, which are the structures involved in the production of the water jet. Assessment of the jet velocity at the feed ing groove level suggests the keg role of LPB beating frequency in the jet intensity, and consequently the magnitude of the processing rate. Analysis of data further indicates that obligate suspension feeders such as Cs. mors itans must sustain a larger flow pattern around the larvae to ensure suffic ient particle entrapment than facultative suspension feeders (or even brush ers) such as Cs. quinquefasciatus.