Video Microscopy of Biphasic and Continuous Hemolymph Flow in the Circulatory Systems of Developing Embryos of the Waterstrider <I>Gerris paludum insularis</I> (Hemiptera: Gerridae)

Abstract

Hemolymph flow patterns, deduced from movements of single plasmatocytes (PLs) in the heart-dorsal vessel system were observed in developing embryos of the waterstrider Gerris paludum insularis Motschulsky. Video images of single moving PLs successively captured at 0.033 s intervals were followed to reveal their passage during each cardiac cycle, and a structural cardiogram was used to analyze the movements of individual PLs in terms of the cycle. In hearts of G. p. insularis embryos, cultured for 80 h after katatrepsis (K+80 h embryos; K stands for katatrepsis), forward flow with systole and backward flow with diastole occurred alternatively during each cycle. In K+100 h embryos, however, forward flow was observed only with systole and ceases at other times in the cycle. Velocity of single moving PLs in K+80 h embryos, estimated from distance traversed by PLs for each 0.033 s, was smaller than that in K+100 h embryos similarly estimated. This might indicate that the force generated by each systolic contraction in the heart of G. p. insularis embryos increased as embryogenesis advanced. Velocity of single moving PLs was suggested as a useful parameter to assess functional development of embryonic heart in insects.