EARLY ONTOGENY OF WALLEYE, STIZOSTEDION-VITREUM, WITH STEPS OF SALTATORY DEVELOPMENT

Frequent in vivo observations of arbitrary stages revealed a saltatory pattern of development in the early ontogeny of fluvial spawning walleye. The requirement for an environment rich in dissolved oxygen was indicated by i) spawning site characteristics, ii) the lack of carotenoid pigments, iii) swim-up at hatching, iv) a planktonic (pelagic) existence by means of immobile surface suspension and subsequent surface swimming, and v) a poorly developed temporary embryonic respiratory system, including a subintestinal-vitelline vein, hepatic-vitelline vein and duct of Cuvier. Between the start of hatching and development of the ability to remain planktonic, the temporary embryonic respiratory system was enhanced by an increase in the proportion of the total blood volume passing through the subintestinal-vitelline vein - the largest respiratory surface. Immobile surface suspension was possible due to both the buoyancy of the large oil globule and the forces of surface tension. Also, immobile surface suspension would provide low energy transport from the fluvial spawning grounds to the lacustrine environment where zooplanktonic prey would be relatively more abundant. An intimate relationship between oil globule size (shape) and a dynamic behavioral transition (including the consumption of larger particles, cannibalism, and swimbladder inflation) suggested that energy expenditures occurring during fluvial transport were necessary for appropriate developmental synchrony. © 1979 Dr. W. Junk Publishers.