Physiological energetics during the larval and metamorphic stages of marine invertebrates

Studies on the physiological energetics during the larval lifehistory stage of three marine invertebrates, the oyster, abalone and sea urchin are presented. The hypothesis that hybrid vigor should result either from a higher metabolic intensity or a more efficient conversion of acquired energy into growth by hybrids was tested using measurements of growth and respiration on larvae of the pacific oyster. Results from this study support the metabolic efficiency hypothesis in that superior growth of hybrids occurred in conjunction with similar or lower metabolic rate. The energetic cost of metamorphosis in the abalone was followed to determine the metabolic significance of this event. Morphogenesis associated with metamorphosis was rapid such that by 1 d after metamorphosis was initiated, most of the larvae had lost their velum and grown juvenile shell without experiencing elevated rates of oxygen consumption. Energy demands associated with these morphogenetic events are either minimal or the cost of other metabolic processes are reduced at this time. Changes in the abundance of a yolk protein that may serve as energy source and the percentage that is fully oxidized for energy yield during larval development were followed during development of the abalone. The decline in the abundance of this protein concomitant with mass stasis of elemental nitrogen and a lower than expected rate of ammonia release suggests that it may provide nitrogen to differentiating tissues and not be used to fuel the metabolic cost of development. Biochemical characteristics and histological location of this protein are presented. Video microscopy and gut analysis of feeding echinoderm larvae were used to determine where particles flavored with algal exudate (to mimic phytoplankton cells) were selected. Selection was inconsistent at the sites of capture and transfer to the mouth (flavor selected for, against or not at all). Flavored particles were consistently preferentially selected at the mouth and esophagus, however, occasionally overriding selection against flavor at the initial site of capture and during transfer to the mouth. Selection at these two sites may be somewhat independent and based on different criteria.