About 90% of the extant species of the Decapoda live in oceans and adjacent coastal and estuarine regions, and most of them pass through a complex life history comprising a benthic (juvenile-adult) and a planktonic (larval) phase. The larvae show a wide array of adaptations to the pelagic environment, including modifications in functio-nal morphology, anatomy, the molting cycle, nutrition, growth, chemical composi-tion, meta-bo-lism, energy partitioning, ecology, and behavior. Due to these adaptive traits, which are the principal subject of this volume, decapod larvae are more like unrelat-ed holoplanktonic organisms rather than resembling the conspecific benthic juveniles and adults. Emphasis is here on the lesser known anatomical, bioenergetic, and ecophysiologi-cal aspects of larval life, because morphology has already extensively been documented in the literature. Changes in biological parameters (e.g. rates of feeding, growth, metabolism) are shown in successive developmental stages, within individual stages, and as repsonses to environmental factors. Particular attention is paid to interrelationships between intrinsic phenomena (molting cycle, organogenesis, growth) and the overlaying effects of extrinsic factors (e.g. food, temperature, salinity, pollution). Concluding from the available data, we may identify major bias and gaps in our present knowledge of larval biology. For instance, biochemical, physiological, and anatomical aspects have been investigated much less than larval morphology, ecology, and behavior, and bioenergetic parameters have large-ly been studied as isolated physio-lo-gi-cal traits rather than attempting to quantify the overall partition-ing of chemical energy. Little is known also about intraspecific variability within or between separate populations. This remains a major challenge for larval biologist, because knowledge of phenotypic plasticity and genetical divergence, e.g. in larval morphology or stress tolerance, is of utmost importance for the understanding of evolutionary adaptation and speciation. In particular, early ontogenetic adaptations to extreme or unpredictable ecological conditions are important in the evolutionary transitions from marine to limnic or terrestrial environments. We also need more compari-sons between field and laboratory observations in order to "calibrate" data from the field with those obtained under controlled conditions; inversely, those comparisons should help to identify "domestication effects" and other artifacts that are potentially pertinent to laboratory data. Furthermore, future research should increasingly consider effects which persist through successive life-history phases, e.g. those of embryonic acclimatization on larval stress tolerance, or the significance of larval condition for later settlement and recruit-ment success.