Developmental patterns in decapod crustaceans are commonly considered as canalized, i.e. as constant species-specific traits, which are relevant for phylogenetic analyses. However, there are numerous examples of intraspecific variability in larval morphology and developmental pathways, especially in caridean shrimps. This background noise has widely been ignored, although it may affect conclusions drawn from interspecific comparisons in the contexts of taxonomy and life-history evolution. Intraspecific variability in the number and morphology of successive stages also impedes the identification and staging of field-collected larvae, impairing studies of their ecology, growth, dispersal, and recruitment. On the other hand, experimental studies of the extent and causes of developmental variability under controlled conditions may provide new criteria (in addition to rates of survival, moulting and growth) that can be used for the evaluation of larval fitness in relation to different environmental conditions: Morphologically stunted forms occurring after a given number of moults may indicate sublethal physical or nutritional stress prevailing during the period of larval development, while rapid morphogenesis should reflect favourable conditions. Variability in developmental patterns may also result from carry-over effects of previous conditions persisting from the embryonic through the larval phase. Similarly, variations in larval traits may affect the recruitment success and postmetamorphic fitness of benthic juveniles. Plastic developmental traits are therefore potentially relevant for population dynamics, distribution patterns, and the formation of metapopulations in benthic species with complex life cycles. Moreover, the testing of cultivation techniques, especially in shrimp aquaculture, should benefit from the introduction of additional evaluation criteria. In conclusion, intraspecific variability remains a frontier in larval biology that should no longer be neglected.