In the evolution of decapod crustaceans, interspecific variation in egg size is considered as an important life-history trait that is linked with the durations of embryonic and larval development, the number and type of larval stages, and with juvenile size. Aiming to provide a quantitative characterization of reproductive traits in related decapod taxa differing in life style (freshwater, estuarine, marine) and geographic-climatic distribution (tropical-temperate), we compared size, biomass, and elemental composition of eggs of caridean shrimps from three families: 7 species of Palaemonidae (3 congeners of Macrobrachium: M. olfersii, M. carcinus, M. acanthurus; 4 species of Palaemon: P. northropi, P. pandaliformis, P. elegans, P. adspersus), 2 Atyidae (Potimirim potimirim, Atya scabra), and 1 Pandalid (Pandalus montagui). Egg size was measured as larger and smaller diameter (D1, D2), volume was calculated from D1 and D2, and biomass was measured as dry mass (W), carbon (C), nitrogen (N), hydrogen (H), and energy (E, estimated fom C) contents. The smallest size and lowest biomass were found in the eggs of two freshwater atyids (both originating from Brazil), the largest size occurred in a marine species, P. montagui (from the North Sea), and intermediate values in freshwater, estuarine, and marine palaemonid species (from Brazil and the Baltic Sea, respectively). Among the Palaemon species, the most limnic (P. pandaliformis) showed a significantly larger egg size and volume (P<0.001) than the estuarine and marine congeners, P. elegans, P. adspersus and P. northropi. This suggests that the generally postulated relationship between egg size and life style (freshwater vs. estuarine or marine) may appear at a generic but not at the family level. On the other hand, individual biomass (in µg or Joules per egg) of early eggs was significantly higher in P. elegans and P. adspersus, indicating interspecific variability in biomass and energy concentration (in µg or Joules per unit volume, mm3). Generally lower biomass concentrations in early eggs of freshwater shrimps may be caused by a higher average water content. Eggs in late embryonic stages were generally larger than earlier eggs of the same species, reflecting an increase in the water content, while an increasing D1:D2 quotient indicated an increasingly elongated egg shape. The biomass per egg decreased during embryonic development due to metabolic degradation of organic reserves. As a consequence of inverse ontogenetic changes in size and organic biomass of developing eggs, the mass-specific biomass values (C, N, H in % of W; E in Joules per mg W) and volume-specific concentrations (µg or Joules per unit volume) decreased. This change was consistently stronger in the C, H, and E contents than in other measures of biomass (W, N). In consequence, the C:N mass ratio also decreased, suggesting that lipid degradation rather than protein utilization was the principal fuel for embryonic development. Our results indicate high intra- (mainly developmental) and interspecific variation in reproductive traits of closely related species. While volume-specific biomass and energy concentrations of early eggs appear to be associated with variation in habitat salinity (freshwater brackish marine), individual egg size and biomass may be related more with the climatic-geographic distribution (temperate tropical) of different taxa.