A test of the general occurrence and predictive utility of isochronal, equiproportional, ‘variable proportional’, and ‘mixed’ development among arthropods

Abstract

In isochronal (ICD) and equiproportional development (EPD), the proportion of total immature (egg, larval, and/or juvenile) development spent in each stage (developmental proportion) does not vary among stages or temperatures, respectively. ICD and EPD have mainly been reported in copepods, and whether they occur in other arthropods is not known. If they did, then rearing studies could be simplified because the durations of later developmental stages could be predicted based on those of earlier ones. The goal of this study was to test whether different taxa have ICD, EPD, or an alternative development type in which stage-specific proportions depend on temperature, termed variable proportional development (VPD), and also how well each development type allowed later-stage durations to be predicted from earlier ones. Data for 71 arthropods (arachnids, copepod and decapod crustaceans, and insects) were tested, and most (85.9 %) species were concluded to have VPD, meaning that ICD and EPD do not occur generally. However, EPD predicted later-stage durations comparably well to VPD (within 19-23 %), and thus may still be useful. Interestingly, some species showed a mixed form of development, where some stages developmental proportions varied with temperature while those of others did not, which should be further investigated.\n\nHighlightsO_LIWhether arthropod development is generally isochronal or equiproportional was tested\nC_LIO_LIDevelopmental proportions of most species stages varied with temperature\nC_LIO_LIMany species had mixed development between variable and equiproportional types\nC_LIO_LIThe general occurrence of isochronal and equiproportional development was rejected\nC_LIO_LIEquiproportional development did make reasonable predictions of stage durations\nC_LI