Filtration and respiration of filter-feeding marine invertebrates are linked through allometric power-law functions - verification of hypothesis

Filter feeding in marine invertebrates is a secondary adaptation where the filtration rate (F) that provides the food energy to cover the respiration (R) increases with increasing body dry weight (W), and therefore it may - as an hypothesis - be suggested that the exponents in the equations F=a₁W^b1 and R=a₂W^b2 have during the evolution become near equal, b₁≈b₂, ensuring that the F/R-ratio=a₁/a₂ is nearly constant. Based on published data, we verify the “hypothesis of equal allometric power-law exponents” and we test to what degree the F/R-ratio may be used to characterize various adaptations to filter-feeding. The available b-values for very different taxonomic groups of filter feeders (bivalves, ascidians, crustaceans, polychaetes, jellyfish) covering 8 decades of body dry weight support in most cases the hypothesis of b₁≈b₂. For obligate phytoplankton filter feeders where b₁≈b₂ the F/R-ratio was used to estimate the critical phytoplankton biomass below which the animal would starve. However, if the food-particle retention efficiency is not constant during an animal's ontogeny the F/R-ratio may change according to the size-range of particle being captured at the specific stage of development.