The Size and Shape of Traps of Utricularia vulgaris L.

Abstract

An individual of the aquatic carnivorous plant Utricularia vulgaris L. simultaneously bears many traps ranging in size from about 1 to 5 mm long. The traps are dimorphic, one type being in the vast majority. The shape, volume and biomass of majority-type traps conform to scaling relationships that allow various attributes of functional and ecological consequence to be predicted from an easily measured length. Trap size is not a reflection of the duration of development or age since maturity of a trap, since each cohort of traps consists of a range of trap sizes, resulting from differential rates of cell division and expansion. The investment of carbon, nitrogen and phosphorus resources in an individual trap scales with biomass such that about 40 small traps can be produced for the same initial outlay as one large one. Larger traps have a wider aperture and much more capacious lumen than small traps, potentially accommodating larger prey and more of them, but it remains to be discovered whether the benefits due to more prey caught by large traps scale to offset the greater costs of production. Key-words: Carnivorous plant, scaling of traps, Utricularia vulgaris