Plankonvexe

Plankonvexe is a descriptive term used in plankton biology to characterize planktonic organisms whose outer surfaces or outlines are convex when viewed along the principal axes. The word combines references to plankton with the notion of convexity. It is not a formal taxonomic category, but a morphological descriptor used in various contexts to summarize shape attributes of planktonic forms.

Origin and usage: The term appears as a descriptive neologism in some morphometric and paleoecological studies. It is employed to indicate convex outlines or surfaces in shells, tests, or bodies, and may be applied across protists, microcrustaceans, and other planktonic taxa. As a descriptor, it helps summarize a specific aspect of form without implying a strict evolutionary relationship.

Morphology and measurement: Convex features include bulging apices and domed tests or shells. Convexity is quantified using metrics such as convexity index, curvature distribution, solidity, sphericity, and aspect ratio. Analyses typically rely on two-dimensional outlines from light microscopy or scanning electron microscopy, or on three-dimensional reconstructions from imaging techniques.

Ecology and function: Convex shapes influence buoyancy, sinking velocity, hydrodynamic drag, and stability in the water column. These properties can affect residence time, nutrient uptake, feeding efficiency, and vulnerability to predators, particularly in vertically stratified environments where water movement and density gradients vary.

Taxonomic and comparative use: As a descriptive descriptor, plankonvexe is not a standalone taxon. In paleoecology and systematics, convex outlines of fossil plankton tests or shells assist in distinguishing morphological types and interpreting past environmental conditions.

See also: Plankton morphology, morphometrics, buoyancy, sinking rate.