Two New Novophytoptus Species (Acariformes, Eriophyoidea) from Chile and a Novel Hypothesis on the Functioning of the Eriophyoid Digestive System

Endoparasitism is a highly specialized form of symbiosis, prominently manifested among phytophagous eriophyoid mites in the genus Novophytoptus Roivainen 1947. These mites have been traditionally thought to be restricted to the subepidermal lacunae of herbaceous monocots of the order Poales, which they penetrate to feed and reproduce. Based on surveys in Chile, two new species of Novophytoptus are described: N. cyperi n. sp. from Cyperus eragrostis (Cyperaceae) and N. eryngii n. sp. from Eryngium paniculatum (Apiaceae), with the latter representing the first record of Novophytoptus from a eudicot host. In accordance with the concept of “ecological fitting”, this unexpected association can be explained by the morphological similarity of E. paniculatum leaves with sedges, suggesting that convergent host morphology may drive host-switching between phylogenetically distant plant taxa across Eriophyoidea. Beyond taxonomy, modeling of Novophytoptus revealed a high volumetric disproportion (211-fold) between the microcapillary oesophagus and the massive midgut, along with a high body surface-area-to-volume ratio (~0.134 µm−1). Combined with structural constraints of musculature and intestine morphology, these findings challenge the traditional concept of mechanical pharyngeal pumping in Eriophyoidea. Alternatively, fluid ingestion is hypothesized to be driven by a synergy of an endodermal osmotic gradient and cuticular transpiration.