Morphological and molecular study of Californian species of the genus Aporcelaimellus Heyns, 1965 (Dorylaimida: Aporcelaimidae)

Abstract

Several species of Aporcelaimellus collected in natural areas in California, USA, are characterised on the basis of morphological, morphometric and molecular data. Two new species are identified and described here. Aporcelaimellus californicus sp. n. is characterised by its body length of 2.46-3.42 mm, lip region offset by constriction and 24-26 μm broad, odontostyle 23-24 μm long, neck 611-765 μm long, pharyngeal expansion occupying 50-52% of total neck length, a dorsal cellular mass present at level of cardia, uterus simple and 246-408 μm long, V = 53-58, short conoid tail (43-50 μm, c = 56-71, c′ = 0.8-1.0) with a large hyaline portion occupying more than half of its total length, spicules 98 μm long, and 8-9 spaced ventromedian supplements. Aporcelaimellus salicinus sp. n. is distinguished by its body length of 1.45-1.94 mm, lip region offset by deep constriction and 16-18 μm broad, odontostyle 18-20 μm long, neck 393-521 μm long, pharyngeal expansion occupying 45-51% of total neck length, presence of a dorsal cellular mass at level of cardia, uterus simple and 21-45 μm long, V = 51-57, tail conical to conoid (31-38 μm, c = 39-59, c′ = 1.0-1.4), and male unknown. Measurements, sequences and taxonomic comments are provided for the other three Aporcelaimellus species. Californian Aporcelaimellus display a notable morphological homogeneity but a remarkable molecular diversity, putting into question the monophyly of this group.