Morphological, molecular characterisation and phylogenetic position of Longidorus mindanaoensis n. sp. (Nematoda: Longidoridae) from a Philippine Avicennia mangrove habitat

Abstract

Longidorus mindanaoensis n. sp. is described from samples associated with riverine mangroves in the Philippines and is the first Longidorus species collected from such a habitat. Its relationship within the genus is inferred from molecular and morphological data. Phylogenetic inferences were performed for D2-D3 and SSU rDNA using appropriate phylogenetic algorithms. The new species is characterised by a thickened basal layer of the body cuticle with prominent spiral fibres, a dome-shaped continuous lip region, an oval to elliptical fovea with pore-like opening, the guiding ring at 2.2-2.5 lip region diam. from the anterior end, very weakly developed odontophore, all three pharyngeal gland nuclei at about the mid-point of the basal bulb, vulva at 30-39%, tail convex-conoid to hemispherical, shorter than anal body diam., males with 19-24 ventromedian supplements, and four juvenile stages, all with the replacement odontostyle at a short distance from the functional one. On the basis of amphid shape and structure, shape of anterior body region and general body shape, L. mindanaoensis n. sp. comes close to L. caespiticola, L. eridanicus, L. helveticus, L. macrosoma, L. poessneckensis, L. orongorongensis, L. waikouaitii and L. belondiroides. D2-D3 analysis placed the new species as sister to L. pisi and the two combined are sister clade to a monophyletic group that includes (L. poessneckensis (L. caespiticola (L. helveticus, L. macrosoma))). However, on the basis of SSU phylogeny, L. mindanaoensis n. sp. is positioned within a clade that includes (Longidorus sp. (L. mindanaoensis n. sp. (L. poessneckensis (L. helveticus, L. macrosoma)))). The ‘close’ relationship of the new species with L. pisi in the D2-D3 tree is incongruent with the widely different morphology of the two species. The other species that are close to the new species in the cladogram are in agreement with the morphology.