Molecular and morphological characterisation of Trichodorus species (Nematoda: Trichodoridae), with description of T. pseudoaequalis n. sp. from California and other states of the USA

Summary During surveys for stubby root nematodes in the natural vegetation of California, Oregon and Washington, USA, three known species, viz ., Trichodorus californicus , T. intermedius and T. obscurus were recovered together with ten unidentified Trichodorus species. The three known and one new species were studied using an integrated approach. Trichodorus pseudoaequalis n. sp. is characterised by a medium-sized body about 800 μ m long on average, male with two ventromedian cervical papillae anterior to secretory-excretory pore and three precloacal supplements all located anterior to the retracted spicules; spicules 39 μ m long (average), slightly ventrally curved, more so in head region and blade with slight indentation mid-way and striation more pronounced in posterior half. Females possess a rather short (average 33% of corresponding body diam.) pear-shaped vagina with small vaginal sclerotised pieces ( ca 1.5 μ m long), rounded triangular in shape, obliquely orientated and close together; one pair of sublateral body pores anterior (about four vulval body diam.) to vulva and one pair of post-advulvar sublateral body pores. Trichodorus pseudoaequalis n. sp. differs from the most similar species, T. aequalis , in male characters like general spicule shape and ornamentation and in the position of the dorsal pharyngeal gland nucleus in both sexes (at same level of posterior ventrosublateral pair vs clearly separated). The phylogenetic relationships of the recovered species were reconstructed using the ITS2 rRNA and the D2-D3 expansion segments of 28S rRNA gene sequences.