Morphological Comparison of Meloidogyne Female Head Structures, Perineal Patterns, and Stylets

Abstract

The external morphology of female heads of three populations of each of two cytological races of Meloidogyne hapla (race A-meiotic, race B-mitotic) and single populations of M. arenaria, M. incognita, and M. javanica was compared by light (LM) and scanning electron microscopy (SEM). Perineal patterns of all nine populations were observed with a LM and then examined with a SEM. In addition, female stylets of each population were excised, viewed with a SEM, and compared with observations made with a LM. Head morphology of the females, including shape of medial and lateral lips, expression of sensilla, and head annulation, was distinct for each species, each race of M. hapla, and each population of M. hapla race A. The morphology of a given perineal pattern appeared similar with the SEM and the LM. The SEM emphasized surface details, whereas the LM revealed subcuticular structure as well. Stylet morphology was unique for each species but similar in all populations of M. hapla. There were differences between species in the shape of the cone, shaft, and knobs and in the distance of the dorsal esophageal gland orifice from the stylet knob base. Several of the morphological characters first detected in the SEM were seen subsequently with the LM and are helpful in species identification. Key Words: cytological races, root-knot nematodes, Meloidogyne hapla, M. arenaria, M. incognita, M. javanica, scanning electron microscopy.