On Growth and Form in Nematoda: Oesophagus and Body-Width in Tylenchida

Abstract

Results from some fifty studies on post-embryonic growth and variability were used to compare oesophageal length, stylet length and body width in relation to body length during development and maturation. Oesophageal length follows closely body length; growth in volume of the median bulb depends on the widening of the female. The position of the median bulb determines the maximal stylet length and, to some extent also, the development of the median bulb. Between the Criconematoidea and the Tylenchoidea some differences were noticed in stylet structure (constant shaft length in Criconematoidea), in stylet length (more dependent on body length in Criconematoidea), in body shape during growth (during the later stage of the post-embryonic period Criconematids show an increase in the a-value and Tylenchids show a decrease in the a-value), in body shape during maturation (Criconematids with large annules and no lateral field become longer and relatively thinner, Tylenchids with lateral field become less long and relatively thicker). A lateral field is needed to realize in every circumstance a close contact between body wall and egg so that the somatic musculature can help with egg-laying. When in older females the elasticity of the lateral field (and of the rest of the cuticle) diminishes, eggs have to develop within their mother's body; this process is known as endotokia matricida.