INTRODUCTION TO PLANT PARASITIC NEMATODES: 1. WHAT ARE NEMATODES?

This is the first of a series of short articles describing nematodes that affect plants.

What are nematodes?

Nematodes are worms. As a group (classified as Nematoidea) nematodes are one of the most numerous of all animals and are aquatic organisms, requiring moisture, fluids, and water in order to be active and to move. Nematodes are found in almost all environments where there are liquids, including soil, fresh water bodies, and the ocean. Nematodes have diverse lifestyles. A vast number of species are free-living in the soil, where they are herbivores (feeding on algae and fungi), saprophytes (feeding on dead organic matter), and predators (eating other animals, including other nematodes). A smaller number of nematodes species are parasites on plants or animals.

Nematode bodies are mostly filiform or thread-like (“worm” shaped) and are unsegmented, in contrast to other worms, such as earthworms, that have bodies divided into segments or sections. In later articles we will describe some plant parasitic nematodes that have mature body shapes that are not worm-like and are enlarged into various forms. Size-wise, most nematodes that live freely in the soil or are parasitic on plants are tiny (Photo 1). This means that virtually all plant parasitic nematodes with worm-shaped bodies are not visible with the unaided eye (Photos 2 and 3).

Future articles will describe plant parasitic nematodes, impact from nematode pests, and specific plant parasitic nematode groups.

Prepared by Steve Koike and Kristi Sanchez

Photo 1. Adult females of the plant parasitic burrowing nematode (Radopholus) placed next to a 2 lb test monofilament fishing line (diameter of the line is 0.005 inches or 0.13 mm wide).
Photo 2. Under the microscope, one adult female plant parasitic nematode (Aphelenchoides, red arrow) is next to two segmented worms (oligochaetes) that are free-living in soil; the green arrow points to a single fiber from a paper towel.
Photo 3. Oligochates have been placed on top of a penny, to show relative sizes and to emphasize the very small size of nematodes (not on the penny).

© 2018 Steven Koike | TriCal Diagnostics All Rights Reserved.

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