more individual animals are nematodes than anything else (80)
- found in all habitats at many trophic levels
Role in ecosystem services
Agriculture (animal and plant)
Science model to study animal biology
3 Nematodes in the Tree of Life Eukaryotes Animals Bilateria 4 Phylum Nematoda Nematoda Stilbonematids are marine nematodes that are coated with sulfur-oxidizing bacteria. They live few centimetres below the sea bottom where they migrate between superficial sand layers and deeper ones. These migrations allow the microbial symbionts to alternatively obtain oxygen and sulfide. In turn the microbes constitute the major component of the worms diet. Plant Pathogens http//www.univie.ac.at/shallow-water-symbiosis 5 Plant Pathogens Nematodes are ecologically diverse Diversity indices of nematode communities are used as ecological indicators. 6 (No Transcript) 7 (No Transcript) 8 (No Transcript) 9 sensory organs touch receptor chemoreceptor stoma (mouth) Feeds on bacteria Plant feeding nematode Nematodes use their nervous and muscular systems to locate and obtain food 10 Plant feeding nematodes are obligate parasites that feed using straw-like stylet mouthparts. Peter M. Sforza and Jon D. Eisenback Department of Plant Pathology Physiology and Weed ScienceVirginia Polytechnic Institute and State UniversityBlacksburg Virginia USA 11 Stylet morphology is diagnostic. The shape and size of the stylet is related to how and where the nematode feeds. 12 stylet reproductive system esophagus intestine 13 Features common to plant parasitic nematodes
Vermiform shape (some or all life stages)
14 Nematodes move through soil pores to locate roots. Nematodes are too small to move soil particles so are restricted to living in soil pores. Needle and sting nematodes are restricted to sandy soils due to pore size requirements. Nematodes are classified as mesofauna S. Rose and E.T. Elliott 15 Nematodes move easily in water films on a solid surface but not in free water. Nematodes have four sets of muscles that run the length of the body causing them to move in a dorsal-ventral plane. nematode tracks on agar Water films facilitate movement too much or too little soil water decreases nematode activity. 16 Their adaptations and strategies may differ but all nematodes share similar challenges in completing the life cycle. Egg J2 J3 J4 Adult molt molt molt molt
Developing / molting
Receiving and processing information
Infecting / feeding
17 Nematodes are animals that develop from a juvenile state to sexual maturity. Nematodes grow a new cuticle and stylet with every molt. egg For many genera juveniles have the same general appearance as adults but are smaller and sexually immature. Adults can be distinguished by the presence of a fully-formed reproductive system. 18 Life cycle differences Stubby Root nematodes (Paratrichodorus spp.) have a relatively short generation time 2 ½ to 6 weeks. Oregon State University (http//mint.ippc. orst.edu/stubbynemaid.htm) Dagger nematodes (Xiphinema spp.) may take up to a year to complete one generation. Other features that vary include egg-laying habits life stage that hatches from the egg obligate dormancy for some species dispersal strategies 19 Top 15 Regulated Nematode Pests in the World
Countries Plant Part
Pest Nematode Regulating Infected
Globodera rostochiensis 106 roots tubers
Aphelenchoides besseyi 70 leaves
Ditylenchus dipsaci 58 leaves bulbs
Radopholus similus 55 roots
Globodera pallida 55 roots tubers
Ditylenchus destructor 53 roots seeds tubers
Heterodera glycines 52 roots
Aphelenchoides fragariae 47 leaves
Bursaphelenchus xylophilus 46 trees
Xiphinema index 42 roots
Nacobbus aberrans 38 roots tubers
Xiphinema americanum 30 roots
Anguini tritici 24 seeds
Heterodera schachtii 22 roots
Bursaphelenchus cocophilus 21 trees
Occurs in Wisconsin 20 Nematodes are often classified by their life style ectoparasitic nematodes - only the stylet enters roots 21
enter into the root and feed from the inside
sedentary root knot and cyst nematodes
migratory root lesion nematodes
female 22 Sedentary Endoparasites All sedentary endoparasites have specialized feeding sites in the root. 23 root galls on infected lettuce roots Root knot nematodes Meloidogyne spp.
Most spp. have wide host range.
4 major species
adult female nematode on the head of a pin juvenile next to a human hair 24 Root-knot affects both quality and yield 25 Root Knot life cycle
Second stage juveniles enter behind root tip.
Nematodes change in shape as they feed on 4-6 specialized plant cells.
Root cells increase and enlarge forming a gall.
Males change form when they reach the adult stage and leave the root.
Adult females lay eggs into an egg mass.
26 egg juvenile male juvenile stages adult stages 27 nematode feeds on 4-6 giant cells 28 (No Transcript) 29 Diagnosing a root knot nematode problem Which plants are infected with root knot nematode symptoms sign 30 sign root knot egg masses 31 (No Transcript) 32 cyst nematode Heterodera spp. Many species - narrow host range - named for primary host SCN Management Guide cyst dead body of female 33 SCN is the most important disease of soybean in the U.S. 34 susceptible cultivar on left / resistant on right 35 Heterodera glycinessoybean cyst nematode 36 J3 J2 nematode feeding cells 37 soybean cyst nematode Heterodera glycines SCN 38 Symptoms stunting chlorosis patchy distribution in field 39 Microbivorous nematodes have open stoma (mouth) 40 (No Transcript) 41 Nematodes that live in soil are - microscopic - transparent 42 Plant parasitic nematodes have stylets 43 root knot female (on the head of a pin) egg 44 (No Transcript)
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