Nematology 101: Biology and Ecology

Nematology 101: Biology and Ecology

Deb Neher

University of Vermont

Dept. of Plant and Soil Science

deborah.neher@uvm.eduhttp://www.uvm.edu/~dneher/

Nematode Workshop 1st Morning Session

Soil Biological Indicators Lab

Dr. Deborah Neher uses soil nematode & microarthropods for monitoring soil quality and measuring progress of soil remediation (http://www.uvm.edu/~dneher/)

-1.0 +1.0

-1.0

+1.

0

cellulose

EC

cellulose/lignin

organic carbon

moisture

pH

pyrene

phenanthrenefluoranthene

5-ring

clay

benzo[a]pyrene

sand

bulk density

Hym enopteraL

Sym phylaPauropoda

O nychiuridae

other m itesfungi

O ribatida

proturans

Hym enopteraA

bacteria

D ip lopodaL

Isotom idae

Hom optera

Abundance of soil animals per square meter in European grassland

General characteristics of nematodesGeneral characteristics of nematodes

Aquatic

Unsegmented

Appendageless

Transparent

Bilaterally symmetrical

Generally bisexual

Vermiform roundworms

Non-coelomate

BiotrophsMeloidogyne hapla

No eyes, appendages or segmentation

Mechanosensory

Chemosensory

Fig. 2. Spiral-shaped chemosensory organs called amphids in an anterior position of Achromadora sp. collected from soil of Jumbo Valley fen in Cherry County, Nebraska.

Sensory organsSensory organs

Well developed digestive & reproductive & sensory systems

Lack circulatory & respiratory systems

Phytonematode anatomy & morphologyPhytonematode anatomy & morphology

Nematode identificationNematode identification

Pratylenchus Xiphinema Criconemella

Tolerate harsh habitats avoid interspecific competition and many

environmental selection pressures

Regulate uptake of O2 between 100 to 5%

Permeable, hydrostatic skeleton osmoregulation of Ca, Mg, K

Tolerate pH from 1.6 to 11.0

Temperatures from sub-zero to 60C +

Physiological versatilityPhysiological versatility

Aphelenchus, anhydrobiosis

SurvivalSurvival

a) bacterivore

b) bacterivore

c) bacterivore, predator

d) Fungivore and/or herbivore

e) omnivore

f) herbivore

g) herbivore

h) predator

Head structures of soil nematodesHead structures of soil nematodes

May feed on nematodes, protozoa, bacteria, etc

Figure 5. Teeth of oral opening of predator Mylonchulus montanus (1000x magnification), collected in soil with big blue stem in the Konza Prairie (96W35’ 39N05’) near Manhattan, Kansas. Photograph

is provided courtesy of Peter Mullin/2000.

Predatory nematodesPredatory nematodes

Simple tubular mouthpart

Elaborate cuticle around oral opening

Figure 4. Cuticle ornamentation of oral opening of Acrobeles ctenocephalus (1000x magnification), collected in soil with little bluestem (Andropogon scoparius) in the Konza Prairie (96W35’ 39N05’) near Manhattan, Kansas. Photograph is provided courtesy of Peter Mullin/2000.

Bacterial-feeding nematodesBacterial-feeding nematodes

Paulo Vieira (Mactode publications)

Respond to CO2 & root exudates

Move few cm per day

Probe with stylet

Ecto-parasites

Endo-parasites

Lifecycle: 3 weeks (root-knot) to 2 yrs + (dagger)

Figure 3. Variation in morphology of spear-like structure in oral opening a) male plant-parasite Hoplolaimus galeatus (1000x magnification) collected from soil with big bluestem (Andropogon gerardii Vitman) in the Konza Prairie (96W35’ 39N05’) near Manhattan, Kansas, and b) female fungivore Enchodelus hopedorus (400x magnification) collected from the summit of Long’s Peak, Colorado (105W35’ 40N16’). Photographs are provided courtesy of Peter Mullin/2000.

Plant-parasitic nematodesPlant-parasitic nematodes

Generalists or specialists

Hosts range from 1 to 100’s

All crop plants are susceptible to at least one nematode species

Plant-parasitic nematodes con’tPlant-parasitic nematodes con’t

Most are root parasites but species have adapted to parasitize most plant tissues

More damage can be associated with coarser textured soils – sands (larger pore space)

Major impacts of nematodesMajor impacts of nematodes

Decomposition of organic matter and

recycling of nutrients (soil food web)

Major impacts of nematodesMajor impacts of nematodes

Decomposition of organic matter and

recycling of nutrients (soil food web)

Biological control agents, esp. for insects

Research biological models

Diseases of animals and humans

(heartworm, Trichinosis, hookworm, etc.)

Important plant pathogens

Other nematodes...Other nematodes...

Animal parasites– Human: Night blindness,

Elephantiasis– Pets: Hookworm– Insects: biocontrol

Caenorhabditis elegans– Model system– Studies of aging,

neurology, ecotoxicology

Major impacts of nematodesMajor impacts of nematodes

Decomposition of organic matter and

recycling of nutrients (soil food web)

Biological control agents, esp. for insects

Research biological models

Diseases of animals and humans

(heartworm, Trichinosis, hookworm, etc.)

Important plant pathogens

Agrios

Morphology and relative size of major plant-parasitic nematodesMorphology and relative size of major plant-parasitic nematodes

Ectoparasites: feed from outside the plant

Migratory: moves, feeding from plant to plant (dagger)

Sedentary: remains on same plant (spiral)

Endoparasites: feed from inside the plant

Migratory: moves within and feeds on tissues (lesion)

Sedentary: remains within same plant and feeds at specialized sites (root-knot)

Types of Plant-Pathogenic NematodesTypes of Plant-Pathogenic Nematodes

Migratory endoparasite (lesion)

Sedentary endoparasite (root-knot)

Migratory ectoparasite (dagger)

Sedentary ectoparasite (spiral)

Essential Plant Pathology, 2006 NC State Univ.

Typical lifecycle of a plant-parasitic nematodeTypical lifecycle of a plant-parasitic nematode

H

M

MM

M

Egg1st stage juvenile

2nd stage juvenile (J2) mobile in soil

J2 infect root

Formation of giant cells and galls

3rd stage juvenile 4th stage juvenile

Egg mass

Modified from Agrios, 1997

Meloidogyne hapla

Agrios

Lifecycle of Pratylenchus penetrans – Root-lesion nematode

Lifecycle of Pratylenchus penetrans – Root-lesion nematode

Meloidogyne, Root knot nematode damage

Plant productivity lossesPlant productivity losses

Direct feeding on plants (metabolic sinks)

Malformation of host tissues (morphological &

physiological)

Predispose host plant to physical stress

Provide entry for secondary pathogens (disease complexes)

Breakdown of resistance to other pathogens

Vectoring of plant pathogens (virus & bacteria)

Suppression of beneficial organisms

How do nematodes damage plants?How do nematodes damage plants?

Nematology 101: Biology and Ecology

Nematology 101: Biology and Ecology

Questions?Questions?

Coming up next...signs and symptoms