Laboratory Exercise 8
Purpose: Migratory endoparasitic nematodes: morphology, anatomy, biology, feeding habits -- Hoplolaimidae, Pratylenchidae (Tylenchina, Tylenchoidea)
1. Powerpoint presentation of characteristics.
2. Specimens of the following nematodes are provided for study in lab periods 8 and 9:
Hand-pick live adults of the Helicotylenchus sp., Pratylenchus sp. and Hirschmanniella sp. Draw the nematodes, observing the following characteristic features:
length and morphology.
b) esophagus, type and anatomy, nature of postcorpus interface with intestine.
c) male and female reproductive structures.
d) general shape when heat-relaxed.
3. Key the specimens of three populations of Pratylenchus provided to species using the key to the nine common Pratylenchus species of California.
4. Based on general anatomy and morphology, presence or absence of males, etc. would you consider it likely that the two Helicotylenchus examples are the same species of nematode?
5. Pratylenchus penetrans and Hirschmanniella pomponiensis are in the same nematode family, Pratylenchidae. There stylets and esophageal structures are morphologically similar. According to the species the original species descriptions they have the following average morphometric characteristics:
|Pratylenchus penetrans||Hirschmanniella pomponiensis|
|Body length (mm)||0.58||1.9|
|a (=body length (μm) / body width (μm)||25||66|
|b (= body length / esophagus length)||6.6||14|
|Stylet length (μm)||16||20|
For the purpose of this exercise, and for class discussion, consider both nematodes to be cylindrical. What can we infer from these dimensions about resource partitioning, growth rates, and population increase if rates of feeding are similar? Or if they are not similar?
6. Note the taxonomic position of these nematodes in the suborder Tylenchina.
7. Examine descriptive charts of the migratory endoparasitic nematodes in the Hoplolaimidae and Pratylenchidae.
Behavior of Pratylenchus penetrans
9. Study photographs of characteristics and damage by migratory endoparasites: Pratylenchus
10. Lab Project introduction:
Powerpoint presentation: Nematodes as Bioindicators.
11. Homework Assignment:
Review Pratylenchus including some of the species
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12. Nemabase Exercise
Review the host range of
these nematodes. What are the indicated non-hosts? Are there
resistant cultivars available?
From the Nemaplex main Menu, select Management and Decision Support, then Nemabase 2012.
Alternatively, you can access the data from the descriptive page for each nematode.
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Key to the Nine Common Pratylenchus
Species in California
|1.||Monosexual species, no sperm in spermatheca, males rare or unknown.||2|
|Bisexual species, sperm in most spermatheca, males common.||7|
|2.||Very large, round stylet knobs, stylet averages 19 Ám in length; V% 82-89; 2 lip annules||P. brachyurus|
|Stylet knobs oval or flattened, stylet generally less than 19 Ám long||3|
|3.||Tail tip annulated, 3 lip annules||P. crenatus|
|Tail tip smooth||4|
|4||Lip annules 2||5|
|Lip annules 3||6|
|5||Average V%=84, lip annules about same width; stylet knobs often flattened; vulval lips somewhat smooth||P. neglectus|
|Average V%=78%, anterior lip annules markedly narrower than posterior; vulval lips protrude somewhat||P. scribneri|
|6||Tail normally truncate, stylet averages 18 Ám in length; V% averages 76; normally assumes a "J" or "C" shape when heat killed||P. zeae|
|Tail narrowly rounded, stylet averages 16 Ám in length; V% averages 71; normally almost straight when heat killed||P. thornei|
|7||Lip annules 2, occasionally 3 on one side||P. coffeae|
|Lip annules 3, occasionally 4 on one side||8|
|8||Spermatheca normally round, posterior uterine branch 1 to 1.5 body widths long; large stylet knobs||P. penetrans|
|Spermatheca normally oval, posterior uterine branch generally greater than 2 body widths long; moderate sized stylet knobs||P. vulnus|
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