NEMATOLOGY 100

Laboratory Exercise 11

Rev. 01/01/2020

Purpose:  Above-ground feeding nematodes:  morphology, anatomy, biology, feeding habits -- Ditylenchus and Anguina (Rhabditida - Tylenchina, Tylenchoidea, Anguinidae).

1.   Powerpoint presentation of characteristics, including a review of Ditylenchus and Anguina.

2.   Tease apart galls on leaves of Wyethia mollis collected at at Donner Pass in summer 2000 and earlier.  Observe Anguina balsamophila in the coiled anhydrobiotic condition.  What stages are present in the galls? 

3.   Examine Anguina agrostis extracted from ryegrass seed after more than 25 years of storage.  What stages are present?

4.  Examine dried nematodes of Ditylenchus dipsaci and Anguina agrostis stored since 1964.  Are they still viable?

5.  Examine seed galls caused by Anguina tritici.

6.  If available, select green stem galls from Poa annua golf course turf.  Dissect the galls to release nematodes (Anguina pacificae).  What stages are present?  Is there evidence of bacteria in mature galls?

7.  Hand-pick live adults of Anguina balsamophila and Ditylenchus. dipsaci.  Draw the nematodes, observing the following characteristic features:
          a)   stylet 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.

8.   Note the taxonomic position of these nematodes in the Order Rhabditida, Suborder Tylenchina

9.   Examine descriptive charts of these plant-parasitic nematodes in the Anguinidae.

10.  Lab Project; Faunal Analysis Reports: Report to the class on your conclusions regarding the state and functions of the soil ecosystem represented by your sample.

11.   Videotape:
          a)   The Stem Nematode: a pest in agriculture.

12.  Anhydrobiosis Experiment:

Objective:  To compare the survival of nematodes in soil allowed to dry with that in soil kept moist. 

• Work in pairs (or in 6 groups).
• Each group is provided with six beakers of sand inoculated with around 300 nematodes of various species.
• Place the sand from four beakers in separate Petri dishes.
• Weigh each of the four dishes with sand to determine the initial weight.
• Place a lid on two of the Petri dishes to retard drying, leave the other two open.
• Place the two open and two covered dishes in front of a fan to facilitate air drying.
• Place the soil from the final two beakers on a Baermann funnel to be taken down at the next lab (lab 12) so that we can determine nematode types and abundance at the start of the experiment.
• At lab period 12  we will place the soil from one covered and one uncovered dish, after 5 days of drying, on a Baermann funnel to determine survival of various nematodes at lab 13.
• Also at lab 12, bring the remaining moist dish up to its initial weight by adding water. One week later (lab 14) we will extract nematodes from the second moist and dry dishes to be counted and identified at lab 15..

Questions:

Are there differences in the survival rates of different nematode taxa or of nematodes with different feeding habits?

Other than differential survival in dry and moist soils, are there other explanations for differences among the samples?

12.  Study photographs of characteristics and damage by stem, bulb, bud and seedgall nematodes.

13.   Homework Assignment:

          NEMAPLEX Exercise
          Main Menu:
               Select...Biology and Taxonomy
                Select..Phylogenetic Classification
                 Select...Rhabditida then Tylenchina
               Select...Anguinidae
                           Review Anguina, including A. tritici, A. agrostis and A. pacificae.
                           Review Ditylenchus, including D. angustus,   
                           D. destructor, D. dipsaci and D. myceliophagus.
                

14.   NEMABASE Exercise
       

         Review the host range of nematodes in the genera Ditylenchus and Anguina.  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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