nematodes

List three take-away lessons from lecture 1

1. Nathan Cobb is known as the "father of American Nematology" and states that if all matter in the world, except nematodes, were to disappear, we would still be able to recognize outlines of mountains, valleys, bodies of water, and human settlements from our world. 2. Nematodes have diverse feeding modes. Different species feed on algae, bacteria, fungi, plants, and/or animals. Because of this, nematodes are economically important. 3. Another type of worm is segmented worms, or Annelids. This phylum includes Earthworms, which can play beneficial or harmful roles in the environment, depending on the ecosystem.

What is the number of molts in a nematode life cycle? (Use a numeral to indicate your answer)

4

Give a brief overview of a pathogenic nematode described in the slides

A pathogenic nematode is one that causes disease through parasitism. It goes through several stages in its lifecycle, beginning with Primary Inoculum, where the nematode contacts the host and begins disease cycle (for plant parasites, is the J2). This is followed by Secondary Inoculum and Synergism, when the effect of several parasites in a host becomes greater than the individual effect of each parasite. Pathogenic nematodes can cause mechanical, physiological, and nutritional damage on the host, as well as inject the host with toxic substances.

The predominant neurotransmitter in nematodes is:

Acetylcholine

What is a possible reason Ascaris produces so many more eggs than C. elegans in a day?

Ascaris is a parasite and many eggs are likely to be killed by host immune system

Briefly describe, in your own words, a nematode life-cycle that includes a form of dormancy. (you may use the prompts in the slides, or find your own)

Facultative diapause: a J1 stage C. elegans can make a decision to enter the dauer (dormant) stage based on stressful environmental conditions. The nematode can then continue into the J2 and J3 dauer stages if the environmental conditions are still stressful. C. elegans must leave dormancy after J3 dauer and continue to J4 and adulthood.

Differentiate vertical and horizontal nematode transmission

Horizontal nematode transmission involves parasites of the same generation. Vertical nematode transmission differs because it involves parasites of different generations.

Compare and contrast utilizing host resistance and crop rotation as methods to control plant parasitic nematodes

Host resistance and crop rotation are both methods used to control plant parasitic nematodes in agriculture. Some limitations to host resistance include that some root-knot nematode populations can circumvent this method and the genes may not be effective at higher temperatures. Meanwhile, crop rotation is an environmentally sustainable method and potentially one of the most successful. A downside to this method is that it can take careful planning due to root-knot nematodes having a large host range. (???)

Briefly summarize a nematology Nobel prize winning research and its impact

In 2015, half of the Medicine Nobel Prize was awarded to Satoshi Omura and William C. Campbell for their research on a new therapy for roundworm parasite infections. They tested several different cultures of streptomycetes, which are known to produce antimicrobial compounds, by treating mice infected with nematode parasites with them. They were able to isolate a nematicidal compound, now called Avermectin, from one of the cultures and modify it into Ivermectin, a compound with greater efficacy. Ivermectin is now used to treat humans and animals for diseases caused by threadlike parasitic nematodes. (???)

Why are nematodes hypothesized to have more radiations involving mutualism?

Nematodes are hypothesized to have more radiations involving mutualism because they are a very old group of organisms. The amount of time they've been around, compared to other invertebrates, indicates that they've had many opportunities for selection of mutualistic relationships (specifically marine nematodes).

How do you extract nematodes from soil?

Nematodes can be extracted from the soil either passively or actively. Passive extraction involves sieving, sugar floatation, and centrifugation. Active extraction uses the Baermann Funnel and requires living nematodes to move out of the soil into water at bottom of the funnel's stem.

Where can nematodes be found? (less than 3 sentences please)

Nematodes can be found in almost all marine, freshwater, and terrestrial environments. When in terrestrial environments, they're typically found in active association with water/high humidity.

Using external resources find and describe how do nematodes enter insect hosts.

Nematodes can enter an insect host through natural openings (mouth, anus, spiracles) and then move into the body cavity. Nematodes such as Heterorhabditis can pierce the insect's body wall to enter.

Can nematodes see light?

Nematodes cannot see light because they do not have eyes, but they have sensory structures that allow them to be aware of light, along with other parts of their external environment.

Describe nematode locomotion in your own words.

Nematodes use undulatory propulsion to move. This involves contracting the somatic muscles in the dorsal field and relaxing muscles in the ventral field, and vise versa. This causes bending in the nematode that moves it forward.

How is a heart different from a nematode esophagus?

Only nematode esophagus is ectodermal

Which of the following factors would be considered a biotic stress?

Pathogen attack

The disease triangle consists of

Pathogen, host, environment

How do nematodes locate each other for mating?

Pheremones

What is phylogenetics and how is it done?

Phylogenetics is the study of relationships between different organisms. Scientists have looked at morphology, embryological data, and genetics to group organisms together. From this data, relationships can be inferred based on similarities. Currently, genetic data is used to identify relationships between organisms.

Why are plant parasitic nematodes important?

Plant parasitic nematodes are important because they can significantly impact agriculture. Plant parasitic nematodes can damage crop plants mechanically (through feeding) and chemically (through injecting pharyngeal glad secretions into plant cells). Nematodes may carry plant pathogens (viruses, bacteria, and fungi). Plant parasitic nematodes can also predispose plants to diseases by being part of disease complexes. Overall, plant parasitic nematodes may introduce new diseases and shift current disease distribution patterns.

Nematodes are:

Pseudocoelomate, protosomes

What nematode morphology is used to sense the environment?

Sensilla

What is a benefit to the nematode body shape/size in a soil environment?

They can fit into soil pores to find food that other organisms can't.

Describe, in your own words, how an insect can defend itself from an internal bacterial parasite.

To defend itself from an internal bacterial parasite, an insect can use hemolymph and induced antibacterial proteins. Passively, the insect will have protection from its natural body structure (gut physiochemistry, cuticle).

Describe in your own words how vertebrate parasitism has evolved in nematodes

Vertebrate parasitism has evolved at least 3-4 times independently, from terrestrial nematodes. This occurred at least once in each class (Enoplea, Chromadorea).

Match the control method with its classification

applying a nematode anatgonistic bacterium to the field -- biological fumigant application -- chemical planting cotton instead of peanut -- crop rotation using different farm equipment between fields -- sanitation

This egg layer provides structural strength.

chitin

Match the corresponding symbiosis with its definition

commensalism -- symbiont benefits with no effect on host (phoresy) mutualism -- symbiont and host benefit from association parasitism -- symbiont benefits at expense of host

Match the nematode body orientation with the correct features.

dorsal -- teeth ventral -- vulva, anus lateral -- amphids

Which is not a method of plant parasitic control management

education

The __________ is responsible for worm architecture.

epidermis

Which is the correct order of nematode cuticle parts from internal to external?

epidermis, basal, median, cortical, epicuticle

Mutualism between cells is less intimate than mutualism at the population level.

false

Nematode coiling often occurs during diapause.

false

Quiescence is the form of dormancy where there is no metabolism.

false

Which nematode trophic groups usually have a needle shaped mouth part called a stylet?

herbivore fungivore

Which is NOT a part of the nematode digestive tract?

isthmus

Which of the following is NOT a theory of aging?

lack of rest

This egg layer is impermeable.

lipid

Match the plant parasitic lifestyle with its definition

live and feed externally -- ectoparasite live and feed internally -- endoparasite head inside host, body outside host -- semi-endoparasite locomotion is possible throughout lifecycle -- migratory nematodes lose mobility through life cycle -- sedentary

Match the nematode order with the correct pharynx.

monocchus -- 1 part dorylaimus -- 2 part pelodera -- 3 part

Which of the following are invertebrates?

nematodes flatworms earthworms

Nematode muscles are ____ striated, and have ____ filaments than vertebrate muscles. Vertebrate muscles are _____ striated and have _____ filaments than nematode muscles.

obliquely thicker and longer not obliquely thinner and shorter

A nematode with a barrel shaped stoma, with teeth, would likely feed on

other nematodes

Which is a characteristic a non-fumigant nematicide

percolate with water

Morphology of the __________ can be useful to classify nematodes.

pharynx

Which of the following is not a way an insect can defend against a nematode parasite?

physically combating the nematode

Needle nematodes are:

plant parasitic, vectors, and cause disease through nutritional drain and mechanical damage

What roles do nematode play in soil ecology?

primary, secondary and tertiary consumers

Correctly order the parts of the nematode esophagus/phaynx

procorpus, metacorpus, isthmus, posterior bulb

Which is not a part of the nematode nervous system?

sarcomere

Order the three steps of nematode molting

step 1: apolysis step 2: formation of new cuticle step 3: ecdysis

Order the steps of nematode hatching

step 1: juvenile movement step 2: enzymatic breakdown of eggshell step 3: change in egg permeability

This part of nematode anatomy is common and acts as an identifying character among all plant parasites

stylet

Etonecy is when the nematode completes its life cycle within a living host

true

If a nematode is isolated by spinning a water sample in a centrifuge, this is considered a passive extraction.

true

In a stressed environment, nematodes may enter a lower metabolic rate, or even a mode of dormancy.

true

In nematodes, neuromuscular process are sent out to the nerve.

true

Is parasitism a type of symbiosis?

true

Mutualism between cells is direct, while mutualism between populations is indirect

true

Necromeny is when the nematode uses its host's cadaver as food

true

Nematode diversity is greatest in the soil (if including plants and invertebrates within soil habitats)

true

Nematodes are preadapted to phoresy because they can form dauers

true

Nematodes are roundworms

true

Nematodes embryogeny begins with the formation of the mouth from or near the blastopore.

true

Which is the correct order of egg layer development?

vitelline, chitin, lipid