Use of Trail Pheromones - Zoology - Lab Handout, Exercises for Zoology. Allahabad University
amidii5 January 2013

Use of Trail Pheromones - Zoology - Lab Handout, Exercises for Zoology. Allahabad University

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Its the important key points of lab handout of Zoology are: Use of Trail Pheromones, Termites, Chemical Communication, Brushes for Manipulating Termites, Manipulation of Odor Plume, Trail-Following Accuracy, Different Te...
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Zoology Lab

Termites and the Use of Trail Pheromones

Chemical communication is perhaps the most ancient means of communication in the

animal world. Animals send and receive chemical messages that hold information

about food location, danger, territory, and mates. Chemical messages are private,

effective in darkness, long-lasting, and they may operate over long distances.

Reliance on chemical communication ranges from not-at-all in some species to

extreme in others. Humans, for example, live in a sensory world dominated by acute,

3-dimensional color vision. Other mammals such as mice and deer rely heavily on

chemical communication to interact with conspecifics. The insects are particularly

well-known for pheromone production and their acute olfactory ability. The most

spectacular insects in terms of pheromone use are highly social species such as

honeybees, ants, and termites. Their body compartments are loaded with

pheromone-secreting glands and their antennae have many olfactory neurons that are

highly-sensitive to airborne signals.

Termites live in highly organized societies that are built around physical castes and

defined divisions of labor. The key castes that maintain and defend the colony are the

workers and soldiers, respectively. As the name implies, soldiers are devoted to

colony defense and have the anatomy to repel invaders. Workers do routine nest

maintenance and are responsible for finding and retrieving food. After a foraging

worker finds a food source, it deposits a trail pheromone on the ground as it returns to

the nest. The trail pheromone represents a temporary signal that nest-mates may

follow to that same food source. If subsequent workers also find food, they reinforce

the signal by taking the same path back to the nest while depositing their own trail

pheromone. As the food source dries up, the specific trail back to the nest is no

longer used and the pheromone signal dissipates. Dissipation below olfactory

detection limits eliminates the chemical trail which reduces the likelihood of workers

wasting time investigating unproductive foraging areas.

A great deal is known about the chemistry, concentration, and glandular source of trail

pheromones used by ants. Among the ants, trail pheromones are mixtures of volatile

substances that include diverse chemical structures secreted from multiple glands.

Quantities of stored trail pheromones are vanishingly small. In Camponotus, one

worker’s body contains about 2-10 ng of trail pheromone. In Pristomyrmex, trail

pheromone quantities have been detected only at the picogram level. These ultralow

quantities, however, are more than enough to provide powerful signals at easily

detectable ground concentrations for these ants. It’s likely that pheromone

concentrations in termites are similarly small.

An odd but interesting discovery is that ink from certain ball-point pens contains

volatile substances that seemingly mimic trail pheromones of termites. If a line is

drawn on paper, a worker termite will follow it, stopping only when the line ends.

Google termite trail following and select video to see termites orienting to ink trails.

Our Lab

This lab is an opportunity to gain understanding and appreciation for the world of

chemical communication by termites. You will join one of several lab groups that will

be designing and executing their own unique experiment(s). No two groups will have

the same research design or do the same work. A good strategy for each group

would be to do some background reading before reconvening for a barnstorming

session. This is a difficult lab because you are not being told what to do. The prelab

lecture along with this lab handout will provide some basic background information.

Also, several relevant journal articles are posted on e-reserve. When formulating the

design, each group should make decisions about

- Hypotheses/Objectives/Questions

- Dependent and independent variables

- Ways of quantitatively measuring behaviors

- Replication and sample sizes for each type of test

- Needed number of pre-chilled (= anesthetized) termites

- Production and use of termite odors

- Possible use of ink

- Backup or alternative ideas to ensure use of the entire lab period

- Special requests for needed equipment or supplies

The following will be present on lab day

- Dissection tools

- Brushes for manipulating termites

- Solvents (water, propanol, other?)

- Small fans

- Timers

- Handcounters

- Rulers and calipers

- Ink pens

- Super glue

Group Goals

After gaining some background knowledge, each group should meet and create a

research design. The design should investigate some aspect of pheromone use

and/or chemical communication by termites. The termite available in lab will be

Reticulitermes. Research topics of interest might include

- Trails laid by walking workers

- Manipulation of odor plume

- Antennae manipulation

- Trail-following accuracy

- Termite body parts as odor sources

- Extracts of body parts (head-thorax-abdomen) as odor sources

- Feces as odor source (trail pheromone?)

- Soldiers vs workers

- Termite species vs different termite species

- Continuous vs intermittent trail

- Height above trail

- Rotten wood and/or fungi from rotting wood as a termite attractant (you supply

the wood/fungi)

Strong research designs will be those that show real creativity, involve replicated

quantitative data that permit statistical analyses, and are grounded in biological

realism. Running your design by Dr. Rehnberg ASAP is advisable … especially if you

need special supplies. Orders for living items would have to be placed by Tuesday.

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