there is no observable movement. Alternatively, if anesthesia is
not available, hold the millipede down on a flat surface and
remove the head with the razor blade, then loosen the last one
or two posterior-most segments and firmly pull the loosened
segments, which will extract the intestine (see video for demonstration at https://www.youtube.com/watch?v=ssCMJhZcJ5w).
• Place the removed intestine in a Syracuse watch glass or small
Petri dish filled with distilled water.
• Using a pair of fine-tip forceps, gently pull the intestine apart,
thereby exposing the inner contents.
• Once the nematodes are observed, gently squirt distilled water
on the dissected intestine to dislodge them or gently remove
them with a minuten pin or a probe.
• Under the dissection microscope, sort into taxonomic categories
(e.g., Coronostoma, Heth, Rhigonema, Thelastoma, Stauratostoma,
Aorurus, Aoruroides, and unknown). The shape of the head and
esophagus determines the taxonomic ranking (genus or species).
Count the number of nematodes for each genus and record on
data sheet (for bright-field and scanning electron microscopy
images of these genera, refer to plates 1 and 2 at http://epp.
• Discard the millipede carcass into a plastic bag or place it back
in its natural environment for decomposition. Nematodes can
be preserved on permanent glass slides using methods designed
by Seinhorst (1959), stored in 95% ethyl alcohol, or discarded
down the sink.
• Clean work station, wash hands with warm soapy water, and
work on the lab report.
• Discuss findings within groups, analyze data, determine Shannon’s
and Simpson’s diversity indices, calculate equitability, and share
results with the class upon completion of the lab report.
• Grade the lab report and offer constructive comments.
Students should record their data in a spreadsheet or a lab notebook (we recommend using Excel since the calculations will be
fairly straightforward). Once the nematodes have been removed,
sorted, and taxonomically classified, students should record the
number of each species. After obtaining frequency counts, Shannon’s and Simpson’s diversity indices can be easily calculated. To
calculate Shannon’s diversity index and equitability, the following
equations are applied:
Shannon’s diversity index ¼ H ¼ −∑ pi ln pi
Hmax ¼ ln of the number of different species collected
Equitability ¼ E ¼ H=Hmax
where H = Shannon’s diversity index, pi is the proportion of nematodes of one genera or species divided by the total number of
nematodes removed from the millipede intestine, ln is the natural
log, ∑ is the sum of the calculations, and Hmax is the theoretical
maximum nematode diversity contained in each millipede
Table 1. Selected recommendations from Next Generation Science Standards (NGSS; NGSS Lead States,
2013) and K–12 Framework for Science Education: Practices, Crosscutting Concepts, and Core Ideas (NRC;
National Research Council, 2012) addressed by this activity.
Science & Engineering Practices Disciplinary Core Ideas Crosscutting Concepts
NGSS: HS-LS2-1: Using Mathematics and
Use mathematical and/or
computational representations of
phenomena or design solutions to
NGSS: LS2.A: Interdependent
Relationships in Ecosystems: Ecosystems
have carrying capacities, which are
limits to the number of organisms and
populations they can support (HS-LS2-1
NGSS: Cause and Effect: Empirical
evidence is required to differentiate
between cause and correlation and
make claims about specific causes and
effects (HS-LS2-8 and HS-LS4-6).
NGSS: HS-LS2-6: Engaging in Argument
from Evidence: Evaluate the claims,
evidence, and reasoning behind
currently accepted explanations or
solutions to determine the merits of
NGSS: LS2.C: Ecosystem Dynamics,
Functioning, and Resilience: A complex
set of interactions within an ecosystem
can keep its numbers and types of
organisms relatively constant over long
periods of time under stable conditions
(HS-LS2-2 and HS-LS2-6).
NGSS: Stability and Change: Much of
science deals with constructing
explanations of how things change and
how they remain stable (HS-LS2-6 and
1. Asking questions
3. Planning and carrying out
4. Analyzing and interpreting data
5. Using mathematics and
6. Constructing explanations
7. Engaging in argument from
NGSS: LS4.C: Adaptation: Changes in the
physical environment, whether naturally
occurring or human induced, have thus
contributed to the expansion of some
species, the emergence of new distinct
species as populations diverge under
different conditions, and the decline –
and sometimes the extinction – of
some species (HS-LS4-6).
3. Scale, proportion, and quantity
6. Structure and function
7. Stability and change