Dissection Lab II (week 3)

Transcription

Insect Physiology (Ento 306)
Name:______________________
Insect Dissection Labs
Part 2
Introduction
Identical to the last lab, this handout provides you with the basic instructions for dissection and an outline
of the tissues, organs, and structures that you will need to be familiar with and draw. All questions you
need to ask or things you need to draw are underlined. You will make all your drawings, which must
include a short description and magnification used, in the drawing handout. Make use of the appendix,
which is a collection of diagrams from textbooks, websites, and literature that will be helpful in finding
the correct structures and organs.
Supplies
Isopropanol
Saline Solution
Dissection probes
Forceps
Scissors
Razor blade
Insect/dissection pins
Dissection pan
Stereoscopic dissecting microscope
Compound microscope
Microscope slide and coverslip
American bird grasshopper (Schistocerca americana)
South American cockroach (Blaberus sp. )
I Grasshopper
Cut off the grasshopper’s legs. Cut open the grasshopper’s body cavity by using sharp small
scissors to cut along the side of the grasshopper through the membrane between the sternites and
tergites. Keep cutting through the side of the thorax and through the membrane behind the head.
The cut should be completely through the exoskeleton but no deeper. Avoid cutting the soft tissue
under the exoskeleton. Using forceps spread open the body cavity and pin the sides down to a
dissecting tray. Bathe the internal organs in several drops of saline solution.
The Hemocoel
Identify the Pericardial, Perivisceral, and Perineural sinuses.
Adapted from Paul Lenhart 2011 (page 1)
Metabolic systems
Fatbody
Identify the whitish/yellowish fatty substance. This is the fat body which allows for storage of
lipids and intermediary metabolism with a function similar to the vertebrate liver. Estimate the
percent of the body cavity content which is made up of the fat body.
________% of body cavity
Respiratory systems
Look for small silvery white tubes leading into the body cavity from the spiracles. These are
trachea and are used for respiration. These tubes deliver oxygen to the various tissues in the body
and allow for the expelling of carbon dioxide. 1) Draw a trachea as viewed under the stereoscope
or compound microscope. Identify the taenidia in your drawing. These structures support to
trachea and prevent them from collapsing.
Circulatory systems
Dorsal heart
Tease open the pericardial sinus on the dorsal side of the hemocoel in the abdomen using your
probe or forceps and identify the heart. It is an inconspicuous transparent tube on the dorsal
midline of the abdomen and thorax. Insects have an open circulatory system, meaning there are
no arteries delivering blood to the insect tissues. Instead organs within the hemocoel are bathed in
blood which is circulated through the pumping of this dorsal heart.
Nervous systems
Ventral nerve cord
Carefully remove the gut and reproductive organs of the grasshopper from the body cavity and
tease open the perineural sinus along the ventral side of the hemocoel from the abdomen through
the thorax. Identify the nerve cord which is a transparent pair of parallel tubes which connect a
chain of ganglia on the floor of the perineural sinus. To make the nerve cord more visible pour
or pipette out any excess saline solution and bath the area in isopropanol. This will make the
nerve tissue opaque.
The ganglia consist of three large thoracic ganglia, and five smaller abdominal ganglia. Notice
the abundant nerves entering and leaving the thoracic ganglia in contrast with the relatively few
of the abdominal ganglia (Remember that the muscles that control the legs and wings are housed
within the thorax).
2) Draw a ganglia and its connecting nerve cord as viewed under the dissecting scope.
Locomotor systems
Flight muscles
Identify direct and indirect flight muscles in the grasshopper thorax.
Mating systems
Reproductive organs
Study both male and female reproductive systems by passing around the adults in the classroom.
In the male specimen identify the testis and the following structures:
Follicles
Vas efferens
Vas deferens
Accessory glands
In the female specimen identify the pair of ovaries and the following structures:
Ovarioles
Oviducts
Seminal receptacle
II Cockroach
Cut off the cockroach’s legs. Cut open the roach’s body cavity by using sharp small scissors to
cut along the side of the roach through the membrane between the sternites and tergites. Keep
cutting through the sides of the thorax and through the membrane behind the head. The cut should
be completely through the exoskeleton but no deeper. Avoid cutting the soft tissue under the
exoskeleton. Using forceps pull off the dorsal surface of the roach and lay it in the dissecting tray
so that the inside surface is upright. Bath the internal organs in several drops of saline solution.
Metabolic systems
Fatbody
Identify the fatbody. Estimate the percent of the body cavity content which is made up of the fat
body. Compare this to your estimate for the grasshopper.
________% of body cavity
Cockroach digestive system
Identify the following parts of the cockroach digestive system (if necessary pull the gut out on the
side):
Salivary glands
Esophagus
Crop
Proventriculus
Midgut
Gastric caeca
Malphigian tubules
Hindgut
Rectum
4)Draw the lining of the foregut at the proventriculus under the stereoscope.
5)Draw the lining of the rectum under the stereoscope.
Circulatory systems
Dorsal heart
Locate the heart as you did for the grasshopper. 3) Draw it under the stereoscopic dissecting
scope.
Nervous systems
Ventral nerve cord and ganglia
Remove the gut, fat body, reproductive organs from the thorax and abdomen. Remove the
longitudinal body wall muscles (sternal muscles) and connective tissue as necessary from the
floor of the abdominal cavity to reveal the ventral nerve cord.
6) Identify and draw one of the three thoracic ganglia. From each extend several pairs of nerves to
the abundant muscles of these segments.
Cockroach brain
Using your scissors and forceps or a razor blade carefully remove the epicranium (top of the
head) from the region between the compound eyes and antennae. Remove muscles as necessary
to reveal the bright white, dorsal brain between the compound eyes.
7) Draw the cockroach brain in as much detail as possible. Label at least two of the following
features:
Optic lobe
Protocerebrum
Deutocerebrum
Tritocerebrum
Corpora cardiac
Corpora allata
Circumesophogeal connective
Appendix
I Grasshopper
Diagrammatic cross section of a generalized insect abdominal segment. Redrawn from Snodgrass
(1935)
Illustrations by Richard Fox (http://webs.lander.edu/rsfox/invertebrates/romalea.html)
Internal anatomy of the grasshopper (lateral view).
http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb6pg17.htm
Internal anatomy of the grasshopper (lateral view).
Florida Center for Instructional Technology
Dorsal dissection of a male Romalea showing the digestive system. The dorsal diaphragm and heart
have been removed, most of the Malpighian tubules and most of the epiproct has been
removed. The few Malpighian tubules in the drawing are shown much shorter and much less
numerous than in life. The testis has been removed but its position is indicated by a dashed line.
The ovary occupies a similar position in females.
The grasshopper respiratory system.
http://www.entomology.umn.edu/cues/4015/morpology
The grasshopper circulatory system.
The grasshopper nervous system.
Dorsal dissection of the postcranial nervous system of a male Romalea. Heart, fat bodies, dorsal and
ventral diaphragms, and gut have been removed.
Insect flight muscles
http://www.biology-resources.com/insects-02.html
The wings are jointed to the second and third thoracic segments and are moved up and down
by the action of muscles. As in the case of limbs, the muscles are attached to the inside of the
exoskeleton. There are two types of attachment for either direct or indirect flight muscles
joint
when this muscle
contracts it pulls the wing
down
when this muscle contracts
it pulls the wing up
Section through the thorax to show direct muscle attachment
Direct flight muscles
One end of each muscle is attached to the inside of the thoracic segment; the other
end is attached to the wing near the joint. The muscles act directly on the wing
these muscles deepen the
thorax and flip the wing down
these muscles
slightly flatten
the thorax and
flip the wing up
Attachment of indirect flight muscles
Indirect flight muscles
These act on the thorax and distort it, so flipping the wings up and down. This produces a
rapid wing beat. There are also muscles which adjust the angle of the wings
The grasshopper reproductive system.
Dorsal view of the reproductive system of a male Romalea. For clarity, the testis is shown as a
dashed line. Most of the accessory glands have been omitted. The ejaculatory duct is stippled.
Dorsal view of the reproductive system of a female Romalea. Malpighian tubules are drawn much
shorter and less numerous than in life.
The testes of a male Romalea in ventral view. G = germarium, M = zone of maturation, T = zone of
transformation
A single ovariole from a Romalea ovary.
II Cockroach
Dorsal view of a female smoky brown cockroach, Periplaneta fuliginosa
Illustrations by Richard Fox http://webs.lander.edu/rsfox/invertebrates/periplaneta.html
Ventral view of a female P. fuliginosa. The distal articles of the legs have been removed for
clarity. S = sternite, T = tergite.
A late instar, 24 mm Periplaneta nymph
Dorsal view of the perivisceral coelom of a male P. americana. The dorsal diaphragm, heart, and
tergal muscles have been removed. Abdominal segments are numbered. Malpighian tubules have
been shortened and reduced in number for clarity.
Oriental Cockroach (Blatta orientalis), Female. Dissected so as to show its digestive, nervous, and
reproductive systems; the fat body and a considerable portion of the dorsal integument have been
removed.
a. Antennae
b. Tibiae
c. Cerci
d. Nerve on the crop
e. Salivary duct/gland
f. Salivary bladder.
g. Proventriculus
h. Gastric caeca
i. Midgut
j. Malpighian tubules
k. Ileum
l. Colon
m. Rectum
n. Abdominal ganglion
o. Ovary
p. Accessory glands
Interior of the proventriculus.
Dorsal view of a male P. americana. Thoracic nota and abdominal terga 1-7 have been
removed. T = tergite
Dissection of P. americana showing nervous system. T = thoracic ganglion, A = abdominal
ganglion. The abdominal segments are numbered.
Anterior view of the head of Periplaneta fuliginosa
Generalized insect brain frontal view.
http://www.animalbehavioronline.com/insectbrain
Generalized insect brain in lateral view.

Dissection Lab II (week 3)

Transcription

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