In this article we will discuss about the study of non-chordatas under microscope.
1. Amoeba sp.:
Collection:
It is a fresh water protozoan. Collect water from a stagnant pond with a little bottom mud, floating scum, slime, along with the stems and leaves of aquatic weeds. Put all those in a glass jar and leave undisturbed for a few days.
Preparation of a permanent slide:
Draw a small amount of water with a pipette from the surface of a leaf or from the bottom close to the wall of the jar. Examine a drop of the water on a glass slide under the low power of a microscope to be sure that Amoebae are present in the jar.
Put a drop of water containing amoebae on a slide. Leave it for a few minutes to allow the amoebae to attach themselves to the slide. Take a narrow strip of blotting paper and place a corner of it on the slide at 45° angle, just touching the water drop.
The water is soaked by the blotting paper leaving the amoebae on the slide. Wait for a few minutes to allow the residue water to evaporate and fix the amoebae with Schaudinn’s fixative. Amoebae are successfully fixed with absolute alcohol also.
Amoebae are generally stained with borax carmine. If over-stained, differentiate with acid water.
Dehydrate in upgrades of alcohol, clear in clove oil, wash in xylol and mount in Canada balsam or DPX.
For temporary preparation mount the stained Amoebae in glycerine.
Structure (Fig. 28.1)
1. Unicellular animal.
2. Finger-like pseudopodia.
3. Plasma-lemma, ectoplasm and endoplasm distinct.
4. Endoplasm granular.
5. Nucleus one.
6. Contractile vacuole and food vacuole present.
2. Monocystis SP.:
Collection:
Open the viscera of earthworm. Take out the seminal vesicles on a clean grease- free slide; put a drop of saline solution (0.7%); tease the seminal vesicles, spread it to form a thin smear and allow to semidry.
Fixation and staining:
The semidried slide is put in a petri dish and covered with Schaudinn’s fixative. The set is covered with another petri dish. Allow 15 minutes for proper fixation. Take out the slide, wash in 70% iodinated alcohol (two crystals of iodine in 70% alcohol). Wash in 70% fresh alcohol and gradually come down to 50% alcohol. Wash in distilled water. Stain with Delafield haematoxylin for one minute. Wash in distilled water.
If necessary, differentiate in acid water. Wash thoroughly in distilled water. Dehydrate through the grades of alcohol. Mount for permanent preparation and observe under microscope the stages of development of Monocystis sp.
Structure:
1. Unicellular animal.
2. Body usually flattened, elongated, more narrow at the posterior end.
3. Cilia absent.
4. Nucleus anterior to the centre.
5. Spores biconcave, cylindrical.
3. Paramecium sp.:
Collection:
Paramecium is a very active, free swimming protozoan. They are common in fresh water with decaying vegetable matters and abundance of bacteria. To the naked eyes paramecia appear as small, white, slightly elongated, fast moving objects. Paramecia multiply rapidly in water containing decaying organic matters and high bacteria population. They also thrive well in hay infusion.
Culture of Paramecia:
1. Simple method:
Collect submerged fresh and decomposing weeds with a small amount of water from a pond in which paramecia are present. Mix all those in distilled water in a glass jar, cover it and leave. The weeds decompose within a few days and the culture is rich in Paramecium.
2. Hay culture:
Moisten and smash 20 wheat grains. Cut hay stems into small pieces. Place the grains and 20 to 25 pieces of hay stem in a conical flask containing 500 ml distilled water. Boil for about 15 minutes. Make up the volume with distilled water. Keep the flask in a dry and cool place for about four days. Inoculate the culture medium with Paramecia. Within a few days numerous Paramecia will grow in the culture.
Preparation:
Since the paramecia are fast-moving animals they must be made non-motile before fixing them on a slide. Of the many methods suggested, the formaline method is most convenient and suitable for large practical classes.
Filter about 50 ml culture medium and add a drop of formaldehyde (40%) to the filtrate. Take a measured amount of culture medium with paramecia in a watch glass. Add equal volume of formalinated culture medium to it. The movements of paramecia will slow down and they will die in about 10 minutes time.
Put a drop of water with dead paramecia on a slide. Removal of water, fixation of the specimens on the slide with Schaudinn’s fluid, staining, dehydration, clearing and mounting are done following the technique used for amoebae. Structure (Fig. 28.2)
1. Shape like a crude slipper, anterior end round, posterior end pointed.
2. Body covered with cilia arranged in rows.
3. Oral groove and cytopharynx present.
4. Nucleus two, a large macro and a small micronucleus.
5. Contractile vacuoles two, at the opposite poles with radiating canals
4. Hydra sp.:
Hydra is a fresh water cnidarian. To naked eyes they appear as small, whitish threads attached to submerged plants, rocks and other objects.
Collection:
Collect water from a pond with some aquatic plants. Keep it in a glass jar and allow to stand for a few hours or overnight. Hydras are found attached to the leaves and stems of plants and the walls of the glass jar. Sprinkle a few crystals of menthol on water surface. The Hydras are narcotized and the movements of the tentacles cease.
Preparation:
Carefully collect a few hydra with a pair of fine forceps or a fine brush. Place them on a slide and fix with Schaudinn’s fluid. Stain with borax carmine, dehydrate, clear and mount.
Structure (Fig. 28.3):
1. Body almost cylindrical.
2. A flat basal disc at one end and a conical hypostome at the other end.
3. Mouth at the tip of the hypostome.
4. Hypostome surrounded by a circlet of tentacles.
N.B. A bud or gonad may be present.
5. Obelia sp.:
Obelia is a marine cnidarian. The students are supplied with specimens preserved in formaldehyde or alcohol.
Preparation:
Cut a portion of the Obelia colony containing hydranth and blastostyle. Wash thoroughly with distilled water. Stain with borax carmine. Mount in glycerine or make a permanent preparation.
Structure:
(Fig. 28.4)
1. Colonial animal.
2. Colony surrounded by a cuticular perisarc.
3. Two types of zooids, the hydranths and blastostyles present.
4. Hydranth—barrel-shaped zooid, surrounded by hydro theca.
a. A conical hypostome with a mouth opening.
b. Tentacles arranged around the base of the hypostome.
5. Plastostyle—an elongated zooid surrounded by gonotheca.
a. Numerous umbrella-like zooids attached to the blastostyle.
6. Head:
The head is distinguishable from the trunk by the absence of parapodia in it. It consists of an anterior prostomium and a posterior peristomium.
Preparation:
Place a preserved or freshly killed specimen on the dissecting tray. Slightly press the anterior region of the animal a little behind the head and the terminal portion is extended forward. Cut the specimen transversely with a sharp scalpel along the groove between the peristomium and the first trunk segment. Transfer the head to a large watch glass containing water.
Wash thoroughly, dehydrate and mount on a grooved slide in glycerine. For permanent preparation, clear it in clove oil, wash in xylol and mount in Canada balsam or DPX. As the components of the head have colours of their own, no staining is required.
Structure:
(Fig. 28.5)
Prostomium:
1. Appears as a trilobed structure.
2. Presence of four large, round eyes towards the base and two short, cylindrical tentacles in front.
3. A pair of somewhat longer, stout, lateral palpi present.
Peristomium:
1. Resembles a trunk segment but without parapodia.
2. Four pairs of long, slender,, cylindrical tentacles present.
3. A transversely elongated mouth at the anteroventral border.
7. Parapodium (Nereis):
These are paired, lateral outgrowths of the body present in all segments of Neanthes except head and the last segment.
Preparation:
Make a V-cut of the lateral walls of the body close to the base of a parapodium of a segment at about the middle of the trunk by giving two incisions. The anterior one is directed postero-medially from the anterior border of the parapodium and the posterior one directed anteromedially from the posterior border.
The parapodium with a portion of the body wall is separated. Separate the body wall from the parapodium with a pair of fine scissors, taking care not to damage the acicula which extend inward. Wash with water in a large watch glass, dehydrate and mount in glycerine or make permanent preparation following standard procedure. No staining is needed.
Structure:
(Fig. 28.6)
1. A biramous structure with a dorsal notopodium and a ventral neuropodium.
2. Notopodium divided into an anterior larger and a posterior smaller lobe.
3. Lobes of the neuropodium two, but smaller and fleshy.
4. Presence of a dorsal cirrus in notopodium and a ventral cirrus in neuropodium.
5. Both notopodium and neuropodium bear:
a. Bundles of fine setae projecting outwards.
b. Acicula lodged in setigerous sacs.
8. Setae:
Pheretima sp. (Earthworm):
Setae are locomotory structures of earthworm. They are partially embedded in the body wall, at the middle of a segment, arranged in a ring.
Setae in situ:
In situ means in natural state. A piece of skin with partially embedded setae in it is prepared for observation.
Preparation:
A piece of skin of the ventral surface except that of the clitellar region, measuring 1 cm square is cut, washed and put in a hard glass test tube containing 5 to 10 % caustic potash (KOH) solution. Boil for 5 to 10 minutes. Wash with water for several times in a watch glass to remove the trace of KOH. Mount in glycerine.
If a stained preparation is needed the boiled and washed skin may be fixed on a slide and stained, or stained in a watch glass. Staining is usually done with borax carmine. Dehydration, clearing and mounting are done following routine technique.
If the staining and subsequent processing are carried in a watch glass, the piece of skin becomes rolled. It should be fully stretched on the slide with two needles before mounting.
Structure:
(Fig. 28.7B)
1. Light yellow, narrow, elongated structures partly embedded in the skin.
2. The arrangement in the skin is in a line.
3. The free projected end is slightly curved and narrows terminally.
Setae (Isolated):
Preparation:
Boil a piece of skin in KOH solution with constant stirring till it disintegrates. Pour the contents in a large watch glass. Allow it to cool. Add water, allow to stand for a few minutes and the setae will drop at the bottom.
Decant the fluid. Repeat the process for several times and only the setae will be left in the watch glass. Collect them with a narrow pipette, put on a slide, remove the water by soaking with blotting paper. Allow to dry and mount. It is difficult to stain setae but they are quite prominent under the microscope due to their yellow colour.
Structure:
(Fig. 28.7A)
1. Light yellow, narrow, elongated structure.
2. The shape is in the form of a ‘f’.
3. One end is pointed and the other end is blunt.
4. A swelling, the nodule may be present at the middle.
9. Septal Nephridium (Earthworm):
Open the coelom (body cavity) of a freshly killed earthworm. The coelom is divided into a large number of compartments by means of thin transverse partition walls or septa. The nephridia are arranged on both the faces of a septum.
Preparation:
Remove a septum from between two segments posterior to 15-16. Place it on a slide with a drop of water. With the help of two sharp pointed needles separate one undamaged nephridium under a powerful dissecting binocular. Spread it carefully. Remove the water, fix with Schaudinn’s fluid, stain with borax carmine or any other dye, dehydrate, clear and mount.
Structure:
(Fig. 28.8)
1. Nephrostome round and ciliated.
2. A short duct, the neck, connects the nephrostome to the body of the nephridium.
3. The body consists of two lobes.
a. A short lobe.
b. A spirally twisted lobe.
c. The twisted lobe consists of a proximal limb and a spirally twisted distal limb.
4. The terminal duct short and narrow.
10. Ovary (Earthworm):
Expose the ovaries in a mature earthworm following the procedure for dissection of the reproductive system. They are two minute, white bodies attached to the posterior face of the septum 12/13 segments, one on either side of the nerve cord.
Preparation:
With a pair of fine forceps carefully remove the ovaries. Place them on a slide, fix, stain and make a temporary or permanent preparation.
Structure:
(Fig. 28.9)
1. A compact white digital mass attached to the septum.
2. Numerous digitate processes, narrow proximally and broader distally.
3. The processes are close set at the base but spread out at the free ends.
4. Ova in linear series in different stages of development.
5. Large, mature ova towards the distal end, while those towards the proximal end are small and immature.
11. Seminal Vesicle (Earthworm): Smear Preparation:
With the opening of the coelom the seminal vesicles are exposed in earthworm. They are two pairs, whitish-yellow bodies, one pair in each of the 11 and 12 segments (Fig. 2.5).
Preparation:
Cut one seminal vesicle with a pair of fine scissors and place it on a slide. Tease it with two needles and prepare a smear of the seminal fluid. Fix the smear with Schaudinn’s fluid or 90% alcohol for about 15 minutes.
Proceed for a stained permanent preparation following routine procedure:
The smear contains:
1. Spermatogonia.
2. Spermatozoa.
3. Occasionally trophozoites, gametocyte and sporozoite stages of Monocystis.
12. Nerve Ring (Earthworm):
It is oriented vertically. Expose the nerve ring following the procedure for dissecting the nervous system.
Preparation:
Cut the adjoining tissues and the nerves running from the cerebral and sub-oesophageal ganglia. Cut the ventral nerve cord just behind the sub-oesophageal ganglia and the nerve ring is free. Remove it with a brush and put on a slide. Clear and mount in glycerine. For stained preparation follow the standard technique.
Structure:
(Figs. 2.3 & 2.5)
1. A dorsal brain or two fused cerebral ganglia.
2. Two lateral peripharyngeal connectives.
3. A ventral, fused sub-oesophageal ganglionic mass.
13. Jaw:
Hirudinaria sp. (Leech):
The triradiate mouth of leech is guarded by three semicircular jaws, one dorsomedian and two ventrolateral.
Preparation:
Open the buccal cavity and remove a jaw by cutting its muscles of attachment. Clean extra tissues from the jaw and mount on a slide in glycerine. For permanent stained preparation follow the standard technique, keeping the jaw for about an hour in clove oil to make it partially transparent.
Structure:
(Fig. 28.10)
1. A thick structure, semicircular in shape.
2. A cuticular rim-like thickening covers the free margin.
3. A large number of small denticles on the cuticular rim.
4. Presence of numerous button-shaped salivary papillae.
5. Antagonistic muscles along the cut (inner) border.
14. Testicular Nephridium (Leech):
Only one type of nephridia are present in leech. Dissect a freshly killed leech. Remove the crop and the Botryoidal tissue. The testicular nephridia are present on the lateral sides of the nerve cord.
Preparation:
Carefully remove one or more nephridia with a pair of fine forceps and fix on a slide with Schaudinn’s fluid. Mounting may be done in glycerine or stained, permanent preparation may be made.
Structure:
(Fig. 28.11)
1. The main body horse-shoe-shaped with two unequal limbs.
2. The anterior limb is longer than the posterior one.
3. A vesicle duct from the anterior limb ends in the vesicle.
4. The sac-like vesicle opens through a round nephridiopore.
5. The apical lobe is stout and anteroposterior in position.
6. The inner lobe located at the concavity of the main lobe.
7. The initial lobe long and slender twined round the apical lobe.
15. Green (Antennary) Gland:
Macro-brachium sp. (Lobster):
A pair of thick, somewhat ovoid bodies, one situated in the coxa of each second antenna. Its presence is identified by the excretory pore on the inner side of the coxa.
Preparation:
Separate one second antenna from the cephalothorax of prawn by cutting it at its base. Insert the pointed arm of a pair of stout scissors in the coxa and basis, close to the outer border, opposite the excretory pore and give an incision along the border. Give a transverse incision along the distal border of the basis and turn the flap inside out.
The green gland is exposed. Carefully remove it from the antenna after cutting the ureter close to the renal pore. Place it in a watch glass containing water. Cut the gland sagittally with a shaving blade or a sharp razor and examine under a powerful dissecting binocular.
Structure:
(Fig. 28.12)
1. End sac, a small bean-shaped portion at the centre.
a. The wall of the end sac two layered.
b. Radially arranged septa project inwards from the inner layer.
2. Labyrinth, the glandular part, outside the end sac.
a. Branched and coiled excretory tubules present.
b. The tubules open in the end sac.
3. Bladder, a thin walled sac, on the inner side of the end sac.
a. It ends in a small ureter.
b. The ureter opens through a renal pore.
16. Statocyst (Lobster):
Statocysts are the balance organs of prawn. They are a pair, one in each antennule, located in the cavity of the precoxa or the basal segment.
Preparation:
Separate one antennule from the prawn by cutting it at its base close to the body. Expose the cavity of the precoxa by cutting along its inner margin and also transversely at its distal end. The statocyst is a sub-spherical cuticular sac attached to the inner surface of the dorsal wall of the precoxa. It opens to the outside through a narrow pore.
Cut across the protruberance with a sharp scalpel close to the base and the statocyst is separated from the precoxa. Put it in water in a watch glass and remove the sand particles with a fine, soft brush. Mounting may be done in glycerine. For staining, borax carmine or picro-indigo carmine may be used in the preparation of permanent slides.
Structure:
(Fig. 28.13)
1. A small, cuticular hollow sac with a narrow pore.
2. Sensory setae arranged in the sac in the form of an oval ring.
3. Each seta has a swollen base and a pointed shaft.
4. Sand grains in the space surrounded by the setae.
17. Hastate Plate (Lobster):
The cardiac stomach is embedded in the hepatopancreas.
Preparation:
Take out the cardiac stomach by cutting the oesophagus and the junction of the cardiac and pyloric stomachs. Give an incision on its roof to expose the cavity. The hastate plate, which looks like the head of a spear occupies the floor of the cardiac stomach.
Separate the hastate plate from the stomach by cutting along its border with a pair of fine scissors. Put it in water in a watch glass, clean with a fine brush and mount in glycerine. For a permanent preparation it is better to stain the hastate plate in a watch glass and mount following usual procedure. Picro-indigo carmine gives excellent result.
Structure:
(Fig. 28.14)
1. Shape like the head of a spear.
2. Upper surface covered with a thick growth of setae.
3. A distinct ridge is present at the middle.
4. The lateral sides are supported by cuticular rods.
18. Mouth Parts of Cockroach:
Hold the head of a chloroformed cockroach with your left hand, the ventral surface facing upwards.
Preparation:
Separate the mouth parts one by one and place in water in a watch glass. Cut the attachment of labrum, mandibles and hypo- pharynx with a pair of scissors. Other mouth parts can be separated simply by pulling them out laterally with the help of a pair of fine forceps.
Arrange the mouth parts on a slide in their natural orientation. Mount in glycerine. For permanent preparation, the structures being coloured, staining is not effective. Dehydrate, wash in xylol and mount in Canada balsam or DPX.
Components of mouth parts:
(Fig. 28.15)
Labrum:
An almost semicircular structure with a notch at the free end.
Mandibles:
Two curved bodies with serrated inner border.
Hypo-pharynx or tongue:
A cylindrical body, narrower at the free end. The efferent salivary duct opens on the ventral surface near the base.
Labium:
A median structure with a proximal submentum and a distal mentum. The mentum bears paired, many jointed labial palps and short paraglossae.
Maxillae:
Paired, many-jointed; the segments from basal end are cardo, stipes, lacina and galea.
Salivary Apparatus of Cockroach:
Preparation:
Remove the salivary apparatus from water in the watch glass with a spatula or a pair of fine forceps. Place it on an albumen coated slide and stretch properly with two needles. Remove water from the slide and leave to allow evaporation of residual water. The salivary apparatus is fixed on the slide. Make a temporary or permanent stained preparation as required.
Structure:
(Fig. 6.3)
Salivary glands:
Much branched, cream white, paired bodies.
Salivary ducts:
Two from the two glands unite to a common duct.
Receptacles:
Two thin walled sacs.
Ducts of the receptacles:
Two from the receptacles unite to a common duct.
Efferent duct:
Common salivary and receptacle ducts unite and opens at the base of the hypo-pharynx.
Hypo-pharynx:
A cylindrical body narrower anteriorly.
19. Mouth Parts of House-Fly:
It is convenient to use the whole head for study of mouth parts in a fly. Observe the components under a dissecting binocular.
Preparation:
Separate the head of a fly. Boil the head in 5 to 10% KOH solution for about 8 to 10 minutes. Cool, decant the solution, wash repeatedly with distilled water to remove the last trace of KOH. Mount the whole structure on a slide in glycerine. If required, stain in a watch glass and make a permanent preparation.
Components of mouth parts:
(Fig. 28.16)
Labrum:
Labrum fused with epipharynx and forms a slender tube opening ventrally.
Mandibles:
Absent.
Hypo-pharynx:
Cylindrical, narrower at the free end. Salivary duct opens near the base on the ventral surface.
Labium:
Forms a tube enclosing labrum— epipharynx and hypo-pharynx.
Maxillae:
Paired, short, maxillary palps un-jointed.
Wing:
Wings are symmetrical structures.
Preparation:
Cut one of the wings of a fly close to its base on the thorax. Treat it with 70% alcohol and mount in glycerine (Fig. 37.91)
20. Mouth Parts of Mosquito:
The basic components of the mouth parts of both the Culex and Anopheles are same. The sizes of the proboscis (Labium), maxillary palps and antennae differ not only in the two species but also in the male and female members of the same species.
Preparation:
Separate the head. Put it in 5 to 10% KOH solution in a watch glass for about 10 minutes. Remove the KOH by repeated washing with distilled water and mount in glycerine.
Components of mouth parts:
(Fig. 28.17)
Fig 28.17: Mosquito Mouth Parts
A. Culex sp. Male, A’ Culex sp. Female. B. Anopheles sp, Male B’ Anopheles sp, Female
Culex:
Male (Fig. 28.17A)
1. Proboscis shorter.
2. Antennae stout.
3. Maxillary palp long.
Female (Fig. 28.17A’)
1. Proboscis longer.
2. Antennae slender.
3. Maxillary palp short.
Anopheles:
Proboscis is of same length in both male and female.
Male (Fig. 28.17B)
1. Antennae long and stout.
2. Maxillary palp club shaped and equal to proboscis.
Female (Fig. 28.17B’)
1. Antennae short and slender.
2. Maxillary palp simple and nearly equal to proboscis.
Larvae:
Mosquitoes spend their larval life in water.
Collection:
The head of the Culex larva hangs downwards in water, while the Anopheles larva lies parallel to the water surface. The larvae are collected either with certain amount of water in a container or by fine collecting nets and released in water in a container.
If a pot with water is left in a dark corner, mosquitoes will lay eggs there and the larvae will hatch out. The larvae are killed by addition of a few drops of formaldehyde in the water.
Preparation:
The larvae are transparent. It is better to stain, dehydrate and clear the larvae in a watch glass and mount in Canada balsam or absolute glycerine. In the latter case the cover slip should be sealed with bee’s wax or nail polish.
Structure:
(Figs. 28.18 & 28.19)
1. The body is divisible into head, thorax and abdomen.
2. A pair of compound eyes, a pair of simple eyes, a pair of jaws and two feeding brushes present in the head.
3. Thorax un-segmented and bears three pairs of un-jointed lateral tubercles with tuft of bristles.
4. The abdomen bears 9 segments.
5. Tracheal opening on the dorsal surface of the 8th segment.
6. Tracheal gills present in the 9th segment.
Culex larva:
(Fig. 28.18)
1. The respiratory siphon in the 8th segment and long.
2. Posterior part of the abdomen forked in appearance.
3. Palmate hairs absent in the abdomen.
Anopheles larva:
(Fig. 28.19)
1. The respiratory siphon in the 8th segment and short.
2. Fork absent.
3. Palmate hairs present in the abdomen.
21. Pupa:
Unlike majority of the insects, mosquito pupae are active. They live in water.
Collection and preparation:
The technique for collection and preparation of larvae are quite suitable for pupae.
Culex pupa:
(Fig. 28.20)
1. Comma-shaped, cephalothorax smaller and dorsal, and the abdomen ventrally placed.
2. Outermost covering translucent; developing eyes, antennae, wings and legs are visible through it.
3. Cephalothorax somewhat rounded; abdomen narrow and nine-segmented.
4. Two respiratory trumpets present on the cephalothorax.
5. A pair of large tracheal gills, also functioning as swimming paddles are present in the penultimate abdominal segment.
Anopheles pupa:
(Fig. 28.21)
The pupa is similar to that of Culex except for the respiratory structure.
1. The respiratory tubes are funnel- shaped.
22. Pollen Basket; Pollen Packer:
Apis sp. (Honey bee) (Fig. 28.22
Both pollen basket and pollen packer are present in the metathoracic or hind legs.
Preparation:
The legs of honey bee like those of other insects bear 5 segments, viz., coxa, trochanter, femur, tibia and tarsus. Separate both the metathoracic or hind legs of a chloroform killed worker honey bee, cutting at their base. Cut the tibia from one leg, and both tibia and first tarsal segment together from the other one.
Mount the pieces separately on glass slides, keeping the outer surface of the tibia of one leg and the inner surface of the other leg having both tibia and tarsus upwards. Examine with a high power hand lens or under a simple microscope.
Structure: pollen basket
(Fig. 28.22A)
1. The pollen basket is a simple depression on the outer surface of the tibia.
2. The basket is partially covered by rows of long, curved, bristles arising from its margin.
3. Collected pollens are temporarily stored in the pollen basket (Figs. 28.22B, C).
23. Structure: pollen packer:
(Fig. 28.22A)
1. Distally the tibia bears a series of spines or pecten.
2. The auricle, a concave plate, is present at the proximal upper end of the first tarsal segment on its inner surface.
3. The pecten and the auricle together constitute the pollen packer.
24. Poison Apparatus (Honey-bee):
The poison apparatus is lodged in the last 5 abdominal segments.
Preparation:
Pin down a chloroform-killed worker honey bee on a paraffined petri dish and expose the abdominal cavity following the procedure adopted for blue bottle fly Calliphora sp. (p. 33). Remove the gut and the poison apparatus is exposed.
Structure: poison apparatus:
(Fig. 28.23)
The poison apparatus has three components.
The sting:
1. The sting or terebra (Fig. 28.23B) is a hollow organ formed by three pieces bounding a central canal (poison canal).
2. The dorsal part is the stylet sheath, and the two ventral pieces are stylets or lancets.
3. The apices of the stylets and their sheath bear forwardly directed barbs.
4. The stylet sheath expands at its base to form the bulb of the sting and latter a pair of diverging arms.
The plates:
Three pairs of plates (Fig. 28.23A) associated with the sting act as a lever.
The innermost oblong plate represents the divided ninth sternum and the basal arm of the stylet sheath is attached to each of it.
a. Distally, the oblong plate carries a pair of palp-like appendages.
3. A small triangular or fulcra plate remains attached with the basal arm of the stylets.
4. The triangular plate is again articulated with a large outer or quadrate plate at its ventral angle.
The poison gland:
1. A pair of filiform poison glands (acid glands) open through a common duct into a large poison sac.
2. The poison sac opens at the anterior end of the bulb of the sting.
3. A small alkaline gland opens separately, close to the opening of the poison sac (Fig. 28.23A).
25. Book Lung:
Palamnaeus sp. (Scorpion):
Book lungs are four pairs, attached to the inner surface of the sternum, one pair in each of the third, fourth, fifth and sixth mesosomatic segments, close to the lateral borders. A book lung opens to the exterior through a slit-like aperture, stigma.
Preparation:
Give a longitudinal incision along the middle line of the mesosomal sternum. Cut the posterior border of half of the sternum by giving a transverse incision, starting from the first incision and ending at the lateral side. Proceed anteriorly along the lateral border of the mesosoma up to the second segment and give an inward transverse incision on the sternum.
Half of the sternum is separated from the body. Remove it and place inside turned upward, on a petri dish containing water. Remove the surrounding tissues and cut one of the book lungs at its junction with the stigma and take it out. The book lung may be cut into two longitudinal halves for examination. Follow the routine procedure and mount on a slide. Structure (Fig. 28.24)
1. Sac-like, consists of a dorsal pulmonary and a ventral atrial chamber.
2. The pulmonary chamber contains about 140 vertical and parallel lamellae.
3. The lamellae are attached to the sac by one edge while the other edge is free.
4. The atrial chamber communicates with the stigma.
26. Pectine (Scorpion):
A pair, attached to the sternum of the second mesosomite segment.
Preparation:
Cut a pectine at its junction with the sternum. Place it in a watch glass containing water. Clean with a fine brush and mount in glycerine.
Examine under a powerful dissecting binocular.
Structure:
(Fig. 28.25)
1. Comb-like in appearance and consists of a shaft and movable processes.
2. The shaft is three segmented.
3. Movable processes are 4 to over 30 and attached in a row along the posterior margin of the shaft.
27. Gill Lamella:
Lamellidens sp. (Fresh water mussel):
Gills are two, one situated between the body and mantle of each side. Each gill has -two laminae. Each lamina is made up of two lamellae.
Preparation:
Cut a small portion of a gill lamina, remove the surface water with a piece of blotting paper or filter paper and place it on a slide containing a few drops of Bouin’s or Schaudinn’s fluid. Remove the excess fluid after about fifteen minutes. Leave for a few more minutes to allow the fixative to dry up. Holding the slide with the fore finger and thumb of your left hand gently scrape the surface of the gill lamina with the back of a blunt seeker.
Gradually the upper lamella of the gill lamina is removed leaving only the lower lamella attached to the slide. Remove the debris, wash the slide gently with water and stain with borax carmine. Dehydrate and mount in glycerine. Permanent preparation may be made following routine procedure.
Structure:
(Fig. 28.26)
1. A large number of gill filaments connected by narrow interfilamentar junctions.
2. Ostia present in the interfilamentar junctions.
3. Cells of the gill filaments bear cilia.
4. Traces of damaged inter-lamellar junctions may be present.
28. Radula:
Pila sp. (Apple snail):
Expose the buccal mass (p. 44). Remove the buccal mass by separating it from the snout at the anterior end and cutting the oesophagus. The radular sac is located on the ventral part of the buccal mass.
Preparation:
Cut the radular sac. The radula is a chitinoid ribbon. Carefully separate the muscles of attachment and take it out. Boil the radula for about 5 minutes in 5% KOH solution. Wash thoroughly with water and it will be free from muscles.
It is a curved, spoon-shaped body. Place it in between two glass slides and press them slowly, taking care that the radula is not damaged. Tie the two slides in that position with a piece of thread and dip in aqueous Bouin’s fluid for about 10 minutes. Remove the slides. The ribbon is almost flat now. Wash thoroughly with water.
To remove yellow colour of the Bouin’s fluid, treat the radula with lithium carbonate solution. Wash with water, and mount in glycerine. If stained, permanent preparation is necessary, it is better to process the radula in a watch glass and mount on a slide.
Structure:
(Fig. 28.27)
1. A somewhat spoon-shaped, chitinoid ribbon.
2. Teeth restricted to a narrow median strip in the broad anterior portion but occupy whole of the narrow posterior part.
3. Numerous transverse rows of cuspid teeth present.
4. Teeth in a transverse row are, one rachidial and three laterals* on either side.
29. Osphradium (Apple snail):
The osphradium or the taste organ for water and food is small and suspended ventrally from the anterior border of the mantle. In an active Pila it is located close to the base of the left nuchal lobe.
Preparation:
Separate the osphradium from the mantle with a pair of fine scissors. Make a frontal section of it with a sharp scalpel or a pair of fine scissors. Wash with water and mount in glycerine. For a stained, permanent preparation fix it on a slide and follow the routine procedure.
Structure:
(Fig. 28.28)
1. Shape elongate oval.
2. A row of leaflets varying from 22 to 28 are arranged along its inner border attached with their broad bases.
3. Leaflets are fleshy and narrow down in the free end.
4. The middle ones are largest, being gradually smaller toward the ends of the osphradium.
30. Statocyst (Apple Snail):
The statocysts are two. It is a cream white sac posterior to the pedal ganglion of the pleuropedal ganglionic mass, close to it, and kept in position by muscles.
Preparation:
Locate the pyriform sac and carefully remove it with a pair of fine scissors. Wash with water, remove extra tissues and make a temporary or permanent preparation. It may be fixed to a slide for processing.
Structure:
(Fig. 28.29)
1. A pyriform, cream white, leathery sac.
2. The internal lining epithelium contains sense cells.
3. A number of particles, the statoconia are present in the cavity lined by epithelium.
31. Pedicellariae:
Asterias sp. (Star fish):
These are very small bodies in between the spines of the oral and aboral surfaces. They are attached to the surface and are of different sizes.
Preparation:
The pedicellariae are somewhat like minute jaws of birds. Locate and identify them with a powerful hand lens. Separate a few, both of small and large sizes, from the body wall and examine in glycerine under a powerful dissecting binocular.
Structure:
(Fig. 28.30)
1. A pedicellaria consists of a flexible stalk and three calcareous components—one basilar plate and two jaws.
2. Jaws are attached to the basilar plate and directed outward.
3. Pedicellariae are of two types.
a. Straight pedicellaria:
The jaws are more or less straight and when closed meet almost throughout the whole length.
b. Crossed pedicellaria:
Basal portion of the jaws curved and cross each other.
32. Tube Foot (Star Fish):
Expose a part of the radial canal with its lateral branches following the technique adopted for dissection of ambulacral system.
Preparation:
Carefully remove the wall of an ambulacral pore through which tube foot projects out; Cut the lateral canal and separate it with its branches from the surrounding tissues. Put it in a watch glass containing water. Wash, stain, clear and mount on a glass slide. A lateral canal has two branches. A tube foot is connected with each branch.
Structure:
1. A round, sac-like ampulla.
2. A narrow tubular portion, the tube foot.
3. A sucker-like structure at the tip of the tube foot.