EXERCISE.18 PmPAMTIION OF PE MOUNTS OF MOUTH-PARTS OF COCKROACH AND MOSQUITO

Transcription

1 EXERCSE.18 PmPAMTON OF PE MOUNTS OF MOUTH-PARTS OF COCKROACH AND MOSQUTO Structure ntroduction Objectives 18.2 Material Required 18.3 Method for Preparation of Mount of Mouth-Parts of Cockroach 18.4 Observation of Cockroach Mouth-Parts under Microscope 18.5 Metliod for Preparation of Mounts of Mouth-Parts of Mosquito 18.6 Obse~.vation of Mosquito Mouth-Parts under Microscope 18.7 Ter~ninal Questions 18.1 NTRODUCTON The insects inflict losses and illjuries to lii~mans and their possessio~~s by eating or feeding or by transmitting diseases through their bites. Hence, mouth-parts forin very important organs of an insect. Depending upon tlie feeding habits, moutli-parts of insects show many specializatio~ls in form and development. The study of the mouth- 1 parts of insects is one of the most important aspects as they play a major role in planning tlie pest control strategies. Mouth-parts include two distinct pairs of appendages, i.e. mandibles, and the$rstpair of tnaxillue; one media11 labium or lower lip represented by a united pair of second maxillae, and lahrunz or upper-lip and a hypopharynx. Two important modifications of the mouth-parts in consideration with tlie nature of food and tlie manner of feeding (biting and chewing type and piercing and sucking type) will be described in this exercise. Objectives After performing this exercise you slio~~ld be able to: identify, and prepare tlie mounts of mouth-parts of cockroach and mosquitoes, distinguisl~ between moutlt-parts of cockroach and mosquitoes, distinguish between rnoutli-parts of Cz~lex and Anopl7elcs mosquitoes, and distinguish between mouth-parts of male and female Cu1c.x and Anopheles mosquitoes MATERAL REQURED Co~npound ~n icroscope Potassium lydl.oxide (Caustic soda) Test tube Test tube l~older Bunsen burner Petri dishes/watcli glass Dissecting needles Forceps (small) Absolute alcohol Clove oil/xylol Canada Balsam Microslides Cover glass Glycerine Practical Record book Speci~nens of Cockroacli Culex Mosquitoes (Male and Female)

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3 j Dehydration and mounting: Dehydrate the mouth-parts directly by soaking in 70% and then absolute alcohol. Clear in clove oil. Mou~it in balsam. i (Note: To make a tidy mount, place the mouth-parts in tlie arrangement sliown in Fig c and as close together as possible without actl~ally toucliing. Make a ring of balsam round them. The ring should be smaller in diameter tlia~i the cover-slip. Place a drop of balsam on tlie cover-slip. nvert tlie cover-slip rapidlyarid lower it gently into place so that tlie drop of balsam on it strikes the niiddle of tlie ring of balsa111 on tlie slide) OBSERVATON OF COCKROACH MOUTH-PARTS 1 UNDER MCROSCOPE i i i You are now familiar with the mouth-parts of cockroach. You should sketch the mouth-parts as you observe these under llie lnicroscope in the record notebook. Label and describe tlie various palls. / Mouth-parts of Cockroach: v) vi) Mo~~tli-parts are of biting and chewing type or ~nalidibulate type. Mandibles broad and plate-like with inner margins serrated, adapted for biting and chewing the food. Maxi1 lae corisist of : a) Basal part protopod ite formed of cardo and stipes. b) Outer part exopodite forms ~naxillary palp. c) nner part eridopodite formed of lacilia and galea. Labium forms the lower lip and is formed ot a) Basal part liavi~ig submentu~n, neliturn and pre~nentum. b) Outer part represented by paired labial palps. c) ~iner part - formed of paired glossae and paraglossae. Hypopllyrynx tongue-like with opening of salivary ducts. Labru~n and epipliary~ix form upper-lip. (Fig. 18.2) Preparation of Permanent Mounts of Mouth-Parts of Cockroach and Mosquito t LABUM Fig. 18.2: Mouth-parts of Cockroach.

4 Animal Diversity Lab. 18. Anopheles Mosquitoes (Male and Female) 18.3 METHOG POR THE PREPARATON OF MOUNT OF For examination of the mouth-parts, take out the head of a fresh specimen. Macerate the muscle tissue of the head by boiling in 10 per cent caustic soda solution (Fig a). Use a pin in the test tube to reduce "bumping". Remove the test tube from the flame at frequent intervals and observe the head. When it sinks quickly and remains on the bottom of the test tube, it has been boiled enough. Rinse thoroughly, being careful not to get any of the caustic soda on hands, clothes or table. Removing the Mouth-Parts: Hold the cockroach head by means of a dissecting-needle inserted through the neck and remove the mouth parts one by one as described below. Use fine forceps to lift the labium, hold it near its base and pull gently (Fig b). base base of Fig. 18.1: (a) Boiling the macerated muscle tissue of head. (b) Lifting the labium with forceps. (c) Arrangement of mouth points to make tidy mount. f the labium does not come away easily the muscle is insufficiently rnacerated and the head should be boiled again in caustic soda. (NOTE: BE VERY CAREFUL NOT TO DAMAGE THE OTHER MOUT--PARTS. USE A LENS F NECESSARY TO DENTFY THE PARTS. NEVER LET THE HEAD OR MOUTH-PARTS BECOME DRY). Place the labium in water in a watch glass/cavity block in a safe place. Similarly, remove the maxillae and the hypopharynx, slipping the forceps under each part in turn and holding it as near the base as possible when making the final pull. Place the maxillae and hypopharynx with the labium. Similarly, remove the mandibles. Cut off the labrum with a sn~all piece of the clypeus. Place the mandibles and labrum with the otller mouth-parts.

5 Preparation of Permanent Mounts of Mouth-Parts of Cockroach and Mosquito labella Cules mi~lc Culcs lk~nalc Fig. 18.3: ~outh-parts of ~ulex, A - Male, B - Femalc. labella Anopheles male ladc~~a Anoplicles 'cmalc Fig. 18.4: Mouth-parts ofanoplreles, A -Male B -Female TERNPNAL QUESTONS 1. Draw a labelled diagram of mouth-parts of cockroach and mention the method of feeding.

6 Animal Diversity Labb 18.5 METHOD FOR THE PREPAMTON OF MOUNTS OF MOUTH-PARTS OF MOSQUTO 1. Decapitate (remove the head) tlie mosquito (Culex or Anopheles wliicliever is provided) and treat the head with 10% potassiu~n iydroxide solution eitlier by leaving it in the solution for several hours at room-temperature or heating to boiling for 1-2 minutes. This process softens the stiff mouth-parts so tliat they will spread when tlie liead is transferred to mounting media. 2. Rinse tlie head in water. 3. Transfer tlie liead with the help of a dissecting needle to a drop of glycerine on a slide. 4. Put the coverslip. 5. Apply gentle pressure on coverglass with a needle to spread out tlie mouth-parts at least near tlie tips to make identification easier. Mouth-parts of mosquito include the following: i) Tlie labium, which normally encloses several otlier parts making up tlie proboscis. Tlie labium is grooved dorsally to receive tliese paits and provided distally with a pair of short labella that iave been interpreted as tlie labial palp. ii) A pair ofjointed nzaxillary palps. iii) Apair of 17raxillae which may be recognized by the distinct serration or teeth along the edge of tlie distal tip. iv) A pair of mandibles with a blade-like tips whicli are very finely serrated. v) Tlie labrunz-epipharynx which is much heavier than the ~nand ibles aiid maxillae and is grooved ventrally and vi) The slender hypopharynx with tlie salivary duct extellding through tlie middle of it OBSERVATON OF MOSQUTO MOUTH-PARTS UNDER MCROSCOPE You are now familiar witli tlie mouth-parts of a niosquito. Sketcli tlie mouth-parts of Anopheles and Culex mosquitoes (male and female) as you observe under tlie microscope, label and describe the vario~ls parts. Mouth-parts of Culex i) Mouth-parts piercing and sucking type with labium modified into an elo~igated proboscis. ii) Maxillary palps very small at the base of proboscis in female and pointed and longer than tlie proboscis in male. iii) Maxillae and lnandibles in tlie form of elongated needle-like styles in females and adapted for cutting and making wound in the host skin, mandibles and maxillae reduced in males, iv) Antennae are pilose with short and few liairs of bristles in female and bushy (plumose) in male. (Fig. 18.3) Mouth-parts of Anopheles i) Mouth-parts piqcing and sucking type with labium modified into an elongated proboscis. ii) Maxillary palps are simple, and nearly equal to the proboscis, in males ~naxillary palps are club-shaped at the distal end. iii) Mandibles, maxillae and liypopliarynx in the form of elongated stylets. Mandibles and maxillae reduced in males. iv) Antennae less bushy i.e. with small scanty hair in female and plumose (bushy) in males. (Fig. 18.4)

7 EXERCSE 19 STUDY OF THE FRUTFLU DROSOPHLA FROM MOUNTED SPECMEN Structure 19.1 ntroduction Objectives 19.2 Material Required 19.3 Metliod and Observations 19.4 Ter~nirial Questions 9. NTRODUCTON Drosophila co~n~nollly known as fruitfly or vineger fly, belongs to tlie order Diptera of class nsecta under Phylum Artliropoda. t is a small insect about 2 lnln size, lias a yellowisli brown to rusty brown body and clear, untnarked wings. D. nzelanogastar is well-known as an excellent genetic material for cllro~noso~nal studies and is easy to culture. ts larvae can easily be reared on artificial media for experimental investigations. Objectives After performing tliis exercise you should be able to: e e a identify tlie fly, describe its diagnostic features, draw a diagram to show its external features, 19.2 MATERAL REQURED. Hand lens 2. Cornpound microscope 3. Mount of Drosophila 4. Practical Record Book METHOD AND OBSERVATONS Examine the permanent nounts of the specimens of adult fruit fly under low power of ~nicroscope and note tlie following features: i) ii) iii) iv) v) v i) vii) viii) ix) Small insect having only one pair of forewings with few veins. Hindwings are represented by a pair of balancers or halteres. Body divided into head, thorax and abdomen. Head bears large compound eyes, 3 ocelli and plumose type antennae, having 2 basal seglne~its and a fringed flagellum. Mouth-parts are of sucking type, Feeds up011 fermenting fruits. Broad thorax bears bristles. Abdomen has dark posterior bands. Metamorphosis is complete consisting of egg, larva, pupa and adult. Examine the specimen to verify tlie features listed above. You sliould sketch what you observe under the microscope in the record note book, label and give the descriptive features.

8 Animal Diversity Lab. 2. List the differend'es between mouth-parts of i) male and female Culex and ii) male and female Anopheles.....