Insect Senses PDF

For insects to exist, they ______ the 20,000 IN DRAGONFLIES realities of the environment and govern 12,000 OR MORE IN LEPIDOPTERA their activities accordingly. - MUST SENSE 4,000 IN MUSCA (HOUSEFLI...

For insects to exist, they ______ the 20,000 IN DRAGONFLIES realities of the environment and govern 12,000 OR MORE IN LEPIDOPTERA their activities accordingly. - MUST SENSE 4,000 IN MUSCA (HOUSEFLIES) ______ is achieved by a number of different sense organs, and behavior results from FEWER THAN A DOZEN IN WORKERS OF integration of information and stimulation CERTAIN ANTS by the nervous system. - Perception STRUCTURE OF THE CE/HOW THE CE SENSES OF INSECTS – basic senses and WORKS their groups of organs/receptors (ECTODERMAL IN ORIGIN) Light is gathered in _______ lens or cornea. – OMMATIDIUM Sight – Photoreceptors The Light-receptor apparatus (LRA) Smell (Olfaction) – Chemoreceptors comprises __– __ retinula cells (RC) which Taste (Gustation) – combine to produce a central light sensor Mechanoreceptors (______). 6-8 RETINULA CELLS, RHABDOM Hearing – Auditory organs Touch – Temperature and Humidity Central light sensor is also called _____. – receptors RHABDOM RC turn light into _____ energy which is carried to nerve fibers by the brain. – _________ It detect presence and quality of ELECTRICAL ENERGY incident light; when images are produced it is called ______. – PHOTORECEPTORS, Images produced by ommatidia are SIGHT believed to result in an overall ____object, each ommatidium supplying only a piece of _____ is the most complex photoreceptor vision. – MOSAIC OBJECT involved in forming images. – EYES Eye type present in many immatures of _______ not found in primitively wingless Endopterygota. Also believed to perceive insects (have evolved along with flight); images although probably produce a less Lacking in immature of most advanced complete mosaic; – SIMPLE EYES/OCELLI insects; Most insects with _______ also have simple eyes. - COMPOUND EYES _______ distinct from the CE thru the presence of a single corneal lens. – SIMPLE Principal visual organ, characterized EYES externally by the cornea being divided into ________ facets. – HEXAGONAL 2 CLASSES OF SIMPLE EYES/ OCELLI Each facet is part of the individual sensory Dorsal ocelli – 3 arranged in a units called ______. – OMMATIDIUM triangle on frontal region of head or on the vertex THE NUMBER OF FACETS TO A CE VARIES  Lateral ocelli – no general substances, some reacting to sugars, others uniformity, singly (e.g.sawfly to salts or to H2O larvae) or in groups on Detect movements, vibrations, other either side of the head (e.g. mechanical disturbances. – Lepidoptera larvae) MECHANORECEPTORS SOME INSECTS HAVE NO EYES, THUS THEY TOUCH – monitored by hair _______, DETECT LIGHT THRU THE ____ (DERMAL innervated by a single neuron. – SENILLA PHOTORECEPTION) - CUTICLE HEARING - perception of _____ vibrations Detect the presence of chemical substances by long, slender, trichoid sensilla. – AERIAL in the air thru the sense of smell (OLFACTION) OR on substrates thru the FOR THE TYMPANUM to vibrate = perceived sense of taste (GUSTATION) – by chordotonal organs made up of CHEMORECEPTORS scolopidia FORMS OF CHEMORECEPTORS Where is the tympanum? short pegs or hairs on various body parts In grasshoppers, on 1st abdominal segment (antennae,palps) In crickets, on tibiae SMELL RECEPTORS Perceived by olfactory In moths, abdomen and metathorax sensilla characterized by the presence of Johnston’s organ in the pedicel of adult numerous _____. - pores insects responds to movements of More numerous on males: e.g last 8 antennae; maybe involved in hearing antennal segments in male Apis about 30,000 sensilla compared to workers = 6,000 & queens = 2,000 SMELL RECEPTORS Play an important role in the life of insects since many behavioral and developmental changes are caused by _________. – PHEROMONES _______ highly specific, volatile substances perceived thru the olfactory sensilla after being secreted by other members of the same species. – PHEROMONES TASTE RECEPTORS Sense molecules from liquids. Have fine nerve endings exposed to the environment at hair tips Individual sense cells of a single gustatory sensillum respond specifically to particular Outer covering of the living tissues of __________ composed of insects; sclerotized for protection from mucopolysaccharide secreted by abrasion as well as water proofing. – hemocytes. Along it run the nerves, INTEGUMENTARY SYSTEM Tracheaoles. – BASEMENT MEMBRANE CUTICLE, EPIDERMIS, BASEMENT MEMBRANE CUTICULAR EXTENSIONS Single layer of cells – EPIDERMIS __________is a multicellular with CUTICLE – epicuticle, exocuticle, endocuticle undifferentiated epidermal cells. – SPINES PROCUTICLE - exocuticle and endocuticle _________ is a multicellular with specialized cells. - SETAE OR HAIRS OR MACROTRICHIA Membrane between cuticle and epidermis – OR TRICHOID SENSILLA APOLYSIAL MEMBRANE _________ are unicellular in origin. – Epicuticle comprised of cement, wax, outer ACANTHAE and inner cuticle _________ a subcellular from several to Cuticle is produced by ______. EPIDERMIS many extensions per cell. – MICROTRICHIA It is thin outer layer, a 3 – 0.1 mu thick which permeable to chemicals and nutrients for growth but impermeable to SETAE sense much of insect’s tactile enzymes that breakdown parts of old cuticle environment before it is shed. – EPICUTICLE BRISTLES/CHAEETAE – LARGE SETAE When first laid on the surface, it is deeply Scales in lepidoptera are flattened setae folded and later, straighten after _____ (insect swallow air). -ECDYSIS LIPOPROTEIN – layer of cuticulin, critical in 3 Separate cells form each seta growth process TRICOGEN CELL - hair formation ________ is tanned protein with lipids TORMOGEN CELL – socket serving as a varnish-lik covering of the wax formation or maybe in the form of an open meshwork SENSORY CELL – providing a reservoir of lipids to replace lost surface lipids). – CEMENT ___________are passageways of secretions by the epidermis from inside to outside. Thicker layer, Forms the exuvium at molting, Epidermal secretions make possible the Gives the cuticle its characteristic strength repair of cuticle, secretion of wax and and resilience. – EXOCUTICLE release tanning agents. - PORE CANALS _________ a polymerized compound, a THE BODY WALL THAT SUPPLIES A SUPPORT nitrogenous polysaccharide linked to a SYTEM KNOWN AS ______. EXOSKELETON protein. This is common in nature as a base for materials like wood, hair, horn. – CHITIN Functions of the exoskeleton Provides rigid foundation of th body  Serve as point of attachment of ecdysis happen and fully expand the new muscles one. Serve as covering to protect internal 8. Sclerotization /Tanning – made more organs resistant to degradation, Cuticular proteins Helps prevent desiccation are cross-linked by the action of quinones, MOLTING (casting of the old cuticle) IS cuticle change to darkm hard, insoluble TRIGGERED BY _______ RELEASED WHEN material. A day or two. Controlled by AN INSECT’S GROWTH REACHES PHYSICAL bursicon LIMITS OF ITS EXOSKELETON. – HORMONES QUINONES= tanning subst for the cuticle 2 PROCESS OF MOLTING coming from tyrosine or para-OH phenylalanine in the hemolymph APOLYSIS – –separation of cuticle from the epidermis Β – sclerotization = for hardening ECDYSIS - the actual process of without development of new color shedding off of the old skin Quinone sclerotization = hardening with colors 1.Changes in epidermal cells 9. Start of wax secretion 2.Secretion of molting fluid PHARATE CONDITION = INSECT ACTIVELY 3.Secretion of cuticulin layer – protect EC CONSTRUCTING NEW EXOSKELETON TAKES from molting fluid’s digestive action, CL bcm DAYS OR WEEKS WITH VERY LITTLE prt of the new exoskeleton’s epicuticle EVIDENCE OF CHANGE 4.Activation of molting fluid – after TENERAL CONDITION = NEWLY MOLTED activation of CL, MF becms activativated INSECT, SOFT UNPIGMENTED (WHITE OR and chemically DIGESTS the endocuticle of IVORY), UNTIL THE TANNING PROCESS IS the old exoskeleton. COMPLETED (A DAY OR TWO) 5.Absorption of the digested remains of old cuticle and start of secretion of new procuticle – AA and chitin pass thru CL PHYSIOLOGY OF MOLTING/DISTINCT recycled by EC =EXO AND ENDOCUTICLE SEQUENCE OF EVENTS (SOFT AND WRINKLED) 1. Changes in epidermal cells 6.Formation of wax and cement layer - 2. Secretion of molting fluid PORE CANALS WITHIN THE PROCUTICLE 3. Secretion of outer layer of cuticulin 4. Secretion of homogenous layer of ALLOW MOVEMENT OF LIPIDS AND cuticulin PROTEIN TOWARD THE NEW EPICUTICLE 5. Activation of molting fliid WHERE WAX AND CEMENT LAYER FORM. 6. Absorption of the digested remains 7. Ecdysis and expansion of the new cuticle of old cuticle – muscle contraction and intake of air to 7. Start of secretion of new procuticle swell the body, old E split open along lines (exo/endocuticle) of weakness (ECDYSIAL SUTURES) and 8. Ecdysis and expansion of the new cuticle  9. Sclerotization The cuticle along these lines consists only 10. Start of wax secretion of undifferentiated pro and epicuticle ELASTIC AND EXTENSIBLE CUTICLE CONTROL OF MOLTING AND ASSOCIATED Some parts of the cuticle contains a PROCESSES colorless, rubber-like protein called resilin e.g. those found in elastic hinges such as wing-hinge ligament lying between the ECDYSONE – ROLE IN EVENT IN MOLTING, pleural process and the 2nd maxillary MOLTING HORMONE sclerite BURSICON – CONTROLS SCLEROTIZATION also in clypeo-labral spring keeping the hormone released from the corpora allata- labrum pressed against the mandibles corpora cardiaca complex with ecdysone to control wax secretion A hormone with ecdysone controlling endocuticle production Ecdepteroids induce sclerotization in ligated abdomen of blowfly larvae resulting to the induction of de novo synthesis of enzyme dopa-decarboxylase in the epidermal cells DIFFERENT TYPES OF CUTICLE RIGID CUTICLE - nymphs of Schistocerca (grasshopper) = the exocuticle of the sclerites is sharply differentiated from the endocuticle which never tans. MEMBRANOUS CUTICLE - sclerites are joined by flexible arthrodial membranes, in these the procuticle remains untanned [arthrodial=permitting motion in any direction in articulations] e.g. Membrane between 2 adjacent sclerites resulting to unrestricted movement exocuticle also absent along ecdysial lines of larval holometabolous insects. MODE OF REPRODUCTION IN INSECTS Produce spermatophores, proteinaceous pouch-like structures that encase sperm, Sexual protecting them as they are delivered to the Asexual female’s genitalia during copulation. Sexual and asexual for some insects REPRODUCTIVE SYSTEM MALE’S REPRODUCTIVE SYSTEM Pair of ovaries Pair of testes, back of abdomen, subdivided into several hundred follicles (sac-like tubes) Oogonia (first stage in the differentiation of where sperms are produced an egg cell) Group of germ cells near distal end of each ovariole, ________ a group of sperm cells at the distal end of each follicle, divided (mitosis) oogenesis (egg maturation) & increase in size to form spermatocytes. Oocytes SPERMATOGONIA Undergo meiosis: yields 4 cells, 1 egg and 3 ______migrate toward at end of the follicle, polar bodies which disintegrate or may push along by continued cell division of accompany egg as nurse cells spermatogonia, undergo miosis: 4 haploid spermatids, mature spermatozoa linear series of eggs in progressive stages of maturation (chain of beads) - increase in _______ where mature sperm from the size by absorbing yolk (vitellogenesis = testes pass out. _ Vas efferentia deposition of yolk in the oocyte) 100,000 X _______ (storage chamber) – where mature larger than original oocyte reaching base of sperms collect. SEMINAL VESICLE ovariole(calyx) – mature leaves thru short lateral oviducts a common oviduct opening _______ join one another near midline to into a genital chamber - (BURS form a single ejaculatory duct. – VAS COPULATRIX) or copulatory pouch DEFERETIA where sperm passes out of the______males body thru a copulatory organ called Female accessory glands aedeagus. EJACULATORY DUCT 1 or more pairs; usually connected by small ducts to common oviduct or bursa copulatrix supply lubricants for the system Accessory glands Secrete protein-rich egg shell (chorion) that 1 or more pairs of secretory glands in surrounds the egg Periplaneta, form dense bunches of tubules called the “mushroom gland” of Huxley Copulation (male deposits spermatophore Functions: in bursa copulatrix. Manufacture of seminal fluid that sustains Peristaltic contraction force spermatophore and nourishes mature sperm while in the into female’s spermatheca (pouch-like, for male’s genitalia storage of sperm for weeks, months, even years) Spermathecal gland produce: types of parthenogenesis), aphids, some wasps Enzymes to digest protein coat of spermatophore. Nutrients to sustain sperm ATYPICAL MODES in storage PAEDOGENESIS - reproduction in an immature stage Ovulation takes place larval paedogenesis - e.g. gall midges (Cecidomyiidae) Eggs to spermatheca release few sperm – sperm swim to small opening called Pupal paedogenesis - embryos are formed micropyle of egg shell - fertilization occur in the haemocoele of paedogenetic mother- sperm;s nucleus fuses with egg cell’s pupa (hemi-pupa) nucleus – oviposition or egg laying follows NEOTENY - non-terminal instar develops closely – begins embryonic development reproductive features of an adult, SCALE The growth and transformation of the insect INSECTS - Strepsiptera – female from egg stage to the embryo, immature development ceases at puparium stage and adult stages. - INSECT DEVELOPMENT HERMAPRODITISM - having individuals that Two phases: possess both testes and ovaries, Ovotestis = part testis, part ovary e.g. cottony cushion 1. Embryonic development— INSECT scale – Icerya purchasi THE BODY 2. Post-embryonic development— males arise from unfertilized eggs, HATCH, INSECT DEVELOP AND Fertilized eggs develop from females GROW OUTSIDE THE BODY POLYEMBRYONY - production of more than (METAMORPHOSIS) one embryo (often many) from one egg by The immature insect from the egg subdivision; restricted to parasitic insects will transform into another stage, that is, after transforming into a bigger and, in many cases, different forms until it reaches the adult Reproductive Strategies: “To Lay Eggs or stage. Not To Lay Eggs” ATYPICAL MODES OF REPRODUCTION Oviparity - Egg laid shortly after fertilization, No retention, No PARTHENOGENESIS – development from an nutrients to embryo after unfertilized egg fertilization THELYTOKOUS – PRODUCE ONLY FEMALES Ovoviviparity - Eggs retained until (DIPTERA AND COLEOPTERA) embryogenesis complete, Embryo fed by egg reserves, Female ARRHENOTOKOUS – PRODUCE ONLY MALES deposits nymph/larva, Example: (HYMENOPTERA, SCALE INSECTS, many Aphids WHITEFLIES) Viviparity - Eggs retained and Embryo fed by mother, Immatures AMPHITOKOUS OR DEUTEROTOLOUS – may complete development before BOTH SEXES (THYSANOPTERA), (undergo all Deposition Tends to inhibit appearance of adult character in the developing Insect – Juvenile Hormone Various small, paired glands in the anterior part of the body producing TOWARDS THE END OF JUVENILE hormones that play very important LIFE, the CA become less active, role in the control of molting and molting is accompanied by more or metamorphosis and may also exert less development of adult features other physiological effects as strikingly shown in hormones - THE ENDOCRINE holometabolous insects SYSTEM CA resume activity in the adult TYPES OF ENDOCRINE ORGANS when secretions may be necessary for the full development of the NEUROSECRETORY CELLS OF THE ovaries and accessory reproductive BRAIN glands in both sexes Groups of modified nerve cells in the dorsal part of the A pair of diffused glands at the back protocerebrum that produce: of the head or in the thorax. Each Peptide hormone which activate the gland had a rich tracheal supply and thoracic glands. Prothoracicotrophic often a nerve supply. Produce hormone (brain hormone). Bursicon ecdysone - THORACIC/PROTHORACIC GLANDS SPECIALIZED ENDOCRINE GLANDS (molting hormone), Induce Usually a pair of small bodies lying immature insect to molt, Induce one on each side of the aorta, immature insect to molt immediately behind the brain, to breakdown/ degenerate soon after which they are connected by 2 pairs the final molt to adult except in of nerves - CORPORA CARDIACA Thysanura where molting continues after sexual maturity and in solitary A pair of small, ovoid cellular bodies locusts), Initiates tanning, Also of ectodermal origin associated required for egg production with the stomodaeal ganglion antagonizes the effect of behind the brain. Produce juvenile vittelogenesis = stimulatory action hormone (JH) - CORPORA ALLATA of juvenile hormone – Ecdysone (CA) OTHER HORMONES Controls metamorphosis and regulation of reproductive Cerebral neurosecretions released development such as synthesis of from the peripheral nerve endings, yolk precursors or vitellogenins Involved in pupariation, Involved in (regulates yolk deposition in eggs) – the production of DOPA (di-hydroxy Juvenile Hormone phenyl alanine) – decarboxylase - ANTERIOR SEGMENT REFRACTION FACTOR (ARF) Other hormone that also released from peripheral nerve endings, Also involved in pupariation. Regulates synthesis of enzymes at the transcriptional level necessary for the hydroxylation of tyrosine HOW THE DIFFERENT HORMONES REGULATE DEVELOPMENT A stimulus from the environment is received by the insect’s brain This is passed on to the nerves, then to the ganglia. Gland release hormone and is transported by the haemolymph Hormone reaches target site