Cockroach – Periplaneta americana

Introduction :

Nocturnal, omnivorous and scavenger.

IN each segment , EXOSKELETON is

present in form of HARDENED PLATES c/d SCLERITES.Tergite (1) – sclerite of dorsal side

Sternite (1) – sclerite of ventral side

Arthrodial membrane – joins both

Tergite and sternum. It is a THIN and

FLEXIBLE membrane.

Exoskeleton is chitinous.

Can survive without head.

Phylum – Arthropoda

Class – Insecta

Order – Dictyoptera

family – Blatedea

Genus – Periplaneta

Species – americana

Morphology of an Insect – Head

Segmentation Head is formed by fusion of 6 segments.

Thorax – 3 segments.

Abdomen – 10 segments.

Head Head is hypognathous(triangular and directed towards downwards.)

One pair compound eyes are situated.

Between compound eyes and antenna, ocellar spots or

fenestra, undeveloped ocelli (simple eye) are present.

On antenna: tactile and olfactory smell receptors are

present.

Respond to small , touch.

Chewing and biting type.

Labrum, Mandibles, Maxillae, Hypopharynx and Labium

are the mouth parts. Mouth Type

Mouth Parts of Cockroach: also called as upper lip. It is movable.

having teeth like cutting plates at inner edges.

These are jaws – for crushing and cutting of food.

Labrum

Mandibles

Maxillae

hold the food and bring it to

mandibles for mastication.

These are used for cleaning the

antenna, labial palps and front

legs.

Labium or lower lip

maxilla prevents the loss of

food particles from mandibles.

Hypopharynx

It is equivalent to tongue.

Common salivary duct opens at

its base.

Morphology of an Insect – Thorax and Abdomen-

Thorax

Prothorax – largest thoracic segment

Mesothorax – 1st pair wings arises.

Metathorax – 2nd pair wings arises.

Tergite of thorax Also known as Pronotum.

Walking legs for fast moving, long and narrow

Legs are five segmented and nine jointed.

Wings Forewings (1st pair of wings), called as elytra or tegmina, protects and

covers the hind wings at rest.

Hindwings (2nd pair of wings) are used for flight.

Abdomen On the 10th tergum one pair long, anal cerci are

present. On anal cerci auditory receptors are present.

In 9th sternum of male, one pair anal styles or style are present.

IN MALES: Genital chamber is formed by 9th and 10th TERGUM dorsally and 9th STERNUM ventrally.

IN FEMALES: formed by 7th,8th, 9th STERNUM.

Anatomy: Body wall Consists of cuticle, hypodermis and basement membrane

Cuticle Cuticle is chitinous, amino polysaccharide (N – acetyl glucosamine).

Hardening of cuticle is called as sclerotization and plates are formed,

called as sclerites.

Hypodermis

Muscles are striated and present in bundles.

Coelom is greatly reduced, represented by cavity of reproductive organs.

BLOOD of cockroach is called haemolymph which is

made up of COLOURLESS PLASMA and blood cells

called as HAEMOCYTES..

Digestive System – Alimentary Canal:

Alimentary Canal It is divided into foregut, midgut and hindgut. Foregut and

hindgut are lined by cuticle.

Foregut:

Pre – oral cavity (buccal cavity) is

surrounded by mouth parts which lead

in to pharynx.

Pharynx leads in to oesophagus,

which opens into a sac like structure

called CROP.

Crop is a reservoir for storing the

food.

Gizzard (Proventriculus) is externally lined by THICK CIRCULAR MUSCLES and INTERNALLY lined by THICK CUTICLE.

It is for GRINDING OF FOOD.

Digestive System – Alimentary Canal and Digestive Gland

FOREGUT

Hindgut: At the junction of midgut and hindgut, malphigian tubules are

present.

Digestive glands

In saliva – amylase (zymase), chitinase, cellulose enzymes and mucus is present.

Salivary glands

Digested food is absorbed in midgut and hepatic caeca.

Midgut leads in to ileum, which leads in to colon. Colon leads in

to rectum, which opens through anus.

The lining of rectum forms 6 longitudinal folds, called as rectal

papilla which absorb maximum water from faeces.

MIDGUT:

CIRCULATORY SYSTEM:

It is open type.

Haemocoel In haemocoel, no coelomic epithelium, so it is not true coelom.

The diaphragms are perforated, pores are called as fenestrae.

12 pair alary muscles are attached.

Heart

Heart is 13 chambered.

One pair ostia are present on each side which allow the blood to only

enter in heart.

The first chamber is continued in to an anterior aorta.

The first chamber is continued in to an anterior aorta

Blood It is colorless with no respiratory pigment.

It consists of colourless plasma and colourless corpuscles, called

haemocytes, these are phagocytic, helps in coagulation.

Circulatory System And Respiratory System:

Alary muscles contract → Percardial sinus

enlarges → Blood enters in it from

Perivisceral sinus → Alary muscles relax →

haemolymph enters in heart through ostia

→ Heart contracts from posterior to

anterior end → haemolymph through

anterior aorta in to haemocoel of head →

haemolymph in Perivisceral and

Perineural sinuses.

Respiratory System

It consists of a network of trachea, that open through 10 pairs of small holes called

SPIRACLES.

Tracheal tubes subdivided into tracheoles. Exchange of gases at the tracheoles by

simple diffusion.

Excretory System:

Excretion is performed by Malphigian tubules, lined by glandular and ciliated

cells.

Three ganglia lie in the thorax, and six in the abdomen.

Brain is represented by supra – oesophageal ganglion which supplies nerves to

antennae and compound eyes.

They absorb nitrogenous waste and convert them into uric acid. This insect is

called uricotelic.

Fat body, nephrocytes and urecose glands also help in excretion.

Nervous System

Brain Nerve cord 10 ganglia Ganglia nerves

Excretory System

Sense organs:

Except the photoreceptors (eyes), all the sense organs are situated in

epidermis of integument and are modified epidermal cells, called sensillae.

Olfactoreceptors – present on antenna.

Gustatoreceptors – present on maxillary and labial palps.

Thermoreceptors – present on plantulae (pads between first four tarsomeres).

Auditory Receptors – present on anal cerci.

Photoreceptors – Compound Eyes : situated at dorso – lateral sides of head.

Ommatidia are visual units, number – 2000 in each compound eye.

Mosaic vision havind MORE SENSTIVITY and LESS RESOLUTION.

Male Reproductive System: Testes

One pair lying dorso-laterally in 4th, 5th and 6th abdominal segments.

Vasa deferentia

Each testis run backwards upto posterior end, bend forwards and join in middle and

open in to ejaculatory duct.

Ejaculatory Duct

Opens to outside by male genital aperture.

Cells of ejaculatory duct secrete middle wall of spermotophore.

Utricular or Mushroom Gland

Accessory reproductive gland at the junction of vasa deferentia and ejaculatory duct.

Utriculi majoris (Uricose glands) – secrete inner wall of spermotophore.

Utriculi braviores – secretion nourishes sperms.

Short bulbous tubules – form seminal vesicles, filled with sperms.

Phallic or Conglobate Gland – secretes outer wall of spermotophore and open into

genital pouch

Genital Chamber (Pouch)

Bounded dorsally by 9th and

10th terga and ventrally by 9th

sternum.

It contains anus, male genital

aperture and gonapophysis.

External Genitalia

Formed by three gonapophysis or phallomeres.

Right Phallomere – It contains two plates, a hook and one serrate lobe.

Left Phallomere – Contains titillator, a pseudopenis and aspirate lobe.

Ventral Phallomere – bears male genital aperture.

Spermotophore

Sperms in seminal vesicle are

glued together in the form of

bundles, called as

SPERMATOPHORE, which are

discharged during copulation.

Female Reproductive System -:

Ovaries It is one pair, lying laterally in 2nd, 3rd, 4th , 5th and 6th segments.

Each ovary is a group of 8 ovarian tubules or ovarioles.

Oviducts One pair.

Stalks of 8 ovarioles of one ovary join and form a oviduct.

Vagina

Collaterial

Glands These are accessory reproductive glands.

FORMS ootheca around ova.

Spermatheca Receive sperm during copulation.

Genital Pouch

(Gynatrium) or

Brood

Is BOAT SHAPED.. Formed by 7th sternum, 8th and 9th sterns.

Genital chamber (atrium) – contain female genital aperture,

openings of spermatheca and collaterial glands.

Oothecal chamber (vestibulum) – ootheca are formed.

External Genitalia Concealed inside gynatrium.

It consists of an ovipositor, formed by two gonapophysis.

It assists in copulation, in laying eggs and formation of ootheca. Ovipositor

Copulation Occurs at night, Spermatophores are deposited in spermathecal

papilla, at this time 3rd layer of wall of spermotophore is secreted.

Fertilization is internal, By

the secretion of collateral

glands on eggs,

ootheca is formed.

Eggs are centrolecithal.

Cleavage is superficial.

Young ones hatch out are

called as nymphs.

Metamorphosis: Metamorphosis It is incomplete and paurometabolic (gradual).

Exoskeleton of nymphs cast off called as shedding or

moulting or ecdysis.

Nymphs undergo about 13 times ecdysis to reach ADULT

COCKROACH stage.

Male Female

Smaller body Relatively large body

Abdomen is slender Abdomen is broader

Terminal segment is pointed Terminal segment is blunt

Abdomen – 9 distinct segments Abdomen – 7 distinct segments

One pair anal styles in 9th segment Absent

Wings are larger and extend beyond

hind end of body.

Wings are relatively small and extend upto hind

end of body.