Thorax & Body: Cockroach | Additional Study Material for NEET PDF Download

COCKROACH

Parental Care does not found in Cockroach

Cannibalism - if food is not available, then own species eaten as food.

Cockroach word - originated from Spanish word  "Cucaracha"

Cockroach belong to tropical climate of Africa

Cockroach (Periplaneta) - on 25^oC run 130 cm/sec.

Cockroach chromosome no. = 34

Classification :-

Phylum :- Arthropoda

(a) Joined appendages

(b) Blood containing cavity called "haemocoel"

(c) Exoskeleton made up of chitin

Largest phylum :- 90% animals out of total animals belong to this phylum

Class :- Insecta :- largest class

(a) 75% animals included in class Insecta

(b) body divided into head, thorax, abdomen

(c) Three pair of legs (hexapoda )

Subclass :- Pterigota

(a) two pairs of wings

order :- Orthropetra

Wings dissimilar type.

Genus :- Periplaneta americana → "Common Cockroach" or "American cockroach, or Ship cockroach or Bombay canaris.

Blatta (Stylopaga) orientalis

Blatta germanica - smallest cockroach

Male Blatta have wings - female vestigeal wings.

Blatta name - Linnaeus

Periplaneta - "Burmeister"

(a) "Nocturnal animal"

(b) Cursorial animals - fast runner and less capacity of flight.

(c) Body divided in to three parts called "tegmeta".

some segment fuses in adult stage.

Head 1 (6 segments fused)

(d) Exoskeleton of chitin plates occurred in each segment. Chitin plate called "sclerites".

(e) Sclerites joined each other by "membrane" called "articular a arthroidal membrane."

Sclerites of dorsal side - tergum or tergite

Sclerites of ventral side - Sternum or sternite

Sclerites of lateral side - pleurons orpleurites.

Head :-

(a) "Hypognathus Condition ":- Bent downwards at an angle of 900 from the long axis of body.

(b) sclerites of the head joined fully and form head capsule.

(c) Top part of Head is called "Vertex" and on the vertex a chitin plate present called "Occiput".

(d) on the lateral side of head apex 1 pair of compound eye

(e) each compound eye made up of 2000 units called "ommatidia"

(f) A small light coloured spot called fenestra or ocellar spot is located upon dorsal surface close to each eye. In insect it function as a photoreceptor organ. 

In Cockroach - Inactive and called "Vestigial simple eye".

(g) lateral side of head apex bear of 1 pair of antennae.

Main receptor of touch, temperature vibration in cockroach.

Antennae :- long filliform, unbranched. each antenna extending forwards from an antennal socket located dorsally upon head capsule near the compound eye of its side. These are free moving.

(h) A big chitin plate situated below the vertex called frons or forehead.

(i) two long flattened chitin plates situated on lateral side called "gena" or "cheeck"

(j) A big chitin plate present in Anterior part of frons called "Clypeus". a movable chitin plate joined with Anterior part of clypeus known as "labrum" or "Upper lip".

(k) A big pore situated in the ventral part of head called "Occipetal foramen".

(l) Neck joined with head on the "Occipetal foramen.

(m) Occipetal foramen - surrounded by two pair of chitin plate.

Internal :- Post occiput External :- Post gena

(n) A mouth situated in the anterior side of head which is surrounded by many chitinous structure called "mouth parts"

(o) mouth part :- According to food habits.

"Mouth Parts of Cockroach " :- "Bitting and chewing type"

A cavity formed due to mouth parts called "Preoral cavity" or "cibarium".

(1) Labrum or upper lip :- Broad and flattened terminal sclerite of the dorsal side of head capsule moving articulated to the clypeus. It dorsally overhangs the mouth and hence referred to as "upper lip". Several gustatory sensory setae are located on both sides of the indentation.

(2) Mandibles :- Jaw

1-pair of mandibles.

They form the lateral wall of pre-oral cavity. Their Margins towards the mouth are serrated in to three large and a few small, strong and pointed teeth like processes called Denticles.

Horizontal movement occurs in mandibles abductor and adductor muscle associated with mandibles.

A soft structure present base of mandibles called "Prostheca" prostheca have sensory setae.

(3) First maxillae :-

One-pair and form lateral wall of preoral cavity.

Three parts

(1) Protopodite :- articulates maxillae with head capsule

(a) Cardo (b) Stipe

(2) Endopodite :- surrounds preoral cavity laterally.

"lacinia" - inner →spine attached on free end. and help in chewing food outer - Galea

(3) Exopodite :- "maxillary palp"

(a) made up of five segment

(b) first segment joined on stipe called "palpifer"

(c) setae present on maxillary palp sensory for touch, olfactory and gustatory.

(d) With the help of maxillary palp cockroach pickup its food and put it in preoral cavity for chewing.

Maxillary palps also used as brush to clean antenna and wing.

(4) II^nd maxillae or "labium"or lower lip.:-

(1) Form floor of preoral cavity

(2) coverventralside.

(3) made up of three flat chitin plate. ie. submentum, mentum, prementum.

(4) All three plates denote "protopodite".

Three pair of appendages joined from prementum

1-pair - labial palps - which joined to prementum with the help of chitin piece called "palpiger". These represent "exopodite". These are 3 segmented structures and have touch, gustatory, olfactory setae.

Glossa + Para glossa - "ligula"

These are "Endopodite". These prevent outwarding of food from pre oral cavity. labium are one pair in embryo stage. both labium fuses in adult stage.

Hypopharynx :- or "lingua"

This is a small, cylindrical mouth part sandwiched between first maxillae on the sides and covered by labrum and labium respectively on dorsal and ventral sides. It bears several sensory setae at its free end, and the opening of common salivary duct upon its basal part.

Salivarium r Posterior part of ciberium

II segment of head - antennae

III segment of head - labrum

IV segment of head - mandibles

V segment of head - Imaxillae

VI segment of head - IImaxillae(labium)

I segment do not from appendages.

"Neck" - "Soft Neck". or "Cervicum"

8 chitin plates form exo-skeleton of neck.

2- tergum

2-sternum

2 pairs - pleurons.

2. THORAX

Prothorax

Mesothorax

Metathorax

exoskeleton of each segment made up of

4- chitinplate 1- tergum , 1 sternum and one pair pleurone tergum of thorax - "notum"

One-pair of legs present in each segment of thorax.

3-pairs of legs(6 legs)

legs - five main segment

(1) segment - "Coxa" :- broadest segment

(2) segment - trochanter :- small segment

(3) - long segment - femur

(4) - tibia - longest segment

(5) - tarsus- tarsus made up of five sub-segments piece of chitin on end segment called "pretarsus" two structure

(1) Arolium or Pulvilus :- These are adhesive pads

(2) One pair claws :- move on the smooth surface by the help of "arolium" and on rough surface with the help of claws.

In Blatta - arolium is absent .

Small pads present in between of tarsus segment called "Plantuli"

Cockroach climb on the wall by the help of plantuli and Arolium.

Tactile setae present on each segment of legs.

Wings

These called Elytra or Tegmina. wing originate as evagination of body wall and made up of two layers of cuticle.

A network of fine tubules called "nurvures" is present between two layers.

tubules communicate with haemocoel hence, haemocoelmic fluid circulates in these.

These tubules provide nutrition to wings After ageing these tubules dry and provide strength to wings.

Two - pair muscles connected to each wing.

1-pair to tergum

1-pair to sternum

These are called flight muscle. these are not more active in cockroach.

"ABDOMEN"

(3) 7 segment in female remaining segment :- "modified and reduced.

7^th tergum largest in male and female and covers 8^th and 9^th terga Stink gland present in between 5^th and 6^th tergum smell - repel the enemies.

10th tergum - bowl shaped and bifurcated. 10^th tergam 1 pair - "anal cerci"

Each "anal cerci" - "15 segmented" :- These are main sound receptor.

Sternum - In male - 9 sternum in female - 7 sternum

Projected one-pairs of spine like structure from 9^th sternum of male called "analstyles". these are non segmented and help in copulation.

7^th sternum of female - special type of boat shaped.

Free end - divided in to two plates

Plates :- "Gynavalvular plates" or "apical lobs".

These plate surround a pore called "ootheca pore"

All characters of sexual dimorphism in cockroach present in abdomen

"ENDOSKELETON" (1) made up of chitin plates called "apodemes". (2) Apodemes formed from invagination of Sclerites. (3) 1-Apodeme in head - Tentorium (Tentorium - Tent like)

Plate like apodems occur in each segment of thorax. Apodemes absent in abdomen.

"Body Wall"

Made up of three layers :-

outermost- thick cuticle. It is differentiated in to two parts. 

Outer - epicuticlee inner - procuticle

Epicuticle- chitin- absent made up of brown scleroprotein. A waxy layer occurs on epicuticle.

Procuticle :- made up of alternate layer of protein and chitin.

Procuticle :- two parts

(a) Outer - thin (1) exocuticle

(b) Inner - thick (2) endocuticle

Exocuticle :- Attached with protein, and granules of quinones and melanin dark in colour.

Endocuticle :- melanin and quinone - absent, light coloured.

"Epicuticle and exocuticle - discontinuous, absent in joints of sclerites.

Endocuticle :- Continuous, endocuticle become thin in joints and form articular membrane".

2 Hypodermis

(Epidermis)

(a) made up of columnar epithelium

(b) It contains some special cells.

(i) Dermal gland :- Secretion of chitinase and proteinase enzyme at the time of moulting. They separate old cuticle from body and secrete new cuticle.

(ii) Trichogen cell:- elongated cell and reach up to the epicuticle.

These secrete "sensory setae" on epicuticle.

(iii) Tormogen cell :- long, cup like cell

These cell secrete flexible membrane on the base of setae.

(iv) Neuro - sensory cells :-

(a) These situated in the invagination of tormogen cell. One end of neurosensory cells join setae and other end joined with nerves.

(b) Trichogen + tormogen + neurosensory cell :- All three form sensory unit called "sensilla".

(v) "Oenocytes" :- function - uncertain perhaps these secrete wax on epicuticle

(3) "Inner Most Layer"

"Basement Layer"

(a) "simple squamous epithelium"

"BODY CAVITY"

(a) called heamocoel

(b) blood filled cavity

(c) blood of cockroach - "haemolymph"

(d) "blood almost colourless 

(e) Blood not related with respiration

(f) Trehalose sugar in blood - disaccharide.

"HAEMOCOEL'

(a) Not true coelom

(b) It is a "large blood sinus"

(c) In embryo stage several small blood sinuses" fuse and form "Large Blood sinus".

(d) All arthropods - "True coelomate" But highly reduced and found only in the form of cavity of gonads".

Cavity of Gonads :- "True Coelom"

(f) large fat body present in haemocoel of cockroach.

(g) analogous to liver of higher animals four types of cells present in fat body :-

(i) Trophocytes :- these store food in the form of glycogen + Protein + Fats.

(ii) Mycetocytes :-

(a) Presence of "Symbiotic bacteria".

(b) These symbiotic bacteria synthesize amino acid and vitamine.

(c) These change glucose in to glycogen (glycogenesis)

(d) Possibly "Uric acid" is converted in protein. this reaction called" reverse-assimilation".

(iii) Oenocytes :- These cells related with metabolism of moulting.

(iv) Urate cell :- Absorption of extretory material from heamocoel and storage in the form of "Uric acid" so called "storage excretion".