PERIPLANETA AMERICANA
(COCKROACH)
Cockroaches are brown or black bodied animals that are included in class insecta of phylum Arthropoda. Bright yellow, red and green coloured cockroaches have also been reported in tropical regions. Their size ranges from 0 inches to 3 inches (0.6-7.6) and have long antennae, legs and flat extension of the upper body wall that conceals the head. They are nocturnal omnivores that live in damp places throughout the world. They have become residents of human homes and thus are serious pests and vectors of several diseases.
Systematic : position
Kingdom : Animalia
Phylum : Arthropoda
Class : Insecta
Order : Blattodea
Morphology of cockroach :
The adults of the common species of cockroach, periplenta Americana are about 34-35mm long with wings that extend beyond the tip of the abdomen in males.
The body of a cockroach is segmented and divisible into three distinct regions: head, Thorax and abdomen.
The entire body is covered by a hard chitinous exoskeleton (Brown in colour).
In each segment, the exoskeleton has hardened plates called sclerite.
There are ten segments present on the dorsal side which is called tergum and the ventral Side is known as sternum.
Adjacent segments are joined by thin, soft and flexible arthrodial membranes.
Head is triangular in shape and lies anteriorly at right angles to the longitudinal body axis.It is formed by the fusion of six segments and shows great mobility in all directions due to flexible neck.
The head capsule bears a pair of compound eyes. A pairs of thread like antennae arise from membranous socket lying in front of eyes
Antennae have sensory receptors that help in monitoring the environment.
Anterior end of the head bears appendages forming biting and chewing types of mouth parts.
The mouth part consists of a labrum (upper lip), a pair of mandibles, a pair of maxillae and a labium (lower lip). A median flexible lobe, acting as young (Hypopharynx), lies within the cavity enclosed by the mouthpart.
Throx consists of three parts : Thorax, mesothorax and metathorax.
The head is connected with thorax by the short extension of the pro thorax known as the neck.
Each thoracic segment bears a pair of walking legs.
The first pair of wings arise from mesothorax and the second pair from metathorax.
Forewings(mesothoracic) called tegmina are opaque dark and leathery and cover the hind wings when at rest.
The hind wings are transparent, membranous and are used in flight.
The abdomen in both males and females consist of 10 segments.
In females, the 7th sternum is boat shaped and together with the 8th and 9th sterna forms a brood or genital pouch whose anterior part contains female gonophore, spermathecal pores and collateral glands.
In males, genital pouch or chamber lies at the hind end of the abdomen bounded dorsally by9th and 10th terga and ventrally by the 9th sternum.
It contains dorsal anus, ventral male genital pore and gonopophudis.
Males bears a pair of short,thread-like anal style which are absent in females.
In both saxes, the 10th segment bear a pair of jointed filamentous structures called anal cecerci.
ANATOMY OF COCKROACH
DIGESTIVE SYSTEM : Alimentary canal is long and somewhat coiled. Digestive system is complete. It is divisible into three Main parts:
Foregut
Midgut
Hindgut
FOREGUT (stomodaeum) : Foregut is differentiated into five parts: Buccal chamber, pharynx, esophagus crop and gizzard. The mouth opens into a short tubular pharynx, leading to a narrow tubular passage called oesophagus.
Oesophagus opens into a sac-like structure called crop used for storing food.
The crop is followed by gizzard or proventriculus.It has an outer layer of thick circular muscle and thick inner cuticle forming six highly chitinous plates called teeth.
Gizzard helps in grinding the food particles.
The entire forget is lined by cuticles.
MIDGUT : A ring of 6-8 blind tubules called hepatic or gastric caeca is present at the junction of foregut and midgut, which secrete digestive juice.
HINDGUT : At the junction of midgut and hindgut is present another ring of 100-150 yellow colored thin filamentous malpighian tubules. They help in removal of excretory products from haemolymph.
The hindgut is broader than midgut and is differentiated into ileum, colon and rectum. The rectum opens out through the annus.
Circulatory system :-
Blood vascular system is an open type.
Blood vessels are poorly developed and open into space (Hemocoel).
Visceral organ located in the haemocoel are bathed in blood (Hemolymph)
The hemolymph is composed of colourless plasma and haemocytes.
Heart of a cockroach consists of an elongated muscular tube lying along the mid dorsal line of the thorax and abdomen.
It is differentiated into funnel shaped chambers with ostia on either side.
Blood from sinuses enter the heart through ostia and is pumped anteriorly to sinuses again.
Respiratory system :
The respiratory system consists of a network of trachea, That open through 10 pairs of small holes called spiracles present on the lateral side of the body.
Thin branching tubes(Tracheal tubes subdivided into tracheoles) Carry oxygen from the air to all the parts.
The opening of the spiracles is regulated
by the sphincters.Exchange of gases take place at the tracheoles by diffusion.
Excretion :
Excretion is performed by malpighian tubules.
Each tubule is lined by glandular and ciliated cells.
They absorb nitrogenous waste products and convert them into uric acid which is excreted out through the hindgut. Therefore, this insect is called uricotelic. In addition, the fat body, nephrocytes and urecose glands also help in excretion.
Nervous system :
The nervous system of cockroaches consists of a series of fused segmentally arranged ganglia joined by paired longitudinal connectives on the ventral Side.
Three ganglia lie in the thorax,and six in the abdomen.
The nervous system of cockroaches is spread throughout the body.
The head holds a bit of a nervous system while the rest is situated along the ventral (belly-side) parts of its body.
When You Cut the Head of cockroach. It will live for as long as one week.
In the head regions, the brain is represented by supra - oesohageal ganglion which supplies nerve to antennae and compound eyes.
In cockroach they sense organs are antennae, eyes, maxillary palps, labia palps, anal cerci, etc.
The compound eyes are situated at the dorsal surface of the head.
Each eye consists of about 2000 hexagonal ommatidia. With the help of several ommatidia, a cockroach can receive several images of an object.
The kind of vision is known as mosaic vision with more sensitive but less resolution, being common during night (hence called nocturnal vision).
Reproductive system :
Male: Male reproductive system is divided into following parts:
Tastes : There is a pair of three lobed tastes lying dorsoventrally in the 4th and 5th abdominal segments. Tastes become non-functional and reduced in old adults while well developed and elaborate structure in young cockroaches.
Vasa deferentia : From each testes arise a thin thread like white vasa deferens.Both vasa deferentia pass backwards almost to the posterior end of abdomen and then bend forward to meet in the middle and open into a ejaculatory duct.
Ejaculatory duct : It is an elongated White median duct which runs backwards in the abdomen and opens out by male gonopore situated ventral to annus.
Utriculus or mushroom shaped gland : It is a large accessory reproductive gland,whitish in colour and situated at the junction of vasa deferentia with the ejaculatory duct. It has a mass of glandular tubules of three kinds:peripheral long tubules or utriculus majors, central tubules are small short tubules.
Phallic or conglobate gland :
It is a long club shaped accessory gland. It's anterior broader end lies in the 6th segment slightly to the right of the nerve cord. It narrows posterior into a tubular structure and finally tapers to open by a separate apparatus located close to the male gonopore.
External genitalia : Some chitinous asymmetrical structures are found surrounding the male gonopore at the end of the abdomen. These are three phellomeres or male gonapophysis which constitute the external genitalia.These are left phallomere(largest), ventral phallomere (smallest) and right phellomeres
Female : Female reproductive system of cockroach consists of following organs :
Ovaries : There are two large,light yellow coloured ovaries lying laterally to the segments 4th, 5th, 6th embedded in the fat body. Each ovary is a group of eight ovarian tubules or ovarioles containing f all eight ovarioles on one side join to form an oviduct which is lateral, small and with muscular wall.
Vagina : Both the lateral oviducts are called vagina. It opens by female gonopore into genital chambers.
Genital pouch : It is a large boat shaped structure where the floor is formed by the seventh sternites, roof and sides are formed by the 5th and 9th sternites.
Collateral glands :There is a pair of white much branched collateral glands, the left is much larger than the right. Both these glands continue as collateral ducts which join to form a common duct which opens into the dorsal side of the genital chamber.
Spermatheca : These are a pair of club shaped, unequal size one spermatheca being larger than the other structure. Both the spermatheca unite to form a short common duct which opens into the genital chamber on a small spermathecal papilla.
External genitalia of female : It consists of an ovipositor formed by two gonapophysis.The ovipositor lies shove and behind the gonopore, it is short and has three pairs of long thick arms lying dorsally and enclosing two pairs of long thick arms lying dorsally and enclosing two pairs of slender tapering arms.
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