MORPHOLOGY AND ANATOMY OF COCKROACH

Morphology and Anatomy of cockroach

Habitat:

Cockroach generally inhabits unhygienic areas and damp places.

Morphology of Cockroach:

Ø  Body of cockroach is dorsoventrally flattened. Periplanata Americana, a common species of cockroach.

Ø  It is brown in colour.

Ø  It shows bilateral symmetry.

Ø  Males are larger than females.

Ø  Body is covered by brown chitinous exoskeleton. Exoskeleton is thick and hard and is made up of calcareous plates called sclerites. There are ten segments are present on dorsal side which is called tergum and ventral side is known as sternum.

Ø  Adjacent segments are joined by thin, soft and flexible anthroidal membrane.

Ø  Exoskeleton is coated with wax which is impermeable to water. It protects the body of cockroach from loss of water and provides rigidity and surface for the attachment of body muscles.

Ø  Cockroach is nocturnal animal, means most active at night or in dark.

Ø  It has three pairs of jointed appendages and two pairs of wings: Forewings are mesothoracic and are called wing cover or tegmina or elytra. They cover the hind wings and are protective in function. These are dark, stiff, opaque and leathery. Hind wings are large, thin, membranous and transparent. They are kept folded below the tegmina and used for flying.

Ø  Body of cockroach is segmented. It is divided into three distinct parts:

Head, thorax and abdomen.

Head: It bears sessile compound eyes, one on each side, two threads like long antennae arise from membrane sockets. Anterior end of head bears mouth which is provided with mouth parts which consists of a pair of mandible, a pair of maxillae and labium. There is a median lobe hypopharynx which acts like tongue.

Thorax: It consists of three segments Prothorax, Mesothorax and Metathorax. Head is connected with the thorax by short extension of the prothorax called neck. Large sclerites covers the prothorax and shields the mesothorax. Each thoracic segment bears two walking legs. Each leg has five segments: Coxa, trochanter, femur, tibia, tarsus. First and second pair of wings arises from mesothorax and metathorax respectively. Forewings are called tegmina. Wings are

Abdomen: In both male and female ten segments are present. The seventh sternum is boat shaped in females and together with eighth and ninth sterna makes a broad genital pouch. The tenth segment bears two jointed filamentous structure which are called as anal cerci. The ninth segment bears a pair of short thread like style which lies ventral to anal cerci. Anal system is not found in female cockroach.

 

 

Anatomy of Cockroach:

Digestive System:

Ø  Alimentary canal is long and somewhat coiled.

Ø  Digestive system is complete.

Ø  It is divisible into three main parts: Foregut, midgut, hindgut.

Ø  Foregut ( stomadaeum) is differentiated into five parts: Buccal chamber, Pharynx, oesophagus, crop and gizzard. Gizzard is muscular an internally provided with six cuticle teeth which crushes the food.

Ø  Midgut or mesenteron or ventriculus is short, tubular and lined with glandular endoderm. At anterior end of mesenteron there are eight blind globular hepatic caecae which secrete digestive system.

Ø  Hindgut or proctadaeum comprises ileum, colon and rectum. Wall of rectum is provided with six rectal papillae which help in absorption of water and salts.

Ø  Cockroach is omnivorous, feeds on all sorts of organic debris.

Ø  Digestive enzymes of saliva are mainly zymase and amylase.

Ø  Most of the nutrients of food are digested in the crop.

Ø  Absorption of digested food takes place in mesenteron.

Nervous System:

Ø  It consists of three system: Central nervous system, peripheral system, sympathetic or visceral system.

Ø  Central nervous system consists of Brain or supra oesophageal ganglion. Brain gives off a pair of short, stout cords, the circumoesophageal connective, that encircle the oesophagous and passes downwards or backward over the suboesophageal ganglion situated below oesophagous. From the suboesophageal ganglion passes backwards into the thorax and double central nerve cord which bears three ganglia in the thorax and six in the abdomen.

Ø  Peripheral nervous system consists of nerves, which are given off from the ganglia so as to innervate all parts of the body.

Ø  Sympathetic or somatogastric or visceral nervous system consists of frontal a ganglion which is situated on the dorsal side of the oesophagous in the head. From this ganglion, a median unpaired recurrent nerve reaches the visceral ganglion situated on the crop. Various nerve branches are given off from visceral ganglion. Frontal ganglion is jointed with the CNS by nerves which connect the circumoesophageal commissures.

Sensory Structures:

        I.            Thigmoreceptors: They are the receptors of touch. They are present on body, antenna, maxillary palps and legs.

      II.            Olfactory receptors: They receive various smells. They are present on antenna and palp.

    III.            Gustatory receptors: They are of sense of taste. They are present on maxilla and labial palps.

    IV.            Thermoreceptors: These receptors detect changes in temperature. They are present on the pads between the first four tarsals.

      V.            Auditory receptors: This receptor detects sense of hearing. It is present on the anal cerci. It responds to air or earth borne vibrations.

Circulatory System:

Ø  Blood vascular system is open and lacunar type. Body cavity contains blood, which bathes viscera in it. Therefore called as hemocoel. Blood vascular system consists of tubular heart, a blood vessel called anterior aorta and a system of ill defined blood spaces or sinuses.

Ø  Blood sinuses are large body cavities or haemocoel is divided by two membranous horizontal partitions into three wide and flattened sinuses. The dorsal pericardial sinus containing the heart, middle perivisceral sinus containing the gut and the ventral perineural sinus or sterna sinus containing the nerve cord. The partition between pericardial and perivisceral sinus are called dorsal diaphragm and between perivisceral and perineural sinus is called ventral diaphragm. The sinuses intercommunicate by pores in the respective diaphragm. A pair of fan like triangular alary muscles in the floor of the pericardial sinus in each segment reinforces the dorsal diaphragm by their broad bases and also connects it by the pointed tips with the tergite of the segment.

Respiratory System:

Ø  Respiratory system consists of system trachea that open through 10 pairs of small holes called spiracles. It is present on the lateral side of the body.

Ø  Thin branching tubes called tracheal tubes which further subdivided into tracheoles which carry oxygen from air to all parts.

Ø  The opening of the spiracles is regulated by the sphincters. Exchange of gases takes place at the tracheoles by diffusion.

Excretory System:

Ø  Excretion is performed by malphigian tubules.

Ø  Each tubule is lined by glandular and ciliated cells. They absorb nitrogenous wastes products and convert them into uric acid which is excreted out through hindgut. Therefore, insect is called ureotelic. In addition, the fat body, nephrocytes and urecose glands also helps in excretion.

Reproductive System:

Male:

Male reproductive system is divided into following parts:

                                I.            Testes: There is a pair of three lobed testes lying dorsoventrally in the 4th and 5th abdominal segments. Testes become non-functional and reduced in old adults while well developed and elaborate structure in young cockroach.

                              II.            Vasa deferentia: From each testes arises a thin thread like white vasa deferens. Both vasa deferentia pass backwards almost to the posterior end of abdomen and then bend forwards to meet to meet in the middle and open into a ejaculatory duct.

                            III.            Ejaculatory duct: It is an elongated white median duct which runs backwards in the abdomen and opens out by male gonopore situated ventral to anus.

                            IV.            Utriculur or Mushroom shaped gland: It is a large accessory reproductive gland, whitish in color and situated at the junction of vasa deferentia with the ejaculatory duct. It has mass of glandular tubules of three kinds; Peripheral long tubules or utriculis majors, central tubules are small short tubules.

                              V.            Phallic orConglobate gland: It is a long club shaped accessory gland. Its anterior broader end lies in the 6th segment slightly to the right of nerve cord. It narrows posterior into a tubular structure and finally tapers to open by a separate aperture located close to the male gonopore at the hind end of the body.

                            VI.            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 phellomere (largest), ventral phellomere (smallest) and right phellomere.

Female:

Female reproductive system of cockroach consists of following organs:

 

        I.            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 ovarion tubules or ovarioles containing a chain of developing ova. Oviduct is a stalk of all eight ovarioles on one side join to form an oviduct which I lateral, small and with muscular wall.

      II.            Vagina: Both the lateral oviducts unite to form a brown median common oviduct called vagina. It opens by female gonopore into genital chambers.

    III.            Genital pouch: It is large boat shaped structure where floor is formed by the seventh sternites, roof and sides are formed by the 5th and 9th sternites.

    IV.            Collaterial glands: There is a pair of white much branched collaterial glands, left is much larger than the right. Both these glands continue as collaterial ducts which join to form a common duct which opens into the dorsal side of the genital chamber.

      V.            Spermathecae: These are a pair of club shaped; unequal sized one spermathecae being larger than the other structure. Both the spermathecae unite to form a short common duct which pens into the genital chamber on a small spermathecal papilla.

    VI.            External genitalia of female: It consists of an ovipositor formed by two gonapophyses. The ovipositor lies above and behind the gonopore, it is short and has three pairs of elongated process, a pair of long thick arms lying dorsally and enclosing two pairs of slender tapering arms.

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