7.5 Cockroach:Savinay Kumar JC
Cockroaches are brown or black bodied animals that are included in the class insect of Phylum Arthropoda.
The Scientific Name of Cockroach is Periplaneta americana.
7.5.1 Morphology of Cockroach:
An adult cockroach is about 34 – 53 mm long.
Wings extend beyond the tip of the abdomen in males.
The body is segmented into three distinct regions, viz. head, thorax and abdomen.
The whole body is covered by a brown colored hard exoskeleton which is made up of chitin.
In each segment, the exoskeleton has hardened plates called sclerites (Gr: Hard).
The sclerites are called tergites dorsally; and sternites ventrally.Savinay Kumar JC
The ventral and dorsal sclerites are joined together by a thin and flexible articular membrane called arthrodial membrane.
7.5.2 Head of Cockroach:
Head is triangular in shape and lies anteriorly at right angles to the longitudinal body axis.
Head is formed by fusion of six segments, with a flexible neck.
The head bears a pair of compound eyes, a pair of antennae.
Antennae have sensory receptors.
Head bears appendages meant for biting and chewing types of mouth parts.
The mouth parts consists of:
A labrum (upper lip)
A pair of mandibles.
A pair of maxillae
A labium (lower lip)
A median flexible lobe acting as tongue (hypopharynx).
7.5.3 Thorax of cockroach:
The thorax consists of three parts, viz. prothorax, mesothorax and metathorax.
The head is connected with the thorax by a short extension of prothorax called the neck.
Each vertical thoracic segment bears a pair of walking legs.
The dorsally first pair of wings arises from mesothorax and the second pair arises from metathorax.
Forewings are called tegmina. They are opaque dark, leathery and cover the hind wings when at rest.
The hind wings are transparent, membranous and are used in flight.
7.5.4 Abdomen of Cockroach:
The abdomen consists of 10 segments.
In females the 7th segment is boat shaped and along with the 9th and 10th segment it forms the brood or genital pouch.
Genital pouch in females contains female gonopore, spermathecal pores and collateral glands.
In male the genital pouch is bounded dorsally by 9th and 10th terga and ventrally by the 9th sternum.
Male bears a pair of anal style but absent in female.Savinay Kumar JC
Anal cerci present in both sexes at 10th segment.
7.5.5 Difference between male and female cockroach:
Note:Savinay Kumar JC
In certain fish, frogs, and invertebrates eggs are protected in the pouch before hatching is called Brood pouch.
7.5.6 Digestive System of Cockroach:
Alimentary canal is divided into three regions; foregut, midgut and hindgut.
The mouth opens into a short pharynx leading to oesophagus.
Oesophagus opens into a sac like a crop (stomach), which stores food.
Crop is followed by gizzard or proventriculus.
Gizzard contains 6 chitinous teeth for grinding the food.
The entire foregut is lined by cuticles.
A ring of 6-8 blind tubules called hepatic or gastric caeca present at the junction of foregut and midgut, which secretes digestive juices.Savinay Kumar JC
Midgut is a long tube-like structure.
At the junction of midgut and hindgut, another ring of 100-150 yellow colored thin filamentous Malpighian tubules are present.
Malpighian tubules are meant for excretion from haemolymph (blood).
The hindgut is broader and differentiated into ileum, colon and rectum.
7.5.7 Open Circulatory System of Cockroach:
Blood vessels are poorly developed and open into space called haemocoel.
Visceral organs located in the haemocoel and bathed in blood called haemolymph.
The haemolymph is composed of colorless plasma and haemocytes.
Heart is elongated, multi-chambered, funnel shaped with ostia on either side.
Blood enters into the heart through ostia and is pumped anteriorly into the sinuses (Cavities, hollow).
The haemocoel differentiated into three sinuses;
Pericardial sinus.
Perivisceral sinus.
Perineural sinus.
Note:
Cockroaches have white blood because cockroaches lack hemoglobin in their blood.
Hemoglobin is primarily made up of iron and is what gives human blood its red color.
Cockroaches don't have blood vessels like a mammal does, and their blood is not used to carry oxygen.
7.5.8 Respiratory system:
The respiratory system consists of a network of trachea.
Trachea opens to the outside by 10 pairs of small holes called spiracles on the lateral side of the body.
Trachea gives rise to branching tubes called tracheal tubes which are subdivided into tracheoles.
The opening of the spiracles is regulated by the sphincters. Exchange of gases takes place at the tracheoles by diffusion.
7.5.9 Excretory System:
Excretion is performed by malpighian tubules.Savinay Kumar JC
They absorb nitrogenous wastes from the haemocoel and convert into uric acid and pour into the hindgut.
Hence cockroaches are uricotelic in nature.
In addition, the fat body, Nephrocytes and uricose glands also help in excretion.
7.5.10 Nervous system:
Consists of a series of segmentally arranged ganglia joined by paired longitudinal double ventral nerve cord.
Three ganglia lie in the thorax and six in the abdomen.
Head contains a bit of a nervous system.
The brain is represented by supra-oesophageal ganglion which supplies nerves to the compound eye and antennae.
7.5.11 Sensory system:
The sense organs are antennae, eyes maxillary palps, labial palps, anal cerci, hypopharynx etc.
Each compound eye consists of about 2000 hexagonal ommatidia.
Each ommatidium forms a part of the image, called mosaic vision.
Mosaic vision is more sensitive but less resolution, being common during night (hence called nocturnal vision).
7.5.12 Reproductive System:
Cockroaches are dioecious and sex organs are well developed.
7.5.12.1 Male reproductive System of cockroach:
Male reproductive systems of cockroaches consist of Testis, Phallic gland, seminal vesicle, vas deferens, Ejaculatory duct, phallomere, Titillator, Pseudopenis, Anal Cercus and caudal style.
Testis helpful for production of sperm.
Phallic Gland helps in protection and nourishment of Sperm
Vas deferens help in transporting sperm to the Seminal Vesicle.
The sperms are stored in the seminal vesicles and are glued together in the form of bundles called spermatophores which are discharged during copulation.
Ejaculatory duct, Phallomere, Titillator, Pseudopenis and caudal style help at the time of copulation.
7.5.12.2 Female Reproductive System of Cockroach:
It consists of Ovary, Oviduct, Vagina, Collateral Glands, Genital Pouch and Spermatheca.
Ovary helps in the production of egg/ovum.
Oviduct help in transport of egg at the time fertilization
Vagina and Genital pouch helps in participation of copulation.
Spermatheca helps in storage of sperm.
Collateral glands are two highly branched tubular glands in female cockroaches, which are unequal in size. It helps in formation of ootheca.
7.5.13 Fertilization of Cockroach:
Fertilization is internal.
Females produce 10-40 ootheca bearing developing embryos.
After the rupture of single ootheca, around 14 to 16 young ones are released called nymphs.
7.5.14: Life cycle of Cockroach or Paurometabolous: (Gr: Pauro = Small / little; metabolous = undergoing metamorphosis)
Paurometabolous is the process of gradual metamorphosis. It is also called hemimetabolous.
It includes just three stages, i.e. egg, nymph, and adult.
It is called incomplete metamorphosis or paurometabolous since it lacks the pupa stage.Savinay Kumar JC
It means there is a development through the nymphal stage.
The nymphs look very much like adults. The nymph grows by molting about 13 times to reach the adult form.
The next to last nymphal stage has wing pads but only adult cockroaches have wings.
7.5.15 Interaction with Humans:
Most of the species are wild and have no economic importance.
Some species live in and around human habitat. They destroy food and contaminate food with their excreta.
Many bacterial diseases can be transmitted by food contamination by cockroaches.
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