Biology XI: 7 Stru Orgn in Animals(7 Anatomy of the Cockroach)

Anatomy of the Cockroach Digestive System The alimentary canal is divided into: Foregut Midgut Hindgut Foregut: Is lined by a cuticle Consists of a mouth which opens into the tubular pharynx, leading into the oesophagus, which further opens into a sac-like crop that stores the food The crop leads to a gizzard (proventriculus). The gizzard helps in grinding food as it has an inner layer with six chitinous teeth. The junction of the foregut and midgut has rings of 6 to 8 tubules called hepatic or gastric caecae, which secrete digestive juices. The hindgut is broader than the midgut, and consists of: Ileum Colon Rectum (opens through the anus) Circulatory System Cockroach has an open type of circulatory system. Poorly developed blood vessels which open into the haemocoel Organs located in the haemocoel bathed by blood (haemolymph) Haemolymph = Colourless plasma + Haemocytes Heart consists of an elongated muscular tube along the mid-dorsal line of the thorax and the abdomen. Differentiated into funnel-shaped chambers, with ostia on each side Flow of Blood: Sinuses → Ostia → Heart → Sinuses   Respiratory System Consists of a network of trachea, which opens through 10 pairs of small holes called spiracles Spiracles are present on the lateral side of the body. Opening of the spiracles is regulated by sphincters. Tracheal tubes are subdivided into tracheoles which carry oxygen to all parts. Exchange takes place in the tracheoles by diffusion. Excretory System Excretion: Performed by yellow-coloured Malphigian tubules (100−150) Location: At the junction of the hindgut and the midgut Each tubule is lined by glandular and ciliated cells. Cockroach is uricotelic. Fat body, nephrocytes and urecose glands also help in excretion. Nervous System Consists of a series of fused segmentally arranged ganglia (fusion is by longitudinal connectives on the ventral side). Three ganglia lie in the thorax and six in the abdomen Spreads throughout the body, with the head holding just a bit of the nervous system In the head, the brain is represented by the supra-oesophageal ganglia which supplies nerves to the antennae and the compound eye. Sense organs: Compound eye − composed of 2000 hexagonal ommatidia (cockroach has mosaic vision and is nocturnal) Antennae Maxillary palps Labial palps Anal cerci Reproductive System Cockroaches are dioecious Both sexes have well-developed reproductive organs Male Reproductive System Consists of: A pair of testes; one each on the lateral side of the 4th, 5th and 6th abdominal segments Vas deferens arises from each testis. Vas deferens opens into the ejaculatory duct through the seminal vesicle. Ejaculatory duct opens into the male gonophores. A characteristic accessory reproductive gland (mushroom-shaped) is present in the 6th to 7th abdominal segments. The male gonapophysis represents the external genitalia. Sperms are stored in the seminal vesicles; glued together in bundles called spermatophores and discharged during copulation Female Reproductive System Consists of: Two large ovaries − formed by a group of 8 ovarioles; contain chains of developing ova Ovary lies laterally in the 2nd to 6th abdominal segments. Oviducts of each ovary unite into a single median oviduct (vagina). Vagina opens into the genital chamber. A pair of spermathecae is present in the 6th segment. Fertilisation Sperms are transferred through spermatophores. Fertilised egg is encased in capsules called oothecae (Dark brown in colour) Female produces 9−10 oothecae with 14−16 eggs. Development is paurometabolous (means passing through nymphal stage). Nymps look like adults and grow up to 13 times by moulting.