Cockroach — Revision Notes

⚡ 30-Second Revision

Phylum: — Arthropoda, Class: Insecta, Order: Blattodea.
Metamorphosis: — Incomplete (Egg $\rightarrow$ Nymph $\rightarrow$ Adult).
Body Segments: — Head, Thorax (Prothorax, Mesothorax, Metathorax), Abdomen (10 segments).
Mouthparts: — Chewing type (Labrum, Mandibles, Maxillae, Labium, Hypopharynx).
Wings: — Forewings (Tegmina - leathery, protective), Hindwings (Membranous, for flight).
Sexual Dimorphism: — Male has anal styles; Female has boat-shaped 7th sternum (brood pouch).
Digestive System: — Crop (storage), Gizzard (grinding), Hepatic caeca (digestive juices), Midgut (digestion/absorption), Malpighian tubules (excretion at midgut-hindgut junction), Hindgut (water absorption).
Circulatory System: — Open type, Hemocoel, Dorsal tubular heart (13 chambers), Hemolymph (colorless, no respiratory pigment).
Respiratory System: — Tracheal system (10 pairs of spiracles: 2 thoracic, 8 abdominal).
Excretory System: — Malpighian tubules (Uricotelic).
Nervous System: — Ventral nerve cord, Segmental ganglia, Supra-oesophageal ganglion (brain).

2-Minute Revision

The cockroach (Periplaneta americana) is a key model for insect biology, exhibiting incomplete metamorphosis (egg, nymph, adult). Its body is divided into head, thorax, and abdomen, covered by a chitinous exoskeleton.

The head bears chewing mouthparts, antennae, and compound eyes. The thorax carries three pairs of walking legs and two pairs of wings: leathery tegmina (forewings) and membranous hindwings. Sexual dimorphism is evident, with males possessing anal styles and females a boat-shaped 7th sternum forming a brood pouch.

Internally, the digestive system includes a crop for storage and a gizzard for grinding, with hepatic caeca secreting digestive enzymes. The circulatory system is open, with colorless hemolymph pumped by a 13-chambered dorsal heart.

Respiration occurs via a tracheal system opening through 10 pairs of spiracles. Excretion is handled by Malpighian tubules, making them uricotelic. Reproduction involves distinct male and female systems, with females laying eggs in a protective ootheca.

Focus on specific organ functions and male/female distinctions for NEET.

5-Minute Revision

For a comprehensive revision of the cockroach, start with its classification: Phylum Arthropoda, Class Insecta, Order Blattodea. Remember it's a hemimetabolous insect, meaning incomplete metamorphosis (egg $\rightarrow$ nymph $\rightarrow$ adult).

External Morphology: Note the body division into head (antennae, compound eyes, chewing mouthparts: labrum, mandibles, maxillae, labium, hypopharynx), thorax (three segments, each with a pair of legs; mesothorax with tegmina, metathorax with hindwings), and abdomen (10 segments, anal cerci on 10th). Crucially, differentiate sexes: males have anal styles on the 9th sternum, females have a boat-shaped 7th sternum forming a brood pouch.

Internal Anatomy:

Digestive: — Alimentary canal (foregut: pharynx, oesophagus, crop, gizzard; midgut: hepatic caeca; hindgut: ileum, colon, rectum). Functions: crop for storage, gizzard for grinding, hepatic caeca for digestive enzymes. Malpighian tubules are at the midgut-hindgut junction for excretion.
Circulatory: — Open type. Hemolymph is colorless (no respiratory pigment), flows in hemocoel. Dorsal, tubular, 13-chambered heart with ostia.
Respiratory: — Tracheal system. 10 pairs of spiracles (2 thoracic, 8 abdominal) lead to tracheae and tracheoles for direct gas exchange.
Excretory: — Malpighian tubules are primary, excreting uric acid (uricotelic). Fat body, nephrocytes also aid.
Nervous: — Ventral nerve cord with segmentally arranged ganglia. Supra-oesophageal ganglion (brain) in head.
Reproductive: — Male: Testes, vasa deferentia, ejaculatory duct, mushroom glands (spermatophore formation), phallomeres. Female: Ovaries (ovarioles), oviducts, vagina, spermatheca (sperm storage), collateral glands (ootheca formation). Ootheca contains 14-16 eggs.

Remember key numbers (13 heart chambers, 10 spiracles, 6-8 hepatic caeca, 100-150 Malpighian tubules) and specific terms. Practice labeling diagrams and correlating structure with function.

Prelims Revision Notes

Cockroach (Periplaneta americana) - NEET Revision Notes

I. Classification & General Features:

Phylum: — Arthropoda, Class: Insecta, Order: Blattodea.
Metamorphosis: — Incomplete (Paurometabolous/Hemimetabolous) - Egg $\rightarrow$ Nymph $\rightarrow$ Adult.
Habitat: — Nocturnal, omnivorous, found in damp, dark places.

II. External Morphology:

Body: — Dorsoventrally flattened, reddish-brown, chitinous exoskeleton (sclerites joined by arthrodial membrane).
Divisions: — Head, Thorax, Abdomen.

* Head: Triangular, highly mobile. Bears: * Antennae: Pair, filamentous, sensory (touch, smell). * Compound Eyes: Pair, for vision. * Mouthparts: Chewing type (Labrum, Mandibles, Maxillae, Labium, Hypopharynx).

* Thorax: 3 segments (Prothorax, Mesothorax, Metathorax). * Legs: 3 pairs, one on each segment, for running. * Wings: 2 pairs. * Forewings (Tegmina): Mesothoracic, dark, leathery, opaque, protective, non-functional in flight.

* Hindwings: Metathoracic, thin, membranous, used for flight. * Abdomen: 10 segments in both sexes. * Anal Cerci: Pair, jointed, filamentous, on 10th segment (both sexes). * Anal Styles: Pair, short, thread-like, on 9th sternum (ONLY MALE).

* Female Genital Pouch: Formed by 7th (boat-shaped), 8th, 9th sterna.

III. Internal Anatomy:

A. Digestive System: — Alimentary canal (mouth to anus).

* Foregut (Stomodaeum): Pharynx $\rightarrow$ Oesophagus $\rightarrow$ Crop (food storage) $\rightarrow$ Gizzard/Proventriculus (grinding, chitinous teeth). * Midgut (Mesenteron): Short, narrow tube.

Hepatic/Gastric Caeca (6-8 finger-like): Secrete digestive juices, at gizzard-midgut junction. * Hindgut (Proctodaeum): Ileum $\rightarrow$ Colon $\rightarrow$ Rectum (water absorption, feces).

Opens via anus. * Malpighian Tubules (100-150): At midgut-hindgut junction, primary excretory organs.

B. Circulatory System:

* Type: Open circulatory system. * Hemocoel: Body cavity where hemolymph flows. * Heart: Dorsal, tubular, 13-chambered, funnel-shaped, with ostia (pores). * Hemolymph: Colorless, contains hemocytes, LACKS respiratory pigment (does not transport O$_2$).

C. Respiratory System:

* Type: Tracheal system. * Spiracles: 10 pairs (2 thoracic, 8 abdominal) on lateral sides, openings to tracheae. * **Tracheae $\rightarrow$ Tracheoles:** Direct O$_2$ delivery to cells, CO$_2$ removal.

D. Excretory System:

* Primary: Malpighian tubules (absorb nitrogenous wastes from hemolymph, convert to uric acid). * Nature: Uricotelic (excretes uric acid to conserve water). * Accessory: Fat body, nephrocytes, cuticle.

E. Nervous System:

* Organization: Ventral nerve cord, segmentally arranged ganglia (3 thoracic, 6 abdominal). * Brain: Supra-oesophageal ganglion (in head), innervates antennae, eyes.

F. Reproductive System: — Dioecious (separate sexes), sexual dimorphism.

* Male: Testes (4th-6th abd. seg.) $\rightarrow$ Vasa deferentia $\rightarrow$ Ejaculatory duct. Mushroom Glands (6th-7th abd. seg.): Accessory glands, form spermatophore. Phallomeres: Chitinous external genitalia.

Sperms stored in seminal vesicles, bundled as spermatophores. * Female: Ovaries (2nd-6th abd. seg., 8 ovarioles each) $\rightarrow$ Oviducts $\rightarrow$ Common Oviduct (Vagina). Spermatheca: Pair, stores sperm.

Collateral Glands: Secrete ootheca material. Fertilized eggs in Ootheca (dark capsule, 14-16 eggs/ootheca, 9-10 oothecae/female).

Vyyuha Quick Recall

To remember the parts of the Cockroach's Mouthparts: Lazy Mandibles Make Little Hypopharynx.

Labrum
Mandibles
Maxillae
Labium
Hypopharynx