Wednesday, July 29, 2020

Structural Organisation In Animals - Notes | Class 11 | Part 4: Cockroach - Morphology

7. STRUCTURAL ORGANISATION IN ANIMALS


MORPHOLOGY & ANATOMY OF COCKROACH

·    Morphology: Study of external features of organisms.

·    Anatomy: Study of morphology of internal organs.

·    Cockroach (Periplaneta americana) are nocturnal, omnivores and live in damp places.

·    Colour: Brown or black. Bright yellow, red & green coloured cockroaches are also seen in tropical regions.

·    Size: ¼ inches to 3 inches (0.6-7.6 cm).

Systematic position


Phylum     : Arthropoda

Class         : Insecta

Genus       : Periplaneta

Species      : americana


MORPHOLOGY OF COCKROACH


·   The adults are about 34-53 mm long.

·   Body is covered by a hard brown chitinous exoskeleton.

·   In each segment, exoskeleton has hardened plates called sclerites (dorsal tergites & ventral sternites). They are joined to each other by a thin and flexible articular membrane (arthrodial membrane).

·   The body has 3 regions – head, thorax and abdomen.



Head


·   Triangular head is formed by 6 fused segments.

·   It shows great mobility in all directions due to flexible neck.

·   Head bears a pair of thread-like antennae, a pair of compound eyes and biting & chewing type mouth parts.





·   Mouthparts: a labrum (upper lip), 2 mandibles, 2 maxillae, hypopharynx (tongue) & a labium (lower lip).

Thorax


·   It has 3 parts: prothorax, mesothorax & metathorax.

·   The head is connected to thorax by a neck (short extension of the prothorax).

·   Each thoracic segment bears a pair of walking legs.

·   2 pairs of wings: Forewings (2) and Hind wings (2).

o  Forewings (mesothoracic) or tegmina: Opaque, dark and leathery and cover the hind wings when at rest.

o  Hind wings (metathoracic): Transparent, membranous and are used in flight.


Abdomen


·   It consists of 10 segments.

· In females, 7th (boat shaped), 8th & 9th sterna form a brood (genital) pouch. It contains female gonopore, spermathecal pores & collateral glands.

·   In males, genital pouch lies at the hind end of abdomen bounded dorsally by 9th & 10th terga and ventrally by the 9th sternum. It contains dorsal anus, ventral male genital pore (gonopore) and gonapophysis.

·   In both sexes, 10th segment bears a pair of jointed anal cerci. Males bear a pair of short, threadlike anal styles.


Differences between male & female cockroaches


Male

Female

  i.  Larger size

Smaller

 ii.  Wings extend beyond the tip of the abdomen.

Wings do not extend beyond the tip of abdomen.

iii.   Narrow abdomen

Broad abdomen

iv.  Anal styles present

Absent

 v.   Brood pouch absent

Present

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