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 |
