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THE COCKROACH

This unit is based on how cockroaches operate and the functionalities of their different body parts.

Classification

taz

Scientific Name: Periplaneta Americana

External features used to identify the sexes

sr

Posterior dorsal view of a male cockroach.

coackroach

External feature

  1. Head features
  2. Oval, flat heat.
  3. A pair of large black compound eyes.
  • A pair ofd very long slender jointed antennae (sensitive to touch, smell and vibrations)
  1. White oval structures near bases of antennae known as tenestrae.
  2. It is composed of 6 segements, fused together, ie the 2 epicranial plates on top and back, the frons, clypeus, covering the front and 2 genae besides.
  3. Has 5 mouth parts, maxilla with long jointed maxillary palps, for holding food.
  • Mandibles with toothed edges for chewing.
  • Labrum (upper lip)
  • Hypopharunx

Anterior view of the head of a cockroach

anterior

A drawing of the external features of one pair of the wings of the cockroach.

 

wing

Outer wing (Fore)                 Inner wing (Hind)

Rigid/stiff                               Flexible

Chitinous/thick                     Membrane/thin

Opaque                                   Translucent

Smaller surface                      Large surface

Curved                                   Flat

Oval shaped                           Triangular shaped.

Structure of the alimentary canal

canal

Functions of parts of the alimentary canal and zoology.

Mouth

During chewing; the food is mixed with saliva, brought into the pre-oral cavity by the common salivary duct.

Salivary amylase converts starch receptacle.

Crop

Enzymes from the gut also come into the crop through the gizzard for digestion of some fats and proteins. The gizzard helps to masticate the food further by chitinours teeth and is filtered by the bottles.

Mid-gut (mesenteren).

The food, here mixes with secretions from the mid-gut lining and from the hepatic/digestive caroa which contains many enzymes e.g.

  1. Protedytic enzymes which convert proteins to amino acids.
  2. Lipase which breaks fats into fatty acids and glycerd.
  • Amylase which completes digestion of starch into finally product glucose (reducing sugar).

Ileum. The end of the mid gut whose lining absorbs digested food.

…..gut (color). The undigested food passes into the hind gut tat absorbs H20.

Rectum

  1. The last part of the hind gut helps to absorb further more water changing it almost into solid faeces.

The feaces are temporarily stored in the rectum from where it is passed out at intervals through the anus.

Malphigian tubules are excretory organs attached to the ileum responsible for uric acid excretion but is not part of the alimentary canal.

The water in the uric acid can further be absorbed by the rectal glands in rectum to produce solid uric acid.

Mouth parts of cockroach under light microscope/hand lens after separation.

mouth

Functions of major mouth parts and adaptations.

red

The THORAX

  1. Has three segments:- Prothorax (The most prominent), Mesothorax, Metathorax.
  2. Each segement bears a pair of legs.
  • Mesothorax and metathorax have a pair of wings each.
  1. Those on the mesothorax are brown, opaque, thick, hard and leathery and provide protection to the lower wings of metathorax and to the body. These upper wings are called tegnina or elytra.
  2. Wings on the metatherax are large, soft, transparent 3 membranous. They are supported by braiding network of veins. These inner wings are usual for flights.
  • Has 2 pairs of spiracles cut of a total of 90 pairs found in the whole organism. (The remaining 8 pairs are found on the abdomen).
  • Each spiracle has hair like bristles along its walls that keep act dust particles or water.
  • Thorax spiracles are larger than abdominal spiracles. They are oval in shape while the abdominal are annular.

THE LEGS

– Each is jointed with 5 segments.

  1. A long wide flat coax that attach it to the body.
  2. A very small triangular trochoniter.
  • Long and fairly broad ……………………….
  1. A thin long spiny tibra
  1. The tarsus which has segments (or podo…..) with different lengths and sizes. The last has a pair of ……..between which is a glandular pad know as arolium.
  2. Removal of 10th tergum exposes the female gonadopophyses and anus in females and male gonadopophyses and anus in males.
  • Abdomen has 8 pairs of spiracles.

Summary of differences between thoracic and abdominal spiracles.

Thoracic                                     Abdominal

– 2 pairs                                      – 8 pairs

– Larger                                       – Smaller

– Oval shaped                            – Annular or round shapes

REPRODUCTIVE SYSTEM

  1. a) Male

malez

Functions of draws

– Enables it to grip rough surfaces

Function of arolum

  • To grip on slippery surfaces.

NB    A combination of the above help the cockroach run first on any surface, even upside down, in coils etc.

  • Most segments of the leg have spires for protection.
  • Hind legs are longer than the rest to provide necessary propulsive force during locomotion. (The hind leg is equal to twice the length of the core leg)

Structure of the leg

leg

ABDOMEN

  1. It has 10 segments

Each segment had dorsal tergum, ventral sternum and a narrow membranous plauron on each size joining them

abdomen

The 10th segment bears a pair of anal cerci in both sexes. Males have anal styles at the 9th segment which are absent in females.

  1. Not all the 10 segements are visible
  • 9 (ventrally) are visible in males.
  • 7 sterna are visible in females.
  • 8th tergum of male is largely covered by 7th

The only 7 out of 10 segments are clearly visible in both cases

Circulatory system

circ

Respiratory system

1a) How many parts of spiracles are found on;                  i) The thorax

  1. ii) Abdomen
  2. bi) Remove a spiracle from the thorax region, mount on microscope, draw and label.

) Remove another spiracle from the abdominal region mount on microscope. Draw and label.

  1. c) State the observable differences between thorax and abdominal spiracles.
  2. Dissect and display the respiratory system of the specimen.

Habitat of stomach. It is terrestrial living in narrow species eg behind cupboard

Adaptation’s to survive in the environment.

  1. It is dorsal-ventrally flattened to enable it to ship easily into narrow species.
  2. Fragment, shape and length of legs makes soft running or flight.
  1. Short fore legs full body forwards at the larger hind legs push it forwards.
  2. Longer hind legs provide strong propulsive force to lift off the cockroach during flight, while the short ones act as shock absorbers on landing.
    1. Has wings that help in flight. Inner wing soft, flexible…………
    2. Claws provide from grip on sough surfaces. Arolum provide grip on slippery surfaces during locomotion.
    3. Long filament, hairy antennae for sensitizing the environment.
    4. Jointed anal cerce which are also sensory.
    5. A pair of compound eyes for seeing.
    6. Spines on legs for protection against anomies.
      1. Spiracles to allow and out respiratory gases.
      2. Manduvar mouth parts

      Male has and style for reproduction.

Non structural adaptations.

  1. Omnivorous diet ensures food every where and it does not move far from its biding grainds.
  2. Nectumal habitat and hiding inaccessible places during the day time afford protection from the predators.
  3. Removal of nitrogenous excretory product in form of uric acid conserves water.
  4. Laying eggs in cothecae and depositing the latter in small ac…….. ensure a good deal of safety for the progeny

Economic importance.

  1. Cockroach destroys human possessions like food, clothes, paper etc.
  2. The spread obhxious smell in the kitchen.
  • Eaten in certain parts of the World.

Used as laboratory specimens

 

 

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