Introduction
Mouthparts of cockroach are specialised head appendages surrounding the mouth. These consist of the labrum or upper lip,a pair of mandibles,a pair of maxillae,the labium or lower lip and the hypopharynx. The cockroach mouthparts remain unspecialised due to its omnivorous habit. Appendages adapted for mastication, food handling, and ingestion.
- Type: Biting and Chewing type mouthparts (Mandibulate type)
- Nature: They are unspecialised due to their omnivorous feeding habit.
Functions:
Lap up liquid
Bite hard food material
1. Labrum (Upper Lip)
Location & Structure
- Labrum is the appendage of the 3rd head segment
- It is a broad and oblong, movably attached to the margin of clypeus and forms the anterior margin of the mouth cavity in the mouthparts of cockroach.
Key Features
- At its junction with clypeus , it bears a small sclerite called torma on each inner side
- Inner surface also bears two rows of gustatory (sensory) setae , one on each side.
- Labrum overlaps toothed parts/portion of mandibles
2. Mandibles
Location & Structure
- These are appendages of 4th head segment.
- Mandibles are small, triangular, strongly sclerotised structure present in cockroach mouthparts. They are attached with the sides of head capsule and articulate by means of a condyle with the Gena ( cheek ) of same side.
Key Features
- Inner margin has two parts:
- Distal incisor lobe: cutting/serrated lobes
- Proximal molar lobe: 3 tooth-like denticles of thickened cuticle
- Prostheca: membranous lobe with sensory hairs.
- Denticles act as the interlocking structure whereas smooth molar area as masticatory surface.
- Molar area helps in grinding
Functions
Mandibles act like jaws
Both the mandibles show horizontal sideways movement brought about by the action of adductor & abductor muscles
3. Maxillae (First Pair of Jaws)
Location & Structure
- These are appendages of 5th head segment and known as first pair of maxillae. Lie beneath mandibles and articulate with the posterior surface of head capsule , one on either side of mouthparts of cockroach. They are biramous in structure
- Biramous (two-branched)
Parts of Maxilla
- Cardo: consists of a distal cylindrical stipes hinged to a proximal basal cardo at an obtuse angle.
- Stipes: It bears three processes and cylindrical , attached to cardo
- Lacinia: inner part which is sclerotised with denticles and blunt lacinula
- Galea: middle part which acts as a hood-like structure for lacinia
- Maxillary Palp: which is 5-segmented and sensory in nature. It is borne on a small basal sclerite , the palpifer. maxillary palp represents the exopodite while lacinia and galea represents endopodite
Functions
Help in mastication of food and to convey food morsels into oral cavity
They also serve to clear antennae and forelegs
Both maxillae act as accessory jaws
4. Labium (Lower Lip)
Location & Structure
- Labium or lower lip is the appendage of 6th head segment
- It is the posterior-most of all mouthpart. It is formed by the fusion of two maxilla like embryonic appendages or second pair of maxillae
Parts of Labium
- Submentum: Its fused protopodite is 3-segmented consisting of a large proximal part or proximal submentum
- Prementum: A small middle mentum and distal part or distal prementum
Ligula (tongue-like): It is partially fused endopodites forms a ligula. Each half of ligula consists of the inners and outer part
Glossa (inner)- Paraglossa (outer)
- Labial Palp: Prementum bears,on each side, a 3-segmented sensory labial palp borne on a basal projection , the palpiger. Terminal segment of palp is covered thickly with sensory setae
Functions
Forms lower lip
Salivary duct opens at front end
Labial palp is sensory
5. Hypopharynx
Location & Structure
- It lies between maxillae and above labium , inside the mouth cavity of cockroach mouthparts.
- It is median, somewhat cylindrical structure also known as lingua (tongue-like)
Key Features
- Its distal end bears superlingua (comb-like plates). Common salivary duct opens at its front
Functions
Mixes food with saliva
Helps in swallowing food
Conclusion
Thus, the mouthparts of cockroach are well adapted for biting and chewing type of feeding. The coordinated action of different parts of the cockroach mouthparts helps in efficient ingestion and processing of food.
Reference:-
- A Textbook of Invertebrates — R. L. Kotpal
- Jordan & Verma — Invertebrate Zoology
- Modern Textbook of Zoology: Invertebrates
- A Manual of Practical Zoology: Invertebrates
Suggested reading:-
- Digestive System of Cockroach
- Gizzard of Cockroach