Sensory receptor in insects


Sensory receptor in Insect

   The sensory organ are primarly responsible for the reception of stimuli and passed them on to the neuromolecular system resulting in the varied behaviour patterns of insect. It of 6 different types---

--1. Mechano receptor:
Respond to the sense of touch due to contact with external solid object, curent of air and water or even because of internal body pressure. The principle MRs are

 a)The tactile organs or trichoid sensilla. 

B)The company from organs 

c) The chordotonal organs

2. Chemoreceptor- Chemoreceptr is sensitive to chemical stimulation by chemical can occur in following different ways.

A)Olfactory or smell chemo R: they sense of smell provide.

B) Gustatory CR: They provide provide sense of taste.

3. Photo receptor- Ability to percine light in visible or near visible range of electromagnetic spectrum. Insect are capable of absorbing light of a given wavelength and produces a nerve impluse
as a result of disobsortion.

4. Auditory receptor-

* Delicated in tactile hairs present in pulmose antennae of male mosquito

* Tympenum: this is a membrane across the tymphanic cavity response to sound produces at some distance transmitted by in bone vibration.

5. Thermo receptor- present in poikilothermic insect & sensitive to tempr. Changes.

6.Hydro receptor- insect are able to monitor the amount of water vapur in surrounding air.

Malpighian tubules: The main excretory organ of the insect is the Malpighian tubule. Insects contain anything from 2 to 150 or more Malpighian tubules depending on the genus. Malpighian tubules are tubular outgrowths of the gut. They typically develop as pouches emerging from the junction between the midgut and the hindgut, though there actual final position varies — they may be attached to the midgut, hindgut or the midgut-hindgut junction as is the case with our ant above. Each Malpighian tubule is a blind-ending tube whose lumen is continuous with the lumen of the gut. Each consists of a single layer of epithelial cells, forming the tubule wall, enclosed by an elastic membrane (basement membrane — a fibrous and porous protein mesh). In most insects there is a thin layer of striated muscle around this membrane. Typically muscle cells spiral around the distal end (the end furthest from the gut) of the tubule,
causing it to twist and turn in gentle writhing movements as the muscles contract. The proximal end (near
the gut) may be coated in circular and longitudinal muscle fibres, giving rise to peristalsis or squeezing movements which empty the contents of the tubule into the gut. In some cases, such as in caterpillars, the Malpighian tubules on each side (3 on each side in this case) empty into a small bladder, which then empties into the gut. In this case only the bladder may be muscular and its lumen is lined by cuticle (suggesting that the bladder is an extension of the hindgut).The tubules do not just hang around in the air!

The body cavity of the insect is filled with a fluid, usually colourless, called Haemolymph. This fluid bathes the organs and tissues and is circulated around the insect body. The tubules are also typically loosely or firmly anchored in place by the tracheae which attach to them.The twisting and turning of the Malpighain tubules presumably keeps them in contact with fresh haemolymph (perhaps by circulating the heamolymph around the tubule). Metabolic wastes and other unwanted chemicals that entered the insect system pass into the haemolymph, or are excreted into the haemolymph by the cells. These include nitrogenous waste and plant toxins such as alkaloids. It is the job of the Malpighian tubules to keep the haemolymph cleansed of these wastes — they remove wastes from the haemolymph and then excrete them into the gut lumen.Outside the muscle layer is a ‘peritoneal covering’ of cells with embedded tracheoles, which carry oxygen to the Malpighian tubules which their mitochondria use to generate the needed ATP by aerobic respiration.

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