Practical 5
SLIDE PREPARATION OF MOSQUITO LARVAL – MALAYSIAN SPECIES
Title: Mosquito larva collection, identification and processing.
Introduction
There are many type of the mosquito that exist on the world, the common infect human and give diseases are the aedes ,culex mansoni,and anopheles. Mosquitoes go through four stages in their life-cycle: egg, larva, pupa, and adult. Adult females lay their eggs in standing water, which can be a salt-marsh, a lake, a puddle, a natural reservoir on a plant, or an artificial water container such as a plastic bucket. The first three stages are aquatic and last 5–14 days, depending on the species and the ambient temperature; eggs hatch to become larvae, then pupae. The adult mosquito emerges from the pupa as it floats at the water surface. Adults live for 4–8 weeks. Male eat nectar and female feed blood.
Objective:
1. To understand the purpose and method of larva processing.
2. To identify the function of each reagent.
3. To identify the processing procedure.
4. To identify the morphology of mosquito larva.
5. To differentiate morphology of Anophelinae and Culicinae larva.
Materials:
Water bath (37oc), acid acetic 10%, Kalium hydroxide 2%, alcohol solution (30%, 50%, 70%, 90% and 100%), xylene, clove oil, mounting DPX, stereozoom microscope, needle, glass slide, section lifter, dissecting pin, cavity block.
Procedure:
1. Mosquito larva was collected from various water sources.
2. The mosquito larva collected was killed in waterbath (37oc).
3. The thorax of the larva was penetrated using fine needle.
4. The larva was place in 2% KOH and left it to room temperature until the larva become clear (2-4 hours).
5. The larva was rinsed two times with distilled water and immersed in 10% acid acetic for 30 minutes.
6. The preservation method was performed as the following:
a) The sample was immersed in 70% alcohol to kill the insect.
b) Soaked in KOH for at least 30 minutes.
c) Rinsed with distilled water.
d) Dipped in the following alcohol for 30 minutes each; 30%, 50%, 70%, 90%, 100%, 100%
e) Next, in clove oil and finally in Xylene.
f) After that, the larva was placed on slide and DPX was dropped.
g) The cover slip was used to cover.
7. The slide was observed under microscope.
8. The observation was recorded and identified the family of mosquito larva observed.
Discussion
In the preparation of the larva slide the larva that has been taken will be immersed in certain alcohol for some purpose, it were used to as the preservative to the larva. The alcohol used are 30%, 50%, 70%, 90%, 100%, 100% alcohol.it also make the larva are death ,by doing the preservation it can make the larva can be maintain it shape for long time.it also make the larva are not effect by the mold or dust that damaged the slide for the observation,it also make the larva can be maintain it shape without damaged the shape morphology,if we use the big insect we will insert some cotton inside it body to maintain it shape.the changes of the concentration are to ensure the enzyme inside the larva removed also the other substances.it also the factor to maintain the structure of the larva for long period.
The female aedes mosquito bites as it needs the protein in blood to develop its eggs.The mosquito becomes infective approximately 7 days after it has bitten a person carrying the virus. This is the extrinsic incubation period, during which time the virus replicates in the mosquito and reaches the salivary glands.Peak biting is at dawn and dusk.the average lifespan of an Aedes mosquito in Nature is 2 weeks.The mosquito can lay eggs about 3 times in its lifetime, and about 100 eggs are produced each time.The eggs can lie dormant in dry conditions for up to about 9 months, after which they can hatch if exposed to favourable conditions, i.e. water and food.the identification of the aedes are know by the leg that it have that is the striated the black and white. Aedes aegypti is a vector for transmitting several tropical fevers. Only the female bites for blood which she needs to mature her eggs. Understanding how the mosquito detects its host is a crucial step in the spread of the disease. Aedes aegypti are attracted to chemical compounds that are emitted by mammals. These compounds include ammonia, carbon dioxide, lactic acid, and octenol.
The culex Eggs of these mosquitoes, typically for culicines, are laid singly or in rafts and although they may stick to the surface, they may sink if the water is disturbed. Culex prefers water contaminated with organic matter for the development of the larvae and in will grow well in septic tanks.Disease is spread by females. Males do not bite. The females take blood meals that are used to support the development of eggs. Culex is described as zoophagic because it takes its meals from animals as well as humans and can also be described as ornithophagic because it frequently feeds on birds. Any disease that is carried by Culex can therefore become difficult to eradicate because any animal community that it feeds on can become a reservoir and mobile species, such as birds, can spread the disease through a large area. This was seen in 1999 in the Eastern United States when West Nile virus was introduced into the area. Culex pipiens feeds at night.Feeding is described as endophagic because the mosquito prefers to feed in and around structures and the mosquito then rests in cool damp spots within structures while the meal is digested (endophilic behavior). A blood meal takes 2-7 days to digest and 1-3 meals are needed to complete development of clutch of eggs. Transmission comes from repeated biting when the mosquito injects saliva that acts as an anticoagulant.
The mansonia is A genus of brown or black medium-sized mosquitoes ,often with banded abdomen and legs; larvae and pupae have modified breathing tubes enabling them to pierce aquatic plants to obtain air. Mansonia mosquitoes are distributed worldwide and, in tropical areas, are important vectors of Brugia malayi; in some areas they also transmit Wuchereria bancrofti. Adults of Mansonia are generally large mosquitoes characterised by the presence of broad, asymmetrical scales on the wing veins. There is often a mixture of dark and pale scales that imparts a speckled appearance to the wings.Mansonia resemble some species of Culex, Aedini and Coquillettidia, but the tarsal claws are simple, the abdomen is truncate in females (distinctions from aedine genera), The larvae of Mansonia resemble those of Coquillettidia in having the spiracular apparatus and siphon distinctively modified for piercing plant tissues. They differ from Coquillettidia in having the distal part of the antenna fused with and much shorter than the basal part.
The Anopheles mosquitoes can be distinguished from other mosquitoes by the palps, which are as long as the proboscis, and by the presence of discrete blocks of black and white scales on the wings. Adult Anopheles can also be identified by their typical resting position: males and females rest with their abdomens sticking up in the air rather than parallel to the surface on which they are resting. The abdomen is specialized for food digestion and egg development. This segmented body part expands considerably when a female takes a blood meal. The blood is digested over time serving as a source of protein for the production of eggs, which gradually fill the abdomen. The duration from egg to adult varies considerably among species and is strongly influenced by ambient temperature. Mosquitoes can develop from egg to adult in as little as 5 days but usually take 10–14 days in tropical conditions.
Like all mosquitoes, adult Anopheles have slender bodies with 3 sections: head, thorax and abdomen.The head is specialized for acquiring sensory information and for feeding. The head contains the eyes and a pair of long, many-segmented antennae. The antennae are important for detecting host odors as well as odors of breeding sites where females lay eggs. The head also has an elongated, forward-projecting proboscis used for feeding, and two sensory palps.
Most Anopheles mosquitoes are crepuscular (active at dusk or dawn) or nocturnal (active at night). Some Anopheles mosquitoes feed indoors (endophagic) while others feed outdoors (exophagic). After feeding, some blood mosquitoes prefer to rest indoors (endophilic) while others prefer to rest outdoors (exophilic), though this can differ regionally based on local vector ecotype, and vector chromosomal makeup, as well as housing type and local microclimatic conditions. Biting by nocturnal, endophagic Anopheles mosquitoes can be markedly reduced through the use of insecticide-treated bed nets (ITNs) or through improved housing construction to prevent mosquito entry (e.g. window screens). Endophilic mosquitoes are readily controlled by indoor spraying of residual insecticides. In contrast, exophagic/exophilic vectors are best controlled through source reduction (destruction of the breeding sites).
The female mosquito lays 30-150 eggs every 2-3 days. Human blood is needed to nourish these eggs and Anopheles shows the most regular cycles of blood feeding and egg laying. As a corollary, by using personal protective measures against mosquito bites, like using mosquito nets, one can deny the blood meal and hence help in mosquito control.
Conclusions
The larva preservation and the making slide of it were made and the morphology of the larva was observed and drew.
Question
Describe the function of the following solution
Potassium hydroxide-it makes the larva flatted and maintains the appearances
Clove oil-it act as the anesthetic
References
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