Specimen preservation:
Specimen preservation means long term preservation of organisms in the best possible condition. So that it can be accessed in the future.
Importance of preservation
It can be used in the future for the scientific research
A preserved specimen takes less space than a live specimen.
It can be used for understanding biodiversity.
It can be used as a reference for the identification and naming of species.
It can be used to track historical and geographical changes in the species and their habitat.
It is used to track the evolution and human impacts on the planet.
It is used to record the trend of environmental pollution.
It document the origin and spread of emergent infectious diseases.
Preservation technique:
A common techniques of preservation are:
1. Narcotization:
Narcotization is the use of the chemicals or drugs during the preservation process. It induce a state of unconsciousness and calmness in the specimen. Narcotization prevent the distortion or fragmentation of the specimen. For narcotization chloral hydrate, alcohol, clove oil, chloroform, ether, magnesium sulphate are used.
2. Killing:
Specimen should be killed in a way that will leave them undamaged and relaxed. Insects are killed by chemicals either in a killing bottle or tube containing volatile poison or in a freezer.
3. Fixation:
This involves the immersing the organisms in a chemical solution that preserves its cellular and molecular structures. The most common fixing agents are formalin and ethanol.
4. Preservation:
Preservation is the process that keeps the dead body of an organisms without decay. It is used for the long term storage of the organism. Both vertebrates and invertebrates can be preserved in a fluid or as dry specimens. The fluid is generally alcohol. i.e. 70-75 % ethyl alcohol or 40-50 % isopropyl alcohol. Formalin is also used for the preservation.
5. Labelling:
Labelling is always done immediately after collecting the specimen to avoid confusion. Labelling includes geographical information, date, time, the collector’s name and the species name.
6. Storage:
After labelling the specimens are stored in airtight vials or jars for long term storage.
Preservation techniques of invertebrates:
1. Dry Method:
a. Sponges:
Sponges are first rinse in a running water and squeezed to drain out excess water. They are placed in a container of alcohol with a lid for 48 hours to remove the smell. They are dried in a sun and kept in small cardboard boxes. Paradichlorobenzene or naphthalene may be added to dry containers.
Stony corals:
For preserving the coral specimen, it should be soaked in alcohol and dry them.
Insect preservation:
Most insects are preserved dry, normally on pins. Insects that are fresh should be pinned immediately after collection. For dry insects it must be relaxed before pinning. Relaxing can be done by placing dry insects to the water saturated atmosphere. Insects can be mounted as follows:
Pinning:
Larger insects are mounted by direct pinning whereas smaller insects are mounted by micropining
.
Pointing:
It is used when a specimen are too small to pin. The tip of the pin is glued and then stuck into the insect.
Carding:
It involves the gluing an specimen by its venter (back) to a rectangular piece of card through which a macro pin passes.
Preservation techniques for vertebrates:
Fishes:
After capture fishes are placed in 10% formalin for quick killing and fixation. For larger fish, fixative should be injected directly into the body. 10% formalin or 70% ethanol can be used for preservation and fixation.
Herpetofauna (Amphibians and Reptiles):
Amphibians are individually kept in plastic and then killed by freezing or chloroform. They are fixed with formalin (10%). They are preserved in 5% formalin or 70% ethyl alcohol.
Reptiles are killed by injecting with 10% Nembutal solution or ether or chloroform. 10% formalin is injected along the length of the body for fixation.
Birds:
All of the body inside the skin is removed. Feathers and skin are stretched flat and dried. Powdered borax can be put on the skin to further preserve it. We can also use cold ashes from a fire. Inner side of the body is filled with cotton.
Mammals:
Mammals are preserved with following basic techniques:
Entire-fluid preservation:
In this technique, specimen is fixed in 10% formalin or 70-90% alcohol. For better fixation formalin is also injected under the skin. After fixation, specimen is washed in flowing water for 24 hours for removal of formalin. Then the specimen is transferred into 50% alcohol for 30 minutes then into 70% alcohol for some time. For long term storage it is then transferred into 80% alcohol.
Skin and mount:
After removing the skin from the animal, it is dried in the sun. powdered borax or ashes from the fire is also used to preserve skin. When the skin is nearly dried it should be folded with the hairy side together.
Entire skeleton:
At first flesh from the bone is removed. It can be done by enzyme solutions, buried in the sand, soil or manure. Then the bone is soaked in ammonia or chlorine bleach solution. The specimen are then dried.
Taxidermy:
Taxidermy is a way of preparing, stuffing and mounting an animal for display or study. It usually involves arranging an animal’s real skin over a fake body top make the animal look alive. It is used in the museum where visitors can see what the animal was like when it was alive.
