INTRODUCTION:
Diatoms are Unicellular,Photosynthetic, eukaryotic organisms often classified as among the algae. They have a siliceous skeleton frustule and are found in almost every aquatic environment including fresh and marine waters,soils, and in fact almost anywhere moisture is present. Diatoms are abundant in houses made up of glasses. The cell wall is composed of transparent silica. Also we can see small lines in the structure
FORENSIC ASPECT :
Diatoms have been used in forensic science in a variety of ways, the most frequent being the diagnosis of death by drowning.
CLASSIFICATION OF DIATOMS :
Cell size : Diameter is 20-200nm and length is 2 μm.
Cell wall : Cell wall is made up of silica ( Si02).
Cell pigment : contains chlorophyll A & C , Keratinoids.
Reproduction : Sexual reproduction is present that is, simple cell division takes place
COMMON GENERA :
1) Chaetoceros
2) Skeletonema
3) Pseudo-nitzschia
Diatoms are divided into two types:
1) Centric diatoms ( radial symmetry)
2) Pennate diatoms ( bilateral symmetry)
DIVISION : Chrysophyta
CLASS : Bacillariophyceae
ORDER : Biddulphiales
Bacillariales
IMPORTANCE OF DIATOMS IN FORENSIC SCIENCE :
In Drowning cases the diatoms will enter into the lungs, brain etc. Of the person through breathing, so if the diatoms are present inside the body, we can conclude that it is a drowning case. If the diatoms are present in the Surface of the body. Then we can conclude that the body of the person is dumped in the water after his death.
EXTRACTION METHODS :
Acid digestion method :
There are two method Nitric acid method and sulphuric acid method.
1) Nitric acid method :
Samples should be collected ( diatoms ) from the femur bones. 50gm of bone marrow is collected and washed with Distilled water then Nitric acid is added to the bone marrow and is kept for 48 hours. Then after 48 hours it is cooled and centrifuged. Heaviest particles will settle down. Then collect and examine under microscope. Supernatant solution is discarded.
2) Sulphuric acid method :
It is the best method to remove the dirt. First of all remove the calcareous compound present in the cell wall. If we forget to remove this, then gypsum crystal will form then add sulphuric acid and potassium bichromate ( to make the saturated solution) to the sample and keep it for 24 hours. After 24 hours we can see that Sediment will look like greyish colour. Discard the supernatant solution and examine the sample.
CONCLUSION :
Diatoms have been used in forensic science in a variety of ways. Diatoms are useful when diagnosing Drowning as a cause of death. Their microscopic size and presence in standing and flowing water means they are often inhaled and swallowed during Drowning.
Author: Ms Athira V
Annai Fathima College of Arts and Science, Madurai
AFRS Student Ambassador.
