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1020 Chiang Mai J. Sci. 2014; 41(5.1)
Chiang Mai J. Sci. 2014; 41(5.1) : 1020-1031http://epg.science.cmu.ac.th/ejournal/Contributed Paper
Detection and Identification of Diatoms in TissueSamples of Drowning VictimsNopparut Sitthiwong [a], Werawan Ruangyuttikarn [b], Somsak Vongvivach [b] andYuwadee Peerapornpisal*[c][a] Program in Biology, Faculty of Science and Technology, Sakon Nakhon Rajabhat University,
Sakon Nakhon 47000, Thailand.[b] Department of Forensic Medicine, Faculty of Medicine, Chiang Mai University,
Chiang Mai 50200, Thailand.[c] Department of Biology, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand.*Author for correspondence; e-mail: [email protected]
Received: 12 April 2013Accepted: 1 July 2013
ABSTRACTForensic diatomology is an important method of gaining supporting evidence in the
investigation of drowning cases. In this research, diatom species were detected and identifiedin the tissues of twelve corpses that were found submerged in water. The diatoms were foundin the gastric contents, lungs, duodenum contents, liver, kidney, blood and brains of all twelveof the corpses. Whilst in the tissues of five alternative corpses who died from accidents anddiseases as our control cases, diatoms were absent. The species of diatoms, which were foundto be dominant, were Cyclotella meneghiniana K tz., Achnanthidium minutissima (K tz.) Czarn.,A. saprophilum (H. Kobayasi & Mayama) Round & Bukht, Aulacoseira granulata (Ehrenb.)Simonsen, and Nitzschia palea (K tz.) W.Sm. The dominant species of diatoms present in thewater at the scenes were similar to the diatoms species found in the tissue samples of each ofthe drowning victims. Dominance Identity (DI) and Species Index (SI) values indicated thatthe sites of the recovery of the corpses were likely to be the drowning sites.
Keywords: drowning victims, diatoms, forensic diatomology, Cyclotella meneghiniana,Achnanthidium minutissima
1. INTRODUCTIONDiatoms are algae in Division
Bacillariophyta. Most of them aremicroscopically unicellular, and aresometimes colonial or pseudofilamentousalgae. Their cell structure is described asfollows. The frustules consist of overlappingvalves; the upper valve or larger valve isknown as the epivalve or epitheca, and thesmaller valve as the hypovalve or hypotheca
[1, 2, 3]. The diatom cell walls are composedof protein compounds and are heavilyimpregnated with silica. Diatoms arewidespread in both marine and freshwaterhabitats. Some diatoms are free-living cellswhich may be found floating in the waterand many species form copious gelatinousmasses on rock, in soil or on plant surfaces.Besides, many species of diatoms occur
Chiang Mai J. Sci. 2014; 41(5.1) 1021
within the soil or the wet surface ofterrestrial substrates [2, 4, 5].
Due to the characteristics of the diatom’ssilica cell walls, their structure can remainstable in the environment for a long periodtime [6]. Diatoms are one of the biologicalmaterials, which are found in corpses, as wellas microaquatic plants [7], insects andarthropods [8], aquatic insects [9], bacteria[10, 11], invertebrate and protozoa [12].Other groups of algae, i.e. green algae, bluegreen algae and dinoflagellates have beeninvestigated to help in the diagnosis ofdrowning victims, too [13, 14, 15, 16].However, these algae can be destroyed by theenzymes or secretory fluids of the victims andas well, by the strong acids that are present inthe digestive process, which can damage thecells [16].
The study of forensic diatomology iswidely applied in the countries of thenorthern hemisphere, i.e. France and Japan[16]. In Asia, forensic diatomology hasbeen applied in India [17], Malaysia [18],China [14, 19, 20] and Japan [15, 21, 22, 23,24]. In Thailand, there has been only onerelated research study on forensic diatomolgy,which was published by Mahidol Universityin 1988 [25].
The main objective of this research studywas to study the possibility of using diatomsto help diagnose the site of the drowningwhich would be useful for forensic medicine/science. The diatom taxa were identified interms of species and were counted for thedominant species comparison between thetissue samples of the drowning victims andthe scene of the drowning. Besides, twosimilar indices; Dominance Identity (DI) andthe Species Index (SI) were applied in theresearch process.
2. MATERIALS AND METHODS2.1 Collection of Tissue Samples
Twelve corpses that were foundsubmerged in water were brought in for acomplete autopsy at the Forensic MedicineDepartment, Faculty of Medicine, Chiang MaiUniversity, Chiang Mai, Thailand. They wereall examined by an expert in forensicpathology and the causes of death wereconfirmed to be drowning. Alternatively, fivecases, which were found to have died fromother causes, i.e. diseases and accidents, werechosen as the control cases. The brains, lungs,livers and kidneys of all of the study caseswere collected separately in dried and cleanplastic bags. Blood was drawn and kept ina plastic tube without any anticoagulant.Gastric and duodenum contents werecollected separately in glass bottles withoutany preservatives, and were kept at 0-4°C.Blood samples and all of the tissues were keptat -20°C before diatom analysis.
2.2 Collection of Samples at the SceneBenthic diatoms from the stones or other
substratum were taken from each of thescenes in all cases. Diatom samples were boiledin concentrated nitric acid (HNO3) andhydrogen peroxide (H2O2). The acid solutionwas removed and then the samples wererinsed 4-5 times with distilled water [26]before being examined under a lightmicroscope.
2.3 Preparation of Samples for DiatomAnalysis
Ten grams of tissue (lungs, liver, kidneyor brain) were washed with distilled water andminced. Ten milliliters of duodenum contents,gastric contents or blood was transferred toa test-tube for digestion. Two sets of samples
1022 Chiang Mai J. Sci. 2014; 41(5.1)
were prepared for acid digestion; all of thesamples were carefully boiled with 10 ml ofconcentrated nitric acid until the tissuehad dissolved. One milliliter of hydrogenperoxide was added and the solutionswere boiled for 10 minutes. After completedigestion, the supernatant was decantedand rinsed with distilled water [27].Distilled water, concentrated nitric acid andhydrogen peroxide were also tested for thecontamination of exogenous diatoms.
2.4 Detection and Identification ofDiatoms
The cleaned diatom samples weredropped on a coverslip and dried on a hotplate (40-45°C). The mounting agent solution,Naphrax was dropped on the dried samplesand the coverslip was placed on a microscopesglass slide. All of diatoms on the preparativeslides were examined under a light microscope(100x) and identified by comparison, in termsof the morphology and size, to the diatomreference books (Krammer and Lange-Bertalot [28, 29, 30, 31], Kelly and Haworth[3], Tuji and Houki [32], Suphan [33]).The diatoms were counted and recorded.Some species of diatoms were photographedusing an Olympus Normaski and scanningelectron microscope to confirm theidentification.
2.5 Assessment of Water Quality at theScenes
The water samples at the scenes wereanalyzed for their physical-chemical propertiessuch as turbidity, conductivity, pH, alkalinity,dissolved oxygen (DO), biochemical oxygendemand (BOD), nitrate nitrogen, ammoniumnitrogen and soluble reactive phosphorus [34].The water quality was assessed using theApplied Algal Research Laboratory - Physicaland Chemical Score (AARL-PC Score)according to Peerapornpisal et al. [35].
2.5 Similarity IndicesThe similarity of the diatoms taken from
the tissue samples and those found at thecorpse recovery site were determined usingDominance Identity (DI) and Species Index(SI) [36].
DI was used to measure the similaritybetween the two samples and calculated as:
DI1,2 = Σqi
Where DI1,2 is the similarity betweensamples 1 and 2 and qi is the smaller of thetwo relative abundances of species i.
SI was used to compare the number oftaxa between two samples and calculated as:
SI1,2 = S1∩2/S1+2 * 100[%]
Where S1∩2 is the number of speciescommon to the diatom communities inSamples 1 and 2, and S1+2 is the total numberof species in the two diatom communities inSamples 1 and 2.
DI and SI can vary between 0% (nosimilarity) to 100% (complete similarity).
3. RESULTS AND DISCUSSION3.1 Diatoms Found in Tissues
The benthic diatoms were collected inthis research because these forms is morediverse than the planktonic, both in terms ofthe number of species and the life formspresent. Besides, the most of planktonicdiatoms are come from the benthic diatomsdrifting [2].
In the twelve cases in which corpseswere found submerged in water, they were10 male and 2 female cases, all aged between4-53 years. Diatoms were found to bepresent in all cases, but there were differencesin the diatom diversity. The highest numbersof diatoms were found in the gastric contents,lungs, duodenum contents, liver, kidney,
Chiang Mai J. Sci. 2014; 41(5.1) 1023
blood and brain, respectively (Table 1).Similar to the study from Ludes et al. [27],the 4 organ samples of 12 immersion caseswere analyzed for diatoms and diatoms werefound to be present in 66% of the lungsamples, of which more than 60 diatoms/10g of tissue were reported. Li et al. [37]examined the diatom quantity in 407 drowningcases. 372 cases revealed positive resultsfrom the diatom test in the lung tissue.
Diatoms were not detected in all of thesamples of the five corpses who had diedfrom diseases or accidents on dry land, andthis result was similar to the report of Auerand M ttonen [38]. In some reports, thenon-drowning corpses can reveal smallamounts of diatoms. This is likely due to thepossibility of the ingestion of diatoms fromair, food or drinking water in daily life[39, 40, 41].
According to diatom morphology,typically were found in oval or elliptical shapebecause this shape was cosmopolitan andeasier to penetrate to the organelle, so thisshape tends to be dominant [2, 36, 42].The species which are small in size, such asCyclotella spp. and Achnanthidium spp. werecommonly present because they can moreeasily reach the blood, brain, liver and kidneysduring drowning. The similar research doneby H rlimann et al. [36] that found thesmall size of diatoms (especially smaller than5 μm.) can pass more easily in to the body.
3.2 The Sites of Corpse RecoveryAll sites of corpse recovery were located
in Chiang Mai Province, Thailand. The waterquality at the scenes was classified in therange of being clean water quality tomoderate-polluted water quality, dependingon the conditions of the sampling site(Table 1).
3.3 Correlation Between Diatoms inDrowned Cadavers and the RecoverySites
The diversity of the diatoms in each casewas found to be different. A concordanceof diatoms collected from the tissue samplesand the site of corpse recovery may behelpful in indicating the place of death. Thesimplest way to accomplish this is todetermine the dominant species of diatomspresent. The dominant species of diatoms inthe tissue samples were found to be similarto the diatoms found at the recovery sites,which indicated that the site of the corpserecovery is likely to be the same as the site ofthe drowning (Table 2). This is similar to thestudies of Pollanen [12], Auer and M ttonen[38], Ago et al. [43] and Horton et al. [44],all of which revealed that the diatomspresent in the tissue samples were also foundat the drowning sites. The most dominantspecies of diatoms found in this study wereCyclotella meneghiniana K tz., Achnanthidiumminutissima (K tz.) Czarn., A. saprophilum(H. Kobayasi & Mayama) Round & Bukht,Aulacoseira granulata (Ehrenb.) Simonsen,and Nitzschia palea (K tz.) W.Sm. Thedominant species are shown in Figure 1 andsome species of diatoms, which werephotographed by scanning electronmicroscope, are shown in Figure 2.
A comparison of only the dominantspecies of diatoms is a simple application andsuitable for short-term work in identifying thedrowning site. However, this method has beenonly tentatively studied to date. Therefore, theappropriate method was compared all of thediatom species from the tissue samplesand diatoms from the recovery scenes todetermine the similarity indices.
Two similarity indices, DominanceIdentity (DI) and Species Index (SI) were
1024 Chiang Mai J. Sci. 2014; 41(5.1)
calculated. DI showed the same number ofcounted diatoms between the two samplesand SI shows the similarity of diatom species.Both indices are expressed as a percentageand the value greater than 60% are regardedas indicating a replicate sample [45]. Fromthe results shown in Table 3, the highestvalue of DI was found to be 79% in Case10, which showed a high similarity ofdominance, The SI value displaying thehighest similarity was found in Case 5, witha percentage value of 79.4%. The DI and SIvalues showed a similarity of nearly 60%or more for at least one sample per case.The diatom distribution in gastric contentsand also that in the lungs and duodenum
contents were all found to be greatly similarto the diatoms found at the site of thecorpse recovery. The diatoms at thedrowning sites and the tissue samples werefound to be similar. It is possible to usethese results as supporting evidence toconclude that the site of the drowning andthe corpses recovery sites were the same.The poor similarity of the SI could be dueto the fact that under normal circumstances,diatom density in corpse samples, such asin those found in the blood, brain,kidneys and liver, are lower than thoserecorded at the drowning site and woulddepend on the volume of water swallowedand/or aspired [36, 46].
Table 1. Diatoms found in tissue samples from drowned cadavers identified to speciesand compared to those diatoms found in water and samples collected from the scenesin Chiang Mai province.
DC - duodenum contents; GC- gastric contents
DrownedVictims
Case1
2
3
4
5
6
7
8
9
10
11
12
Sex
Male
Male
Female
Male
Male
Male
Male
Male
Male
Male
Male
Female
Age
18
28
4
53
30
49
23
30
52
21
24
40
Location ofbody found
Irrigation Canal,Mueang DistrictSansaimul Village,San Sai DistrictSansaimul Village,San Sai DistrictHousing Estate,San Sai DistrictPapong Village,Doi Saket DistrictChiang Mai Moat,Mueang DistrictReservoir oppositeDoi Saket Police Station,Doi Saket DistrictChiang Mai Moat,Kod Cha Sarn Road,Mueang DistrictPaya Kham Irrigation,Wat Ket,Mueang DistrictChiang Mai Moat,Suan Dok Gate,Mueang DistrictChaeng Ku Hueang,Chiang Mai Moat,Mueang DistrictKaw River,Chiang Mai-SanKamphaeng,Mueang District
General waterquality
Clean-moderateModerate
Moderate
Moderate
Clean-moderateModerate
Clean
Moderate
Moderate
Moderate-polluted
Moderate
Moderate
Brain
-
-
-
-
-
9
4
8
-
2
3
4
Blood
-
-
5
-
-
20
1
8
3
7
9
5
Kidney
12
-
-
1
1
10
6
3
4
5
2
118
Liver
204
-
2
2
2
11
9
24
8
126
12
8
Lung
79
65
15
10
98
22
407
1,028
16
1,274
17,736
66
DC
4
10
33
92
30
87
83
683
38
268
14,639
53
GC
69
69
24
474
766
27
86
2,831
148
4,934
27,471
176
Diversity ofdiatoms
22 genera43 species9 genera
11 species8 genera
11 species17 genera33 species9 genera
34 species13 genera20 species13 genera23 species
18 genera34 species
24 genera44 species
35 genera96 species
35 genera95 species
18 genera24 species
Number of diatoms found in(cells/10 g. or 10 ml. of sample)
Chiang Mai J. Sci. 2014; 41(5.1) 1025
Table 2. Comparison of the dominant species of diatoms in tissue samples and the sitesof corpse recovery.
DrownedVictims
Case1
2
3
4
5
6
7
8
9
Tissue Samples
Cocconeis placentula Ehrenb.Cymbella turgidula GrunowGomphonema pumilum (Grunow) Reichardt &Lange-Bert.Navicula cryptotenella Lange-Bert.Navicula phyllepta K tz.
Cyclotella pseudostelligera HustedCyclotella meneghiniana K tz.Achnanthidium minutissimum (K tz.) Czarn.Achnanthidium saprophilum (H. Kobayasi &Mayama) Round & Bukht.Navicula cryptotenella Lange-Bert.
Cyclotella pseudostelligera HustedCyclotella meneghiniana K tz.Nitzschia sp.1Eunotia sp.1Navicula cryptotenella Lange-Bert.
Aulacoseira granulata (Ehrenb.) SimonsenNitzschia palea (K tz.) W.Sm.Cyclotella meneghiniana K tz.Sellaphora pupula (K tz.) Mereschk.Nitzschia draveillensis Coste & Ricard
Achnanthidium minutissimum (K tz.) Czarn.Encyonopsis microcephala (Grunow) KrammerAchnanthes oblongella ∅strupEncyonema minutum (Hilse) D.G.MannGomphonema lagenula K tz.
Aulacoseira granulata (Ehrenb.) SimonsenAchnanthidium saprophilum (H. Kobayasi &Mayama) Round & Bukht.Achnanthidium minutissimum (K tz.) Czarn.Cyclotella meneghiniana K tz.Achnanthidium jackii Rabenh.
Aulacoseira granulata (Ehrenb.) SimonsenAchnanthidium minutissimum (K tz.) Czarn.Encyonema minutum (Hilse) D.G.MannAchnanthidium jackii Rabenh.Pinnularia mesolepta (Ehrenb.) W.Sm.
Aulacoseira granulata (Ehrenb.) SimonsenCyclotella meneghiniana K tz.Gomphonema parvulum (K tz.) K tz.Nitzschia intermedia Hantzsch ex Cleve &GrunowNitzschia palea (K tz.) W.Sm.
Nitzschia palea (K tz.) W.Sm.Cymbella turgidula GrunowAchnanthidium saprophilum (H. Kobayasi &Mayama) Round & Bukht.Achnanthidium jackii Rabenh.Planothidium rostratum (∅strup) Round & Bukht.
Sites of Corpse Recovery
Cocconeis placentula Ehrenb.Cymbella turgidula GrunowGomphonema pumilum (Grunow) Reichardt &Lange-Bert.Myamaea sp.Synedra ulna (Nitzsch) Ehrenb.
Cyclotella pseudostelligera HustedCyclotella meneghiniana K tz.Achnanthidium minutissimum (K tz.) Czarn.Nitzschia sp.1Achnanthidium saprophilum (H. Kobayasi &Mayama) Round & Bukht.
Cyclotella pseudostelligera HustedCyclotella meneghiniana K tz.Achnanthidium minutissimum (K tz.) Czarn.Nitzschia sp.1Achnanthidium saprophilum (H. Kobayasi &Mayama) Round & Bukht.
Aulacoseira granulata (Ehrenb.) SimonsenNitzschia palea (K tz.) W.Sm.Cyclotella meneghiniana K tz.Nitzschia draveillensis M.Coste & RicardSynedra ulna (Nitzsch) Ehrenb.
Achnanthidium minutissimum (K tz.) Czarn.Encyonopsis microcephala (Grunow) KrammerAchnanthes oblongella ∅strupEncyonema minutum (Hilse) D.G.MannCymbella turgidula Grunow
Aulacoseira granulata (Ehrenb.) SimonsenCyclotella meneghiniana K tz.Achnanthidium saprophilum (H. Kobayasi &Mayama) Round & Bukht.Achnanthidium minutissimum (K tz.) Czarn.Cyclotella pseudostelligera Husted
Aulacoseira granulata (Ehrenb.) SimonsenAchnanthidium minutissimum (K tz.) Czarn.Encyonema minutum (Hilse) D.G.MannCyclotella pseudostelligera HustedEncyonema silesiacum (Bleisch) D.G. Mann
Aulacoseira granulata (Ehrenb.) SimonsenCyclotella meneghiniana K tz.Nitzschia palea (K tz.) W.Sm.Gomphonema parvulum (K tz.) K tz.Nitzschia intermedia Hantzsch ex Cleve &Grunow
Nitzschia palea (K tz.) W.Sm.Achnanthidium saprophilum (H. Kobayasi &Mayama) Round & Bukht.Cymbella turgidula GrunowAchnanthidium minutissimum (K tz.) Czarn.Aulacoseira granulata (Ehrenb.) Simonsen
Dominant Species
1026 Chiang Mai J. Sci. 2014; 41(5.1)
Table 2. Continued.DrownedVictims
Case10
11
12
Tissue Samples
Achnanthidium minutissimum (K tz.) Czarn.Nitzschia palea (K tz.) W.Sm.Fragilaria crotonensis KittonCyclotella meneghiniana K tz.Cocconeis placentula Ehrenb.
Cyclotella meneghiniana K tz.Nitzschia palea (K tz.) W.Sm.Aulacoseira granulata (Ehrenb.) SimonsenFragilaria crotonensis KittonCyclotella pseudostelligera Husted
Aldafia sp.Diadesmis confervacea K tz.Achnanthidium saprophilum (H. Kobayasi &Mayama) Round & Bukht.Achnanthes exigua GrunowAchnanthidium minutissimum (K tz.) Czarn.Bukht.
Sites of Corpse Recovery
Achnanthidium minutissimum (K tz.) Czarn.Cocconeis placentula Ehrenb.Cyclotella meneghiniana K tz.Nitzschia palea (K tz.) W.Sm.Fragilaria crotonensis Kitton
Cyclotella meneghiniana K tz.Nitzschia palea (K tz.) W.Sm.Fragilaria crotonensis KittonAulacoseira granulata (Ehrenb.) SimonsenAchnanthes exigua Grunow
Aldafia sp.Diadesmis confervacea K tz.Achnanthidium minutissimum (K tz.) Czarn.Achnanthidium saprophilum (H. Kobayasi &Mayama) Round & Bukht.Achnanthes exigua Grunow
Dominant Species
Table 3. Similarity indices of diatoms in tissue samples and the sites of corpse recovery.
BR-brain, BL-blood, KI-kidney, LI-liver, LU-lung, DC-duodenum contents, GC-gastric contents, SR-site ofcorpse recovery
DrownedVictims Case
1
2
3
4
5
6
Similarity Indices (%)
KI-SRLI-SRLU-SRDC-SRGC-SRLU-SRDC-SRGC-SRBL-SRLI-SRLU-SRDC-SRGC-SRBL-SRLI-SRLU-SRDC-SRGC-SRKI-SRLI-SRLU-SRDC-SRGC-SRBR-SRBL-SRKI-SRLI-SRLU-SRDC-SRGC-SR
Dominance Identity (DI)53.876.566.115.153.974.512.764.05.027.773.640.962.62.75.460.357.072.324.27.742.347.372.839.558.331.244.336.637.048.4
Species Index (SI)22.668.445.76.567.769.28.353.87.77.746.041.733.34.38.721.754.265.63.77.440.711.179.427.840.022.227.825.022.238.9
Chiang Mai J. Sci. 2014; 41(5.1) 1027
Table 3. Continued.
DrownedVictims Case
7
8
9
10
11
12
Similarity Indices (%)
BR-SRBL-SRKI-SRLI-SRLU-SRDC-SRGC-SRBR-SRBL-SRKI-SRLI-SRLU-SRDC-SRGC-SRBL-SRKI-SRLI-SRLU-SRDC-SRGC-SRBR-SRBL-SRKI-SRLI-SRLU-SRDC-SRGC-SRBR-SRBL-SRKI-SRLI-SRLU-SRDC-SRGC-SRBR-SRBL-SRKI-SRLI-SRLU-SRDC-SRGC-SR
Dominance Identity (DI)60.12.346.156.945.549.740.031.665.625.512.657.453.460.019.832.111.236.441.260.40.29.425.334.563.735.079.05.914.30.137.552.451.752.631.011.132.039.954.545.462.4
Species Index (SI)19.04.823.818.268.023.840.97.117.83.617.265.650.042.910.310.313.823.323.365.12.87.04.223.062.313.974.25.77.41.916.766.262.068.416.75.326.316.750.033.357.9
1028 Chiang Mai J. Sci. 2014; 41(5.1)
Figure 1. Light micrographs of some cleaned dominant species of diatoms in drowningtissue samples (scale bar = 10 μm.).(1) Aulacoseira granulata (Ehrenb.) Simonsen, (2) Cyclotella meneghiniana K tz., (3) C. pseudostelligeraHusted, (4-5) Achnanthes oblongella ∅strup, (6) A. exigua Grunow, (7) Achnanthidium minutissimum(K tz.) Czarn., (8) A. saprophilum (H. Kobayasi & Mayama) Round & Bukht., (9) Aldafia sp.,(10) Planothidium rostratum (∅strup) Round & Bukht., (11) Encyonopsis microcephala (Grunow)Krammer, (12) Sellaphora pupula (K tz.) Mereschk., (13) Diadesmis confervacea K tz., (14) Cocconeisplacentula Ehrenb., (15) Nitzschia palea (K tz.) W.Sm., (16) Cymbella turgidula Grunow, (17) Synedraulna (Nitzsch) Ehrenb.
Figure 2. Scanning electron micrographs of some diatoms in tissue samples.(1) Cyclotella meneghiniana K tz., (2) C. pseudostelligera Husted, (3) Achnanthes oblongella ∅strup, (4)Aulacoseira granulata (Ehrenb.) Simonsen, (5) Nitzschia palea (K tz.) W.Sm., (6) Cocconeis placentulaEhrenb.
Chiang Mai J. Sci. 2014; 41(5.1) 1029
4. CONCLUSIONSThe diatoms were present in the tissue
samples of the twelve corpses, which werefound submerged in water, whilst they wereabsent in the five corpses, which were foundto have died from other causes of death, suchas diseases and/or accidents. Diatoms werefound to be present in high density in thegastric contents, lungs and duodenumcontents. The number and species of thediatoms in each case were different dependingon the diatoms that were found to be presentat the drowning site. In terms of a comparisonof the diatoms taken from the tissue samplesand those collected at the drowning sites, thedominant species were the same. Besides, thesimilarity indices DI and SI revealed a 60%rate of similarity of at least one sample percase. From all of these results, the corpserecovery sites were likely to be the drowningsites.
ACKNOWLEDGEMENTSThe authors would like to thank the
Biodiversity Research and Training Program(BRT T_651001), the Conservation andUtilization of Biodiversity Project, BiologyDepartment, Faculty of Science, andNanoscience and Nanotechnology Center,Chiang Mai University for providing aresearch grant. And thanks to the Chiang MaiUniversity Graduate School, Applied AlgalResearch Laboratory (AARL), Department ofBiology, Faculty of Science and the ForensicMedicine Department, Faculty of Medicine,Chiang Mai University for providing both theresearch sampling assistance and the laboratoryequipment.
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