PMC6197134_01
Map of Thailand showing the collection site where the human remains discovered, at Pachangnoi Subdistrict (N 19 19'24.24''; E 100 27'17.28''), Pong District, Phayao Province (green dot), northern Thailand.
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Light micrographs of third instar larvae of Chrysomya chani. (A) Whole body, dorsal view. (B) Anterior end showing the prominent spine bands between the second and third thoracic segments (arrowhead), and prominent tubercles encircling the body, initiating from the first abdominal segment (arrow) and denticles at the surface integument (red arrow). (C) Posterior end showing prominent tubercles encircling the body and a pair of posterior spiracle.
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The prominent features are the protuberant tubercles encircling body segments, of which the prominent tubercles originate from the first abdominal segment and are present until the eighth abdominal segment (Figures 2(A-C) and 3(A)). Spine bands between segments are obvious in the thoracic segments, with the most prominent between the first and second thoracic segments (Figure 2(A)). These spine bands between thoracic segments are relatively sclerotized (Figures 2(A,B). However, spine bands between the abdominal segments are unnoticeable (Figure 2(C)).  A very distinct ultrastructure of the surface integument is seen on the body surface, which is covered with dense variable size of denticles (Figures 2(A-C) and 3(B)). The posterior end of the third instar shows six prominent pairs of tubercles along the peripheral rim of the eighth abdominal segment (Figures 2(A,C) and 3(E)), of which all six pairs (inner dorsal, median dorsal, outer dorsal, outer ventral, median ventral and inner ventral tubercles) are almost equally in their protuberance.
Light micrographs of third instar larvae of Chrysomya chani. (A) Whole body, lateral view; anterior end at left, posterior end at right. Arrows indicate the initial protuberant tubercles encircling body segments at the first abdominal segment (arrow). (B) Anterior end showing cephaloskeleton (c), anterior spiracle (a) and spine bands (s) between the first and second thoracic segments. Anterior spiracle consisted of 9-11 papillae arranging in a single row. Arrow displays surface integument, covering with dense variable size of denticles. (C) Higher magnification of the cephaloskeleton and anterior spiracle (a). Arrows indicate window of ventral cornua. Abbreviation of cephaloskeleton: as, accessory sclerite; db, dorsal bridge; dc, dorsal cornua; den, dental sclerite; is, intermediate sclerite; mh, mouthhooks; pb, parastomal bar; vc, ventral cornua; vp, vertical plate. (D) Posterior view of the eighth abdominal segment showing prominent six pairs of tubercles along the peripheral rim. Posterior spiracle (ps) is apparent. Abbreviation of tubercles: IDT, inner dorsal tubercles; MDT, median dorsal tubercles; ODT, outer dorsal tubercles; OVT, outer ventral tubercles; MVT, median ventral tubercles; IVT, inner ventral tubercles. (E) Posterior view of the eighth abdominal segment showing remarkably sculpture encircling the posterior spiracles (ps) and adjacent to these tubercles (arrow). (F) Higher magnification of posterior spiracles displaying thick, heavily sclerotize complete posterior spiracular peritreme (p) enclosing three spiracular slits. Arrow indicates indistinct button (or ecdysial scar).
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The anterior spiracle consisted of 9-11 lobes (n = 13) arranged in a single row (Figures 3(B,C)). The cephaloskeleton (Figure 3(C)) has large and heavily sclerotized mouthhooks, curved downwards. The ventral cornua have an opening or window (Figure 3(C), arrow). Viewed posteriorly, there is a remarkably sculpture encircling the posterior spiracles and adjacent to these tubercles (Figure 3(E)). Higher magnification of the posterior spiracles revealed thick, heavily sclerotized complete posterior spiracular peritremes enclosing three spiracular slits (Figure 3(F)). The button (or ecdysial scar) is indistinct (Figure 3(F), arrow).
Light micrographs of third instar larva of Chrysomya villeneuvi and Lucilia cuprina. (A) Third instar larva of C. villeneuvi showing large, elongate tubercles on the abdominal segments. (B) Third instar larva of L. cuprina showing smooth abdominal segments.
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Light micrographs of larva of Chrysomya rufifacies and Chrysomya villeneuvi. (A) Third instar larva of C. rufifacies showing large, elongate tubercles on the abdominal segments. (B) Tubercle of C. rufifacies larva bears numerous small spines at tip. (C) Posterior spiracle of C. rufifacies showing large, heavily sclerotized incomplete peritreme. (D) Tubercle of C. villeneuvi larva bears numerous small spines throughout. (E) Posterior spiracle of C. villeneuvi larva showing large, heavily sclerotized incomplete peritreme.
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Third instar larva of Chrysomya nigripes. (A) Posterior spiracle showing gradually enlarged of end of upper peritreme (arrow). (B) Spines between the first and second thoracic segment. (C) A specimen with brown patch on dorsal integument (arrow). (D) A specimen without brown patch of dorsal integument.
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Light micrographs of larva of Chrysomya bezziana and Chrysomya megacephala. (A) Posterior spiracle of larva of C. bezziana. (B) Spines between the first and second thoracic segment of C. bezziana. (C) Posterior spiracle of larvae of C. megacephala. (D) Spines between the first and second thoracic segment of larvae of C. megacephala.
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Light micrographs of larva of Lucilia sinensis, Lucilia cuprina and Lucilia porphyrina. (A-C) Larva of L. sinensis. (A) Posterior spiracle. (B) Spines between the first and second thoracic segment. (C) Cephaloskeleton showing accessory sclerite (arrow). (D-F) Larva of L. cuprina. (D) Posterior spiracle. (E) Spines between the first and second thoracic segment. (F) Cephaloskeleton. (G-I) Larva of L. porphyrina. (G) Posterior spiracle. (H) Spines between the first and second thoracic segment. (I) Cephaloskeleton.
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Neighbour-joining tree based on COI gene (1 205 bp) of Chrysomya chani collected from the human remain from Thailand (pink dot) and other blow fly species. Voucher codes or accession number are presented in parentheses. Bootstrap values (>50%) were shown nearby the node of the trees.
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Based on the BLAST search, our larval sample collected from the human corpse was 100% identical to C. chani (GenBank accession no: KR921606), confirming to be C. chani, based on 1 205 bp of COI (Figure 9).