Table 1.

Selected second derivative peaks of the elytron spectrum, with comparisons to two $\mathrm{\alpha }$-chitin references from shrimp.

Elytron peak frequency (cm${}^{-1}$)	$\mathrm{\alpha }$-chitin Reference40 Peak frequency (cm${}^{-1}$)	$\mathrm{\alpha }$-chitin Reference38 Peak frequency (cm${}^{-1}$)	Band assignment	Tentative interpretation of organic components
3490	3483*	3479	$\nu$(O–H)
3439	3428	3448	$\nu$(O–H)
3266	3254	3268	${\nu }_{\mathit{as}}$(N–H)	Amide A
3099	3100	3102	${\nu }_s$(N–H)	Amide B
2967	2960	2965	${\nu }_{\mathit{as}}$(CH${}_3$)	Lipid
2927	2932	2927	${\nu }_s$(CH${}_2$)	Lipid
2873	2876	2883	${\nu }_{\mathit{as}}$(CH${}_3$)	Lipid
2850	–	–	${\nu }_s$(CH${}_2$)	Lipid
1772	–	–	?
1713	–	–	$\nu$(C=O)	Oxidation
1661	1652	1660	$\nu$(C=O)	Amide I
1623	1621	1627	$\nu$(C=O)	Amide I
1558	1556	1558	$\nu$(C–N) + $\delta$(N–H)	Amide II
1453	–	–	$\delta$(CH${}_2$)	Lipid
1418	1428	1422	$\delta$(CH${}_2$)	Lipid
1379	1376	1376	$\delta$(CH) + $\delta$(C–CH${}_3$)	Lipid
1315	1308	1312	$\nu$(C–N) + $\delta$(N–H)	Amide III
1259	1260	1255	$\delta$(N–H)	Amide III
1207	1207	–	$\delta$(N–H)	Amide III
1163	1156	1157	${\nu }_{\mathit{as}}$(C–O–C, ring)
1120	1114	1113	$\nu$(C–O)	Sugar
1080	1069	1072	$\nu$(C–O)	Sugar
1032	1029*	–	$\nu$(C–O)	Sugar
1015	1008	1021	$\nu$(C–O)	Sugar
992	995*	–	?
955	952	957	$\gamma$(CH${}_3$)

Band assignments are indicative of components identified by³⁸. Frequency bands labeled with “*” are missing from the articles data table, but are found from our own analysis of the presented spectra.