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How do insect parameters compare to those from plants? , Yiyi Wong, Zuo Xue, Geoff Sinclair • Components of insects – Cuticle – Chitin • Amino Acids • Amines, Amides, Alcohols, Ethers • Review components of plants • Results of FTIR, C:N ratio, and δ13C of Grasshoppers • Implications Components of Insects • Cuticle is the main components of insects • Major molecular component chitin Among insects, grasshoppers have the highest total-nitrogen body content but typically feed on food that is very low in nitrogen • Cuticle Chitin • Polysaccharide and polymer • Sometimes considered to be a spinoff of cellulose, because the two are very molecularly similar. • Insect coats contain thick, stiff layers of chitin. The areas around legs and face contain very thin, pliable layers. • Insects molt approximately once a year. Structure of Chitin Most of grasshoppers’ physiological and biochemical processes require amino acids as building blocks • Amino Acids(10 types) Review of Plant Components • Roots – Carbohydrates • Stems – Cellulose • Leaves – Chlorophyll, Rubisco – Misc. Carbohydrates, Proteins Results - FTIR • Fourier Transform Infrared Spectroscopy (FTIR) is an analytical technique used to identify organic and in some cases inorganic materials. • Measures the absorption of various infrared light wavelengths by the material of interest. These infrared absorption bands ID specific molecular components and structures. Expected Components of Spectrums • Looked at the chemical components of chitin and expected to see the following: – – – – Amines Amides Alcohols Ethers Expected Components of Spectrums • Amines – 1650-1580 bend • Amides – 1340-1020 stretch • Alcohols – 3600–3200s stretch – 1260-1000s stretch • Ethers – 1760-1670s stretch – 1260-1000s stretch prp11 green grass prp 8 vein grasshopper Absorbance 0.6 0.5 0.4 0.3 0.2 4000 3500 3000 2500 2000 Wave number 1500 1000 Results - Grasshopper C:N Ratios • Expect the C:N ratios to reflect Chitin • Tried to determine if there were differences within the grasshopper via body parts – Did not any differences High N and C contents in Grasshopper compared to Soil and Plant samples (averaged value) N_Plant N_Soil N_Hopper C_Plant C_Soil C_Hopper 1.91 0.40 11.87 43.43 10.22 51.44 Nitrogen Content(%) Carbon Content(%) 14 60 12 50 10 40 8 30 6 20 4 2 10 0 0 N_plant N_soil N_hopper C_plant C_soil C_hopper Nitrogen Allocation Difference Nitrogen% N contents 14 12 10 8 6 4 2 0 N contents Grasshopper Grasshopper Grasshopper Grasshopper Full Body - Full Body - Full Body - Full Body Head Leg Body Wing Plant N contents influenced by Grasshoppers Research results about the N content on a certain of wheat (G.microcephala) affected by the attack of grasshoppers. Soil N contents influenced by Insects • 1. Insect herbivores can deposit significant quantities of faecal material (frass) onto litter and soil. • 2. Nutrients returned to soils in insect cadavers are more easily decomposed than those in leaf litter and can stimulate the decomposition of litter during defoliator outbreaks. • 3. Insect defoliation changes the nutrient content of precipitation as it passes through plant canopies. • 4. Herbivores can change the quantity and quality of leaf litter that falls from plant canopies to the soil. Soil N contents influenced by Insects • 5. Herbivore-mediated changes in plant community composition not only influence litter quality, but may also affect the utilization of soil nutrients by the new community. • 6. Herbivory may influence root exudates or interactions between roots and their symbionts, both of which are known to influence nutrient dynamics. • 7. Herbivores can influence the structure of plant canopies and the cover that they provide, with concomitant changes in light availability, soil temperature and moisture. Results for δ13C Insect Diet • On the whole, animals have similar δ13C to their food source – Body parts containing more protein are generally 13Cenriched – Body parts containing more lipids are generally13Cdepleted • Did not find many differences between grasshopper body parts – – – – Samples were cross-contaminated Mixed Diet Adult sample Grasshoppers molt yearly δ C13 with grasshopper parts -19 -19.5 Grasshopper Full Body Head δC13 -20 Grasshopper Full Body Leg -20.5 Grasshopper Full Body Body -21 Grasshopper Full Body Wing -21.5 -22 1 Differences Between Plants and Insects • Chitin vs Cellulose – Cellulose contains a hydroxy group and chitin contains acetamide. • Plants have different C:N and δ13C values within the anatomy • Grasshopper samples did not show differences in C:N values b/c most components consist of chitin • Grasshopper samples did not show varying values of δ13C although literature suggests that it is a possibility