1. Nitrogen in Animals: Applications

2. 1) Pregnancy 2) Nutritional Stress 3) Different diets & diet quality 4) Nursing 5) Fasting Spoiler alert! They all have VERY similar results…

3. Studies investigate : δ 15 N & δ 13 C values in body of pregnant women with and without nutritional stress (Fuller et al. 2004, 2005) Methods Examine δ 15 N & δ 13 C isotopes in the body from pre-conception to delivery by: 1) Conducting dietary surveys 2) Collect hair samples of mother post-delivery Pregnancy and Nutritional Stress

4. d13C d15N

5. Fuller et al. 2004 Happy Mommy

8. Sad Mommy Fuller et al. 2005

9. Sick b/w 10-16 weeks Sick throughout 1 st trimester Negative nitrogen balance = increased fractionation

10. Well…not completely understood DECREASES IN δ 15 N due to maternal N conservation:  Assimilation of greater percentage of dietary N with lower δ 15 N values results in a reduction of steady state diet to body trophic fractionation (0.5-1‰)  Decreased urea synthesis and increased urea salvage in colon (peeing out heavy nitrogen)  Mother decreases in N and fetus increases = fetus literally eating mommy and increasing in trophic level

11. Reasoning for INCREASE in δ 15 N: As nutritional stress & weight loss continue, increase of muscle protein breakdown, lighter N is not replaced by dietary protein, & remaining tissues are enriched in heavier N (increased fractionation)

12. 2 Studies: Oreochromis niloticus – “Nile tilapia” (Gaye-Siessegger 2004) Paradosa lugubris – “Wolf spider” ( Oelbermann and Scheu 2001)

13. Study investigates: Influence of different diets on δ 15 N & δ 13 C in fish bodies Methods  32 fish reared on same diet for 11 weeks to equilibrate on diet, then 7 were killed to estimate initial isotopic composition of body  Provide fish with 3 different protein diets in controlled lab for 8 weeks  Analyze all fish at end of experiment after 48 hour fast

14.  No significant decrease in δ 15 N & δ 13 C, body mass, b/w averages of feeding groups  Declining trophic shift for individuals in δ 15 N (6.5‰- 4‰) & δ 13 C (4‰-2.5‰) w/ increasing protein retention in individual fish Experiment demonstrates high influence of individual protein balance of δ15N & δ13C in animals – dietary protein was conserved differently in tissue of individual fish = less fraction.

15. Study investigates: Influence of diet quality on δ 15 N & δ 13 C in spiders on different quality diets Methods: Changes in δ 15 N & δ 13 C w/ time: - Adult females, hatchlings, spiderlings fed intermediate quality food for 3, 6, & 11 weeks Changes in δ 15 N & δ 13 C w/ trophic level and starvation: - Adult and juvenile spiders were fed single species diets (low, med, high quality), mixed (high & low), and starved

16. Changes in δ 15 N & δ 13 C w/ time: - Since 14N is preferentially excreted during metabolism, the hatchling N would be isotopically lighter. - As individuals become larger, more isotopically like food item, then become enriched over food item by ≈3‰

17. Changes in δ15N & δ13C w/ trophic level: 5.2‰ 2.5‰ 3.3‰ 2.2‰ Stepwise trophic level enrichment

18. V. High quality Spiders on high-quality diet were bigger and increased in size faster, & had higher δ15N & δ13C values High quality Intermediate qualityV. Low quality Low quality

19. Starvation leads to enrichment of δ 15 N due to recycling body nitrogen (i.e. “eating yourself”)

20. Methods  Teeth and bone collagen samples from two different species with different weaning behaviors  Using δN values to determine age of pup weaning/ trophic level

21. Northern Fur Seal aka Zalophus (bone collagen) Results

22. Tooth dentin Northern Fur seal

23. Isla Santa Margarita Seal aka Callorhinus (bone collagen)

24.  May lead to a method for investigating pregnancy and fertility patterns in populations of animals (past & present)  Pregnancy, nutritional stress, diet quality findings need to be considered in diet studies (ca not always assume ≈3‰ fractionation factor for δ 15 N)  Non-invasive monitoring of nitrogen balance in women during pregnancy – examine overall health  Applied to medical studies of protein stress & N balance: anorexia, bulimia, exercise, disease, weight loss, & burns  Do other tissues detect pregnancy, nutritional stress, changes in diet quality?  Determining feeding habits in animals.  More research to discover the biochemical reasons for δ 15 N increase and decrease in animals