All foods are not equal. Food is not free. All foods are not equal! Fuels are not equal! 1. Different animal 2. Plant vs.

Transcription

1 All foods are not equal Food is not free All foods are not equal Yuxiang Wang 1. Different animal 2. Plant vs. animal as food 3. Different physiological demands (state) 4. Different environment Chap 11.8, 12.7, 13.7, 15.8 OT Chap. 9.8, 10.7, 11.7, 13.8 Food Fuels are not equal! Different animals Trophic levels Habitats Environments Physiological states Type of tissues Life stage and sex Foraging means Life stages Energy balance All foods are not equal! Same Food leads to different energy levels Different partitions House keeping Growth Reproduction Waste Ingestion rates influence usable energy content in food 1

2 Food All foods are not equal! Different food results in different energy content and survival strategies Assimilation efficiency Higher in carnivores than herbivores Higher in endotherms than ectotherms Energy efficiency Higher in aerobic than anaerobic metabolism Available energy Specific Dynamic Action (SDA) Metabolic costs to process food is measured by SDA Post-prandial Metabolic rate increase 30-40% in mammals times in reptile (Ectotherms) Lower fasting metabolic rate Up-regulate enzymes, transporter, GI secretion Increase in size of organs (e.g., python) Duration of SDA is temperature-dependent Expenses associated with guts processing are small 1. Ingestion rate is related to type of animal and body size Assimilation efficiencies differ for different foods Table 6.9 Endotherms IR = 10.7 Mb 0.7 Higher temperature Ectotherms IR = 0.78 Mb 0.83 Little difference Fig

3 2. Plants vs. Animals as food Plants (mainly terrestrial) Tough to penetrate Cellulose and lignin indigestible Hard to hold on with wax and cuticle Poor nutrition for animals Low N Wrong AA balance Poor Na Lack of necessary steroids Possess chemical and physical defense system against herbivores Primary producer for all trophic levels Fig Plants vs. Animals as food (con t) Animals Perfect balanced diets With tough chitinous exoskeleton or bones Hard to capture Resilient to starvation (lurking hunter), spiders and worms Unusual stamina (active hunter) Carnivores have lower population density Herbivores must equip with: Hard mouth pieces Long guts Differentiated guts Differentiated guts Anaerobic cellulase symbionts for fermentation ph homeostasis in guts Salt intake mechanisms 3

4 Insect Herbivores Ingestion through Chemical defense Physical defense Biotic defense Behavioral Avoid defense via spatial and temporal means Cut off defense supply Physiological Excretion of chemical to counter toxins (tobacco hornworm) Enzyme system to oxidize Change internal environment (ph) to eliminate toxic effect alkaline in midgut to neutralize tannin Insect Herbivores Making use of plant toxins Phagostimulant (mustard oil by Pieris butterflies) Aposematism (butterflies) Feeding on wounded plants (galls) Digestion Symbionts in hindgut to digest fibres Bacteria fermentation Endogenous cellulase woodlice Extracorporeal symbionts termites (fungi in nest) Problems Excessive water and sugar ( bypass midguts or excrete honeydew Vertebrate herbivores Acetate Challenges Physical and chemical E.G. Eucalyptus eater (ringtail possums) leaving >40% energy when eating more toxic plants Long GI track and ruminantia Coprophagy to re-digest a portion of faeces (capybara) Postgastric fermentation horse, pig Ruminant stomachs Fig 15.57, OT Fig

5 Carnivores Most leave bones and exoskeleton behind Insect eating bats have chitinase (low MR) Hyenas can eat bones Pharynx to suck blood Toxic venoms to deal with larger preys 3. Physiological states: Aerobic vs. Anaerobic Aerobic metabolism in insects Entirely rely on aerobic metabolic pathway 50x increase of Vo 2 600x increase of ATP turnover rate (Cytochrome Oxidase turnover rates reach theoretical max) Main fuel storage is fat body Triacylglycerol and glycogen Fuel mobilization is regulated by octapeptides and decapeptides from corpus cardiacum Direct fuel Lipid diacylglycerol, trehalose and proline Major aerobic fuel in insects Lipid Orthoptera (grasshooper) & Lepidoptera (butterfly) 5

6 Major aerobic fuels in insects Proline oxidation depletes lipid storage because acetyl-coa is derived from FFA during flight Glossina (tsetse fly) and Leptinotarsa (beetle) Insect flight muscle contains very little LDH and phosphagens Trachael O 2 delivery system allows to tap in high aerobic metabolic rate to supply ATP. Parasites depend entirely on anaerobic glycolysis No -oxidation Limited AA catabolism Permanent process, do not accumulate end products There is a persistent anaerobic flux which is not down-regulated by O 2 Physical activity types and demands (level) affect fuel efficiencies and outputs 6

7 Fuels for human exercise Phosphagen 100m dash phosphagen and Gly-Lac 200m Gly-Lac 400m Gly-Lac Aerobic 800m Aerobic (combine carbo, lipids and AAs) 10k and Marathon Muscle Glycoge en content g/kg 2hr exercise Diets affect recovery time High carbohydrate diet Fat and protein diet 0hr recovery 50hr Extraordinary Animal Athletes (flyer) Humming birds and bumblebees Nectar feeder (high carbohydrate) Greater flyers Endothermic vs. ectothermic 7

8 Humming Birds Wing-beats 60-80/sec to hover Heart rate /min Pack cells with mitochondria (50-55% 55% volume) Switch to ammonotely when cold and more water available, hyposmotic urine Can drop Tb to as low as 18 o C when air temperature decreases Vo 2 Awake Torpor Ambient temp Bumblebees Wing-beats 120Hz aerobic metabolism to support 100L/kg/hr Mo 2 = oxidize 60mg sugar To gain thorax temp o C before it can fly, thermal regulate body temp. Extraordinary Animal Athletes (swimmer) Tuna Keep core body temp high High Mo 2 (2500mg/kg/hr, 3.7 FL/s) High guts clearance rate (4-5x of other teleosts) High aerobic capacity (oxidative fibers) High lactate turnover and clearance rate (0.1-30mg/kg/hr ) higher than mammals High glucose turnover rate (0.9mg/kg/hr) unlike other teleosts 8

9 4. Foods are different for animal living in different environment In terrestrial environment Plants as food are much tougher to eat Animals as food is same as other environment Shoreline grazing animals need to adjust feeding in a rhythm to optimize chances of getting food In freshwater, plant foods are high variable depending on diel and seasonal changes. Temperature affects fuel storage and utilization! seasonal Larvae caterpillar Fig 16.36, OT Fig beetle Gall-Fly Insect cold-acclimation The energy efficiencies vary according to fuel types Glycogen is the source of polyols Glycerol level is also affected by humidity Summary Food is not free, animals must develop proper mechanisms to accommodate their nutritional needs The co-evolution of prey and predator is important for maintain genetic diversity and polymorphisms in the nature Fig OT Fig