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Animal nutrition Heterotrophs-dependent on a regular supply of food Generally animals fit into one of three dietary categories Hebivores: eat autotrophs (plant, algae) Carnivores: eat other animals Omnivores: both autotrophs and animals To satisfy three nutritional needs: fuel, organic raw material, and essential nutrients Processing food The main stages of food processing are: • Ingestion • Digestion • Absorption • Elimination Fig 41.12 C&R Ingestion Feeding mechanism of animals Suspension feeders Fluid feeders Substrate feeders Bulk feeders Fig 41.2 C&R Substrate feeders Earth worm Ingestive organ: A muscular mid-dorsal pharyngeal bulb Fig 13-63B OH Fluid feeders Lepidoptera Sucking mouth part Fig 21-3 OH Bulk feeders 33.29 Digestive compartments • Intracellular digestion • Extracellular digestion • gastrovascular cavity (gastrovaskulär håla) • alimentary canal (matsmältningskanal) Porifera-intracellular digestion • Filter food particles from water through their body • Suspension feeders • Size of food: 1-50 µm: unicellular plankton, bacteria, virus, small organic debris • Both choanocytes (kraggisselceller) and archeocytes (amöbaceller) engulf and digest particles = intracellular digestion • Internal transport of food by diffusion or by archeocytes but in glass sponges: intrasyncytial Extracellular digestion • Makes possible to use larger food particles • Require less gut surface area • Need secretory gastrodermal cells that release enzymes into the digestive compartment • May also serve as a circulatory system • Cilia or muscles Cnidaria-gastrovascular cavity • Cnidaria (or ctenophores) first evolved a cavity for extracellular digestion • A blind, saclike cavity lined by gastrodermis =coelenteron: digestion & distribution • Opening to the exterior via the mouth • Large polys: partioned by septa • Medusae: stomach, radial canals, ring canals • Extends into each tentacle • Hydrostatic skeleton, circulatory, digestive and absorptive function Fig 7-12 Cnidaria- bulk feeder Enzymatic glands cells in gastrodermis Hydrozoa: Absorption by epitheliomuscular cell and others Hydra eating 33.05 Cnidaria - bulk feeder Anthozoa Fig 7-17 OH Most Plathyhelminthes -gastrovascular cavity • A blind sac (blindtarmsäck) and mouth is used both for ingestion and egestion • Circulatory, digestive and absorptive function • Wall of gut: single-layered with phagocytic and gland cells • Both extracellular and intracellular digestion ceca Planaria (Turbellaria) Fig 33.10 C&R Fig 10-14,15,16,17 OH Cestoda (Plathyhelmithes) • Tapeworms • Endoparasites of the gut of vertebrates • Neodermata (trematoda, cestoda, monogena) : Partial or complete replacement of the cellular embryonic epidermis by a new, nonciliated, syncytial layer: neodermis • No gastrovascular cavity • Neodermis is highly specialized for nutrition uptake from the host. Fig 10-33, 10-45 OH Other animals- alimentary canal matsmältningskanal • Complete digestive tract • A digestive tube with separate mouth and anus • Ability to ingest additional food before complete digestion of earlier meals • Can be organized into specialized regions that carry out digestion and nutrition absorption in a stepwise fashion • (Mouth) • Foregut • Midgut • Hindgut • (Anus: egestion) Fig 9-10 Fig 9-10, page 204 Embryonic origin • Foregut: from embryonic ectoderm (stomodeum) • Hindgut: from embryonic ectoderm (proctodeum) • In animals such as arthropods and roundworm, which have an exoskeleton secreted by ectoderm: the foregut and hindgut are also lined by exoskeleton • Specialized as grinding, piercing or filtering teeth • Valves and other structures in hindgut • Midgut: from embryonic endoderm (adult gastrodermis) lacks exoskeleton, adapted for secretion and absorption Foregut Ingestion and mechanic digestion, may secrete digestive enzymes and mucus Specialized into several regions: • mouth • (buccal cavity: anterior chamber that receives the food and may bear teeth) • Pharynx: -long or short often muscular tube, -bear sometimes teeth -can be a feeding or digging organ that can be everted (turned inside out) or protruded ≠ a proboscis (not part of the gut) = mobile appendage for food collection, locomotion and defense, in some taxa the proboscis –connected to gut (secondarily) Fig 9-10 Foregut • Oesophagus: links the foregut and midgut, (muscular), ciliated • Can be modified to (animals that lack teeth) -Crop: a storage organ (kräva) -Proventriculus (förmage, mage) arthrophods, simetime = crop and/or gizzard or thin-walled part of stomach (midgut) -Gizzard: a muscular sac with chitinous cuticle used for grinding food (muskelmage) Midgut Digestion and absorption Specialized into several regions: • Stomach (proventriculus): - extracellular digestion • Intestine: -absorption -connection to hindgut -formation of feces • Cecum (blindtarm, pl ceca): -digestive gland, sometimes large: hepatopancreas (molluscs, crustaceans) -a simple outpocket from stomach or intestine -(intracellular) digestion -absorption -nutrient storage Hindgut Formation, storage and egestion of feces, water reclamation and ion regulation Specialized into several regions: Rectum: -an enlargement of hindgut - receive undigested food -formation and storage of feces -reclamation of water Cloaca: rectum that is also a gonoduct or/and excretory duct Anus: egestion of feces Small Bilateria: Hindgut and anus are either differentiated or absent Annelida Fig 41.14a C&R Insecta Fig 41.14b C&R Excretion Homeostatic processes: Osmoregulation: balance the uptake and loss of water and solutes (marine invertebrates isoosmotic=osmoconformer, other =osmoregulators: transport epithelium, regulates solute movements) Excretion: get rid of metabolic waste Nitrogenous waste Fig 44.8 C&R 1. Ammonia -very soluble -very toxic -aquatic animals -as ammonium ion (NH4+) 2. Urea -low toxicity, higher concentration -cost energy to transform ammonia to urea -terrestrial and aquatic animals -amphibians 1 and 2 3. Uric acid (urinsyra) -low toxicity, very costly -insoluble: semisolid paste with very little water loss -insects, land snails Excretion Disposal of metabolic waste (nitrogen-containing waste) To avoid their accumulation to toxic level -Diffusion -Active transport: -epithelial excretory surface (salt pumps in brine shrimps) -tubular excretory organs=nephridia -waste product: urine Basic process of excretion 1. Body fluid is collected that involves filtration=filtrate (primary urine) 2. Selective reabsorption of valuable solutes 3. Selective secretion of wastes and nonessential solutes (osmoregulation) 4. The processed filtrate is excreted from the body as urine (final urine) Fig 44.9 C&R Different types of Nephrida (kidney) • Protonephridia: small bilateria that lack a hemal system and/or a coelomic system. In same taxa: mainly used for osmoregulation • Metanephridia: large bilateria • Malpighian tubules: terrestrial arthropodes (insects, many arachnida) and Tardigrada • Vertebrate kidney Protonephrida Fig 44.10 C&R Protonephrida A ciliated excretory tubule that opens to the exterior at a nephridopore but is capped at its internal end by one (or several) terminal cell (solenocyte (one flagellum) or flame bulb/cell (several flagella)). Fig 9-20 OH Metanephridal system Glomeruli: Hemal site for ultrafiltration 1 2 3 Nephrostome njurtratt nephridophore Metanephridia Fig 9-18 OH Fig 44.11 C&R Malpighian tubules Fig 44.12 C&R Malpighian tubules • Do not need: – Coelomic space – Source of pressure – No filter • Nitrogenous wastes are absorbed from blood by the tubule epithelium and secreted into the tubule lumen and then moved to gut lumen Porifera-excretion Simple diffusion (ammonia) Cnidaria-excretion • Simple diffusion (ammonia) • Tentacles and general body wall are gill surface and circulation of water over the body by ciliated epidermal cells Hydra: high Na+ in coelenteric fluid =influx of water Plathyhelmites-excretion -ammonia by diffusion -water and other waste by protonephrida-scattered widely throughout the body Arthropods excretion Diffusion: through permeable surface (gills); aquatic Arthropoda (have also excretory organs: osmoregulation) Saccated nephridia (modified metanephridia): -end sac organs, sacculi, coxal glands, green glands, antennal glands, maxillary glands -aquatic Arthropoda and many terrestial Chelicerata and few terrestrial Tracheata Malpighian tubules (malpigiska kärl/körtlar) -terrestrial arthropods: Tracheata and Arachnida Nephrocytes: excretory cells, common in Arthropoda -Large pinocytic cells in hemocoel -process waste and toxins and return they or store them