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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