Feeding Flashcards
feeding definition
gathering and ingesting food
digestion
breakdown and transferring required nutrients into the body
Ways of obtaining nutrients
Autotrophic – including plants algae and some bacteria – able to produce their own food and energy
Heterotrophic – consumers – all animals must obtain nutrients from other plants or animals for energy and nutrients
Short food chains vs long
Short food chains deplete less energy prior to consumption thus more efficient than long food trains
Why did animals evolve within the sea
The ocean was a source of more of a more constant environment, so they didn’t have to evolve ways of dealing with so many different environmental factors
earliest metazoan marine life
Ediacaria period - 550myr ago
Feeding behaviours within ediacara period
detrivores and carnivores were able to capture protists and bacteria
* Primary productivity was and still is limited to the surface areas of the ocean
* Benthic organisms were and are dependent on organic detritus falling from the surface of the ocean
Exceptions of benthic organisms feeding on detritus
hydrothermal vents and cold seep ecosystems
Feeding methods
Small particle feeding
Large particle feeding
Fluid feeding
Small particle feeding
suspension or filter feeding – consume material suspended in water column
* Specialized flagellated cells – choanocytes – move flagella to draw in water through pores
* No gut – direct cellular ingestion of captured food
Filter feeding – mucociliary
- External mucociliary mechanisms – use motile cilia and mucus to capture food particles of the appropriate size
1. Create a current of water bearing particles
2. Separation of particles from the water
3. Transfer of particles to mouth
4. Ingestion occurs
Filter Feeding - Amphiuridae
- Feed by holding their arms into the water column and trapping particles in flowing water
- Particles are moved to the mouth using groove on their oral side
- In stagnant water they switch to deposit feeding
Deposit feeding
ingestion of living and non-living organic matter (crabs)
Setae
external setae or cirri = long closely spaced feeding setae on numerous appendages used to collect food
Baleen whales
– two sets of baleen plates – (keratin) sieve food particles from the water
Basking sharks
can strain 2000 L of water per hour swim with mouth continuously open to feed on the zooplankton – gill rakers trap and filter out plankton – mouth closes to swallow
Deposit feeders
- Consume large amounts of organic matter within sediments
- Vital for the regeneration of nutrients and enhance benthic productivity
- Eg. Ragworm
Radula adaption
found in many gastropods – used for scraping algae off rocks – can be found in carnivorous snails to rasp flesh off dead animals
- Structure = many sets of small teeth in which move back and forth to scrape off algae the structure is then pulled back into the buccal cavity to ingest the particles
Aristotles lantern
- Sea urchins possess a very intricate mouth apparatus – Aristotles lantern which is comprsed of a powerful set of jaws – makes them a very successful herbivore
Hunting behaviour
some species feed by targeting and subduing individual food items, but others will work together in teams and in pods to chase the prey that they are after
Orcas
- Eat fish, squid, sea otters, and seals by attacking them with sharp teeth.
- Behavioural specialists depending on prey
- Hunt in packs (e.g., pods of five) for higher success rates.
- Prey is divided among the group after catching it.
Dolphins
- Hunt in pods.
- They corral bait balls by swimming around them to bunch up the fish.
- Dolphins slap the bait ball with their tails to stun the fish - float to the surface, making them easier to catch.
- Dolphins also use a technique called mud nets to trap fish
Specialised radula
- drill snails- that cuts a hole through shells – either sucks out living tissue OR injects venom to paralyze
Nematocyctes
- Exclusively found in the phylum Cnidaria
- Coiled, hollow, barbed thread that quickly turns outward
- Often contains poison
- Prey capture and defence
Photosynthetic symbiosis
endosymbiotic algae produce nutrients through photosynthesis – passed on to corals cells
Coral emit waste produce (NH4 etc) consumed by endosymbiotic algae
Chemosynthetic symbiosis
(hydrothermal vent worms)
-They have a symbiotic relationship with chemoautotrophic bacteria and lack a mouth, gut, or anus.
Food comes from sulfur-oxidizing chemoautotrophic bacteria within a trophosome.
Require hydrogen sulfide, found near hydrothermal vents.
Sulfate is produced in the trophosome and voided across the gills.
Bacteria produce energy and transfer it to the worm.
Intracellular digestion
- Gastrovascular cavity - has one opening and a blind tube or cavity that serves as mouth and anus
- Digestive enzyme in tubular cavity break down food and food particles are engulfed by cell lining within the gastrovascular cavity
Extracellular digestion
- Alimentary canal – digestive tract with a mouth at one end and anus at the other end
- Food is ingested in through the mouth passes through the esophagus and stored in the crop
Evolution of the through gut
- Allowed for continuous food processing
- Increased ability to process bulky and low quality foods
- Multiple mechanical and chemical processes along length of gut such as changing pH to optimise enzyme activity
Gut structure
- Foregut
- Midgut
- Hindgut
Foregut
ectodermal in origin = ingestion and mechanical breakdown of food
* Buccal cavity – saliva to lubricate passage of food and enzymes to start digestion
* Pharynx – pump food down to gut – aid mechanical breakdown and mixing of food
* Esophagus/crop – either carries food directly to stomach (crop is associated w animals that have large infrequent meals)
Midgut
– endodermal in origin = nutrient absorption
* Muscular stomach – starts or continues the comminution of food = sometimes mechanical breakdown
* Secretory caeca – branch off immediately after stomach = production of digestive enzymes and absorption of digested food
* Intestine – intracellular digestion in lower invertebrates = extracellular digestion in animals processing large masses of food
Hindgut
– ectodermal in origin = elimination of waste through anus
* Rectum – selective reabsorption of water and salts from food
- Site of faecal pellet formation - highly distinctive shapes can be used to identify species presence
Types of meal processing – reactor models
- Batch reactor
- continuous flow reactor with mixing
- continuous flow reactor without mixing
- Batch reactor
– each meal is processed before the next meal enters
- Continuous flow reactor without mixing
meals line up so they don’t mix but each meal processed for longer than batch reactor
- Continuous flow reactor with mixing
– new meals mix with meals that have already undergone some processing
Secondary loss of the through gut
- 25% of 30,00 fish spp have lost ability to use stomachs because of a change in diet - no need for stomach enzymes
- Lost gene for gastric proton pump and for pepsinogens
- food is passed into the stomach in a cord of mucus
- Stomach acids reduce viscosity of mucus and particles are released
- Remaining gut is alkaline – restores viscosity of the mucus and production of faecal pellets occur
Chordates
mucus chord moved to stomach by cilia of the pharyngeal basket and esophagus
Bivalve digestive strategies
- 2-phase digestive system: rapid intestinal pathway OR slower, glandular pathway
- Evolved this digestion strategy to avoid excess assimilation of metals
- Reduced ingestion rates under high Cr
- Reduced proportion processed by glandular digestion under high Cr
- Able to modify processing to reduce exposure to Cr
Gut microbes – herbivorous fish
- Different algae types have unique compositions of polysaccharides.
- Herbivorous fish use specific enzymes to break down these large polysaccharides to obtain energy from algae.
