Lecture 3

Question 1

Food sources

Answer 1

• Remove microbes / particles from the water
• Pick particles from sediment
• Feed on dead / decaying material
• Feed on plants / algae
• Feed on living animal tissue
• Some foods are more nutritious – some are harder to obtain

Question 2

features of gut

Answer 2

• Gut with anterior opening (mouth), often posterior opening (anus)
• One opening in those with incomplete gut
• 3 basic region in gut: foregut, hindgut, midgut * each region may be further diversified
• Specialized digestion structures will depend on food source

Question 3

food types

Answer 3

1. Detritus
2. Plants / Algae
3. Heterotrophic Microbes / Other animals
   a. Particles
   b. Fluids

Question 4

what inverts want

Answer 4

• No matter how or what they eat, all invertebrates need the same basic things…
• Obtain enough food to survive
• Avoid becoming food for something else
• May need territory or space to carry out other two roles

Question 5

feeding strategies

Answer 5

• Suspension feeding
• Deposit feeding
• Decomposers
• Herbivores / Algivores * Carnivores
• Parasites

Question 6

suspension feeding

Answer 6

• Capture, trap or filter food from a suspension
• Small particles (<1mm) are abundant in aquatic habitats
  
  • Bacteria
  • Phytoplankton
  • Zooplankton
  • Detritus
• Particles must be separated from water using passive or active means
• Requires a filter:
  
  • ciliary filters
  • setose filters
  • tube feet filters
  • mucus filters (“contact filters”)
• Filtration structures tend to be very delicate
• Some chemosensory ability has also been found
• These animals tend to be sedentary, or attached to surfaces (sessile) and only move when necessary
  →Low metabolic budget
  →Generally not particularly active
• Includes:
• Porifera
• many Cnidarians
• many Lophotrochozan phyla
• some arthropods
• some echinoderms

Question 7

systems of suspension feeding

Answer 7

• sponge choanocyte microvilli
• lophotrochozoa use cilia
• polychaetes may use cilia or mucus
• arthropods use setae and swimmerettes, or secreted structures
• non-vertebrate chordates use cilia
• some echinoderms use tube feet, cilia or mucus

Question 8

porifera choanocyte

Answer 8

• Sponge choanocyte microvilli
  
  • trapped particles are digested directly in the chanocyte or moved to amoeboid cells
  • digestion in a manner similar to phagocytosis
• create areas of high and low pressure with flagella
• draws water in and expels waste water out

Question 9

Ciliary filters

Answer 9

Bivalves, Lophophorata (and others) use cilia-based filters
* actual structure will differ
* many produce mucus to help food capture
* food sorting by the cilia, on the filter itself or elsewhere

Question 10

Ciliary filters, mollusca, bivalves

Answer 10

• Many are lamellibranchs
• respiratory structure, ctendia, enlarged to play a roll in food capture
• include all freshwater bivalves
• Lamellae have 1 row of cilia for moving water, 1 for moving food
• Food groove is ciliated to move food to the mouth
• Waste particles removed as pseudofeces, stored until release

Question 11

Lophophorates

Answer 11

• subset of lophotrochozoa
• have lophophore
• ring of ciliated tentacles used for food capture and gas exchange
• include Bryozoa, Brachiopoda, and Phoronids

Question 12

brachiopod

Answer 12

non-retractable lophophore

Question 13

bryozoan lopophore

Answer 13

• a ring of hollow tentacles surrounding the mouth
• anus is downstream so that waste is not refiltered
  
  • could damage if there are any large particles
• Tentacles covered in cilia and direct food to a central mouth
• Protecting the feeding structures is important
• Most will be able to retract the tentacles, and live in hard cases or burrows

Question 14

ciliary suspension feeding, sedentaria polychaetes

Answer 14

• sedentary polychaetes (members of the Sedentaria) – tube/burrow dwellers
• may use tentacles with cilia alone (radioles), or together with secreted mucus
• many live within burrows for protection
• Stiff, ciliated tentacles surround the mouth
• filter different sized particles
  
  • small (eating)
  • medium (building)
  • large (waste)

Question 15

arthropod suspension feeders

Answer 15

• No cilia!
• Use setae on their appendage to form a filter
• To make currents, they must make swimming movements
• Setose filters are much coarser than cilia
  →only filter larger particles

Question 16

setose filters

Answer 16

Arthropod filter feeders:
* Primarily Crustaceans
* numerous aquatic insect larvae filter feed in a similar way (i.e. mosquito larvae)

Question 17

Calanoida copepods

Answer 17

• Often dominate plankton populations (esp. marine)
• Important food source
• Setae on mouthparts (mandible, maxillae, maxilliped) create current to direct particles to mouth
• Setose swimming legs for swimming
• 1st antennae >1/2 body length

Question 18

Barnacles

Answer 18

• optimizes moving filter feeding depending on flow of water
• active when there is low flow of water
• passive when there is high flow of water
• Greatly reduced crustaceans
• Strictly marine
• Mostly sessile, with motile larval stages
• Cirri are setose thoracic appendages for collecting food

Question 19

tube feet filters, sea cucumber

Answer 19

• Modified tube feet secrete mucus on to tentacles
• Tentacles retrace and move food to mouth (no cilia involved)
• Non-specific feeding, often also involved with deposit feeding

Question 20

sedimentation interceptor

Answer 20

• Captures particles as they fall to sea floor
  
  • No ability to create water currents of their own
• Common among the Echinoderm filter feeders, especially Crinoids
• Tube feet and cilia move food to mouth

Question 21

mucus filters

Answer 21

• Secreted mucus traps particles on contact
• Often eat the filter; specialized digestive systems (i.e. lower pH) for digesting extra mucus
• May use cilia to create currents / not food capture
• Found in:
  
  • some sedentarian annelids
  • some echinoderms
  • few marine gastropods
  • Ascidiaceans (c; sea squirts, member of Tunicata)

Question 23

parchment worm

Answer 23

• Cilia moves mucus-net ball to mouth
• draw water in with modified parapodia; creates negative pressure at borrow opening
• mucus bag catches food
• once bag is full it is eaten
• larger gut to fit mucus
• excrete lots because they aren’t choosy of what they initially eat

Question 24

tunicate feeding

Answer 24

• ciliated slits called stigmata make up inner pharynx surface
• endostyle produces mucus net that covers the pharynx
• cilia move mucus net toward
  esophagus

Question 25

deposit feeders

Answer 25

• Detritivores, eating particles from sediment
• majority of invertebrates (terr. or aquat.) eat detritus or litter, but precisely what they ingest is unknown
• i.e. earthworm eating dead leaf includes bacteria, protozoa, algae, fungi, nematodes, mites…
• Detritus is nutrient-poor, so these associated communities may comprise most of the nutrients in diet
• Guts are elongated and largely unspecialized
• Specialized lobes, tentacles or proboscis may be present as mouthparts
• Generally, a simple mouth will feed on sediment
• Include:
  
  • Many Annelids
  • Holothurians (c; within Echinodermata)
  • some Hemichordates (p; within Deuterostomes)

Detritus is abundant, but…food is relatively nutrient poor, so…
* large amounts of sediment needs to be eaten (ecologically important for bioturbation)
* large amount of fecal waste produced
* these animals must constantly eat, and are generally sluggish
* growth rate & density «< than filter feeders

Question 26

bioturbation

Answer 26

Aquatic : freshwater
* bottom-dwelling fish
* worms (tubificid worms)
* inset larvae (chironomids) * crustaceans
* molluscs
Aquatic : marine
* sedentarian annelids * bivalves
* burrowing shrimp
* amphipods
Terrestrial
* tree roots
* earth worms
* burrowing mammals