1. Red = algae
Blue = indigestible particles
Bivalves are particle selective (on gills in case of oyster Crassostrea gigas); right shows ciliated tract where particles accepted, left shows ones that are rejected.
Ward et al. 1997, Nature 390:

2. Suspension Feeders Sea squirt Styela montereyensis
Passive suspension feeding mechanism,
combined with active ciliary pump

3. Passive Suspension Feeders - Issues
Orientation in current
Current velocity - pressure drag
Particle concentration - saturation of feeding structure (e.g., polyp processing)

4. Recap - Deposit Feeders and Suspension Feeders
Deposit Feeders - process particles on bottom
Particles range from inorganic (e.g., sand grains) to organic
Organic range from indigestible (cellulose) to very digestible (living digestible bacteria, microalgae)
Quantity important (e.g., bacteria not sufficient as food for most larger deposit feeders)
Selectivity important, digestive strategies important (type of digestion, throughput), recycling of microalgae and external supply of particles important (e.g., deposition after spring phytoplankton bloom to bottom, deposition of seaweed detritus)

5. Recap continued
Suspension feeders - gather particles either passively (protrude structure into current) or actively(suck water into siphon)
Suspension feeders have access different particle qualities - clay, non-living organic matter, microalgae of varying quality (some poisonous some indigestible)
Gathering of particles important, but selectivity also important
Digestive strategies and throughput also important issues
Flow very important - causes change in form

6. Carnivores Polychaete Oystercatcher Bivalve Cuspidaria Glycera
Gastropod Nucella
Crab Callinectes sapidus

7. Carnivore Issues Low population size, movement to patches of prey
Capture of prey
Physiological limitations (depth of swimming, sensory biology, intertidal zone)
Feeding, while avoiding predation by other species

9. Conus, over 500 spp. mainly in coral reefs
Poison: cysteine-rich peptides - attack ion channels, each species has many different peptides

10. Conus geographus Conus striatus

11. C. striatus
C. geographus

12. Diversity of poisonous peptides arise with evolution of multiple gene families, result from gene duplications and later divergence of toxic function

13. Herbivores Polychaete Nereis vexillosa Parrot fish radula Urchins
Chiton

14. Herbivore Issues Ability to mechanically attack plants
Chemical defense of plants
Feeding, while avoiding predation by other species

15. Cellulose Feeder
Obtains nitrogen with symbiotic nitrogen fixing bacteria

16. The End