Here are a few methods a scientist could use to determine the population density of barnacle species on the dock post: 1. Count the number of individual barnacles within a defined area on the post (e.g. within a 1 square foot quadrat) and extrapolate the total population based on the total surface area of the post. 2. Take photographs of defined areas on the post and count the barnacles visible in the photos back in the lab. Extrapolate totals as above. 3. Carefully scrape off all the barnacles from a defined area and count directly to determine density for that area. Extrapolate as above. 4. Use image analysis software to process high resolution photos of the post surface

1. Chapter 9
Phylum Arthropods
“joined appendages”

2. Characteristics of all Arthropods
• Hard exterior (exoskeleton)
• Joined appendages
• Highly evolved nervous systems
• Segmented body
• 2 main groups
– Chelicerates and mandibulates

3. Chelicerates
• Primitive Arthropods
• Characteristics
– 6 pairs of appendages
• 1 oral appendage
(chelicerae) used for feeding
– Lack actual mouth parts for
chewing so “suck up
predigested food”
– Cephalothorax-largest
– Abdomen –contains gills

4. • Representative species
– Horseshoe crabs and sea spiders
• Reproduction
– Sexual: separate sexes
• Sea spiders: males carry fertilized eggs ( only marine
invert to do this!!!!!)
• Horseshoe crabs: external fertilization; females lay
eggs in sand and when hatch carried to sea by high tide
• Digestion
– Horseshoe crab: scavengers; will eat anything
– Sea spiders: carnivores; feed on cnidarian juice!!

5. Mandibulates (Crustaceans)
• Characteristics
– Mandible: pair of appendages at anterior end
used for feeding
– 3 main body regions: head, thorax and abdomen
– 2 pairs of antennae
– Remaining appendages used for locomotion
– Molting: as animals grows, new exoskeleton is
formed and old one is shed
• The shell does not grow with the crustacean

6. Order Decopoda (“decopods”)
• Representative species
– Crabs, lobster, and shrimps
• Characteristics
– 5 pairs of walking legs
• 1st pair pincers for food and defense
• http://www.youtube.com/watch?v=flnMoSghUzs&feature=related&safety_mode=true&persist_safety_m
ode=1&safe=active

7. • Digestion
– Variety of feeding
habits(depend on species)
• Majority are predatory
scavengers
– Large inverts are prey for most
» Ex Alaskan king crab feed on
bivalves
» Hermit Crabs and shrimp-
scavengers feed on detritus
» Fiddler crabs-deposit filter
feeders
• Reproduction
– Separate sexes/internal
fertilization
• Males special appendage
modified for holding onto
female and depositing sperm.
• Eggs are incubated by female;
larvae stage when hatched

8. Crayfish Dissection!!!!!!

9. Get Ready for Dissection Marine
Sciencers!!!!!!!!

11. Order Euphausiacea
• Representative species
– Krill
• Characteristics
– Pelagic
– Shrimp-like (3-6 cm)
– Photospheres: Organ producing bioluminescent
• Used to attract mates; so what is reproduction?
– Can molt so quick that will “jump out of their shells!
• Digestion- filter feeders; eat zooplankton and
diatoms

12. • Ecological Role
– Main diet of certain marine mammals
• Keystone species of Antarctic food web
• Blue whales eat 40 million krill a day
– So why haven't krill gone extinct?
– http://www.youtube.com/watch?v=OPMQaP-
Yj1Y&safety_mode=true&persist_safety_mode=1
&safe=active

13. – Reproduction
• Sexual
– Separate sexes
– Some species internal fertilization/ others spawners
– Life cycle 6 months to 6 years
• Copepods
– Most abundant of zooplankton
– Suspension feeders
– Carnivorous
– Sexual reproduction

14. Class Cirripedia
“barnacles”
• Characteristics
– Only sessile crustaceans
– Shell of calcium carbonate
• Digestion
• Filter feeders: use appendage “cirriped”
• Reproduction
– Hermaphrodites: cross fertilize
– Larvae move until finds a substrate and
metamorphoses into adult-> remain sessile

16. Ecological Roles of Arthropods
• Essential links in food chains
• Nutrient recycling
• Food sources for humans
and many other animals
• Symbiotic relationships
– Some can remove parasites –
cleaner shrimp
• Some have become invasive
when introduced

17. Compete for space
* as a scientist, how would you determine population density of the barnacle
species on this dock post?