Transcript ENVI 21 Life in the Ocean - University of San Diego Home Pages

I.
Mollusca
B.
Bivalvia
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Laterally compressed
Two-valved shell
No head
No radula
Some have muscular foot for burrowing (How?)
Gills used for suspension feeding (active) & respiration
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Water enters and leaves through siphons
Some anchor to substrate with byssal threads
Largest mollusk (giant clam)
Shipworms (boring – use shells as rasps)
Common fouling organisms
Oysters – Produce pearls
Scallops – Swim!
I.
Mollusca
B.
Bivalvia
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•
•
•
•
•
Laterally compressed
Two-valved shell
No head
No radula
Some have muscular foot for burrowing (How?)
Gills used for suspension feeding (active) & respiration
•
•
•
•
•
•
•
Water enters and leaves through siphons
Some anchor to substrate with byssal threads
Largest mollusk (giant clam)
Shipworms (boring – use shells as rasps)
Common fouling organisms
Oysters – Produce pearls
Scallops – Blue eyes, Swim!
I.
Mollusca
C.
Cephalopoda
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Octopuses – Eight arms, no shell; Cryptic
Squids – Shell reduced to pen made of chitin
Cuttlefishes – Carbonate shell
Nautilus – Shell with chambers
Highly mobile predators
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Large eyes
Complex nervous system
Closed circulatory system**
Shell reduced or absent (Why?)
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Type of shell affects prey selection
Foot modified as arms and tentacles bearing suckers
Siphon – Directs water released from mantle cavity
Ink sac for defense
Fig. 7.24
I.
Mollusca
D.
Polyplacophora (Chitons)
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Mostly graze algae on rocky shorelines
Occupy home scar when not foraging
Scaphopoda (Tooth shells)
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Predators on foraminifera and juvenile bivalves
Most common in deep water
Monoplacophora
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Rediscovered in 1952
Some repeated organs (segmentation?)
Possible indication of relationship to Annelida
II. Arthropoda
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Most species of any phylum (1 million+)
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Ubiquitous
Segmented, bilaterally symmetrical body
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Jointed appendages
Exoskeleton made of chitin
Growth requires molting
Crustacea (subphylum)
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Contains majority of marine arthropod species
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150,000+ described species
Exoskeleton often hardened with CaCO3
Gills + two pairs of antennae (sensory)
II. Arthropoda
A.
Copepoda (Copepods)
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Extremely abundant and important plankton
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Among most abundant animals on earth
Benthic forms also important
Important primary consumers of phytoplankton
Some parasitic forms
Fig. 7.28
Herbivorous vs. Predatory Copepod
Fig. 15.7