Transcript Mar 14 - University of San Diego

I.
Mollusca
C.
Cephalopoda
1.
Nautiloids
a.
2.
Nautilus – Shell with chambers
Coleoids
a.
b.
c.
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Octopuses – Eight arms, no shell; Cryptic
Squids – Shell reduced to pen made of chitin
Cuttlefishes – Carbonate shell
Siphon – Directs water released from mantle cavity
Highly mobile predators
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Streamlined body (coleoids)
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
Fig. 9-15
Fig. 9-16
I.
Mollusca
C.
Cephalopoda
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Ink sac for defense
Chromatophores,
iridophores:
Facilitate color
change video
Fig. 9-17
Fig. 9-18
I.
Mollusca
C.
Cephalopoda
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Squid eggs
Reproduction: Dioecious; internal fertilization
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Courtship behavior common
Male transfers spermatophore to female
Females sometimes guard benthic eggs
Often semelparous
I.
Mollusca
C.
Cephalopoda
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Most massive
invertebrates
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Giant squid
(Architeuthis)
may be >15 m
long!!
I.
Mollusca
D.
Polyplacophora (Chitons)
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E.
Mostly graze algae on rocky shorelines
Occupy home scar when not foraging
Scaphopoda (Tooth shells)
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F.
Predators on foraminifera and juvenile bivalves
Most common in deep water
Monoplacophora
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Rediscovered in 1952
Some repeated organs (pre-segmentation?)
Possible indication of relationship to Annelida
Fig. 9-6
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
Chelicerata (subphylum)
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.
Chelicerata
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1.
Terrestrial: spiders, ticks, mites, scorpions
Marine: horseshoe crabs, sea spiders
Merostomata (Horseshoe crabs) (class)
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Not true crabs
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Five living species
Distinctive, horseshoe-shaped carapace
Benthic predators/scavengers on clams and small
invertebrates
No jaws – Grind food with bristles on walking legs
(must be walking to “chew”)
Reproduce on beaches at high tide; eggs buried
Fig. 9-31
II.
Arthropoda
A.
Chelicerata
2.
Pycnogonida (sea spiders) (class)
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Superficially resemble spiders
Mouth at end of large proboscis (unusual)
Carnivores
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Feed on sea anemones, hydrozoans, other soft
inverts
No respiratory or excretory systems
Digestive system extends into legs
Males carry eggs (very unusual for marine inverts)
Fig. 9-32
II.
Arthropoda
B.
Crustacea
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Mandibulates (paired mandibles)
Body regions: head, thorax, abdomen
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Head and thorax may be fused (cephalothorax)
Two pairs of sensory antennae
Other appendages differ between groups
Crustacean Anatomy
Fig. 9-33
Molting
Fig. 9-34
II.
Arthropoda
B.
Crustacea
1.
Decapoda (order)
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Crabs, true shrimp, lobsters
Most species in Crustacea (~10,000)
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Scavengers/Predators/Both
Five pairs of walking legs
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First pair usually modified as claws for feeding/defense
Well-developed carapace = cephalothorax
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Rest of body = abdomen
Lobsters, shrimp – Usually laterally compressed
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Tail/Abdomen behind thorax
Crabs – Usually dorsoventrally compressed
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Tail/Abdomen curled underneath thorax
Largest crustaceans
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Lobster > 42 lbs
Crab > 13 feet “tall”
II.
Arthropoda
B.
Crustacea
1.
Decapoda (order)
•
•
Crabs, true shrimp, lobsters
Most species in Crustacea (~10,000)
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Scavengers/Predators/Both
Five pairs of walking legs
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First pair usually modified as claws for feeding/defense
Well-developed carapace = cephalothorax
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Rest of body = abdomen
Lobsters, shrimp – Usually laterally compressed
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Tail/Abdomen behind thorax
Crabs – Usually dorsoventrally compressed
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Tail/Abdomen curled underneath thorax
Largest crustaceans
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Lobster > 42 lbs
Crab > 13 feet “tall”