Transcript Mar 7 - University of San Diego

Arenicola
I.
Annelida
A.
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Polychaeta
Larva = Trochophore
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Band of cilia around body; tuft on apex
Same larval stage in Mollusca
Fig. 9-25
Diverse lifestyles
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Errant vs. Sedentary
Errant: Free-living predators
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Deposit feeders
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Nonselective
Selective
Suspension feeders
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Often well-developed eyes and sense organs, jaws
Active
Passive
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Solitary
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Colonial
Reproduction
Fig. 9-25
Amphitrite
Arenicola marina
Fig. 13-23
I.
Annelida
A.
•
Polychaeta
Larva = Trochophore
•
•
•
Band of cilia around body; tuft on apex
Same larval stage in Mollusca
Diverse lifestyles
•
•
Errant vs. Sedentary
Errant: Free-living predators
•
•
Deposit feeders
•
•
•
Nonselective
Selective
Suspension feeders
•
•
•
Often well-developed eyes and sense organs, jaws
Active
Passive
•
Solitary
•
Colonial
Reproduction
Phragmatopoma
californica
Chaetopterus
I.
Annelida
A.
•
Polychaeta
Larva = Trochophore
•
•
•
Band of cilia around body; tuft on apex
Same larval stage in Mollusca
Diverse lifestyles
•
•
Errant vs. Sedentary
Errant: Free-living predators
•
•
Deposit feeders
•
•
•
Nonselective
Selective
Suspension feeders
•
•
•
Often well-developed eyes and sense organs, jaws
Active
Passive
•
Solitary
•
Colonial
Reproduction
Nereis succinea
Wikipedia
Epitoky
Fig. 9-27
I.
Annelida
B.
Sipuncula (class)
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Peanut worms
Exclusively marine (250+ species)
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Most common in shallow water
Unsegmented bodies up to 35 cm long
Studded introvert used for locomotion
Cryptic
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Burrow in sediments or hide in shelters
Deposit or suspension feeders
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Consume detritus and microbes
Dioecious
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External fertilization
Sipunculus nudus
glaucus.org.uk
I.
Annelida
C.
Echiura (class)
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Exclusively marine (~150 species)
Deposit feeders
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Non-retractable proboscis
Live in U-shaped or L-shaped burrows
Typically small; may get large in deep sea
Dioecious broadcast spawners
I.
Annelida
D.
Pogonophora (class)
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Beard worms
Long, thin worms (~135 species)
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Most common in deep sea
No mouth or gut
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Not parasitic
Anterior tuft of up to several thousand tentacles
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Tentacles absorb dissolved nutrients
Symbiotic bacteria in trophosome utilize nutrients to
manufacture food
Vestimentifera
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Large deep-sea animals
Found at many hydrothermal vents
tolweb.org
II.
Nematoda
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Free living and parasitic forms
Cosmopolitan/Ubiquitous
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Mostly in sediments (free living) or hosts (parasitic)
Common in fine muds
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Organic rich areas
Described species: 28,000+ (>55% parasitic)
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May be up to 500,000 species total!
Extremely abundant!!
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Up to hundreds of individuals per ml of sediment
90,000 in one rotting apple (not marine)
Hydrostatic skeleton
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Longitudinal muscles only
Move by whipping back and forth
III. Benthos – Soft Bottom
A.
Species Composition
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1.
Animals often categorized by size and location
Location: epifauna vs. infauna
Megafauna
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No standard definition
Some infaunal macrofauna would be considered
megafauna if exposed
Nearly absent from sandy beaches
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High energy environment
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Pressure from terrestrial predators
Conspicuous but less important ecologically than
smaller, more abundant organisms
More important in low energy environments
Benthos – Soft Bottom
III.
A.
Species Composition
2.
Macrofauna
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Large enough to be retained on 0.5 mm sieve
Low diversity on beaches compared to less dynamic areas
In terms of biomass, most important taxa are
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Burrowing bivalves
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Polychaetes
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Crustaceans
All these taxa are:
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Mechanically resistant to sediment movement
(bivalves)
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Highly mobile (polychaetes)
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Both (crustaceans)
Typically display zonation on shorelines
Fig. 14-10
Fig. 13-31
Benthos – Soft Bottom
III.
A.
Species Composition
3.
Meiofauna
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Pass through 0.5 mm sieve but large enough to be
retained on 62 μm sieve
Sometimes termed interstitial fauna: live in spaces
between sand grains
Very diverse group vs. others inhabiting sand beaches
Many individuals move among sediment grains but may or
may not displace them in bulk like burrowing macrofauna
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Endobenthic: larger than interstitial spaces, displace
particles while moving
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Mesobenthic: move within interstitial spaces, do not
displace particles while moving
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Most meiofauna mesobenthic in medium to coarse
sediments, endobenthic in very fine sediments
Fig. 13-29
Loricifera
III. Benthos – Soft Bottom
A.
Kinorhyncha
Species Composition
3.
Meiofauna
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Many taxa represented: Mollusks, crustaceans,
worms from several phyla, etc.
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Some groups entirely or almost entirely
meiofaunal (Ex: kinorhynchs, gastrotrichs,
loriciferans)
Nematoda
Gastrotricha
Benthos – Soft Bottom
III.
A.
Species Composition
3.
Meiofauna
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a.
b.
c.
d.
e.
Body trends in meiofauna include
Reduced body size
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Especially striking in groups whose members typically are
large (e.g. Mollusca, Echinodermata)
Vermiform or flattened shape
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Flexibility and maneuverability
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Flattened shape  Increased surface area for DOM uptake
Strengthened body design
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Protects against abrasion and crushing
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Adaptations may include protective spines or scales
(gastrotrichs), well-developed cuticle or exoskeleton
(nematodes, crustaceans), internal skeleton of calcareous
spicules (ciliates, sea slugs)
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Many soft-bodied animals can contract strongly to protect
against mechanical damage
Adhesive and gripping structures
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Adhesive glands, hooks, suckers, claws
Statocysts
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Sensory organs that detect gravity and help animals to orient
correctly within sediments
Benthos – Soft Bottom
III.
A.
Species Composition
3.
Meiofauna
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a.
b.
c.
Most are:
Deposit feeders (gastrotrichs, nematodes)
Predators (hydroids, flatworms)
Microherbivores (scraping diatoms or algae off sand grains;
ostracods, harpacticoid copepods)
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Some suspension feeding species, primarily sedentary animals
like bryozoans and tunicates
Reproduction
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Most have low fecundities, due primarily to small body size
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Many species produce only 1-10 eggs at a time
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98% of meiofaunal species lack pelagic larvae
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Young are brooded or eggs may be attached to sand grains;
young hatch as benthic juveniles
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No pelagic dispersal phase; dispersal through entrainment in
water currents, attachment to feet of mobile organisms (e.g.
seabirds)
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