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Marine Biology Lecture 3
April 9, 2007
I.
Sponges (briefly)
A.
B.
II.
Basic sponge knowledge
1.
Focus: feeding and the choanocyte
2.
How sponges protect themselves
Local sponges
1.
Haliclona sp.
Phylum Cnidaria
A.
Overall body organization
1.
polyps and medusae
2.
cell layers (epidermis, gastrodermis)
3.
gastrovascular cavity
4.
tentacles
5.
cnidocytes/nematocysts: how do these work?
B.
Cnidarian life histories (brief)
1.
Alternation of generation
2.
Sexual reproduction in anemones
3.
Asexual reproduction in anemones
Local intertidal species (Phylum Cnidaria, Class Anthozoa)
C.
Aggregating anemone: Anthopleura elegantissima
1.
Appearance
a)
Column is green with prominent, branched tubercles
b)
Tentacle tips are pink or purple (but white without symbiont)
c)
Have prominent tubercles (bumps) on column with branched
extensions

Tubercles serve as attachment points for small rocks and shell
bits that help protect them from desiccation
d)
Often occur in groups; recognizable by the bits of shells and rocks
stuck to them
e)
Generally smaller than the “large green anemone” (see below), which
is similar.
2.
Location
a)
Higher in the middle intertidal; often covering a lot of the surface area
on the tops and sides of rocks
3.
Interesting details of life-history
a)
Protist symbiont (“zooxanthellae”) in those exposed to light

within gastrodermis

b)
c)
d)
If the symbiont is present, Anthopleura spp. will move
towards light.

Key question: What does each member of this mutualistic
relationship give to the other?
Higher on rocks, more exposed than A. xanthogrammica

Why are they better able to resist desiccation?
primarily reproduce by fission; also reproduce sexually
clonal boundaries

clone wars , lead to "gap" between clones
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

D.
Fight by using acrorhagi (what are these?)
can sometimes see coloration or other clonal differences.
4.
Common
Large, green anemone: Anthopleura xanthogrammica
1.
Appearance
a)
large, and green (but white without symbiont)
b)
tubercles are less pronounced and fewer attached debris than for A.
elegantissima.
2.
Location
a)
pools and beneath overhangs; common in middle intertidal

E.
F.
Less resistant to desiccation than A. elegantissima
3.
Interesting details of life-history
a)
Protist symbiont (see A. elegantissima for details)
b)
Feed on detached inverts and small fish
c)
Not aggressive towards each other
d)
Reproduce sexually, exist singly (not as clones)
4.
Common
Burrowing anemone, Anthopleura artemisia
1.
Appearance
a)
all-pink or orange tentacles, bright!
b)
Does have protist symbiont (not obvious from appearance), but only
associated with tentacles (not column)
2.
Location
a)
sand or sand/rock, column burrows down up to 5x its diameter.
Generally don't see the column
b)
Mid-intertidal.
3.
Interesting details of life-history
a)
Reproduce both sexually and by cloning, but move apart and exist
solitary after cloning.
4.
Less common than the other two Anthopleura species, but can be locally
common in some sandy areas.
Proliferating anemone, Epiactis prolifera
1.
Appearance
a)
brownish with white, radiating lines
b)
short and squat
c)
very small (usually 1-2 cm)
2.
Location
a)
Attached to algae
b)
Beneath rocks
c)
Mid to low intertidal
3.
Interesting aspects of life-history
a)
juveniles "brooded" on column of adult (move out of gastrovascular
cavity and attach)

as many as 30 juveniles "brooded" at once.

leave at around 4 mm (3 months) but may stay nearby.
b)
younger adults are functional females, older adults are simultaneous
hermaphrodites.
4.
Reasonably common but not always easy to find; well-hidden; sometimes
look like amorphous brown blobs.
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III. Phylum Platyhelminthes: flatworms
A.
B.
C.
General appearance
Feeding behavior: structure/function of pharynx
Movement
IV. Phylum Nematoda
A.
B.
C.
D.
V.
General appearance
Feeding behavior: structure/function of expanding pharynx
Movement
1.
Longitudinal muscles only
2.
The nematode swim!
Just how common are they?
Phylum Nemertea: ribbon worms
A.
B.
C.
General appearance
Feeding behavior
1.
Major predator on smaller animals of the intertidal
2.
Key structure: eversible proboscis
a)
Description of structure and how it works. Know!
Movement
VI. Phylum Annelida: segmented worms
A.
B.
Focus: Class Polychaeta (the marine segmented worms)
1.
Major features
Examples of intertidal polychaetes (habitat, feeding, respiration, and other
aspects)
1.
Free-crawling predators (Nereis, Glycera)
a)
Habitat
b)
Feeding

sensory structures

eversible proboscis
c)
Respiration
2.
Tube worms with tentacular crowns (Sabellidae, Serpulidae)
a)
Habitat
b)
Feeding/tube building

Structure of tentacular crown and how it works

pinnules

food groove and sorting
c)
Respiration
3.
Deposit feeders (Family Terrebellidae)
a)
Habitat
b)
Feeding: structures and behavior

Note different mechanisms of bringing food to mouth
c)
Respiration

Gas exchange over the surface of the tentacles

Some species with separate, blood-filled gills
4.
Chaetopterus: tube-dwelling, mucous-bag feeder
a)
Habitat
b)
Feeding

Mucous bag
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

Water current. How created (name structures)
Role of ciliated cup and ciliated groove
Regeneration: The magic of segment 14
C.
c)
Reproduction
1.
Most polychaetes just shed eggs and sperm, but some species are more
elaborate
2.
Epitokes (Nereidae and others)
a)
Formation
b)
Appearance
c)
Behavior
d)
Adaptive value
3.
Trocophore larvae
VII. Phylum Sipuncula
A.
Key feature
1.
introvert
a)
tentacles at end for deposit feeding (mucus covered)
b)
turns completely inside-out, except for tentacles at the end.
c)
nuchal organs: chemosensory
d)
Control of introvert and tentacles

hydrostatic pressure of coelom (via body musculature) everts
the introvert; it is withdrawn by retractor muscles

hydrostatic pressure of compensatory sacs everts the tentacles
themselves.
2.
Gas exchange over body surface (main part and introvert), tentacles.
3.
Reproduction: gametes spawned into the ocean
Study Questions
1.
How does a sponge move water through itself? How does it feed?
2.
Describe several ways that sponges protect themselves.
3.
What type of organism do you often find associated with sponges? Is their relationship
commensal, parasitic, mutualistic, or predator-prey?
4.
What are the two body forms of Cnidarians?
5.
What are two key functions of the gastrovascular cavity in cnidarians?
6.
Describe the structure of a cnidocyte and how the nematocyst "fires." Also describe two ways
the nematocyst inflicts pain.
7.
Describe what is meant by alternation of generations in Cnidarians. What are some advantages
of alternation of generations? Do all Cnidarians exhibit alternation of generations?
8.
What are the physical differences among Anthopleura elegantissima, Anthopleura
xanthogrammica, and Anthopleura artemisia that you can use to tell them apart? What other
key differences do they have (location, reproduction, substrate, etc…)? What are
zooxanthellae and which species have zooxanthellae? What do the zooxanthellae provide to
Page 4 of 5
the Anthopleura spp., and what do the Anthopleura species provide the symbionts? Is this a
mutualistic relationship?
9.
Describe the unique life-history adaptation exhibited by Epiactis prolifera.
10.
Phylum Platyhelminthes
a.
Where might you find Platyhelminthes in the marine environment?
b.
Describe how members of Phylum Platyhelminthes feed. What do they eat?
c.
Describe how members of Phylum Platyhelminthes move.
11.
Phylum Nemertea
a.
Where might you find Nemerteans in the marine environment?
b.
At what time of day are you likely to find them actively feeding?
c.
Describe how members of Phylum Nemertea feed, being sure to indicate several special
adaptations they have to subdue their prey (i.e. don’t just tell me they have an eversible
proboscis. You should describe several features of that proboscis.)
d.
Describe how members of Phylum Nemertea move.
12.
Phylum Nematoda
a.
How do nematodes feed, and on what?
b.
In which direction are the muscles of Nematodes oriented, and how are they able to do
the “nematode swim?” Why can’t they move via peristalsis like the annelids?
c.
Where are nematodes found?
13.
What key features distinguish Polychaetes from other members of Phylum Annelida?
14.
For each of the intertidal polychaetes introduced in lecture, describe feeding to the level
presented in lecture. The key is to name key structures and explain how they work. You may
wish to include diagrams in your explanation.
15.
For each of the intertidal polychaetes introduced in lecture, describe the major locations of gas
exchange.
16.
What is an epitoke? Describe the formation, appearance, behavior and adaptive value of
epitokes.
17.
What type of larvae do most marine polychaetes have?
18.
How well can polychaetes regenerate? Provide an extreme example…
19.
Name and describe the feeding structure of the Sipuncula, including how it extends the
introvert in general, as well as the tentacles in particular (separate mechanisms.) What mode of
feeding does it use?
20.
What is meant by an “eversible” structure? You should be able to name several eversible
structures and describe how they work.
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