Kingdom Animalia – Phylum Mullusca. Phylum Mullusca – snails, slugs, clams, oysters, squids, octopus, etc. (> 50,000 species – maybe up to 100,000??) General characteristics:. Bilaterally symmetrical (or secondarily asymmetrical), coelomate. Well developed organ systems.
Phylum Mullusca – snails, slugs, clams, oysters, squids, octopus, etc. (> 50,000 species – maybe up to 100,000??)
Bilaterally symmetrical (or secondarily asymmetrical), coelomate
Well developed organ systems
Have mantle with shell glands that secrete calcareous epidermal spicules,
shell plates, or shells
Have large, well defined muscular foot, often with a flattened creeping sole,
(in squids and octopus, the foot is modified into tentacles / arms.
Generalized mulluscan body:
Gastropods – slugs, snails, and nudibranchs
Not all gastropods have shell (blue). There is a high level of variation amongst different
shells; why do you think this is? How do you think nudibranchs that do not have any
Shells defend themselves?
Most gastropods have a large, fleshy foot which is used for locomoation (green)
Most gastropods have a unique file-like mouth part called the radula (orange).
Herbivorous forms use it for grazing, carnivorous forms have modified it into a drill, or
a harpoon that can inject toxins into their prey.
Most gastropods have gills for gas exchange.
What do you think is the function
of this shell?
How do you think this animal
Chitons also have a large foot (green) that
is used for locomotion and clamping down
on rocks; gills (yellow) for gas exchange;
a shell made up of 7 or 8 individual plates
(blue); and a radula (orange) specialized
for grazing on algae and some encrusting
What do you think is the advantage
of having multiple (7 or 8) shell plates?
Bivalves have two shells, hinged along
One edge, with the animal in between (blue).
Most bivalves use their gills (yellow) for both
gas exchange, as well as for food capture. How
do you think this may work?
The foot (green) of some bivalves is reduced,
While in others, it is specialized for digging.
Here is a picture of a clam.
Bivalves also include mussels, oysters,
Cephalopods – octopus, squids, nautilus, and cuttlefish
Cephalopods have generally modified their
foot (green) into tentacles (arms) that allow them
to manipulate potential prey items, as well as to
move around their environments
Their shells (blue) can be complete and external
(nautilus), reduced and internal (squid), or completely
non-existent (octopus). What is the advantage of each?
Most cephalopods use gills (yellow) for gas exchange,
and have a specialized beak (orange) for tearing
Finally, most cephalopods use jet propulsion
for movement and swimming…
Phylum Ehinodermata (spiny skin) – sea stars, brittle stars, sea cucumbers, sea urchins, sand dollars, etc. (~8,000 - 10,000 species)
All echinoderms are marine
All echinoderm adults have basic pentamerous radial symmetry derived from
bilaterally symmetrical larvae
Nervous system diffuse, decentralized, usually of a nerve net, nerve ring, and
Have separate sexes, although hermaphroditic species do exist
Have a water vascular system composed of a series of fluid-filled canals,
usually evident externally as muscular podia
The water vascular system:
The sea star grabs on to the mussel, pulls on the shell until there is an opening,
then ejects its stomach into the mussel for digestion and absorption of the food.
Echinoderm diversity – Asteroids (sea stars):
Ecologically very important carnivores.
Have ability to regenerate arms.
A lot more active than you may think…
Echinoderm diversity – Ophiroids (brittle stars):
Very delicate, these brittle stars
will readily lose their arms in order
To avoid predation.
There are carnivore, planktivore,
and herbivore forms…
Echinoderm diversity – Holotheroids (sea cucumbers):
Mostly detritavores, these animals
defend themselves by toxins in their
skin, but also by evisceration… how
do you think that works?
Echinoderm diversity – Echinoids (sea urchins and sand dollars):
These animals can be herbivores, carnivores,
They are very common, and in some places,
can play a major ecological role:
e.g. off the coast of California,
consider the relationship between
sea urchins, sea otters, and kelp…
Phylum Trdigrada (water bears)
~ 400 – 500 species
Free living or symbiotic, they are
found all over…
Tardigrades are known for their
Anabiosis – state of greatly recuced
metabolic activity during
unfavorable conditions; and
Cryptobiosis – an extreme state of
anabiosis or dormancy where
all external sings of metabolic
activity are missing!!
How tough are they?
check it out…
Tartigrades have recovered from immersion in extremely toxic compounds such as
brine, ether, absolute alcohol, and even liquid helium!!
They have survived temperature ranging from +149 C to –272 C (almost at absolute zero!!)
They have also survived high vacuums, intense ionizing radiation, and long periods with no
Former Soviet zoologists claim that tardigrades survived experiments in outer space!!
In one case, a 120 year old dried moss specimen from a museum was accidentally moistened,
yielding living tardigrades!!! ….. You get the picture….
Major Characteristics found in all chordates:
1. Notochord – a stiff but flexible rod along the length of the body
2. Dorsal hollow nerve chord – neural structure that develops into the
brain and and central nervous system
3. Pharyngeal gill slits – openings or grooves found on the cavity behind the mouth
(found in all chordates at least at some stage of their life cycle)
4. Post-anal tail
Chordates include two invertebrate groups including lancelets and tunicates, and one
vertebrate group that is further subdivided into different groups of fish,
amphibians, reptiles, birds, and mammals.
You are responsible for all the text material on chordates – p434 to p445.