Mollusks

Front 1

adaptive radiation

Back 1

the evolution of many new species from a common ancestor...happens because new niches open up.
(as in molluscs...very diverse;some 50K extant, some 35K extinct, & and about 5% of all animals)

Front 2

extant

Back 2

opposite of extinct...now living

Front 3

symmetry in molluscs?

Body type?

Back 3

bilaterally symmetrical, except gastropods (snails) because of internal twisting.
*primitive snail is bilaterally symmetrical
Body type- they are unsegmented- no metamerism
(repeated parts)

Front 4

secondarily derived

Back 4

after that phylum evolved a mutation occurred and became a staple of that group
(like asymmetry in snails)

Front 5

mollusks: what kind of coelom?

Back 5

eucoelom...like all the rest of the phyla we will study her on out (up the tree)

Front 6

3 features found in all mollusks?

Back 6

-muscular foot- for crawling, burrowing, grasping
-visceral mass- containing internal organs
-mantle- secretes the calcium carbonate shell

Front 7

what has the modifications has the mantle undergone in some mollusks?

Back 7

has been modified into gills, lungs, siphons, apertures, etc. in some mollusks

Front 8

Which mollusk developed the first "jaws"?

Back 8

nautilus

Nautilus also takes air and water into tube in shell to regulate and maintain buoyancy...remember video

Front 9

Mollusks: dioecious or monoecious?

Back 9

most are dioecious, with the exception of the garden snail which is monoecious.

Front 10

What kind of development is found in mollusks? (direct/indirect)

Back 10

BOTH.
Cephalopods, gastropods and a few other mollusks have direct development, but all remaining mollusks have indirect development (trocophore larva)

Front 11

Trocophore larva

Back 11

planktonic larva that emerges from mollusk egg.(also found in polychaetes (seg. worms) and marine turbilarians(flat worms))
-HOMOLOGY- branched off in larval stage, so ancestor of the group is the LARVA

Front 12

mollusk nervous system?

Back 12

-several pairs of ganglia (ceregral, pedal, visceral)
*we saw these (3 little balls) on the squid dissection.
-simpler than in the annelids & arthropod, with the exception of the octopus and squid which is the most advanced of any invertebrate

Front 13

Cephalization in mollusks?

Back 13

-well developed in cephalopods and gastropods (predators)
-most others are grazers, scavengers or filter feeders with little need for external cephalization.

Front 14

Excretory system in mollusks?

Back 14

well developed with 2 nephridia ("kidneys")

Front 15

circulatory system of mollusks?

Back 15

-OPEN system with pumping heart, blood vessels and blood sinuses whereby blood floods and is exchanged and returned to heart
-BUT, Cephalopods have a closed system of arteries capillaries and veins and 3 hearts. (like the squid's true heart and gill hearts we saw in lab)

Front 16

mollusk respiratory system?

Back 16

most have GILLS, derived from the mantle tissue to increase the efficiency of gas exchange
-bivalves (clams, mussels) have incurrent and excurrent siphons

Front 17

Biggest class in mollusks?

Back 17

gastropods 40,000 living species
then bivalves and polyplacophora

Front 18

What class is the most primitive mollusk?

Back 18

Monoplacophora
- found on the ocean bottom, and thought of as extinct until the 1950's.
-exhibit pseudometamerism- segmented gills NOT derived from segmentation

Front 19

Polyplacophora

Back 19

Characterized by 8 dorsal plates.
found in inter-tidal zone grazing on algae.
*Chitons are an example of polyplacophora. (share habitat with barnacles.)

Front 20

What mollusk is commonly referred to as "tooth shells" or "tusk shells"?

Back 20

Scaphopoda
(look like a long tooth, with animal sticking out of "root")

Front 21

What economically important mollusks are highly adapted for burrowing and filter feeding?

Back 21

Bivalvia
(2 shells- clams, oysters, etc.)

Front 22

General characteristics of bivalves?

Back 22

-restricted to aquatic environments
- higher diversity of them in marine ecosystems, but many live in freshwater

Front 23

Smallest and largest bivalves?

Back 23

-seed clam (looks like a pebble)
-giant clam (shell can achieve weight of 500 lbs)

Front 24

Anatomy of bilvalve

Back 24

2 shells connected by HINGE LIGAMENT dorsally
-shell grows outward in rings from the UMBO (can count rings like on a tree to determine age)
-foot is anterior (pulls animal forward)
-siphons are posterior
-ADDUCTOR muscles pulls shell together

Front 25

Oldest clam found?

Back 25

400 years old.
-rings indicative of climate conditions throughout history

Front 26

Adductor muscles?

Back 26

relax and contract to pull bivalve shells together/apart

Front 27

bivalve respiration

Back 27

-gills and all viscera suspended from dorsal interior surface of mantle cavity
- posterior incurrent and excurrent siphons create respiratory water flow

Front 28

Digestive anatomy of bivalves?

Back 28

-GILLS used for filter feeding
(mucus on gills traps food particles)

Front 29

freshwater Bivalve reproduction?

Back 29

-freshwater bivalve eggs are fertilized in SUPRABRANCHIAL CHAMBER above gills and develop in to GLOCHIDIA LARVA that parasitizes a particular species of fish.

Front 30

Glochidia larva

Back 30

released from freshwater bivalve onto fish.
we saw this in a video where bivalve creates a lure and spews glochidia out to attach to fish gills.
(These don't harm the host.)

Front 31

Reasons that freshwater bilvalves are the most endangered animals in the US?

Back 31

-dams & locks prevent fish migartion, so some host fish aren't present for reproductive glochidia.
-siltation & other water pollution foul thier filter feeding apparatus
-overwhelmed by invasive mussels which eat all the food.
-142 out of 300 native species are either extinct, endangered or soon to be listed as endangered.

Front 32

marine bivalve reproduction?

Back 32

-fertilization is external
-there are 2 stages in marine bivalve fertilization (trochophore and veliger) diagram on p.197 of manual

Front 33

What industry almost wiped out clam species along the Mississippi?

Back 33

the button industry.

Front 34

most common invasive bivalve in our region....

Back 34

Zebra mussel- Dreissena polymorpha
and
Asian clam- Corbicula fluminea
-mussels attach to boats,nets, docks, swim platforms, boat lifts, etc and can be transported on them (Zebra mussels can be microscopic veligers when they attach to the substrate & they are the ONLY freshwater mussel that attaches to objects)
*Prevention: Report visible zebra mussels and clean boats.

Front 35

What kind of symbiotic relationship is found in certain bivalves?

Back 35

the mantle tissue of some clams, such as the giant clam, contains photosynthetic zooxanthanella that provide much of the clam's nutrients!

Front 36

Formation of a pearl

Back 36

sand particle gets stuck between mantle and shell and the animal secretes NACRE (calcium carbonate in minute crystalline form) in concentric layers to reduce irritation.

*To make round man-made pearls, a round irritant is placed in between the shell and mantle.

Front 37

Gastropoda

Back 37

means "stomach foot"

Front 38

largest molluscan class?
how many species?

Back 38

gastropoda (snails, slugs, whelks, nudibranchs, etc)
40K species!

Front 39

What process in gastropods is responsible for moving the mantle cavity from the front to the back of the body?

Back 39

TORSION

Front 40

Torsion

Back 40

-in gastropods is responsible for moving the mantle cavity from the front to the back of the body.
-occurs during embryonic stage of life cycle
-space above head allows for head to be drawn into mantle cavity, then foot forms barrier to outside.

Front 41

What process in snails results in spiral winding of the visceral mass and shell?

Back 41

coiling

Front 42

How did "Coiling" evolve in snails and what is its advantage?

Back 42

-original symmetrical arrangement gave way to a CONISPIRAL shape, with shell to one side which resulted in the loss of the right gill.
*advantage- waste expelled from right side of cavity, reducing fouling of gills with waste

Front 43

snail eyes and brain?

Back 43

-cerebral ganglia attached to nerve cord
-eyes are at the ends of tentacles, no hearing
-Nocturnal.

Front 44

"tongue with teeth" in snails?

Back 44

Radula
* it is also modified for feeding, shell boring/prying,harpooning and envenomating prey, chewing.

Front 45

gypsobelum

Back 45

love dart fired by some snails, pre-copulation

Front 46

Gastropod reproduction

Back 46

monoecious
-sperm exchange
- some use "lave darts" (gypsobelum)
-eggs laid singly or attached to substrate as jelly mass
-Direct development- hatchlings are mini adults

Front 47

Which gastropod feeds on cnidarians and reuses the undischarged nematocysts?

Back 47

Nudibranchs "naked gills"
*no shell, but elaborate papillae covering the dorsal surfaces contain reused nematocysts.

Front 48

papillae

Back 48

nodes containing reused nematocysts covering the dorsal surfaces of nudibranchs (marine gastropods)

Front 49

quirk of the Sea Hare...

Back 49

squirts copious (a lot) purple secretion from the PURPLE GLAND in their mantle cavity when provoked.
*marine gastropod.

Front 50

Conus

Back 50

"cone shell"
marine gastropod that can be lethal to humans (or even other cone shells).
stings its prey to paralyze it before consumption

Front 51

4 main subclasses of class cephalopoda?

Back 51

Nautilus
cuttlefish
squid
octopus

Front 52

Cephalopoda

Back 52

very derived but also very ancient.
-most extinct forms had exterior shells.
-all are active predators.

Front 53

advancements of cephalopods over other mollusks?

Back 53

well developed external cephalization
-foot modified into several tentacles with suckers
-CLOSED circulatory system
-complex reproductive behavior

Front 54

Cephalopod nervous system?

Back 54

-sophisticated with external cephalization and large brain.
--sophisticated tactile, visual, olfactory and chemo sensory organs.
-mantle with chromatophores and/or bioluminescence for camouflage and communication
- very intelligent with sophisticated behaviors and communicationabilities.

Front 55

chromatophores

Back 55

pigment-containing and light-reflecting cells.
Cephalopods can operate chromatophores in complex, wavelike chromatic displays, resulting in a variety of rapidly changing colour schemes.

Front 56

eyes of octopi?

Back 56

has cornea, retina, iris, lens, 2 chambers
-Convergence with vertebrate eye structures

Front 57

biggest eye?

Back 57

beloongs to Collosal Squid
this 46 ft 1000 lb squid has an eye with a 10" diameter!

Front 58

repro in cephalopods?

Back 58

Sophisticated...
-males direct COLOR DISPLAYS directed at rival males.
-spem encased in SPERMATOPHORES with one modified tentacle used to pluck the spermatophore from his own mantle cavity and insert it into the mantle cavity of the female.