Chapter 6 - Molluscs Flashcards
today we will be learning abt the molluc
How many living species of Mollusca are there? How many fossil species?
Over 90,000 living species; 70,000 fossil species
Enumerate some of the common shared features of molluscs
- Radula,
- large muscular foot or tentacles for movement,
- mantle for respiration and shell secretion
Which of these are not nutritional modes of molluscs:
a. Filter feeder
b. Parasites
c. Herbivorous grazer
d. Detritus feeder
e. Predaceous carnivore
f. None of the above
f. None of the above
Give the scientific name of a chiton
Tonicella lineata
Give one characteristic (apomorphy) of Caudofoveata
Calcareous spicules form scales
What is the clade containing only Caudofoveates and Solenogasters? What is the clade that contains them and Polyplacophorans?
- Aplacophora
- Aculifera
What are some molluscs considered as pests?
Burrowing shipworms, snails and slugs
True or False: The head-foot region of molluscs contain the feeding, sensory, excretory, reproductive, and locomotry organs.
False
Excretory and reproductive organs are not found in the region
Found in all molluscs except bivalves and some solenogasters
Radula
Up to how many teeth can be found in the radula?
250,000
Describe the radula
Protruding, rasping, tongue-like organ that is a ribbon-like
membrane with rows of tiny teeth
The portion of the radula that supports the teeth and is cartilaginous is called the:
a. spicules
b. visceral mass
c. teeth
d. odontophore
This ain’t in the PPT but it’s cool to know
d. odontophore
Which of these are used by molluscs for attachment to substratum?
a. mantle groove
b. foot
c. pallium
d. glochidia
b. foot
Name some of the modifications of the mollusc foot
- Attachment disc of limpets
- Hatchet foot of clams
- Siphons for jet propulsion in cephalopods
Yellow and pink marine snail
Calliostoma sp.
Example of nudibranch in the PPT
Chromodoris sp.
Example of an octopus in the PPT
Octopus briareus
What do free-swimming forms of the foot use for locomotion?
modified wing-like or fin-like
parapodia
What secretes and lines the shell?
Mantle
outer horny layer of the shell protecting underlying layers from eroding burrowers, with growth occurring only at the margins of the shell
Periostracum
What does the middle prismatic layer consist of?
densely packed prisms of calcium carbonate
laid on protein matrix
Shell layer next to the mantle, secreted continuously by the mantle surface so it increases in thickness as the animal grows
Inner nacreous layer
What type(s) of reproduction can be found in molluscs?
Most dioecious, some hermaphroditic
Mollusc larva
trochophore
What mostly ancestral trait do trochophore larvae directly undergo?
metamorphosis into a small juvenile
molluscan intermediate larval stage in many gastropods and bivalves
veliger
What are veligers hatched with?
beginnings of a foot, shell, and mantle
Which types of molluscs s have no free swimming larvae, with only juveniles hatching directly from eggs?
- Cephalopods
- some freshwater bivalves
- snails
Christmas tree worm
Spirobranches spinosus
Notable for having a trochophore similar to Mollusca, indicating common ancestry among molluscs and annelids
Type of snail whose veliger was shown in the PPT
Pedicularia sp.
Other name for Class Caudofoveata
Chaetodermomorpha
class consisting of about 120 species of worm-like, marine organisms ranging from 2 to 140 mm long
Class Caudofoveata
What does Class Caudofoveata mainly eat?
microorganisms and detritus
How do most species under Class Caudofoveata burrow and orient themselves?
burrow and orient vertically with terminal mantle cavity and gills at entrance
True or False: Solenogasters have radula, gills, and a foot.
False
Solenogasters have no radula, nor do they have gills.
midventral, narrow furrow found in the foot of Class Solenogasters
pedal groove
Other name for Class Solenogasters
Neomeniomorpha
What feeding habit does Class Solenogasters exhibit?
Do not burrow but are bottom dwellers and feed on cnidarians
True or False: All solenogasters are hermaphroditic.
True
Caudofoveate example in the PPT
Chaetoderma elegans
What is visible on the skin of solenogasters and caudofoveates?
spicules
Class of chitons
Class Polyplacophora
What is the body structure of Class Polyplacophora?
Generally flattened dorsoventrally with a convex dorsal surface that has seven or eight articulating limy plates
Where do chitons tend to live?
rocky surfaces along intertidal regions; some found at great depths
What reinforces chiton radula?
magnetite
What is the function of magnetite?
Reinforces the chiton radula to scrape algae from rocks
Mossy chiton
Mopalia muscosa
Class of molluscs previously deemed extinct
Class Monoplacophora
What are the traits of Class Monoplacophora?
- radula
- rounded shell
- creeping foot that resemble limpets
How many living species of Gastropoda are there?
Over 70,000
True or False: No snails are specialized for burrowing
False
Some snails are specialized for climbing, swimming, burrowing
Describe gastropod shells
A one-piece univalve that can be coiled or uncoiled
What is the smallest and oldest part of the gastropod whorl?
Apex
What is the central axis of the gastropod shell?
Columella
The structure of the shell that covers the shell aperture or entry
Operculum
Whelk species that shows the parts of a gastropod shell
Busycon sp. (Busycon contrarium and Busycon carica)
True or False: Some snails release toxic secretions by using stolen cnidocytes or forming poison harpoons to catch prey
True
This species of snail has a modified operculum with a sharp spike to give an active blow to possible predators
Strombus sp.
What is the scientific name of the parasitic flatworm that infests snails of the genus Succinea?
Leucochloridium paradoxum
How do snails detect potential prey?
by detecting chemical cues from metabolic waste
Give the scientific name of the red abalone
Haliotis rufescens
What is the scientific name of the moon snail?
Polinices lewisii
What genus of snail feeds on fish, worms, and other molluscs using a lethal sting to secure prey?
Conus
Conus snails have a modified radula with forms a harpoon with poison gland, containing venom called ____
conotoxin
Why are some species ofConus valuable for research?
their conotoxin can be lethal to humans, so they can help in the research of cell receptors and ion channels of nerve cells
True or false: Copulation in monoecious gastropods can involve exchange of spermatozoa
True
What type of fertilization do most snails have?
Internal fertilization
Primitive reproductive feature is external fertilization forming
free swimming trochophores
Describe how gastropods lay their eggs
Eggs are laid in clusters (sometimes in tough capsules)
True or False: Most freshwater snails are ovoviviparous?
True
Meaning that the eggs develop within the snail body and are not laid
Name the three traditional sub-classes of Gastropoda
Prosobranchia, Opisthobranchia, Pulmonata
What are the Prosobranchs?
Mostly sea snails, but also include freshwater and land snails
Examples are periwinkles, horse conch, limpets, and the flamingo tongue snail
Give the scientific name of a limpet
Patella sp.
What is the scientific name of a flamingo tongue snail?
Cyphoma gibbosum
These are two pairs of tentacles of Opisthobranchs with one modified to increase chemo-absorption
rhinophores
Are the Opisthobranchs all monoecious or dioecious?
Monoecious
What differentiates the Opisthobranchs from the other gastropods?
Hint: it’s in the shell
Shell is reduced or absent
Give the scientific name of a sea hare
Aplysia dactylomela
What is the ancestral respiratory organ of molluscs?
Ctenidia
Pulmonates have lost their ancestral ctenidia, what took its place as a respiratory organ?
The vascularized mantle wall which is now a lung
How do aquatic species of Pulmonates differ from land species?
- Aquatic species have one pair of nonretractile tentacles with eyes at the base
- Land species have two pair of tentacles with the posterior pair having eyes
What’s the scientific name of a banana slug?
Ariolimax columbianus
What are the other names of Bivalvia?
Pelecypoda or “hatchet-foot”
How do most bivalves feed?
As sedentary filter feeds which depend on currents produced by their cilia
What do bivalves lack?
Head, radula, and other aspects of cephalization
True or False: No bivalves are found in freshwater
False
Give the scientific names of some bivalves in the PPT
- Mytilus edulis: Mussel
- Chlamys opercularis: Scallop
- Tagelus plebius: Stubby razor clam
- Tridacna gigas and maxima: Giant clam
- Aequipecten irradians: Surface-dwelling scallop
What holds the two valves of bivalves together?
Hinge ligament
The oldest part of a bivalve shell that grows outward in rings
Umbo
True or False: A mollusc that has its mantle wrapped around the viscera and a shell that is a tube is in the class Scaphopoda
True
Also known as the tusk or tooth shells
True or False: Scaphopods have gills like other molluscs but also can breathe through their mantle
False, gaseous exchange occurs via the mantle but they lack gills
What are the mucus-covered tentacles of scaphopods called? What is their function?
Captacula, it functions to catch food
Other than gills, what other feature do scaphopods lack?
Eyes and other sensory features
Give the scientific name of a scaphopod
Dentalium sp.
How are chromatophores controlled in cephalopods?
contractions of muscle fibers attached to cell boundary
spermatozoa packaged in spermatophores and stored in sac that opens up to mantle cavity
male seminal vesicle
How is the foot different in cephalopods compared to other classes?
Foot merged with head region and modified for expelling water from mantle cavity
True or False: Cephalopods are sensitive to the salinity of the waters they live in.
True
One arm of male cephalopods modified as intromittent organ
hectocotylus
What is the function of the hectocotylus?
remove spermatophore from male mantle cavity and insert to female oviduct
What do Nautiloidea and Ammonoidea have in common?
- Gas chambers for buoyancy
- Shell has transverse septa w/ sequential chambers
- Siphuncle
A cord of living tissue that connects chambers to visceral mass
Siphuncle
In which chamber of nautiloid and ammonoid shell can the living animal be found?
Last chamber
True or False: Nautiloidea has 1 pair of gills while Coloidea has 2
False
Nautiloidea has 2 pairs of gills while Coloidea has 1
What do Nautiloidea tentacles have?
adhesive secretions
What can be found beneath the head of Nautiloidea?
funnel, mantle cavity, and visceral mass sheltered by shell
Which era were Ammonoidea species prevalent? By which era were they extinct?
Prevalent during Mesozoic, extinct at end of Cretaceous
What are the traits of Ammonoidea shells?
Chambered shells with complex and drilled septa
Order of Coloidea with a shell that is small, curved, and entirely enclosed by the mantle
Sepiodea
Give a scientific name for a cuttlefish.
Sepia latimanus
Which orders of Coloidea evolved from straight-shelled ancestors?
Myopsida, Degopsida, Octopoda
Squid shell
Pen
What are the traits of the squid shell?
thin proteinaceous strip enclosed by mantle
Give a scientific name for a squid.
Loligo vulgaris
Order of deepwater vampire squids
Vampyromorpha
What are the traits of the octopus shell?
none lol it doesn’t have one
Which eras did most Nautiloidea populate the Earth?
Paleozoic and Mesozoic eras
What other type of animals are cephalopod eyes similar to?
Vertebrates
