Biol 205 - Bivalves and Cephalopods

What is the main structure of bivalves

It has two shells attached with a hinge

Do bivalves have a radula?

No, they have secondarily lost it. They are the only Mollusca that dont have it

Whats the digestion in bivalves

filter feeders that pump large amounts of water through mantle cavity

What is used to generate the water current for filter feeding

cilia

What traps the food particles in filter feeding

sticky mucus on surface of ctenidia

Are they monoecious or dioecious? And is there external or internal fertilization

Mostly dioecious, fertilization is external

What type of development is it. If its indirect, what are the larval stages

Indirect development, has trochophore and veliger

What is planktonic?

organisms living in water columns and drifting with currents

What is difference in shells in bivalves and scaphopoda when becoming adult/mature

bivalves retain two valves when veliger tries into adult, while in scaphopods, two valves form together to form single, tube shaped shell

Why is there cilia on velum?

produces water current for filter feeding and water movement for respiration

Are mussels bivalves?

Yes

How do mussels attach to hard surfaces

by secreting anchoring threads (byssal threads) from the byssal gland in the foot

What prevents the shell from opening

posterior abductor muscle

what are siphons?

helps move water in and out

What are labial palps

flap like structures near mouth of bivalves that help sort food before entering mouth

Explain digestion in mussels (bivalves)

• small particles will be captured by sticky mucus of ctenidium

• cilia will carry these particles to food groove on ventral edge of ctenidium

• cilia will carry particles along food groove towards mouth

• sorted by labial palps

• if particles are edible, they are pushed into mouth

• if particles are not edible, they are pseudofeces and pushed away

Explain water flow in mussels (bivalves)

• water enters ventral siphon

• moves posterior to anterior, passing over ctenidia

• once at anterior end, it flows dorsally, picking up pseudofeces form labial palps

• On its way back to posterior, It picks up nitrogenous wastes form opening of kidneys and gametes from genital papilla

• water passes under posterior abductor muscle, picks up faces released form anus

• exits via mantle cavity visa dorsal exhalent siphon

Which structure contains gonads

genital papilla

where are gametes released

gonopore

what is crystalline style

releases enzymes into stomach to aid digestion

what type of circulatory system do they have

open, pumps hemolymph into hemocoel spaces

what is ctenidia used for

feeding and gas exchange

What are the names of the two taxa in Cephalopods

Nautiloidea (Nautilus) and Coleoidea

What are the structural features of Nautiloidea (Nautilus)

• single large external shell

• no suckers on tentacles

What are the structural features of Coleoidea

• internal shell or secondarily lost it

• tentacles and arms have suckers

• eyes have lens and cornea to form images

• can swim through jet propulsion

What type of circulatory system do cephalopods have

closed

How many hearts do cephalopods have, what are each of their functions

3 hearts, 2 for pumping blooded into ctenidia, 1 systematic heart that pumps blood to rest of body

instead of have a muscular foot like bivalves, what do cephalopods have

arms and tentacles

what do cephalopods use their arms and tentacles for?

Capturing prey

What do cephalopods use to eat their prey?

They have sharp teeth to bite and inject neurotoxin into, and use radula to rasp small pieces of flesh off large bites of prey

Are cephalopods monoecious or dioecious

dioecious

what type of fertilization do cephalopods have

internal

What type of development do cephalopods have

direct

what is used for respiration in cephalopods, and why

ctenidia, they are feathered shaped which is highly folded to increase surface area

What does the cerebral ganglia control

mantle muscle contractions

How many hearts does a cephalopod have, and what is the name of each and their function

It has three hearts. 2 brachial, brings blood to ctenidia, 1 system, brings blood to rest of body

what doe the siphon release

waste, gametes, water, ink

Explain male reproductive system in Loligo

Testes make sperm, Ciliated funnel moves sperm into vas deferens, vas deferens takes sperm to spermatophoric organ where it is packaged into spermatophores. Spermatophoric sac stores spermatophores, and they are released through vas deferens, and finally hectocotylus arm to transfer them to the female.

Explain nervous system in Loligo

Has cerebral ganglia, eyes that can form images with cornea, lens and retina, has chromatophores controlled by muscles for rapid color change, camouflage and communication

What controls chromatophores on mantle

muscles

Explain digestion loligo

Beak has Sharp, chitinous “teeth” to bite, and injects paralytic neurotoxins from salivary glands. Radula Inside the buccal mass with the beak scrapes and shreds prey flesh. Esophagus passes through the stomach, Caecum (digestion/absorption) Rectum, Anus

Explain female reproductive system in loligo

Ovary to Oviduct to Oviducal gland (adds capsule to each egg). Then Nidamental glands (add gelatinous outer layer to egg masses). Eggs are released into seawater and attach to bottom. Parents die shortly after spawning.

What happens to spermatophores once they enter female

enter mantle cavity, spermatophores attach and release sperm inside the female’s mantle cavity. Fertilization During Egg-Laying.

Where does fertilization occur

mantle cavity