Marine Biology Worms and Molluscs

Osedax worms

“the bone eaters”

How do Osedax Worms bore into inner bone?

with acid and absorb the fats inside with help of bacteria

How to Osedax Worms move?

move by riding ocean currents as larvae and the eventually settle on exposed bone

What is the first step of Osedax Worm reproduction?

the first larvae that settles on bone develop into female with one end tunneling into bone and forming root. The other end grows into feathered fan

What is the “feathered fan” on larval Osedax Worms used for?

the feathered fan from the opposite end of the larvae is used to extract oxygen from the water

How do Osedax Worms become male?

the larvae that arrive later than larvae already on the bone

Do Osedax male worms survive?

No they do not survive past the larval stage

How are Osedax male worms parasites?

they live within the female’s body as parasites where there can be over 100 living in the female host

Can Osedax Worms be specialized burrowers?

Yes because some dig within bone for the fat while others pick apart the bone layers

Where is the bacteria in Osedax worms located?

Located in the root like structures when attached to bone or grow directly on the bone

Chemosynthesis in Osedax Worms

how the bacteria in the root structures utilize the sulfur in the bones to make energy

Phylum Mollusca

mostly shelled invertebrates

What are the major characteristics of Mollusca?

-100,000 known living species

-3 tissue layers

-Mantle that secretes CaCO2 shell

-Have gill

What are the 3 tissue layers of Mollusca?

Bilateral symmetry, complete gut, and coelom

Gill of Mollusca

Suspended in the mantle cavity and is used for respiration and suspension feeding/filter feeding

General anatomy for Bivalvia

-2 shells

-Valve hinged together by calcified teeth and ligament (springs shell open)

-Mantle lines the valve and secretes new shell

-Powerful foot

-Mantle cavity with siphons across ctendium

Foot of a Bivalvia

Can be filled with fluid. Probes into sediment and expands pulling shell behind it. Small in mussels and secretes byssal threads gluing it to surface

Are bivalves infaunal or epifaunal?

Both

Infaunal

Burrow in CaCO2 skeleton of coral or rocks

Epifaunal

Attached to surface or sea floor

What are the feet of bivalves mostly used for?

Used for hydromechanical burrowing

How do bivalves eat?

They eat through filter feeding

What do only mussels secrete?

Secretes byssal threads for attachment to rocks

Eastern Oyster (Bivalvia)

Crassostrea virginica

How do Eastern Oysters eat?

Eat by filter feeding

Where do Eastern Oysters live?

Live in brackish water

Purpose of Eastern Oyster?

To filter 50 gallons of water per day and attach to firm bottom areas to grow into reefs

Gastropoda (Bivalvia) characteristics

-coiled shell

-torsion

-some are poisonous

-feed by mouth and teeth

-move with muscular foot

Gastropoda torsion

Body is twisted during larval stage where the mouth and anus use same opening in shell

How do Gastropoda eat?

They eat buccally using their teeth (radula) to scrape against microalgae

How do Gastropoda move?

Locomotion on flattened muscular foot often with operculum attached which closes off to protect shell

Caenogastropoda

Largest subclass of gastropods which contains marine snails, conch, periwinkle, cone snails and moon snails

How do Caenogastropoda feed?

They are grazers, carnivores and filter feeders

Caenogastropoda conus characteristics

-venomous

-harpoon (toxoglossan radula) to capture prey

detects prey using proboscis and fires harpoon

Caenogastropoda naticidae (moon snail) characteristics

-predatory feeding on bivalves

-envelopes prey and drills hole in shell using radula

-proboscis sucks out prey

-female snails lay egg masses called sand collars

How do Caenogastropoda naticidae eat?

They envelope prey and drill holes through shell using its radula and then use proboscis to suck out flesh

How do Caenogastropoda naticidae reproduce?

Female moon snails lay egg masses called sand collars washed up on beaches

Patellogastropoda characteristics

-true limpets

-flat cone shaped shell

-sit on intertidal rocks with strong muscular foot

-feed with scraping radulla

Vetigastropoda characteristics

-top shells

-secondary holes at top of shell

-abalone and keyhole limpets (differ with hole at top)

Heterobranchia (gastropoda)

-Nudibranch, sea hares, pteropods

-sea hares have an internal shell

-detorsion

What is detorsion in Heterobranchia

It reverses the process of torsion that is undergone in the larva; stage

What are the 2 most common suborders of the Nudibranchs (Heterobranchia)?

Aeolidacea and doridacea

Aeolidacea

-Have protrusions calls cerata back (used for digestion and resp)

-store nematocysts from hydroids consumed for defense mechanisms

Doridacea

Have exterior gill plume surrounding their anus

What is the blue sea dragon?

Glaucus atlanticus (nudibranchs)

Is the blue sea dragon pelagic?

Yes, it floats upside down carried along by wind currents and uses gas sac on stomach to float. Their muscular foot clings to surface

What does the blue sea dragon feed on?

Feeds on PMOW and other poisonous siphonophores storing their nematocysts

Polyplacophora general characteristics

-chitons

-found on hard substrates

-oval and flat with 8 dorsal plates

-flattened foot to adhere

-mouth with radulla

-herbivores

Monoplacophora characteristics

-similar to mollusks

-cap shaped shell with flattened foot

-radula in mouth

Scaphopoda characteristics

-tusk shells

-secrete tusk shaped shell

-foot resembling bivalves and burrow into substrate (infaunal)

-catch food using tentacles

-radula pushes food into mouth

Cephalopoda characteristics

-complex behavior, good vision

-carnivorous with suckers

-swim

-all have photophores

-reproduce by male transferring spermatophore to female

Chromatophores

Specialized pigment cells which are controlled neurally and rapidly enlarged and contracted by attached muscles allowing squid, cuttlefish, and octopods to produce quick color changes

Squid (Cephalopoda)

-found in open water

-feed on large fish to krill

-eight arms and two tentacles to eat

-contract mantle muscles to expel water through siphon to move (Hypnome)

-bites into prey with beak and then seized by arms

Giant Squid and Colossal Squid (Cephalopoda)

Larget invertebrates

Open ocean giant squid

Architeuthis (15m in length)

Colossal Squid

Mesonychoteuthis hamiltoni (most massive)

Octopods (Cephalopoda)

-soft bodied eight limbed

-two eyes, beaked mouth

-alters shape easily

-trail 8 appendages when swimming

-capture prey by entwining them in 8 limbs and attach suckers

-siphon used for respiration and locomotion

Chambered Nautilus (Cephalopoda)

-ancient

-simple eyes (only light and dark)

-perceives water depth and direction/speed

-has over 90 arms

-feeds near bottom (scavenger) highly developed smell

-swims via jet propulsion (expels water through siphon) adjusting direction of siphon

-lives for 20 years (low reproduction)

Cuttlefish (Cephalopoda)

-cuttlebone (internal shell) for buoyancy

-8 arms and 2 tentacles with suckers

-eats small mollusks, crab, shrimp, octopus, worms, cuttlefish

-rapidly change color