Lecture 9 - Phylum Mollusca: Gastropods,Bivalves, and Octopods - Salt Marshes - Crustaceans

what are a mollusk?

soft-bodied, invertebrate animals belonging to the phylum Mollusca, which also includes snails, slugs, clams, oysters, octopuses, and squid

what are the phylum Mollusca characteristics?

• Mantle – surrounds body, secrets a shell

• One foot for locomotion

• Radula - unique feeding organ

• True gills – not derived from other organs

• No segmentation

• Open circulatory system

• Nervous system – brain with nerve cords

  • Brain very well developed in octopus, squids, and various relatives

• Shelled invertebrates (mostly)

• Shell made up of:

  • Calcium carbonate (CaCO3)

About how many types of phylum Mollusca?

over 100,000 species

what are the seven classes in phylum Mollusca

• Aplacophora - worm-like animals with no shell

• Monoplacophora – name that means “bearing one plate” like a shell cap

• Polyplacophora - chitons

• Bivalvia – bivalves (animals with 2 shells)

• Gastropoda - snails

• Cephalopoda – name that means “head-foot” (octopods and relatives)

• Scaphopoda – name that means “tusk shells” or “tooth shells”

what are bivalves?

animals with 3 shells some are burrowers 

• includes clams, mussels, oysters, scallops 

water is drawn through siphons

• phytoplankton collected on gill; ciliated tacts passes food to mouth & digestive system 

• they are filter feeders

some feed on organic matter in the sediment 

freshwater on marine environments 

what is the ecological importance of Bivalves?

• Impact nutrient cycling

• Create and modify habitat

• Affects food webs as prey and by moving nutrients and energy

• Materials accumulated in soft tissue and shells used to monitor environmental conditions

• Filters water (improves water quality)

what is the economical importance of Bivalves?

• fisheries and aquaculture species 

• valuable as ornamental objects, jewelry, collectors’ items, and mother-of-pearl inlay

what are gastropods?

• Has 1 shell, usually coiled

• Flattened foot, and an operculum (a door to protect from predators and drying out)

• Radula: a tooth row which moves back and forth over food

• Marine, freshwater, or terrestrial

• Herbivorous or carnivorous

what is the ecological importance of Gastropods?

• important role in marine food chain

  • many fish and birds feed on them as part of natural diet

• grazers, suspension feeders, scavenging, herbivory carnivore

• can act as a bioindicator for water quality

what is the economical importance of Gastropods?

• edible gastropods are used as food in coastal areas

• pets for fishtanks

what are cephalopods?

• That largest of the invertebrates

• Includes octopods, squids, cuttlefishes, and the chambered nautilus

• Have a mantle and external or internal shell remnant

• Have well-developed nervous systems

• Has advanced eyes (nautilus is the exception)

what is the ecological importance of Cephalopods?

• important in marine trophic (food) webs as predator and prey 

  • prey for tuna, salmon, cetaceans (whales and dolphins), sea lions, and seabirds 

• strong influence on ecosystem dynamics (keystone species)

what is the economical importance of Cephalopods?

• food sources for marine fishery species

  • tuna and salmon

• many species of squid and octopus are eaten by humans

• nautilus shells sold as a calcium source for birds in the pet trade

what are octopods?

• Octopods are major predators of benthic species

  • Individuals may feed on a specific species

    • Crabs or mollusks

  • Usually live in crevices

    • Ambush predators

octopus characteristics?

• 8 arms, no tentacles

  • Octopoda

•  Benthic habitat

• Feed on crabs on seafloor

• Grab pray with arms and inject them with venom

• Have a rounded head and mantle

• Can change colors to hide

  • Chromatophores: cells on the body that contains pigment

• Solitary animals

• invest time into rearing their young, taking care of eggs in de

squid characteristics?

• 8 arms, 2 tentacles

  • Decapoda

• Open ocean habitat

• Feed on shrimp and small fish in the water column

• Use tentacles to catch prey and eat it in chunks

• Have 2 fins at the top of their mantle giving a triangle appearance

• Can live independently or in schools

• Attach their eggs to hard structures like rock or coral, but do not invest time in their young

what are the differences between octopi and squids?

• octopi have not tentacles

• different habitats

• feed on different animals (floor feeders v. open-ocean feeders)

• catch prey differently (arms v. tentacles)

• different looks (round v. triangle)

• living life (independent v. both)

• investing time in youn (much time v. not enough)

• imbedded (den v. on hard surface)

what are the similarities between octopi and squids?

• Both live in marine habitats in the tropics or temperate zones

• Both can use ink as a defense mechanism

• Short lifespans due to reproduction

  • Octopus: 1 to 3 years

  • Squid: 9 months to 5 years

What is a Giant Pacific Octopus?

• Pacific Ocean species 

• average lifespan: 3-5 year

  • most popular esp. in aquariums 

What are ammonites?

• extinct cephalopods

• we seem them as fossils

• approx. over 10,000 to 20,000 species have been discovered

• most predictions about ammonites come from modern day cephalopods

what are some threats to phylum mollusca?

• ocean acidification 

• habitat loss 

• pollution 

• overfishing 

• invasive species 

• increased diseases 

• climate change 

what is a salt marsh?

• followed coastal wetlands drained by tides

• composed of mud and peat

• act as nursing grounds

• protect shorelines from erosion and act as shelter for young marine species

  • “ecological gaurdians of the coast”

• marshy b/c soil may be composed of mud and peat

• also full of tall grasses

what is peat?

• decomposing plant matter, several feet thick

  • spongy, root-filled, water-logged

  • oxygen levels are low (hypoxia)

what do salt marsh grasses do?

• provide natural filtration of debris and impurities 

• help absorb stormwater 

  • reduces erosion and flooding

• help maintain water quality

• provides habitat

what are crustacean characteristics?

• have hard exoskeletons 

• also have a segmented body that is bilaterally symmetrica, more than four pairs of joined appendages, and an open circulatory systerm (body does not flow in closed loop)

• feeding mechanisms

  • carnivores (predators)

  • scavengers (eat sediments and organic debris)

how many crustacean are their approx.?

over 50,000 species (10% in freshwater)

• some may be terrestrial Some

  • burrowers, others walk (benthic) 

  • planktonic (in the surface water) 

what are class Malacostraca an who are considered apart of this class?

• Includes crabs, lobsters, crayfish, shrimp, prawns, krill, amphipods, and some lice (approx. 40,000 species)

• Includes the largest arthropods

• Occur in many habitats, but mostly marine

• Blood also has hemocyanin (aka blue blood)

what are the ecological importances of crabs?

Key organism for connecting aquatic and terrestrial ecosystems

• A vital part of the food chain

• Food source for whales, dolphins, turtles, penguins, etc.

• Larvae are planktonic and eaten by small animals, like shrimp

• Acts as a predator

• Some are scavengers that eat decayed material and recycle nutrients back into ecosystem

• Help sequester carbon dioxide from the atmosphere

• Invasive crabs may impact communities

  • Ex. Asian shore crab and green crab in
    Long Island Sound (LIS)
    

what are the economic importance of crabs?

Aid with shellfish farming

• Filter-feeding oysters eat crab larvae

• Important seafood produc

• Many are wild-caught crabs (fisheries)

• Some species are farmed, including blue crabs, mud crabs

• Invasive species can threaten this economic contribution through ecological disruptio

what is the ecological importance of lobsters?

Important for coral reef ecosystems

• Algae control – forages on algae

• Crucial link in the food chain

• Create burrows and crevices that provide shelter for other reef organisms

inhabitants (habitat engineering)

• Increases biodiversity

• Functions in the transfer of energy and materials

• Link between primary producers and consumers to apex predators

• An important predator of sea urchins, snails, crabs, and other bottom- dwelling organisms

what is the economic importance of lobsters?

Ecological Importance of Lobsters
• Highly-prized source of seafood
• Lobsters are one of the premium ocean resources
• Generates consistent revenue for fishing fleets along New England and Mid-
Atlantic states
• Creates large economic impacts in fishing-related industries
• Distributing, processing, gear manufacturing, vessel building and
maintenance, marine supplies, tourism, etc.
• Generates more than $1.5 billion annually in revenue

how do shrimps help?

some act as cleaners that help rid host fishes of external parasites fungi, bacteria, and dead tissue found on the skin; other species are scavengers 

why are krill important? 

• Food source for some baleen whales and other predators

• Keystone species of marine food webs

• Commercial fishery for krill for aquaculture or pet feed

• There are some used dietary supplements

what are barnacles? 

• Larvae are planktonic and look like the characteristic arthropod larvae (nauplius)

• Sessile or parasitic adult

• Shell made of calcium carbonate (CaCO3)

  • Ocean acidification

• Fouling pests

  • Marine fouling: Organisms attach themselves to underwater objects like boats, rope, pipes and building structures.

• Epibionts: an organism that lives on the surface of another living organism

  • Usually harmless (commensalism)

• What happens when too many settle on one animal?

  • Parasitism

what are copepods? 

• Around 13,000 described species

• Mostly found as zooplankton in marine and lake environments, but some in groundwater and soil or act as parasites (internal or external)

• Important for fisheries: food for larval and small fish, and some large animals (whales)

  • sockeye salmon eat copepods directly (get their pigments from the copepods)

• Important for aquaculture: larvae & juveniles of some marine fish require live food

  • Acartia spp. calanoid copepods are favored in aquaculture

    • They tolerate variable salinities (euryhaline)

    • Females release eggs instead of carrying them

    • Commercial methods and products are available

• Wild-caught copepods also used

what are threats to crustaceans? 

• Pollution

• Harvesting

• Habitat loss

• Ocean acidification

• Cannibalism

• Can be seen among some crab species (e.g., blue crabs) and lobsters

• Possibly due to the fact that they need increased energy to molt