Chapter 13: Phylum Mollusca pp. 329-334

Biology fun facts of the day: Experts claim that about 1,000 oysters must be opened in order to find one usable pearl!

Biology fun facts of the day: The common garden snail, Helix aspersa, can travel about 2 feet in 3 minutes. At that rate, it would travel 1 mile in 5.5 days. (Now you know where the term ‘snail mail’ comes from!)

Biology fun facts of the day: When we hold a large seashell up to our ear, you can hear what sounds like waves because the shell echoes all the sounds around you. If you could listen to a shell in a completely soundproof room, you would hear nothing at all!

Biology fun facts of the day: Many land snails can lift 10 times their own weight up a vertical surface. (If you were this strong, and you weighed 30 kg (about 70 lb), you could carry 300 kg (almost 700 pounds!!!) straight up a wall!

Introduction to Molluscs Molluscs represent the second largest animal phylum, following the arthropods = Old Phylum (500 million years, approx.) 80,000 – 100,000 existing species (estimate) Most species are free-living Inhabit a variety of marine, aquatic & terrestrial habitats Important ecological roles with regards to nutrient recycling; bivalves clean and recycle sediments Empty shells provide habitat for other invertebrates

Where do Molluscs fit in?

Introduction to Molluscs Phylum Mollusca – Latin molluscus = “soft” Protostomes Bilateral symmetry; eucoelomates 3 cell layers (ectoderm, endoderm, mesoderm) Have a coelom (but often reduced to a cavity that surrounds only the heart) Have trochophore larvae (free-swimming ciliated larva) Similar larvae in annelids  likely share a common ancestor

Introduction to Molluscs Molluscs all share similar developmental patterns and a common body plan: Foot (muscle; function varies) Shell (protection; made of CaCO3) Mantle (produces the shell) Visceral mass (contains internal organs) Diagrams of snail, clam, and squid p. 300

Classes of Molluscs 1) Class Bivalvia 2 hinged shells No head or eyes Gills; live in water Example members: clams, oysters, scallops 2) Class Gastropoda One shell Some are terrestrial Example members: snails, slugs, nudibranchs

Classes of Molluscs 3) Class Cephalopoda Fast-moving predators Foot is modified into tentacles Well-developed nervous system Some can use camouflage and jet propulsion (e.g. octopus) when they feel threatened Example members: octopus, squid, nautilus, cuttlefish Nautilus Squid Octopus

Squid are the largest Cephalopods

Colour and Morphology Changes = Camouflage

Form and Function of Molluscs Molluscs vary a lot  clam = representative mollusk Digestive system: Complete digestive tract (mouth  anus) Mouth, esophagus, stomach, intestine, anus Have a radula (scraping/drilling organ) or a beak (cephalopods) Bivalves trap food in their gills – no radula e.g. Gastropod

Form and Function of Molluscs Respiratory system: Aquatic mollusks have gills Terrestrial mollusks have a highly folded mantle for O2/CO2 exchange (must stay moist) *A clam has incurrent and excurrent siphons  sea water passes through; location of gas exchange

Circulatory system: Open circulatory system – the heart pumps blood through open spaces called sinuses instead of through blood vessels Excretory system: Nephridia (primitive kidneys) remove metabolic waste (nitrogen-containing wastes like NH3) Digestive wastes go out anus

Bivalves – reduced nervous system; no head Gastropods – fairly basic Cephalopods – very well developed Good vision, small ganglia near mouth, statocysts (balance), simple chemical and touch receptors Good dexterity and memory – they can learn!

Musculoskeletal system: Muscular foot for movement Bivalves – “two shell”; foot pulls animal forward, and can be sucked back in (for protection) Gastropods – “stomach foot”; they slide forward on broad ventral foot (use muscus) Cephalopods – “head foot”; foot has been modified into many tentacles with suction cups e.g. Gastropod

Reproduction: Some Monoecious (have both sex organs, capable of producing both sperm and eggs) Others are Dioecious (either male or female gonads, can produce one type of gamete only) Separate sexes (usually) External fertilization (broadcast method) in bivalves/marine gastropods)  the female traps sperm Internal fertilization in cephalopods/terrestrial gastropods

Ecology of Molluscs Bivalves used to check pollution levels – “environmental monitors” Range of lifestyles: predators, scavengers, filter feeders, etc. Crop damage – slugs, snails on land Ship damage – shipworms in water Food source for humans: clams, oysters, mussels, etc. Humans can get poisoned by eating mollusks contaminated with toxic protists  cause “red tide”

Molluscs Movie!

Mollusc (5-7-5) Haiku: Slow, slick, sliding slug Terrestrial explorer No protective shield Create your own mollusc haiku in 5-7-5 format!

Works Cited Images taken from the following sources: http://other95.blogspot.com/2007/10/circus-of-spineless- 26-like-being-home.html http://offthemark.com/search-results/key/mollusk/ http://kevinmainjewelry.blogspot.com/2010/06/pearl-fun- facts-and-care-tips.html http://seashellvilla.com/advertise_here.html http://www.zazzle.com/snail_mail_postcard- 239469706654312651 http://bio1151b.nicerweb.com/Locked/media/ch32/trocho phore.html http://www.education.com/study-help/article/biology-help- mollusks-clam-up-would-ya/

Works Cited http://www.thecanadianencyclopedia.com/index.cfm?PgNm =TCESearchMedia&Params=A1&MediaId=385 http://perfectgardeningtips.com/category/plants/pest- control/ http://www.apartmenttherapy.com/sf/insects-pests/slugs- 082896 http://birdhouse.org/blog/2008/05/16/nudibranchs/ http://www.zazzle.com/i_squid_cephalopods_tshirt- 235319078835508111 https://www.mentalfloss.com/blogs/archives/58856 http://radio-weblogs.com/0105910/2004/01/10.html http://ihatetheocean.blogspot.com/2010/08/august-6-2010- nautilus.html http://zollberg.co.cc/bivalve.html

Works Cited http://js082.k12.sd.us/My_Classes/Advanced_Biology/Ch_25 /Clam%20Dissection/Clam_Dissection.htm http://www.sciencewithme.com/learn-about-mollusks/ http://www.bio.miami.edu/dana/106/106F06_12.html http://nashzoology.ning.com/forum/topics/mollusk- classification- choose?commentId=2223964%3AComment%3A10692&x g_source=activity http://sharon-taxonomy2009-p3.wikispaces.com/Mollusca http://www.lifeinfreshwater.org.uk/Web%20pages/ponds/Poll ution.htm http://www.nero.noaa.gov/nero/hotnews/redtide/ http://www.sheppardsoftware.com/content/animals/profile_ mollusks.htm