seashells (mollusks) & beachcombing
DESCRIPTION
Seashells (mollusks) & beachcombing. Maia McGuire, PhD Florida Sea Grant Extension Agent. Mollusks. Includes Gastropods (snails), Bivalves (e.g. clams) and Cephalopods (e.g. octopus) Second largest invertebrate phylum (after arthropods). - PowerPoint PPT PresentationTRANSCRIPT
Seashells (mollusks) & beachcombing
Maia McGuire, PhDFlorida Sea Grant Extension Agent
Mollusks• Includes Gastropods (snails), Bivalves (e.g.
clams) and Cephalopods (e.g. octopus)• Second largest invertebrate phylum (after
arthropods)• Generally have a muscular
foot, a calcareous shell and a feeding organ called a radula
• Have gills, blood vascular system, stomach, heart, sensory organs (e.g. eyes)
Molluscan reproduction• Sexual reproduction• Most are single sex (gonochoric)• Fertilization is external• Larvae are often planktonic (most common
type is called a veliger)
Gastropods
• Snails and sea slugs• “Head foot”• Carnivores and herbivores• There are gastropods in salt water, fresh water
and on land, but all are restricted to that particular habitat. Land snails have lungs.
• Many have an operculum (“trap door”) to seal the entrance to their shell.
Gastropod adaptations
• Operculum (‘trap door”)– Used to help protect snail from predators– Used to help prevent snails from drying out
(especially for intertidal snails)– Different types of snails have different types of
opercula (range from thin and flimsy, to made of calcium carbonate)
Some snails are predators
• Remember that radula?• It becomes a drill or rasp that some snails use
to drill through the shells of other snails or bivalves (e.g. clams)
www.seaslugforum.net
Common gastropods
• Slipper shell• Moon snail/shark’s eye• Olive• Auger• Wentletrap• Baby’s ear• Whelks• Tulips
Gastropod egg cases
• Sand collar (moon snail)
• Whelk and tulip egg cases
www.jaxshells.org
Baby snails
• Often planktonic (carried by ocean currents)• Have a tiny shell, which becomes the tip of the
shell after the animal settles and grows.
Snail growth
• Snails add to their shell (at the opening/lip, and in thickness) as they grow.
• The mantle used calcium and bicarbonate ions from the water to create calcium carbonate.
• We cannot age a shell based on growth lines (unlike trees and corals)
Sea slugs• No external shell• Variety of defense mechanisms• Some are herbivores, others are carnivores
Bivalves• Have two, hinged shells• Examples include oysters, clams, mussels,
scallops• Many can live 20-30 years; some more than
100 years!• Most are filter-feeders• Many attach to hard surfaces; some have threads or cement
Bivalve shells
• Some bivalves have a periostracum (thin, often brown covering over the shell)—provides camouflage.
Common bivalves
• Ark clams
• Pen shells
• Coquina clams
• Jingles
• Cockles
• Scallops
Cephalopods
• Octopus, squid, nautilus, cuttlefish• Swim by producing a jet of water through a
funnel• Most have 2 tentacles with suction cup ends;
8 arms with suction cups• Horny, parrot-like beak; radula functions as a
tongue• Have pigment cells in skin
Cephalopod biology
• Many can squirt ink as a defense• Eyes and nervous system are well-developed• Carnivores• Poisonous saliva• Have gills, heart, brain• Gonochoric• Squid die after mating• Female octopus die after
brooding their eggs
• Paper nautilus
• Ram’s horn shell
www.manandmollusc.net
Cephalopods
www.seabean.comwww.seabean.com
Activities
• “I Have a Shell” (Monterey Bay Aquarium)• “CSI: Clamshell Investigation” (NJ Sea Grant)
Weird and Wonderful things…
• Mermaid’s purse
• Sand dollar
• Sea stars
Jellyfish• Portuguese man-o-war– Don’t touch!– Associated companions—”By-the-wind
sailor”, “blue buttons”, purple sea snail, man-o-war slug, man-o-war fish
www.enature.com
www.amonline.net.au
Cannonball jellyfish
www.jaxshells.org
Moon jellyfish
www.jaxshells.org
Sharks’ teeth
Sea beans
• www.seabean.com• Any of a number of seeds
that are adapted to germinate even after spending a period of time floating in water
• Mostly from tropical plants, many from vines
Activity
• Beach Treasures