Seashells (mollusks) & beachcombing

1. Seashells (mollusks) & beachcombing Maia McGuire, PhD Florida Sea Grant Extension Agent

2. 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)

3. Molluscan reproduction • Sexual reproduction • Most are single sex (gonochoric) • Fertilization is external • Larvae are often planktonic (most common type is called a veliger)

4. 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.

5. 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)

6. 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

7. Common gastropods • Slipper shell • Moon snail/shark’s eye • Olive • Auger • Wentletrap • Baby’s ear • Whelks • Tulips

8. Gastropod egg cases • Sand collar (moon snail) • Whelk and tulip egg cases www.jaxshells.org

9. 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.

10. 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)

11. Sea slugs • No external shell • Variety of defense mechanisms • Some are herbivores, others are carnivores

12. 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

13. Bivalve shells • Some bivalves have a periostracum (thin, often brown covering over the shell)—provides camouflage.

14. Common bivalves • Ark clams • Pen shells • Coquina clams • Jingles • Cockles • Scallops

15. 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

16. 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

17. Cephalopods • Paper nautilus • Ram’s horn shell www.manandmollusc.net www.seabean.com www.seabean.com

18. Activities • “I Have a Shell” (Monterey Bay Aquarium) • “CSI: Clamshell Investigation” (NJ Sea Grant)

19. Weird and Wonderful things… • Mermaid’s purse • Sand dollar • Sea stars

20. 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

21. Cannonball jellyfish www.jaxshells.org

22. Moon jellyfish www.jaxshells.org

23. Sharks’ teeth

24. 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

26. Activity • Beach Treasures