Mollusks

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Mollusks
Liz Tobin Zooplankton Ecology 4/8/09
Photos Marine Invert. Zoo., FHL
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Phylum Mollusca

• Second largest phylum with gt100,000 species
• Highly diverse
• Phylogeny under debate and still in flux (UCMP)
• Most mollusks have a planktonic larval stage

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Mollusk Phylogeny
Bilateria
Aplacophora
Based on 18S rRNA sequence
From Tree of Life Web Project
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7 Classes of Mollusks
Aplacophora with out shells, worm-like,
benthic, deep water (320 sp.)
Cephalopoda - Squid, octopus, nautilus ( 800
sp.)
Bivalvia - Bivalves (clams, mussels, oysters,
scallops) ( 10,000 sp.)
Gastropoda - snails, slugs, sea hares and
limpets (62,000)
Monoplacophora one shell, small group, deep
ocean dwellers (20 sp.)
Polyplacophora Chitons, external shell with 8
overlapping plates, intertidal and
subtidal ( 800 sp.)
Scaphopoda tusk snails, tubular shell open at
both ends, benthic, lack gills and heart
( 400 sp.)
UCMP - Berkley
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Two dominant groups of Gastropods

• Prosobranchs
  gills in front of heart
• (limpets, abalone, marine snails)

Heterobranchs
different gilled
(sea slugs and pteropods )
photo by D. Vaughn, UW
www.noaanews.noaa.gov
Photo TOL
Gastropteron pacificum (sea slug)
Littorina (marine snail larva)
Limacina helicina (pteropod)
Atlanta californiensis (heteropod)

photos by L. R. Page, UBC
www.biol.sc.edu
Tectura. (limpet larva)
Dolabrifera (sea hare larva)
Haliotis (abalone larva)
Clione limacina (pteropod)
Opisthobranchs
www.aquatech-aust.com.au
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Two dominant groups of Cephalopods

• Octopoda
• (octopus)

Teuthida (squids)
www.tolweb.org
Larva
Abraliopsis
seawifs.gsfc.nasa.gov
Larva
Bolitaenidae (small pelagic octopus)
Berryteuthis
Photos Fisheries and Oceans Canada
Fisheries and Oceans Canada
2 main clades of Cephalopods Coleoidea
Nautiloidea (nautilus)
UCMP
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Habitat of zooplankton mollusks

• Global/Ubiquitous
• open ocean, coastal, estuaries, intertidal,
  deep-sea, reefs
• polar, temperate and tropical regions

(UCMP, Kozloff)
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General Mollusk Life Cycle

• Fertilization of eggs
• Freely spawn or deposit egg masses
• Larval stage
• Post larval juvenile stage
• Adult stage

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Generalized Life Cycle of Gastropods
Haliotis asinina (abalone)
Internal or external fertilization
free spawn or egg masses/capsules
(some brood egg masses under foot)
Hatch as trochophore (hours) and/or veliger
larvae (days months)
Post larval, juvenile stage (some forms
maybe planktonic)
Photos commons.wikimedia.org
Adult stage (benthic or planktonic)
Holoplanktonic and Meroplanktonic
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Generalized life cycle of marine bivalves
. Figure Shanks 2001
Meroplanktonic
Photos http//el.erdc.usace.army.mil/zebra/zmis/z
mishelp4/veliger_stages.htm
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Generalized Life Cycle of Cephalopods
Egg bunches or cases
Photo Clark Anderson/Aquaimages
Separate sexes
www.alaskasealife.org
paralarva
Juvenile stage
www.alaskasealife.org
Holoplanktonic and Meroplanktonic
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Unique characteristics/morphology

• Gastropod veliger larvae

Mantle - tissue covering visceral mass
(internal organs) Operculum - shell closure trap
door Torsion - 180 twist of vicera, mantle
and shell Velum - cilia bearing lobes for
feeding and swimming Statocyst balancing
organ Avg. size range 100 1000 µm
Photo Shanks
All mollusks have a mantle
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Unique Characteristics/morphology
Trochophore larvae of more primitive prosobranchs
Shanks 2001
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Unique characteristics/morphology cont.
Bivalves
Cephalopods
www.tolweb.org
http//el.erdc.usace.army.mil/zebra/zmis/zmishelp4
/veliger_stages.htm
Paralarva
Veliger larva
Well developed eyes Feeding tentacles and/or arms
w/suckers Beak Chromatophores Siphon
Ciliated velum Bivalved, hinged shell symmetrical
size range 90 700µm
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General feeding ecology and food sources

• Gastropods radula
• Adult forms herbivorous grazers, specialized
  carnivory, planktivorous, suspension feeders
  -mucus nets (Shanks)
• Larval forms DOM, ciliated prey capture of
  particulate organic matter
• (Shanks, Manahan)
• Bivalves
• Larval forms DOM, ciliated prey capture
• Cephalopods radula, two-part beak, tentacles
  (capture) and arms (secure) with suckers.
• Adult forms active, visual predators
• Larval forms active, visual predators of
  other zooplankton

www.tolweb.org
life.bio.sunysb.edu
life.bio.sunysb.edu
Oxygiris sp. (heteropod)
Gleba cordata (pteropod)
UCMP -Berkley
oceanexplorer.noaa.gov
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Predators of zooplankton mollusks
Fish
Other Zooplankton
Herring Mackerel Salmon
photo by D. Vaughn, UW
Photo from Johnson and Brink, 1998
Birds, Whales, and Crustaceans
(Lalli and Gilmer)
myweb.dal.ca/rpcroll/gallery.html
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Ecological Role

• Important food source for many marine organisms.
  (Lalli and Gilmer)
• Survival and distribution of the planktonic
  larval stage determines the survival and location
  of adult populations.

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A few interesting facts/studies
Reference Biol. Bull. 213 152159. (October
2007)
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Reference Biol. Bull. 182 l-7. (February, 1992)
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Umbo stage Geoduck larva
Video by Karen Chan
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Mollusk Video Links

• Clione sea angle feeding
• http//www.youtube.com/watch?vpqUlKSGcI8Q
• Veliger larvae swimming
• http//www.youtube.com/watch?vYKtJNZGkVkE
• http//www.youtube.com/watch?vf2TKHdpOX4k

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References

• Hermans, C.O. and Satterlie, R.A. 1992.
  Fast-Strike Feeding Behavior in a Pteropod
  Mollusk, Clione limacina Phipps. Biol. Bull. 182
  1-7.
• Johnson, K.B. and Brink, L.A. 1998. Predation on
  Bivalve Veligers by Polychaete Larvae. Biol.
  Bull. 194 297-303.
• Kozloff, E.N. 1990. Invertebrates. Saunders
  College Publishing.
• Lalli, C.M. and Gilmer, R.W. 1989. Pelagic
  Snails the biology of holoplanktomic gastropod
  mollusks. Stanford University Press.
• Shanks, A.L. 2001. An Indetification Guide to the
  Larval Marine Invertebrates of the Pacific
  Northwest. Oregon State University Press.
  Corvallis, OR.
• Strathmann, M.F. and Strathmann, R.R. An
  Extraordinarily Long Larval Duration of 4.5 Years
  from Hatching to Metamorphosis for Teleplanic
  Veligers of Frusitriton oregonensis. Biol. Bull.
  213 152-159.
• University of California Museum of Paleontology.
  Available
• http//www.ucmp.berkeley.edu/taxa/inverts/mollusc
  a/mollusca.php
• Tree of Life Web Project. Available
• http//tolweb.org/Mollusca
• Fisheries and Oceans Canada Pacific Region.
  Available

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• Holoplanktonic mollusks
•  
• Heteropods small group of pelagic relatives of
  snails, snail food developed into a single fin
  good eyes, visual predators
• Pteropods snail foot developed into paired
  wings suspension feeder produce large mucous
  nets to capture prey carbonate shells produce
  pteropod ooze on sea floor