Introduction to Fungi: Evolution, Characteristics and Life...
Transcript of Introduction to Fungi: Evolution, Characteristics and Life...
Lecture Mollusks
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Aculifera – with spicules Aplacophora - mollusks without shells Polyplacophora ( Amphineura) – chiton, eight plates, intertidal
Conchifera – with shells Monoplacophora - mollusks with one shell, ancient Gastropoda ( Univalve) – snails, slugs, abalones, whelks, periwinkles, giant
conch, most species
Pelecypoda ( Bivalve) - clams, oysters, mussels, second largest species.
Scaphopoda - a tubular shell - tusk shells Cephalopoda – squid, octopus, chambered nautilus
Phylum Mollusca Classes
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Mollusk TermsLATIN LIVES
• Phora = Bearing• Mono = One• Placo = Plate• Cephalo = Head• Scapho = Sword• Pelecy = Hatchet• Poda = Foot
• Head = Eyes, Mouth ( Radula –rasping sucking tongue) and Tentacles • Visceral Mass = Mantle which secretes the shell, and the gills,
intestines, kidneys, heart.• Foot = large muscular organ to move the body.
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Mollusk Body Plan• Mantle : A thick epidermis that covers the dorsal side of
the body- the epidermis of the mantle secretes calcium carbonate and conchiolin (protein), and creates a shell.
• Mantle cavity - space between mantle and visceral mass- houses the respiratory organs (ctenidia, or gills) and the openings of excretory, reproductive & digestive organs
• The muscular foot is adapted for locomotion, attachment, food capture-Or a combination of the above
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Mollusk Body Plan
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Haemocoel
• Affinity of blood with oxygen enhanced by haemocyanin.
• Blood receives oxygen by diffusion from water stream into central vessel.
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Shell
• Shield protecting soft-bodied mollusks against predators, mechanical damage and desiccation
• Evolutionary loss of shell : loss of protection balanced by gain in mobility and lightness
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Excretion
• Waste collected from haemocoel filters into the pericardial coelom.
• Waste then discharged into mantle cavity through a duck
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Class Polyplacophora (Chitons)
-Marine mollusks that have oval bodies with eight overlapping dorsal calcareous plates
-Body is not segmented under the plates-Most chitons are grazing herbivores
Photo Credit for Lined Chiton: Kirt L. Onthank, 2007, Wikimedia Commons
Gastropods
Photo Credit for Florida Fighting Conch: LA Dawson, 2006, Wikimedia Commons
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Class Gastropoda (Snails and slugs)
-A primarily marine group-Heads typically have pairs of tentacles with eyes at the ends-During embryological development, gastropods undergo
1. Torsion – Mantle cavity and anus are moved from the posterior to the front2. Coiling – Spiral winding of the shell
Torsion : prosobranchsHappens during larval stageTorsion may have benefits - increased water current - allowing the animal to
withdraw more deeply into the shell
Disadvantage- could result in fouling of the mouth and sense organs.
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Opisthobranchs
• Untwisted : mantle cavity is back
• Feed on hydroids, anemones, and corals
• Immune to nematocysts
Proboscis of a predatory marine snail Mitra mitra.
Kelletia kelletii are feeding on a dead fish using a long, prehensile proboscis.
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Class Bivalvia (Bivalves)• Includes clams, scallops, mussels, oysters and
others• Have two lateral (right and left) shells (valves)
hinged together dorsally• Head and sensory organs lost, Radula lost • Most are sessile filter-feeders
-Water circulation is mediated by siphons and rhythmic beating of cilia on gills- Feeding assisted by ciliated labial palps
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Bivalves
Bysuss
Feeding
The labial palps secrete a mucus that entangles suspended food and nutrient particles within the water to produce a ball of food and mucus called a bolus. Afterwards, cilia on the palps direct the bolus into the mouth.
Razor shell (맛조개)
Gastropods and Bivalves
http://people.bu.edu/veliger/http://oceanlink.island.net/abaloneproject/growthanddevelopment/growth%20and%20development.htmhttp://score.dnr.sc.gov/ktmlpro10/images/uploads/oysterlifecycle.jpg?0.40941442132799155
Larval development
Manila clam culture• sexual maturity is generally attained when the
clams about 20 mm. • Males and females : Eggs and sperm are
released into the water where fertilization occurs
• The fertilized eggs develop into straight-hinge, free swimming larvae within 24 hours. This 90µm shelled larva is called a veliger larva
• The microscopic clam feeds on phytoplankton of a size range of 2 to 20µm. This veliger stage lasts for about two weeks, during which it grows to approximately 200µm.
• a pediveliger crawls with its foot and swims with its velum looking for a suitable habitat
• preferred higher in the intertidal zone than most clams, in shallow depth of sand-gravel substrate. http://innovativeaqua.com/Publication/clam.pdf
Scaphopoda (Tusk shells)
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Class Cephalopoda• Expanded along the dorsoventral axis, and
ventral side becomes anterior.• Foot has evolved into a series of arms equipped
with suction cups -Squids have 10; octopuses, 8; and nautiluses, 80 to 90
• Have highly developed nervous systems• Exhibit complex patterns of behavior and a high
level of intelligence• Closed circulatory system
Cephalopods
http://cas.bellarmine.edu/tietjen/images/Image32.gif
Anatomyhttp://scienceblogs.com/deepseanews/beak1.jpg
Centralized Nervous System
Camouflage :change the color or chromatophores, pigment-containing and light-reflecting cells
Cephalopods
Body evolved for active predation Use funnel for jet propulsion
http://www.squidblog.net/uploads/squid_jet_diagram.gifhttp://www.mbari.org/news/homepage/2004/loligo_close_350.jpg
Cephalopods
Video with Octopus and Cuttlefish: Start at 1:20 minutes http://www.youtube.com/watch?v=zC0zOLqYnRg&feature=related
Chambered Nautilus Photo Credit for Octopus: Albert Kok, 2007, Wikimedia Commons
Cephalopods
Photo Credit for Flamboyant Cuttlefish: Jenny Huang, 2006, FlickrPhoto Credit for Caribbean Reef Squids: Clark Anderson, 2006, Wikimedia Commons
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Mollusk Reproduction• Most mollusks have distinct
male and female individuals• Most engage in external
fertilization• In marine mollusks, embryos
develop through spiral cleavage-Trochophores: Free-swimming larval stage-Veliger: Second free-swimming larval stage (Only in bivalves and snails)
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Mollusk Reproduction