animals - lecture 10 - october 10 2013 - post
TRANSCRIPT
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7/27/2019 Animals - Lecture 10 - October 10 2013 - POST
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OUTLINE
Phylum Mollusca
Animal Diversity 6th Ed.Chapter 10, Pages 186 - 212
5th
Ed. Chapter 10, Pages 178 - 203
1. Introduction
2. Body Form and Structure
3. Reproduction & Development
- simple body plan
- buccal mass and radula- shell structure and formation
4. Colour Change in Cephalopods (?)
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REPRODUCTION AND DEVELOPMENT
-the majority of Molluscs are dioecious (have separate sexes)
Exceptions to this strategy;
- simultaneous hermaphrodites
- eggs/sperm produced by single individual
- gonad referred to as ovotestis
- reciprocal copulation
Mating Helix aspersa (garden snails)
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REPRODUCTION AND DEVELOPMENT
-the majority of Molluscs are dioecious (have separate sexes)
Exceptions to this strategy;
- simultaneous hermaphrodites
- eggs/sperm produced by single individual
- gonad referred to as ovotestis
- reciprocal copulation
13 24
(some species form mating chains)
Aplysia dactylomela
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- protandrous hermaphrodites (e.g. Crassostrea virginica)
REPRODUCTION AND DEVELOPMENT
-the majority of Molluscs are dioecious (have separate sexes)
Exceptions to this strategy;
- simultaneous hermaphrodites
- eggs/sperm produced by single individual
- gonad referred to as ovotestis
- reciprocal copulation (some species form mating chains)
- individual changes sex from male to female
- occurs as the organism grows older
- after changing to female, reversal may occur every few years
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REPRODUCTION AND DEVELOPMENT
Gamete exchange:
- internal fertilization
copulation occurs and gametes exchanged in genital ducts
- external fertilization
gametes released to surrounding water
results in the development of free-swimming larval stages
trochophore larva stomach
anus
mouth
prototroch
(cilia)
- may feed, catching small plankton in
prototroch, planktotrophic. Can havelong planktonic lives
- non-feeding trochophores have large yolk
reserves, lecithotrophic. Have short
planktonic lives
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REPRODUCTION AND DEVELOPMENT
- may exhibit direct metamorphosis into a small juvenile (e.g. in
polyplacophorans, chitons)
Trochophore larval development
- In bivalves, most often develop
into a second, free-swimming,
larval stage. Veliger larva.
-veliger is enclosed within two
valves (shell).
Velum (ciliated organ)
Velum function;- locomotion
- food collection
- gas exchange
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REPRODUCTION AND DEVELOPMENT
Veliger larva modification in freshwater bivalves:
Glochidium larva
- microscopic non-swimming shelled larva
- initially “ectoparasitic” (10 – 30 days) on fish
valve (shell)
hook edgeadhesive thread
sensory bristles
- attaches to fish gills, encyst and feed by phagocytosis
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REPRODUCTION AND DEVELOPMENT
1
2
3
4
glochidium next to a pinhead
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REPRODUCTION AND DEVELOPMENT
Video of Northern Riffleshell:
http://unionid.missouristate.edu/gallery/epioblasma/
Video of “Fish Lure” Mantle:http://unionid.missouristate.edu/gallery/L_reeveiana/
Reeviana.htm
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REPRODUCTION AND DEVELOPMENT
Glochidia package - ovisac
Video of Fish Eating Ovisac:
http://unionid.missouristate.edu/gallery/ouachita/kid
neyshell.htm
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- layers of specialized structures (chromatophore organs) which
contain pigments.
-light reflective cells (iridophores) are located deeper within the
skin.
COLOUR CHANGE IN CEPHALOPODS
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Structure of the Chromatophore Organs:
Composed of 3 major cell types:1) Chromatophore (the pigment containing cell: yellow, brown,
red or black pigment granules) incased in cytoelastic sacculus
2) Muscle fibers (radially arranged around the chromatophore)
3) Nerve fibers (innervate muscles)
- chromatophores are controlled by the nervous system suchthat changes in skin pigmentation occurs very quickly.
COLOUR CHANGE IN CEPHALOPODS
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COLOUR CHANGE IN CEPHALOPODS
Structure of the Chromatophore Organs:
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Radial Muscles
Pigment
Cytoelastic sacculus
- radial muscles RELAXED: little to no pigment visible
COLOUR CHANGE IN CEPHALOPODS
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- radial muscles CONTRACTED: pigment visible
COLOUR CHANGE IN CEPHALOPODS
Pigment
Cytoelastic sacculus
Radial Muscles
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COLOUR CHANGE IN CEPHALOPODS
Video of Colour Change in Cuttlefish:
http://www.youtube.com/watch?v=r3ebL8pX4ZQ
Video of Chromatophores in Baby Octopus:
http://www.youtube.com/watch?v=59x51Zz-
8kg&feature=related
Cool Video About Colour Change in Cephalopods:
http://www.youtube.com/watch?v=pVIVIq4F3x0