7/27/2019 Animals - Lecture 10 - October 10 2013 - POST

http://slidepdf.com/reader/full/animals-lecture-10-october-10-2013-post 1/16

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 (?)

7/27/2019 Animals - Lecture 10 - October 10 2013 - POST

http://slidepdf.com/reader/full/animals-lecture-10-october-10-2013-post 2/16

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)

7/27/2019 Animals - Lecture 10 - October 10 2013 - POST

http://slidepdf.com/reader/full/animals-lecture-10-october-10-2013-post 3/16

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

7/27/2019 Animals - Lecture 10 - October 10 2013 - POST

http://slidepdf.com/reader/full/animals-lecture-10-october-10-2013-post 4/16

- 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

7/27/2019 Animals - Lecture 10 - October 10 2013 - POST

http://slidepdf.com/reader/full/animals-lecture-10-october-10-2013-post 5/16

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

7/27/2019 Animals - Lecture 10 - October 10 2013 - POST

http://slidepdf.com/reader/full/animals-lecture-10-october-10-2013-post 6/16

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

7/27/2019 Animals - Lecture 10 - October 10 2013 - POST

http://slidepdf.com/reader/full/animals-lecture-10-october-10-2013-post 7/16

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

7/27/2019 Animals - Lecture 10 - October 10 2013 - POST

http://slidepdf.com/reader/full/animals-lecture-10-october-10-2013-post 8/16

REPRODUCTION AND DEVELOPMENT

1

2

3

4

glochidium next to a pinhead

7/27/2019 Animals - Lecture 10 - October 10 2013 - POST

http://slidepdf.com/reader/full/animals-lecture-10-october-10-2013-post 9/16

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

7/27/2019 Animals - Lecture 10 - October 10 2013 - POST

http://slidepdf.com/reader/full/animals-lecture-10-october-10-2013-post 10/16

REPRODUCTION AND DEVELOPMENT

Glochidia package - ovisac

Video of Fish Eating Ovisac:

http://unionid.missouristate.edu/gallery/ouachita/kid

neyshell.htm

7/27/2019 Animals - Lecture 10 - October 10 2013 - POST

http://slidepdf.com/reader/full/animals-lecture-10-october-10-2013-post 11/16

- layers of specialized structures (chromatophore organs) which

contain pigments.

-light reflective cells (iridophores) are located deeper within the

skin.

COLOUR CHANGE IN CEPHALOPODS

7/27/2019 Animals - Lecture 10 - October 10 2013 - POST

http://slidepdf.com/reader/full/animals-lecture-10-october-10-2013-post 12/16

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

7/27/2019 Animals - Lecture 10 - October 10 2013 - POST

http://slidepdf.com/reader/full/animals-lecture-10-october-10-2013-post 13/16

COLOUR CHANGE IN CEPHALOPODS

Structure of the Chromatophore Organs:

7/27/2019 Animals - Lecture 10 - October 10 2013 - POST

http://slidepdf.com/reader/full/animals-lecture-10-october-10-2013-post 14/16

Radial Muscles

Pigment

Cytoelastic sacculus

- radial muscles RELAXED: little to no pigment visible

COLOUR CHANGE IN CEPHALOPODS

7/27/2019 Animals - Lecture 10 - October 10 2013 - POST

http://slidepdf.com/reader/full/animals-lecture-10-october-10-2013-post 15/16

- radial muscles CONTRACTED: pigment visible

COLOUR CHANGE IN CEPHALOPODS

Pigment

Cytoelastic sacculus

Radial Muscles

7/27/2019 Animals - Lecture 10 - October 10 2013 - POST

http://slidepdf.com/reader/full/animals-lecture-10-october-10-2013-post 16/16

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