L5: Lophotrochozoa, Phylum Mollusca Flashcards
Describe the general molluscan body form Explain the process of torsion is gastropod development Describe how various organ systems have been affected by the evolution of shell coiling in modern snails Describe the functions of the mantle in gastropods, bivalves, and Cephalopods Trace the movement of water and food through a bivalve
What are some of the animals under the phylum Mollusca?
Snails, bivalves, octopus, squids
Mollusca have ____ organization of their tissue layers
Unicellular/diploblastic/triploblastic
Triploblsastic
Mollusca have what kind of triploblastic body cavity?
Acoelomate/pseudocoelomate/coelomate
Coelomate
Mollusca have what general anatomical features?
- Ventral head-food
- Dorsal visceral mass
- Mantle and mantle cavity
- Chitinous Radula
Visceral mass: the soft, non-muscular metabolic region of the mollusc that contains the body organs
Describe the function of the Radula in mosllusca
Tough band bearing teeth that scrapes/tears off food to bring into the mouth
Name three of the 8 classes of molluscs
- Gastropoda
- Bivalvia
- Cephalopoda
What animals are in the class Gastropoda
Snails, slugs, limpets
In the class Gastropoda..
Describe the environment these animals inhabit
Marine, freshwater, terrestrial
In the class Gastropoda..
T/F are end-hosts for important parasites
False - are important intermediate hosts for parasites
In the class Gastropoda..
What is torsion
The head/anterior of the animal twists 180 degrees during development
In the class Gastropoda..
What is one reason torsion may occur
For protection of the head
Pre-torsion, the head is the last part drawn up into the mantle cavity. Post-torsion, it is the first
In the class Gastropoda..
Describe the pros and cons of coiled shells in modern snails
Pro - allows for smaller size
Cons - had to lose some paried structures that existed in primitive snails (a gill, nephridium, heart oracle)
In the class Gastropoda..
How do land snails prevent water loss?
Control the opening & closing of their mantle cavity (keeping it closed to prevent water loss)
Describe Gastropoda reproduction
egg laying, monoecious, etc
Most are egg-laying, dioecious, or broadcast spawners.
Some monoecious, participating in mutual sperm exchange
Some protandrous
Few live-bearing
Broadcast spawner: releases sperm and eggs into environment hoping they’ll meet
Protandrous: Have male function early in life and female function later in life
In the class Gastropoda..
Describe the function of the mantle
Protection of internal organs, respiration
In the class Gastropoda..
Describe the larvae in most marine forms
Most have trocophore larvae that develop into veliger larvae
veliger larvae: look a lil more like adult form
What animals are in the class Bivalvia?
Mussels, oysters, clams, scallops
Describe the environment Bivalves inhabit
Marine, freshwater
T/F Bivalvia are mostly sedentary
true - most stay on the sea floor except clams & scallops
In the class Bivalvia..
Describe how the bivalves can open and close their shells
Abductor muscle scars
In the class Bivalvia..
Describe the Umbo
Oldest part of the shell, on dorsal side
In the class Bivalvia..
What are the function of the teeth on their shell?
Teeth can interlock when closed to make it harder to open
What kind of feeders are Bivalvia
Filter feeders
Pump water through their system
Describe water circulation in Bivalves
Water enters via incurrent aperture, enters through pores in perforated gills and moves upwards to the suprabrachial chamber, where it exits via the excurrent aperture
