Lecture 5 Flashcards
describe the general molluscan body form
radula (can be extended out through the mouth)
head
foot
mantle
mantle cavity
visceral mass
gill
explain the process of torsion in gastropod development
mantle cavity does a 180 twist towards the head-foot (bigger space for head = protection?
twists to the right
inner structures twist with it
describe how various organ systems have been affected by the evolution of shell coiling in modern snails
coiling causes compactness
less space for internal structures like gill, nephridium and heart
organs are smaller
describe the functions of the mantle in gastropods
shell secretion
gas exchange
- mantle cavity houses gills or lungs
excretions and osmoregulation
- receives waste from nephridia
sensory functions
- light, touch or chemicals
defense mechanisms
describe the functions of the mantle in the bivalves
two lobes, one on each side of the body, attached to the shell and body wall. These lobes can form a mantle cavity, a space between the mantle and the visceral mass (the main internal organ area), which houses the gills and other structures.
shell secretion
feeding
excretion and reproduction
sensory and defense
describe the functions of the mantle in the cephalopods
forms the outer body wall and encloses the mantle cavity, which houses the gills, openings for excretion and reproduction, and in some species, the reduced internal shell (e.g., the pen in squids or cuttlebone in cuttlefish).
It’s usually thick and muscular, especially in active swimmers like squids.
describe the movement of water and food through the bivalve
WATER CIRCULATION ***
- water enters through the incurrent aperture
- passes through water tubes where it interacts with gill bars and gill pores (paired gills which occur within the mantle cavity)
- water enters the gill through a water pore
- passes through the water tube which facilitate gas exchange
- all structures are highly cilliated which moves the water
- water exits the gills via the suprabranchial chamber
- exists the bivalve through the excurrent aperture
DIGESTION ***
labial palp (directs food towards the mouth) - mouth- stomach- style sac and crystalline style- intestine- anus
system is enclosed by a gastric shield
CIRCULATION
- pumps blood in an anterior direction
- foot and mantel artery
-posterior and anterior aorta
- blood sinus of the foot
- foot vein
REPRODUCTION
- most are dioecious some are monoecious
- gametes usually expelled through exhalant opening (external fert)
- trochophore -> veliger stages
- unionids (fresh water muscles) brood larvae in mantle cavity, release veligers (glochidium) to parasitize fishes for survival
phylum mollusca
molluscus = soft
snails, bivalves, octopus, squids, etc.
triploblastic coelomates
morphologically variable but clearly united
- head-foot (ventral)
- visceral mass (dorsal)
- mantle and mantle cavity
- radula (chitinous)
trochophore larvae (top shaped and free moving)
open circulatory system (except for cephalopods)
filter feeders
8 classes
gastropods
snails, slugs, lipets
aquatic and terrestrial
intermediate hosts for important parasites
65,000 species
RESPIRATION
- mantle cavity/lung opens via pneumostome
- respiration occurs through the highly vascularized mantle cavity
REPRODUCTION
- some dioecious (egg layers, broadcast spawners)
- some monoecious (copulation and mutual sperm exchange, some protandrous (start male but end up female)
- most marine forms have trochophore larva which develop into veliger (similar to adult form) larva
Bivalves
bis, twice + valva, leaf
muscle, oysters, clams and scallops
aquatic (marine and fresh water)
mostly sedentary
important food source
30,000 species
GENERAL ANATOMY
- umbo (oldest part of the shell)
- adductor muscle scars
- teeth and teeth grooves
- proteinaceous structure (tough but flexible)
- mantle
- nacreous layer
