13 phylum mollusca Flashcards
Phylum MOLLUSCA
(molluscus = “soft”)
* 90,000 living species (70,000 fossil species)
* Soft bodied invertebrates
* Modes of feeding may be herbivorous, predaceous carnivores, filter feeders, or parasitic
* Marine, freshwater, and terrestrial habitats
* Bilaterally symmetrical
o In some, they display Bilateral Asymmetry (body divided into left and right, but are not equal)
* Unsegmented; often with definite head
* Level of complexity: organ-system grade
* Triploblastic, eucoelomate
Phylum MOLLUSCA
a structure unique to Mollusca; a protrusible, tongue-like
organ which consists of rows of tiny teeth found within the mouth
Radula
– a ventral, sole-like structure for locomotion and capturing food
foot
“visceral” means
organs
a sheath of skin that hangs down on each side of the body to protecting the soft parts
of the visceral mass.
Mantle
the space between the mantle and visceral mass
mantle cavity
secreted and lined by the mantle. Absent in some groups.
Shell
outer layer, composed of conchiolin
Periostracum
middle layer, composed of calcium carbonate
Prismatic layer
very thin inner layer called “nacre” that lies next to the mantle; increases in thickness during life of animal; composed of very crystalline calcium
Nacreous layer
formed in clams.
pearls
– a paired comb-like or feather-like respiratory organ or gill with many filaments that line up in a row
Ctenidium (plural: Ctenidia)
Most have a pair of kidneys called:
metanephridia
of several pairs of cerebral ganglia
brain
main ganglia in head area
Cerebral
main ganglia near gills/ctenidia
Pleural
main ganglia that controls the foot/tentacles
pedal
ganglia that controls the visceral organs
visceral
ganglia around the mouth
buccal
free-swimming larva that emerges from
the egg (or occurs inside the egg in some molluscs)
trocophore
the larval form that follows after trocophore stage in many molluscan groups.
veliger
– a one-piece shell that is coiled (but some species it is uncoiled)Depending on direction of coiling, it may be right-handed or left-handed (this is genetic)
Univalve shell
color changing cell in scattered in the epidermis; they are under nervous and
hormonal control
Chromatophores
secretes a dark fluid called sepia into an ink sac, that empties to the rectum to release a cloud of ink when animal is alarmed.
ink gland
one arm of adult males is modified as an intromittent organ that is used to pluck a spermatophore from his own mantle cavity and insert it into the mantle cavity of a femal. Eggs are attached to stones or other objects.
Hectocotylus
