Lecture 14 Flashcards
Phylum Mollusca Characterisitcs
Includes:Snails, clams, mussels, octopuses, chitons, nudibranchs, squid, etc
• Lophotrochozoan Protostomes
• Triploblastic
• Coelomate (coelom is confined to small area around the heart)
• Bilateral symmetry
• Bilateral asymmetry in some
• Hydrostatic skeleton, and in some, a shell
• Complete gut
• No metamerism
• Reproduction: Sexual reproduction (monoecious or dioecious), no asexual reproduction
• Organ-system grade of organization
• Mostly open circulatory system
• Closed in cephalopods
Classes Phylum Mollusca
Class Gastropoda:
• Snails, limpets, slugs, whelks, conchs, periwinkles, sea slugs, sea hares, sea butterflies
Class Bivalvia: two valves (i.e. shells)
• Mussels, clams, scallops, oysters, and shipworms • Mostly sedentary filter feeders
Class Cephalopoda:
•Squids, octopuses, nautiluses, devilfish, and cuttlefish
• Marine active predators
can Cephalopoda be terrestrial?
No! only marine, however, some gastropods are terrestrial
Mollusca – Form and Function
consists of two basic parts:
• Head-foot:
feeding, cephalic, sensory, locomotor organs
• Visceral mass:
digestive, circulatory, respiratory, and reproductive organs
Many molluscs have a protective shell secreted by the mantle
Head characteristics (mollusca)
• Well-developed head with mouth and sensory organs • Mouth contains a structure unique to molluscs; the radula • Radula is a rasping, protrusible, tonguelike organ found in most molluscs
Foot Characteristics
• Adapted for:
• Locomotion and/or Attachment
• Usually a ventral, sole-like structure
• Modifications (e.g.)
Laterally compressed foot (bivalves)
Funnel (siphon) for jet propulsion in cephalopods
Mantle
In mollusca
• Mantle is a sheath of skin, extending dorsally from the visceral mass, that wraps around each side of the body
Protects the soft parts
Outer surface of the mantel secretes the shell
Mantle Cavity
In mollusca
- houses respiratory organs (gills or a lung)
- exposed surface also participates in gas exchange
- Products from digestive, excretory, and reproductive systems empty into the mantle cavity
Reproduction in mollusca
- Sexual reproduction only (mostly dioecious)
* Most pass through free-swimming trochophore and veliger larval stages
Trocophore larvae
Molluscs and annelids have a trochophore larvae
a free-swimming ciliated marine larva
characteristic of members of the Lophotrochozoa clade
Veliger larvae
free-swimming larva of most marine snails, and bivalves. It develops from a trochophore and has the beginning of a foot, shell, and mantle
Functions of Circulatory system
transports: • Gases • Nutrients • Waste • Hormones • (heat)
Why is diffusion bad for larger organisms
though simple, it takes a very long time so only works for small flat lil fellas
Types of Circulatory Systems
Closed circulatory system
Open circulatory system
Closed circulatory system
- Blood is contained within vessels
* Vertebrates and some invertebrates (e.g. annelids, cephalopods)
Open circulatory system
• Blood is confined to vessels in only a
portion of circuit through body
• Blood mixes with interstitial fluids (i.e. fluids between cells) in the hemocoel
• Because it is mixed with fluid, it is properly called hemolymph
• Arthropods and some molluscs
Class Gastropoda characteristics
Phylum mollusca Very diverse Many, but not all, have shells Terrestrial or aquatic bilateral symmetry but visceral mass is asymmetrical
Adaptations to Avoid Fouling in gastropods
The loss of the right gill reduces the effects of fouling
exhibit bilateral asymmetry
class bivalvia characteristics
two valves (i.e. shells)
• Mussels, clams, scallops, oysters, and shipworms
•Marine and freshwater forms
• Mostly sedentary filter feeders , filter by ciliary action
•No head, no radula
•Very little cephalization
What is Cephalization
concentration of sensory and neural organs
Ocelli
simple eye or eyespot in many types of invertebrates AND BIVALVIA
Bivalvia - Locomotion
sedentary (mussels) or sessile (oysters)
or move slowly
some move by clapping their valves together
Class Cephalopoda charcteristics
- Squids, octopuses, nautiluses, devilfish, and cuttlefish
- Most complex molluscs
- Marine predators
- chiefly eat small fishes, other molluscs, crustaceans, and worms
- Highly mobile
- Vary in size
- Tentacles and arms capture prey by adhesive secretions or by suckers
How does Class Cephalopoda move
Swim by expelling a jet of water from their mantle cavity through funnel (derived from the foot)
Cephalopod - Form and Function
only shelled Cephalopods is Nautilus species
Cuttlefish and squid have an internal
shell called a pen
octopus have no shell