Mollusca toncheva laska mina 10 7Presentation Transcript
Mollusca Phylum Octopuses, snails, squids and many others…
Mollusca – from the Latin mollis – soft;
Symmetry – bilateral (like humans);
Taxonomy: - appeared 542 to 488.3 MYA;
- most closely related to arthropods, but more inferior than them;
- shared common ancestor with people around 550 MYA;
soft body usually protected by external calcium-containing skeleton (shell);
3 distinct body parts: head-foot ( sensory & motor organs) ; visceral mass ( organs of digestion, excretion and reproduction); mantle (specialized tissue that secrets the shell and holds the body of the organism together) [+ mantel cavity ( houses the gills)];
radula – toothed tongue; for digestion and sometimes for protection;
at least two main nerve cords (3 in bivavlves );
Most reproduce externally, but those that are more complex – internally;
Hermaphrodites or dioecious (one individual is male, the other female);
Releasing of eggs and external fertilization;
eggs -> larvae;
Locomotion & Nervous System
Locomotion - move with the help of a muscle on their down part of the body. This “foot” has a pair of statocysts and it secrets mucus .
Nervous System – have two nervous cords – the visceral and the pedal ones.
Blue Mussels ( Mytilus edulis ) – class Bivalvia;
Grove snail ( Cepaea nemoralis) – class Gastropods;
Broadclub Cuttlefish (Sepia latimanus) - class Cephalopoda
used for food;
production of medicaments and drugs;
pearls, shells – valuable items;
sometimes they bite people and sometime the venom is so poisonous that the person dies;
Ø They have three hearts
Ø Their blood is light blue, just like aristocrats J
Ø They have 80 tentacles, each of which has 240 sucking cups (a total of 1920) used for catching their victim.
Ø Just like sea stars, if their arm is cut, they can regenerate it
Ø They have four noses
Ø A disgusting fact: sometimes right before mating slugs each other’s slime
Ø Snails have the ability to slide on the edge of a blade and still not get hurt
Ø If a person hums quietly to a snail for a little bit of time, the animal will come out of its shell.