Phylum Mollusca Flashcards
What are the three layers of the shell?
- Periostratum (conchiolum protein, outer organic layer)
- Prismatic layer (prisms of CaCO3 in (laid down by) protein matrix)
- Nacreous layer (inner layer of calcareous nacre in layers, laid over thin protein matrix)
What are the two parts of a mollusc?
- Head-foot (feeding, sensory, cephalic, locomotory)
- Visceral mass (reproductive, respiratory, circulatory, digestive)
What happens to products of digestion, respiration, reproduction, etc?
- Emptied into the mantle; ‘the everything hole’
What is a mollusc nervous system like?
The mollusc nervous system consists of several pairs of ganglia with connecting nerve cords and is generally simpler than that of annelids and arthropods. Contains neurosecretory cells which may produce a growth hormone and function in osmoregulation.
What is the mantle?
The mantle is a dorsal body wall which typically secretes a calcareous shell.
What is the extent of the coelum?
The coelum is reduced to a cavity around the heart, nephridia, gonads.
Which classes have an open circulatory system?
Every mollusc class besides cephalopods have an open circulatory system. Usually partly open or partly closed.
What is the radula?
The radula is a rasping, serrated tongue that can be used to scrape food off rocks or tear food and acts as a conveyor belt to digestive tract.
The teeth that sit on odontophore cartilage.
when they wear out they are reabsorbed into body and replaced constantly.
What do retractor muscles control?
Rectractor muscles control the ‘foot’
Is there a through gut?
Yes, but contents are emptied into the mantle
What are the characteristics of an open circulatory system?
- Blood is poured from heart over internal organs in haemocoel.
- Some closed aspects around heart at site of oxygenation in gills just before heart.
- Inefficient: causes organism to be slow moving, always a mix of oxygenated and not oxygenated, not high O2 content.
What is the mantle cavity?
The mantle cavity is ‘an everything hole’ of diverse function.
- Anus empties into m.c.
- Contains organs, lungs, gametes, gills, etc
What is the digestive gland?
The digestive gland connected to the stomach is like a liver
What is pearl?
Pearl is the necrous layer, or forms when sand particle gets under mantle and covered in nacrous layer.
What are the molluscs?
Molluscs have soft, unsegmented bodies, consisting typically of an anterior (ventral) head, a ventral head-foot structure and a dorsal visceral mass.
The body is more or less surrounded by a thin, fleshy mantle and is commonly protected by an external calcareous shell.
The coelom is reduced to the cavities of nephridia
(kidney units), haemocoel, gonads and pericardium.
There are 80,000 living species of molluscs and 35,000 fossil species. The phylum includes the most intelligent of all the invertebrates.
