Lophotrochozoa Flashcards
Which clades are combined to form the lophotrochozoans?
Lophophorata and trochozoa.
Describe the phylum annelida.
Triploblastic as an embryo.
Mesoderm goes on to form the coelom in adults.
Long, segmented body covered by a cuticle.
0.5mm to 4m long.
Closed circulatory system.
Define schizocoely.
When secondary body cavities are formed by splitting a solid mass of mesodermal embryonic tissue.
Describe the segmentation of annelids.
Clearly segmented but homonomous.
What are the segments known as in annelids?
The segments are known as metameres and are separated by septa.
What organ systems are found in annelids?
Digestive system.
Circulatory system.
Cephalised nervous system.
Excretory system.
Describe the class polychaeta.
A class of annelids. Possess oblique muscles running at an angle to longitudinal muscles. Each segment has parapodia covered in chaetae.
What gives polychaetes their name?
Each segment has a pair of parapodia that bear bristles (chaetae made of chitin) for movement.
Describe the anatomy of earthworms as a group.
Very similar to polychaetes except for parapodia.
Possess a metanephridium made up of nephrostomes.
What is a metanephridium?
An excretory gland.
Describe the anatomy of leeches as a group.
No septa (no separate cavities). Don't pass food through the gut - blood feeders. Suckers at both ends. Oblique muscles running at an angle. Reduced coelom.
Describe locomotion in segmented lophotrochozoa.
- Longitudinal muscles contract.
- Body expands.
- Circular muscles contract.
- Body elongates.
Describe locomotion in the errantia subclass of polychaetes.
Parapodia movement also contributes to locomotion. Undulation is used to swim.
Describe locomotion in leeches.
Leeches stretch out, then detach and repeat using their sucker pads.
What are the different feeding strategies for small and large food particles?
Small particles are consumed via suspension feeding. An eversible pharynx is used for large food particles.
What are the 3 main groups of earthworms?
Endogeic, epigeic and anecic.
Describe endogeic earthworms.
Rich soil feeders, small in size and produce horizontal burrows.
Describe epigeic earthworms.
Litter feeders, small in size. Non-burrowing.
Describe anecic earthworms.
Litter + soil feeders, large in size and produce extensive vertical burrows.
Describe reproduction in polychaetes.
Gonochronistic but with no permanent sex organs.
Gametes develop in coelom.
Many reproductive strategies, both sexual and asexual.
Define stolonisation.
Each of the small sections of the organism eventually break off to become a separate individual.
Define epitoky.
Entirety/Part of the animal metamorphoses into a sexually mature form.
Describe reproduction in earthworms.
Mainly hermaphrodites.
Cross-fertilisation is most common form.
External fertilisation.
No larval stage.
Describe reproduction in leeches.
No asexual reproduction.
Similar to earthworms (oligochaetes).
Clitellate and hermaphrodite.
Internal mating using a spermatophore is the commonest form of mating.
