Phylum Annelida Flashcards
Annelids have 3 classes, what are they?
- Class Oligochaeta
- Class Hirudinea
- Class Polychaeta
- Class Oligochaeta
Earthworms > No appendages
- Class Hirudinea
Leeches > No appendages
- Class Polychaeta
Marine and Freshwater worms > Have appendages
General Physiology
Terms involved:
Segments
Septa
- Bodies divided into segments that are all very similar.
- Segments are divided by ‘Septa’ >
(small membranes that divide) - Segments are marked by circular grooves called ‘Annuli’.
- Also have internal segmentation of/for organs.
Describe the locomotion of Annelids.
Annelids move by contracting their Circular
and Longitudinal muscles and to anchor themselves forward they use what’s called ‘Setae bristles’ which they have.
Circular muscles contract:
- Segment lengthens
- Diameter decreases
(Opposite for Longitudinal muscles)
Class Polychaeta general overview:
Break down the meaning for ‘Polychaeta’
Clues:
Where are they found?
What feeding methods do they exhibit? (5)
Poly = many / Chaeta = hairs
- Found in all marine and freshwater benthic habitats
- Carnivores, Deposit feeders, Suspension feeders, Grazers and Parasites.
- Great at regenerating body parts and replace missing parts. (Depends on animals energy reserves)
- Loss of head or appendages is not fatal for Polychaetes
Class Polychaeta: Body structure
Terms involved:
Parapodia Peristomium Setae/Chaetae Septa Prostomium Palp Tentacular cirri Pharynx *Exhibits Cephalization! = Bilateral symmetry
- Head = Prostomium
- includes the: antennae, eyes, tentacles, and palps.
- antennae have sensory organs.
- the palps may be sensory or can be used as feeding appendages.
- Some species have one or two pairs of eyes on the prostomium. - Appendages = Parapodia (are paired and lateral)
Pod = foot / Para = like - Setae/Chaetae = Hairs on each segment
- Septa = The membranes which divide the body segments.
- Peristomium = First true body segment after the head.
- includes the tentacular cirrus or cirri which they use to gather and sense food. - Pharynx
- Palps are unique head appendages of annelids. They are used either in feeding or as sensory structures, showing a diversity of external morphology, attachment, and position on the head.
What is Cephalization?
- The gathering of sensory organs and brain structures in the anterior region.
- Organisms with cephalization will always have Bilateral symmetry.
How does new oxygen O2 enter their bodies and carbon dioxide CO2 leave?
Polychaetes have well-developed closed-circuit blood vascular systems.
Functions:
1. Removes wastes, CO2, N (nitrogen) and other metabolites.
2. Brings in O2
***They can have external gills which provide gas exchange as the blood is pumped close to the skin in some species. Others rely on diffusion across the skin.
** Have hearts in each segment.
Class Polychaetes: Reproduction
- Sexual reproduction
(6) types
Sexual reproduction:
- Adults can be **DIOECIOUS
(Having both the male + female reproductive organs in separate individuals) or
- exhibit **sequential Hermaphroditism!!!!!!!!
(Both male + female genitalia) - Broadcast spawning, Copulation, and Epitoky
Class Polychaetes: Reproduction
- Asexual reproduction
Asexual reproduction:
- Budding
- New individuals can bud directly from the adult
Class Polychaetes: Reproduction
- Epitoky
Terms involved: Epitoke Posterior Parapodia Pelagic morph
Epitoky:
- A form of reproduction in some polychaete annelids in which the worms undergo a partial or complete transformation into an epitoke, a pelagic morph capable of sexual reproduction.
Epitoke spawning is when the body or posterior segments of a worm are modified into a gamete carrying machine.
- The posterior segments swim to the surface using the modified parapodia as paddles.
- Eggs and sperm are released into surface waters.
EG: Palolo worms (Samoa)
Class Polychaetes: Feeding methods (4)
> Deposit feeding
Non selective deposit feeding
Selective deposit feeding
Suspension feeders
