Phylum Annelida

What are the three historically grouped classes of Phylum Annelida?

Polychaeta, Oligochaeta, Hirudinida

True or False: Leeches arose within the oligochaetes.

True

True or False: Oligochaetes arose within the polychaetes.

True

What are the general features of Phylum Annelida?

Eucoelomate, Protostomes, Spiral cleavage, Segmented, Setae present

What is the body plan of Phylum Annelida?

Elongated, Two-part head (Peristomium and Prostomium), Segmented body (trunk), Pygidium bearing anus, Non-chitinous cuticle covers body, Parapodia may be present, Coelom walled off by peritoneum, Hydrostatic skeleton created by coelomic fluid

What are the two groups within Phylum Annelida?

Errantia and Sedentaria

What are the characteristics of Errantia?

Free moving, highly active, mostly polychaetes

What are the characteristics of Sedentaria?

Sessile or mostly sessile, some polychaetes, oligochaetes, and leeches

What are the features of motile polychaetes?

Mostly marine, parapodia present, numerous setae, lacking clitellum

What is the function of the prostomium?

Overlies the mouth, contains eyes, tentacles, and sensory palps

What is the function of the peristomium?

Surrounds the mouth, contains setae, chitinous jaws, and tentacles

What is the function of the trunk in motile polychaetes?

Segmented with parapodia

What is the typical nutrition of motile polychaetes?

Predators or scavengers, foregut for acquisition of food, midgut for digestion, hindgut for absorption of nutrients

What are the circulation and respiration methods in motile polychaetes?

Circulation may be open or closed, coelomic fluid may assist in transport, parapodia, gills, and cutaneous respiration are known

What are the excretion methods in motile polychaetes?

Most have metanephridia, some have protonephridia and metanephridia, one pair per segment

What is the nervous system of motile polychaetes?

Dorsal cerebral ganglia, ventral nerve cord, highly developed sense organs

What are the reproductive characteristics of motile polychaetes?

Lack permanent sex organs and clitellum, typically dioecious, external fertilization, trochophore produced, some unique strategies like atokes and epitokes

What are the characteristics of sedentaria polychaetes?

More sessile or sessile

What are Oligochaetes?

Segmented worms with few setae, found in terrestrial, freshwater, and marine habitats.

What are Leeches?

Segmented worms with a modified head and tentacles used for food capture.

What is the body plan of Oligochaetes similar to?

Errantia, except for the modified head.

What do Tubeworms secrete?

A tube they live in, which can be papery or leathery.

What is the feeding behavior of most Tubeworms?

Particle feeding, as well as ciliary and deposit feeding.

What is Clade Clitellata composed of?

Earthworms and allies in Oligochaeta, and leeches in Hirudinida.

What do members of Clade Clitellata share?

A clitellum, a ring of secretory cells in the epidermis.

When is the clitellum visible in oligochaetes and leeches?

Always visible in oligochaetes, and only visible during reproduction in leeches.

What do members of Clade Clitellata lack?

Parapodia, which are appendages used for locomotion in other annelids.

What is the reproductive strategy of all members of Clade Clitellata?

Monoecious (having both male and female reproductive organs) with direct development.

What are the characteristics of Oligochaetes?

Not a monophyletic group, mostly found in terrestrial and freshwater habitats, some are marine, and have few setae.

How do Oligochaetes move?

Circular and longitudinal muscles contract to change the shape of segments, shortening pushes setae from the body allowing for grip against soil.

What is the nutrition of Oligochaetes?

Most are scavengers, they moisten food with their mouth and draw it in with their pharynx, may ingest excess soil, food is stored in crop and then transported to the gizzard for grinding, and they have a typhlosole that enhances surface area.

How does circulation work in Oligochaetes?

Both coelomic fluid and fluid of a closed circulatory system aid in transport, the dorsal vessel pumps blood anteriorly, the ventral vessel pumps blood posteriorly, and there are five aortic arches that help maintain blood pressure.

What is the respiratory system of Oligochaetes?

There is no dedicated organ, respiration is done through cutaneous respiration.

How do Oligochaetes excrete waste?

They have metanephridia, with each segment bearing a pair, at the opening is a nephrostome, and the posterior of the nephrostome is a convoluted tube ending in a nephridiopore.

What is the nervous system of Oligochaetes?

They have both a central nervous system (CNS) and a peripheral nervous system (PNS).

What is the reproductive strategy of Oligochaetes?

They are monoecious, meaning they have both male and female reproductive organs.

What are the characteristics of Hirudinida?

Predominantly freshwater, with some marine and terrestrial species, dorsoventrally flattened, and all are monoecious.

What is the significance of clitellum in these organisms?

Present in these organisms

What is the feeding behavior of these organisms?

Fluid feeders, even if predaceous

What are the characteristics of the respiratory and excretory systems?

Gas exchange through skin, parasites of fish have gills, 10-17 pairs of nephridia

How is the nervous system structured in these organisms?

Two brains (anterior and posterior), presence of photoreceptors and sensilla

Describe the circulation system in these organisms.

Highly variable, some have dedicated vessels, others have sinuses within the body, serve as an open circulatory system

What is the reproductive strategy of these organisms?

Monoecious with cross-fertilization, sperm transferred by penis, cocoon secreted by clitellum, direct development

What is the purpose of false annuli in these organisms?

To give the appearance of more segments

What is the presence of distinct coelomic compartments in these organisms?

Lacking

What is the presence of septa in these organisms?

Absent from all but one species

What are the characteristics of the oral and posterior ends of these organisms?

Suckers are generally present