Annelida

Introduction & General Characteristic

Annulus = ring The nearly 1200 species comprising

the phylum Annelida are vermiform. These animals are soft bodies, The bodies consist of a series of

repeating segments. The serial repetition of segments is

known as metamerism.

Introduction & General Characteristic….

The Annelid outer body wall is generally flexible and can play an active role in locomotion.

The thin body wall can serve as a general surface for gas excange.

The cuticle remains permeable to both water and gases (annelids are restiricted to moist environment).

Introduction & General Characteristic….

Annelids segments are generally separated from each other to large degree by septa.

Although some wastes are excreted across the general body surface, excretion generally occurs by means os structure called nephridia

This type nephridium is called a metanephridium.

Annelids distributed among three classes: Oligochaeta, Polychaeta and Hirudinea.

Class Oligochaeta (G; few setae)

Approximatelly 3,500 species are described

Only 6,5% are marine, most are found in freshwater or terrestrial habitats.

This organism become widely used as a biomonitor pollution stress.

Have few cetae without parapodia. The prostoium have no eyes and

tentacles. Gas exchange is accomplisged by

diffusion across a body wall.

Earthworms: ecological importance

Earthworms bury decomposing plant material from the surface, which builds organic constituent of soils.

• Burrowing aerates the soil and improves drainage.

• "It may be doubted whether there are manyother animals which have played so importanta part in the history of the world as have theselowly organised creatures.“ Charles Darwin,

1881 • “…the intestines of the earth…” Aristotle

Cindy Hale, forest ecologist at Natural Resources Research Institute at the University of Minnesota-Duluth

Cindy Hale, forest ecologist at Natural Resources ResearchInstitute at the University of Minnesota-Duluth

Megascolides australis

Gippsland area of Victoria, Australia. Up to 13 feet (4 meters) in length. Rapid movement in the burrows is accompanied by a distinct gurgling sound. Endangered.

Giant Palouse earthworm, Driloleirus americanus.Specimen collected in 2005 by University of Idaho graduate student Yaniria Sanchez-de Leon, at Washington

Anatomy of earthworms

Anterior ¼-1/3 contains the differentiated portions of the digestive tract and the reproductive organs

Closed circulatory system Separation of coelomic fluid and blood. This

figure shows capillaries associated with nephridia, presumably for secretory exchanges

Chloragogue tissue surrounds gut and major blood-

vessels “liver-like” in synthesizing fat and glycogen

Pheretima

Mating position

Class Polychaeta

Complex head, followed by repetitive body segments.

Segments usually have appendages called parapodia

Pharynx of some polychaetes is eversible

and has mineralized jaws

Ventral view of a polychaete head with jaws visible within the pharynx.

Polychaetes are very diverse

• Errantia- the errant polychaetes are active predators, such as Nereis

• Sedentaria- the sedentary polychaetes are tubicolous or burrowing forms

Choelia

Fan worm

Acrocircus

Portula

Deposit feeders tentacles and mucociliary mechanisms to gather small particles from the substrate

• Suspension feeders- ciliated tentacular fans or mucus nets in ventilated burrows to filter food from the water.

Some sedentary (menetap) polychaete groups

Tubicolous suspension feeders Sabellids- “feather-duster” worms with crowns of tentacles, tubes constructed of mucus and detritusSerpulids- tentacles like sabellids, but hard calcareous secreted tube, sometimes spiral

Chaetopterus (parchment tube worm)

Weird/aneh sex in polychaetes

Many have sexual stage called an epitoke that is morphologically and behaviorally specialized for sexual reproduction

The epitoke may be produced by metamorphosis, or it may be produced by longitudinal fission (budding).

The Palolo worm story

Eunice viridis, Fiji and Samoa. “Explosive” spawning 1-3 nights each year, usually 7th night after the first full moon following autumnal equinox (siang malam waktunya sama).

Epitokes swims to surface, millions burst/pecah in unison, forming a slurry of eggs and sperm

Local people feast on the raw worms. Marks the first day of the traditional Samoan year

Trochophore larva of polychaetes

A spider crab crawling through a colony of Lamellibrachia sp. Tubeworms.

Class Hirudinea

Carnivorous, with oral and caudal suckers used for locomotion and feeding Not all are bloodsuckers- freshwater

leeches that prey on invertebrates are more

diverse and common than blood-feeders There are few marine leeches- they are

mainly ectoparasites on fishes, including sharks

Use in medicine for bloodletting

Characteristics of the Hirudinea

Many leeches lay their eggs singly or in groups within cocoons

In one clade, the females carry the egg cocoon and the juveniles on their ventral body surface.

Includes common Placobdella (turtle leeches)

Significance of leeches

Medical use in blood-letting Source of useful proteins, esp.

anticoagulants Model system for neurobiologylarge, identifiable neurons, simple motor

patterns Popular sport-fishing bait

Leech salivary secretions 1. Anesthetic 2. Vasodilator (histamine-like) 3. Antibiotic properties, useful in the treatment of glaucoma. 4. Anticoagulants/antiproteolytics • hirudin, inhibits thrombin (which activates fibrinogen), bdellin, inhibitor of trypsin, plasmin and acrosin, eglin- potent inhibitor

of elastase, cathepsin G, chymotrypsin and subtilisin- blocks inflammatory response • Decorsin- inhibits platelet aggregation

Leech anatomy

Haemadipsa/Pacet

hirudine

Haemadipsa