Annelids and Allied Taxa

Flashcards about Annelids and Allied Taxa

What are metameres?

Serially repeated units that make up the bodies of annelids.

What are septa?

Partitions that separate the segments of annelids.

What are the benefits of metamerism?

Increased burrowing efficiency, more sophisticated nervous system, and a safety factor due to repeated body parts.

What are annelids in terms of body cavity and development?

A coelomate protostome with spiral mosaic cleavage and schizocoelous coelom formation.

Which phyla, though unsegmented, are now placed within the Annelida based on molecular studies?

Echiura and Sipuncula.

What are setae?

Tiny chitinous bristles found in most annelids, used for anchoring during locomotion or swimming.

What are the two parts that form the head of an annelid?

Prostomium and peristomium.

What is the pygidium?

The terminal portion of an annelid bearing the anus.

What are parapodia?

Flaps on each segment of an annelid.

How does the coelom form in annelids?

By schizocoely.

What is the peritoneum?

Lines the body wall and forms dorsal and ventral mesenteries.

Besides the digestive tract, what structures perforate the septa?

Longitudinal dorsal and ventral blood vessels, plus a ventral nerve cord.

How do longitudinal and circular muscles facilitate movement in annelids?

Contraction of longitudinal muscles causes the body to shorten and expand, while contraction of circular muscles causes the body to narrow and lengthen.

What is the term for alternate waves of contraction that allow efficient burrowing and crawling in annelids?

Peristalsis.

What are the two main groups that Annelida is divided into?

Errantia and Sedentaria.

Give an example of the Errantia group.

The Nereis sp.

Give an example of the Sedentaria group.

The Chaetopterus sp.

What is an errant polychaete?

A marine polychaete worm.

What features characterize errant polychaetes?

Well-differentiated head, specialized sense organs, and paired appendages (parapodia).

What part of Errantia may or may not be retractile and often bears eyes, tentacles, and sensory palps?

Prostomium

What are the parts of the digestive system in errant polychaetes?

Foregut (stomodeum, pharynx, esophagus), midgut, and hindgut.

What do sedentary polychaetes feed on?

Suspended particles or debris in sediment.

Describe the circulation pattern in the Nereis sp.

Dorsal vessel carries blood forward, ventral vessel carries blood posteriorly, with networks around parapodia, septa, and intestine.

What excretory organs are found in Errantia?

From protonephridia to metanephridia, and mixed forms, one pair per metamere.

What are gonads in polychaetes?

Temporary swellings of peritoneum that shed gametes into the coelom.

What are Clam Worms (Nereis)?

They are annelids that live in mucus-lined burrows near low tide level.

What is unique about the setae from fireworms?

Contains poisonous secretions that cause irritation.

How are parapodia modified in Sedentaria?

Modified to anchor the animal in the tube.

What are some ways tubeworms construct the tubes where they live?

Secrete many types of tubes, burrow in sand and mud, particle feeders, or deposit feeders.

What are the characteristics of Tubes from Sedentaria animals?

Tubes have upright orientation and the animal can only move up and down.

Describe the tentacles of sedentaria worms.

They are located on a cephalic lobe, and the nutrients are absorbed from seawater through pinnules and microvilli of tentacles.

How do sedentaria worms derive energy?

A mutualistic relationship with chemoautotrophic bacteria that oxidize hydrogen sulfide.

What houses bacteria in sedentaria worms?

Trophosome.

Describe the nervous system of Echiuridae.

Have a ventral nerve running the length of the body.

What is a clitellum?

A ring of secretory cells found in a band around the body.

Which two classes form the Clitellata clade?

Oligochaeta and Hirudinida.

How do earthworms move?

Peristaltic movements - contractions of circular muscles in the anterior end, anchoring by contraction of longitudinal muscles.

How are paired epidermal setae arranged in Clitellata?

They are set in a sac and project outwards from the body wall.

What do oligochaetes eat?

Scavengers, feeding on decayed organic matter, leaves, refuse, and other animal matter, Calcium in soil.

What increases absorptive surface area in the intestine of oligochaetes?

Typhlosole.

What is the function of chloragogen tissue surrounding the intestine?

Synthesizes glycogen and fat, similar to a liver, and has an excretory role.

How are food, wastes, and respiratory gases transported throughout annelids?

Double transport system: coelomic fluid and blood.

Where is the blood circulated throughout the body of annelids?

Five main trunks running lengthwise through the body.

What is the ciliated funnel called, found anterior of the intersegmental septum, that leads to a small ciliated tubule that connects to the nephridium?

Nephrostome.

What compound do aquatic and terrestrial species of annelids excrete?

Ammonia vs. urea.

Describe the nervous system of oligochaetes.

Pair of cerebral ganglia (brain) connect around the pharynx to the ganglia of the ventral nerve cord.

What do chemical stimuli and tactile responses help aid in the search for, within annelids?

Chemical stimuli and tactile responses.

What stores sperm during sex from other organisms in annelids?

Seminal receptacles.

Are earthworms monoecious or dioecious?

They are monoecious (hermaphroditic)

What creates the cocoon for clitellata worms?

A mucus tube and chitinous band.

How does order Hirudinea differnatite from other anndelida?

Lack setae, and possess anterior and posterior suckers.

What is the segment number of true leeches, and setae count as well?

34 segments, lack setae.

Branchiobdellidae are what to crayfish?

Commensals or Parasitic on crayfish.

What sets the number of segments on a leech?

Fixed number of segments with transverse grooves.

What takes place of the coelomic cavity for leeches (Hirudinida)?

Lacunae.

How do leeches crawl?

Looping movement using suckers.

Freshwater leeches have what structure that is used for ingesting small invertebrates?

Proboscis.

Freshwater leeches have what type of enzymes they secrete to penetrate though skin of prey?

Anesthetic and anticoagulant enzymes.

How do leeches respire?

Through skin or gills (in fish leeches).

Sperm transferred by penis or hypodermic impregnation where spermatophore is expelled by one worm to .

Penetrate another.