Exercise 6 - Annelida

• Phylum Annelida is a large group of segmented worms (around 16,500 species) occurring worldwide in marine and brackish waters, freshwater, and terrestrial habitats.
• Members of this group have elongadte bodies divided into segments or metameres or somites, by grooves or annuli.
• The coelom is large and their body walls bear paired bristles called setae.
• Digestion is extra-cellular and excretion occurs mostly through paired metanephridia.
• The nervous system is composed of nerve cords and ganglia. They may be hermaphroditic or dioecious.
• Embryonic development includes trochophore larvae.
• What are the three classifications of the Phylum Annelida?

  1. Class Polychaeta
  2. Class Oligochaeta
  3. Class Hirudinea
• Class Polychaeta – Mostly marine, head distinct and bearing eyes and tentacles, mostly  segments with  parapodia bearing two tufts of setae, clitellum absent, usually dioecious.
• Class Oligochaeta – Few setae per somite, no parapodia, head absent, hermaphroditic, chiefly terrestrial and freshwater.
• Class Hirudinea – Body with fixed number of segments which is 34, prominent anterior and posterior suckers, setae absent, coelom packed with connective tissue and muscles, hermaphroditic, marine, terrestrial and freshwater.
• Some classification schemes reduce the annelid classes into two based on the presence and absence of clitellum Aclitellata (Polychaeta) and Clitellata (Oligochaeta and Hirudinea).
• Perinereis - This clamworm or sandworm abound in shallow or low tide areas, often under stones and other crevices.
• The body is long and slender with the rounded dorsum and flat venter.
• The head is known as the prostomium, which bears four small eyes on the dorsal side, a pair of fleshy palps, and several pairs of tentacular cirri.
• The first segment after the prostomium is called the peristomium.
• The trunk consists of linear series of somites, each of which bears a flat parapodium on either side.
• Parapodium under the microscope.

  • It consists of two lobes, a dorsal notopodium and a ventral neuropodium, each bearing a bundle of bristle-like setae which are then supported by large and thick acicula.
• Chloeia (fireworm) - Fireworms are predatory or scavenging polychaetes that live in shallow waters near the shore.
• It is called a fireworm because of its sharp and hairy setae that easily break off and penetrate bare skin.
• Lepidonotus - This large scale worm has

  12 pairs of soft elytra (usually already absent in pickled specimen) arranged in its 26 body segments.
• Sabellastarte - This fanworm hide their bodies in a tube made of secreted mucus, sand grains and other debris.
• The head protrudes from the burrow. It bears the mouth which is surrounded by feathery arms, the radioles.
• What are the species under Class Polychaeta?

  1. Perinereis
  2. Chloeia (fireworm)
  3. Lepidonotus
  4. Sabellastarte
• What are the species under Class Oligochaeta?

  1. Pheretima
  2. Limnodrilus
• Pheretima - This earthworm burrows in moist soils, emerging at night to explore the surrounding hence the name night crawler.
• The first segment, peristonium forms the mouth and the last is the pygidium encircles the anus.
• The 14th-16th segments constitute a secretory epithelium, the clitellum.
• Limnodrilus - This tubicifid sludge worm inhabits mud canals and lake benthos. In their natural habitat, they live in mud tubes with mucus.
• The relative of this worm, Tubifex is usually sold in pet shops as food for aquarium fish.
• What are the species under Class Hirudinea?

  1. Hirudinaria
  2. Haemadipsid leech (Alimatik or Limatik)
• Hirudinaria. This is the common Philippine freshwater leech. The body has dark green hue and is tapered at both ends.
• Within the smaller oral sucker lies the mouth while the anus lies at the larger posterior sucker.
• There are 34 segments marked externally by grooves or annuli.
• Haemadipsid leech (Alimatik or Limatik) - This terrestrial leech inhabits high altitude areas of mountains like Mt. Makiling. It is a notorious blood sucking annelid especially among mountaineers. The body is small ranging from 30-40 mm in length. It has brown color with longitudinal bands of green hues with distinct segmentation. Such coloration is perfect for camouflage among vegetation. The anterior and posterior suckers are small.
• What is the class and genus of the photograph below?

  Class: Polychaeta

  Genus: Perinereis

  
• Under what class and genus does the photograph below belong?

  Class: Oligochaeta

  Genus: Pheretima

  
• Under what class and genus does the photograph below belong?

  Class: Polychaeta

  Genus: Perinereis

  
• Under what class and genus does the photograph below belong?

  Class: Polychaeta

  Genus: Sabellastarte

  
• What type of micrograph does the picture below belong under what genus?

  Pheretima (cross-section)

  
• Under what class and genus does the photograph below belong?

  Class: Hirudinea

  Genus: Hirudinaria