Phylum Annelida

Terrestrial, marine, freshwater. Repeating segments. Triploblastic, true coelomate Complete gut, closed circulatory system, well developed nervous system. Respiratory organs. Trochophore larvae in marine forms. Protostome.

Phylum Annelida Class Polychaeta Order Phyllodocida (sand worms, scale worms)

Phylum Annelida Class Polychaeta Order Phyllodocida Order Terebellida (tube worms)

Phylum Annelida Class Polychaeta Order Phyllodocida Order Terebellida Order Sabellida (tubeworms)

Phylum Annelida Class Polychaeta Order Phyllodocida Order Terebellida Order Sabellida (beard worms)?

Phylum Annelida Class Polychaeta Class Clitellata Order Phyllodocida Order Terebellida Order Sabellida Subclass Oligochaeta (earthworms)

Phylum Annelida Class Polychaeta Class Clitellata Order Phyllodocida Order Terebellida Order Sabellida Subclass Oligochaeta Subclass Hirudinoidea (leeches)

What do Polychaetes look like? Long, cylindrical with segments. Head has prostomium and peristomium with mouth. Presegmental without setae. Last segment is the pygidium with anus.

What do Polychaetes look like? Gut separated from body wall by coelom. External trunk segmentation with coelomic compartments separated inside by intersegmental septa. Homonomous if segments are all the same, heteronomous if segments are different.

What do Polychaetes look like? Parapodia with bundles of setae. Parapodia are biramous, with a dorsal notopodium and a ventral neuropodium. Body form depends on lifestyle.

How do Polychaetes support themselves and move? Cuticle secreted by epidermis. Longitudinal and circular muscles along body. Oblique muscles to parapodia.

How do Polychaetes support themselves and move? Circular muscles maintain body form. Longitudinal muscles in bands within each segment. Alternately contract and relax for undulation. Parapodia push off substratum during power stroke and retract during recovery stroke. Free-swimming and crawling species

How do Polychaetes support themselves and move? Circular muscles more developed for peristaltic motion. Septa perforated so contracting a group of segments causes others to extend. Burrowing species

How do Polychaetes support themselves and move? Tube dwellers have reduced parapodia used for anchoring in tube. Tubes used for protection and support. Tubes made of calcium carbonate, chitin, or sediment particles.

How do Polychaetes support themselves and move? Cerebral ganglia specialized with different parts that innervate different parts of the worm.

How do Polychaetes support themselves and move? Well developed sense organs: Complex photoreceptors. Tactile receptors on head and parapodia.

How do Polychaetes support themselves and move? Chemoreceptors across body. Nuchal organs at head which are presumed chemosensory.

How do Polychaetes feed themselves? Hunters with large jaws. Direct deposit feeders.

How do Polychaetes feed themselves? Selective deposit feeders with tentacles. Filter feeders with radioles.

How do Polychaetes feed themselves? Foregut: buccal cavity, pharynx (often eversible) with jaws and teeth, and glands (poison, enzyme, mucus). Midgut: End of esophagus, intestine with modified stomach. Enzyme production. Hindgut: Mucus added to fecal pellets, rectum, anus.

How do Polychaetes maintain homeostasis? Circulation and gas exchange Respiratory organs in one part of the body (parapodia, branchiae in tentacle crown). Well developed, closed circulatory system. No real hearts. Respiratory pigments.

How do Polychaetes maintain homeostasis? Osmoregulation and waste removal Metanephridia with nephrostomes open to coelomic fluid. Lead to nephridioducts which reabsorb wanted materials. Waste released through nephridiopore.

How do Polychaetes reproduce and develop? Sexual reproduction No distinct gonads. Gametes formed from peritoneum and cells stored in coelom. Fertilization external. Many free-swimming benthic polychaetes produce epitokes.

How do Polychaetes reproduce and develop? Holoblastic, spiral cleavage leading to a coeloblastula. Gastrulation by invagination or epiboly. Trochophore larva with ciliated prototroch and apical cilia associated with a sense organ.

How do Polychaetes reproduce and develop? Trochophores grow, elongate, and segment into a polytroch larva. 4d cell divides into two teloblasts which produce bands of mesoderm by schizocoely.

What do Oligochaetes look like? Freshwater, marine and terrestrial. No parapodia and reduced number of setae. Reduced prostomium and peristomium. Clitellum functions in reproduction.

What do leeches look like? Freshwater, marine and terrestrial. No parapodia and no setae. Even more reduced prostomium and peristomium. Clitellum functions in reproduction. Anterior and posterior suckers. Dorsoventrally flattened. Ectoparasites. Coelom reduced to channels which functions in circulation and waste removal.

How do Oligochaetes support themselves and move? Thin cuticle secreted by epidermis. Circular and longitudinal muscles. Coelom segmented so each segment separate.

How do Oligochaetes support themselves and move? Peristaltic contractions. Setae used to anchor. Setae can be retracted. Complex nervous system. Tactile and chemo receptors across body.

How do leeches support themselves and move? Thin cuticle secreted by epidermis. Many mucus glands. Circular, longitudinal, dorsoventral and oblique muscles. Reduced coelom so muscles act against hydrostatic tissues.

How do leeches support themselves and move? Inchworm-like crawling. Relatively few but large neurons. Extremely sensitive to temperature and vibration.

How do Oligochaetes feed and digest? Direct deposit feeders. Specialized areas in foregut: Crop Gizzard Calciferous glands Specialized areas in midgut: Typhlosole Chloragogen cells

How do leeches feed and digest? Ectoparasites, some predators. Suckers with three blade-like jaws. Anesthetic and anticoagulant. Muscular pharynx for sucking. Large crop with cecae for storage.

How do Oligochaetes maintain homeostasis? Respiration and circulation Closed circulatory system 2-5 pairs of hearts with valves.. Three main longitudinal vessels. Hemoglobin. Gas exchange across skin.

How do Oligochaetes maintain homeostasis? Osmoregulation and excretion Paired metanephridia in most segments. Nephrostome in one segment and ducts in the posterior segment. Urea produced. Water and salt balance.

How do leeches maintain homeostasis? Respiration and circulation Gas exchange across body wall. Respiratory gases carried by vessels and chambers from reduced coelomic space.

How do leeches maintain homeostasis? Osmoregulation and excretion Clustered nephrostomes called ciliated organs. Coelomic vessels.

How do Oligochaetes reproduce and develop? Asexual Transverse fission and fragmentation

How do Oligochaetes reproduce and develop? Sexual Simultaneous hermaphrodites. Males: testes make sperm which are stored in seminal vesicles. Released into sperm ducts and out male gonopore during copulation.

How do Oligochaetes reproduce and develop? Sexual Simultaneous hermaphrodites. Females: ovaries produce eggs. Released into coelomic space. Spermatheca store mate’s sperm.

How do Oligochaetes reproduce and develop? Sexual Mutual cross-fertilization. Cocoon formed by clitellum. Albumin added. Eggs from female gonopore, sperm from spermatheca. Sealed and deposited in soil. Holoblastic spiral cleavage, direct development.

How do leeches reproduce and develop? Sexual Simultaneous hermaphrodites with clitellum. Mutual cross-fertilization. Sperm released into vagina for internal fertilization. Cocoon formation with fertilized eggs or embryos deposited after albumin.