Lophotrochozoa

1. Annelida II Ecdysozoa Lophotrochozoa

2. Introduction to Sipuncula（星虫） • “Peanut worms”; coelomate unsegmented spiralian worms, rudimentary neural segmentation similar to that of annelids occurs in the early larval stage • Traditionally considered a phylum, they might be a subgroup of phylum Annelida based on recent molecular work • Some burrow, others filter feed • About 250 species, all marine

3. Sipunculan Biology • Possess an retractable introvert, often with hollow tentacles • Spacious coelom with compensation sacs • No discrete circulatory, respiratory system • Fluid transport and gas exchange are instead accomplished by the coelom, which contains the respiratory pigment haemerythrin

4. Sipunculan Biology • One pair of metanephridia and urns • Free spawners • usually zygote trochophore (pelagosphaera)  adult • Mesoderm forms through schizocoely

5. compensation sac(s) anus tentacles mouth introvert retractor muscle gut pelagosphaera Adult and Larval Sipunculans

6. Unsegmented trunk and a narrower, retractable anterior section, called the "introvert". body wall similar to annelids, consists of a non-ciliated epidermis overlain by a cuticle, an outer layer of circular and an inner layer of longitudinal musculature.

7. Sipunculan

8. 土笋冻 和竹子完全没有半点关系 可口革囊星虫（Phascolosoma esculenta）

9. Introduction to Echiura（螠虫） • Like an unsegmented annelid; ~130 species • molecular data suggests echiurans are annelids • Benthic marine worms; most echiurans: • have a non-retractable ciliated proboscis • they sweep substrate with proboscis to gather food • have a closed circulatory system • have ventral nerve cord with nerve ring • formation of mesoderm through schizocely • are free spawners with trochophore larvae

10. coelom proboscis gut gonad metanephridium seta An Echiuran...

11. Some Echiurans... • weird echiuran: Urechis caupo • feed like chaetopterid polychaetes (with mucus net) Bonellia viridis

12. Urechis caupo

13. “韭菜海肠”是胶东名菜 Urechis as food

15. Clade Clitellata • Class Oligochaeta and Class Hirudinida • Form reproductive structure called a clitellum • Ring of secretory cells found in a band around the body • Permanent in oligochaetes but visible only during reproductive season in leeches • Hermaphroditic (monoecious) animals that exhibit direct development • Young develop inside a cocoon secreted by the clitellum, and emerge as small worms

17. Clade Clitellata • Setae • Bristlelike rods set in a sac and moved by tiny muscles • Project outward through small pores in cuticle • Aid anchoring by digging into walls of burrow

18. Clade Clitellata • Food is stored in a thin-walled crop • Muscular gizzard grinds food into small pieces • Digestion and absorption occur in intestine

19. Clade Clitellata • Circulation and Respiration • Coelomic fluid and blood transport food, wastes, and respiratory gases • Blood circulates in a closed system with five main trunks running lengthwise in the body • Dorsal vessel contains valves and functions as a true heart • Pumps blood anteriorly into 5 pairs of aortic arches = accessory hearts • Aortic arches ensure steady pressure in ventral vessel • No special gaseous exchange organs • Gas exchanged across body surface

20. Clade Clitellata • Nutrition • Scavengers, feeding on decayed organic matter, leaves, refuse, etc. • Food moistened by mouth and drawn in by a sucking action of muscular pharynx

21. Clade Clitellata • General Behavior • Avoid bright light (negative phototaxis) • Damp, rainy weather: Remain near surface • Dry weather: Burrow deep underground and go dormant coiled in a slime chamber • Chemical stimuli are important in locating food • Limited learning ability • Primarily trial-and-error learning

22. Clade Clitellata • Mate at night during warm, moist weather • Aligning in opposite directions, ventral surfaces together • Mucus secreted by clitellum holds worms together • Sperm from each worm are transported to the seminal receptacles of the other along seminal grooves • After mutual copulation, each worm secretes a mucus tube and chitinous band to form a cocoon • Cocoon passes forward and eggs, albumin, and sperm are added • Fertilization and embryogenesis occur in cocoon • Young worms emerge from cocoon

23. “Oligochaeta” • Mostly freshwater or terrestrial • Few setae; reduced cephalic structures • Hermaphroditic; complex mating • Paraphyletic with respect to Hirudinoidea

24. “On a really good night, a picker can earn up to $600. But on a bad night, it might only be $100.”

25. Basic Earthworm Biology • Digestive system with esophagus, gizzard for grinding food, intestine with typhlosole • Setae used to anchor body • 5 hearts, respiration through cuticle • It has a double transport system composed of coelomic fluid that moves within the fluid-filled coelom and a simple, closed blood circulatory system. • Most oligochaetes have no gills or similar structures, and simply breathe through their moist skin.

26. Basic Earthworm Biology • The vascular system consists of two main vessels connected by lateral vessels in each segment. Blood is carried forward in the dorsal vessel (in the upper part of the body) and back through the ventral vessel (underneath) • The blood of oligochaetes contains haemoglobin in all but the smallest of species, which have no need of respiratory pigments • Excretion is through small ducts known as metanephridia. Terrestrial oligochaetes secrete urea, but the aquatic forms typically secrete ammonia, which dissolves rapidly into the water

27. Basic Earthworm Biology • Reproduction: “sperm swapping” • clitellum makes cocoon that picks up eggs, then sperm... • eggs fertilized in cocoon; direct development

28. clitellum seminal receptacle Earthworm Anatomy/Mating

29. Although earthworms are monoecious [simultaneous hermaphrodites], they rely on cross-fertilization. Why? cocoon

33. Most oligochaetes are detritus feeders, although some genera are predaceous The digestive tract is essentially a tube running the length of the body, but has a powerful muscular pharynx immediately behind the mouth cavity.

34. The major benefits of earthworm activities to soil fertility can be summarized as: • Biological: conversion of large pieces of organic matter into rich humus, thus improving soil fertility • Chemical: minerals and plant nutrients are changed to an accessible form for plants to use • Physical: maintaining the soil structure, enabling processes of aeration and drainage

35. Invasive earthworms (suborder Lumbricina) alter the structure of a deciduous forest BEFORE AFTER http://www.nrri.umn.edu/worms/forest/soil_layers.html decrease organic layer, increase mineralization, and increase decomposition.

36. Clade Clitellata Class Oligochaeta • Diversity • Over 3000 species • Occur in habitats from soil to freshwater • Few are marine or parasitic • Nearly all bear setae • Fewer in number than in polychaetes • Sometimes called “night crawlers” • Burrow in moist rich soil and usually live in branched interconnected tunnels

38. Giant Gippsland earthworm Megascolides australis

41. sludge worm The Naididae (formerly known as Tubificidae), Tubifex tubifex. They are key components of the benthic communities of many freshwater ecosystems.

42. Seriously... Worms That Live In ICE? Mesenchytraeus solifugus Snow algae If one warms an ice worm to even a few degrees above freezing the worm will melt Reverse-engineer ‘cold tolerance’ cold-resistant proteins

44. leech leech vs. earthworm

45. Hirudinida • Leeches and allies; many ectoparasites • Most lack parapodia/setae • Have suckers at both ends of their bodies • Segments not separated by septa • annulations donot correspond to segments • constant segment number

46. Clade Clitellata Class Hirudinida: Leeches • Divided into 3 orders • Hirudinea (‘true” leeches) • Acanthobdellidae • Branchiobdellidae • Hirudinea • 34 segments, lack setae and possess anterior and posterior suckers • Acanthobdellidae • 27 segments, setae only present on the first five segments, and have a posterior sucker • Branchiobdellidae • 14 or 15 segments, no setae, and an anterior sucker • Commensal or parasitic on crayfish

47. Like the oligochaetes, such as earthworms, leeches share a clitellum and are hermaphrodites. leeches do not have bristles The external segmentation of their bodies does not correspond with the internal segmentation of their organs Their bodies are much more solid as the spaces in their coelom are dense with connective tissues They also have two suckers, one at each end.

48. Clade Clitellata Class Hirudinida: Leeches • No setae • Developed suckers for attachment • Gut specialized for storage of large quantities of blood • In the crop, some blood-sucking species of leech can store up to five times the body mass of blood. • Most use suckers to attach and “inchworm” along surfaces

50. Nutrition • Not all are parasites, many are predaceous • Most leech species, however, are predatory, feeding primarily by swallowing other invertebrates. • Freshwater leeches have a proboscis for ingesting small invertebrates as well as to suck blood • Some terrestrial leeches feed on insect larvae, earthworms, and slugs • Other terrestrial leeches climb trees or bushes to reach warm-blooded vertebrates such as baby birds • Most are fluid feeders that prefer tissue fluids and blood pumped from open wounds • Some parasitic leeches leave a host during breeding season • Fish leeches may remain on a host