1. Sponges Cnidarians acoel flatworms Deuterostomes Protostomes the clade of Bilaterian animals excluding the acoels was recently named Nephrozoa – “animals with kidneys” the Nephrozoan ancestor - 1 st animal with an excretory system

2. Sponges Cnidarians acoel flatworms Deuterostomes Protostomes Nephrozoan animals are divided into 2 major lineages that are distinguishable by features of their embryos:

3. Sponges Cnidarians acoel flatworms Deuterostomes Protostomes Nephrozoa = coelomates, animals with a true coelom (or at least, their ancestor had one) the coelomate ancestor - 1 st animal with a coelom - all its descendants got a coelom, unless it was lost

4. Deuterostomes Echinoderms Chordates Protostomes Platyhelminthes (flatworms) Annelid worms Molluscs Nematodes Arthropods coelomate ancestor in some groups, coelom is critical to movement & feeding ecology

5. Echinoderms Chordates Platyhelminthes (flatworms) Annelid worms Molluscs Nematodes Arthropods coelomate ancestor in some groups, coelom was lost or reduced

6. Phylum Annelida – coelomate worms - coelom acts as hydrostatic skeleton allowing worms to crawl (polychaetes), dig (earthworms), inflate body regions - embryos develop through spiral cleavage, leading to a trochophore larval stage (shared with molluscs) - segmented bodies divided into repeating blocks (metamerism) - formed by teloblastic growth in larvae - blocks of segments are specialized for different functions - complete digestive system; excretory system w/ metanephridia - closed circulatory system; well-developed nervous system - chetae: spines sticking out of epidermis for movement, defense ~17,000 species

7. Annelida Sipuncula Echiura Pogonophora Polychaeta Clitellata segmentation Old view of coelomate worm phylogeny chetae

8. Segmented (now Family Sibloglinidae) Pogonophora – deep-sea tube worms Vestimentifera – giant vent worms Non-segmented: Sipuncula Echiura – innkeeper worms Former Coelomate Worm “Phyla” All are now just clades nested within Annelida !

9. Old system: 2 classes of annelids (1) Polychaeta– primarily marine worms - errant (free-living) - tube-dwelling - burrowing - interstitial - planktonic - pelagic (2) Clitellata subclass Oligochaeta– earthworms subclass Hirudinoidea– leeches Pareurythoe Potamilla recent evidence: Clitellata is a clade nested within polychaetes

10. Annelida Sipuncula Clitellata Echiura Siboglinidae

11. Used to be: Sipuncula Echiura Pogonophoran Annelida Polychaeta Clitellata DNA data shows all these groups belong to one big clade, interspersed among different polychaete groups

12. Annelida Problem: now, no group we can call “polychaetes” – same as “Annelida” if you include these 4 clades in “Polychaeta” – paraphyletic group if you exclude these 4 but keep using name “polychaete”

13. - parapodia (unjointed appendages) act as walking paddles or gills for respiration - numerous chetae (bristles) on parapodia, each derived from a single epidermal cell - reproductive structures may be simple or temporary - foregut modified as eversible proboscis for feeding - great habitat diversity (mostly marine) - head elaborated into two regions: prostomium with tentacles and palps, and peristomium marine “polychaetes” 25 Orders, 87 Families ~8,000 spp.

14. ventral blood vessel ventral nerve cord nephrostome gut septum CM epidermis LM dorsal blood vessel CM LM segment junction nephridium polychaete cross-section serially repeated segments have a “belly-bone” instead of our backbone CM = circular muscle ring; contracts body LM = longitudinal muscle; pull lengthwise

15. Coelom oblique muscle Circular muscle Longitudinal mus. notopodium chetae neuropodium parapodium Asiculum

16. Parapodium in cross-section Notopodium Neuropodium Close-up of chetae straight, slim short, hooked

17. Dorsal view

18. anchoring in tubes Adaptive diversification of parapodia parapodia in different body regions can be variously modified, some serving as gills, others in locomotion, others in feeding gills

19. Circulatory system of Nereis dorsal vessel = anterior flow esophagus nephridium ventral vessel lateral vessel intestine - No hearts; contractions of dorsal vessel & body wall controls blood flow - In species w/ incomplete septa, blood cells flow through continuous coelom - hemoglobins & other respiratory pigments

20. Nervous system palps eyes Primitive ventral “ladder” gradually fused, evolved into one central nerve chord Forebrain enervates palps, midbrain the eyes and hindbrain the nuchal organ (chemical)

21. Parapodia move out of phase lateral undulations. Chetae contact the substrate, push off with each stroke Coelomic cavities in each segment are hydraulically isolated from each other, allowing independent movement of segments Polychaete locomotion

22. Polychaete locomotion: Variable speed

23. Polychaete locomotion: Burrowing If septa between coelomic spaces are absent, contraction of 1 area produces extension of another region (fluid is continuous) Circular muscles make movements possible that aren’t available to nematodes, which have only longitudinal muscles

24. Polychaete reproduction Benthic polychaetes form epitokes, which swim to the surface & spawn Reproductive structures are simple, often temporary Gametes form in coelom; `released through gonoducts, nephridiopores, or simple tearing of the body wall itself NereisEunice

25. There are a range of larval forms, but most pass through a trochophore larva stage early in development Trochophore locomotory band of cilia Growth zone Juvenile worm

26. 2-day old trochophore of Spirobranchus giganteus Later stage: segmented, or chetigerous, larva w chetae Lecithotrophic: no mouth between prototroch and metatroch bands of cilia no mouth

27. Newly metamorphosed serpulid (juvenile worm) Trochophore larva of a serpulid, posterior view

28. Terebellid Late-stage segmented larvae

29. Polychaete families & their ecology orderfamilyecology Phyllodocida Nereidaeerrant, predatory Glyceridae Polynoidaeoften commensal SpionidaChaetopteridaemucous webs, parchment tubes TerebellidaTerebellidae deposit feeders Pectinariidae sand tubes Sabellaridae SabellidaSabellidae suspension feeders Serpulidae calcareous tubes Spirorbidae

30. Order Phyllodocida Family Nereidae - one pair of large curved jaws, held inside body until deployed to catch prey - bodies typically homonomous: all segments are alike

31. - predatory - extensible proboscis with 4 teeth; used in burrowing and hunting Order Phyllodocida Family Glyceridae Glycera americana

32. Order Phyllodocida Family Polynoidae - short and flattened bodies - homonomous; few segments of fixed number - dorsum covered by scales called elytrae - 1 pair of jaws - often commensal on other invertebrates: live on them, neither hurt (parasite) nor help (mutualist) “Scale worms”

33. Order Spionida Family Chaetopteridae - adult body is highly tagmatic: front and back ends are very different (heteronomous) - trap suspended particles by pulling water through a mucous web - web is balled up, consumed, re-spun every 18 minutes - parchment tube is home to many commensal organisms tube, often in U-shape worm out of tube

34. Thelepus crispus Order Terebellida Family Terebellidae branchial plume - “medusa worm” has elongated tentacles used in selective deposit feeding from inside the safety of its tube (which it builds)

35. feeding tentacles extended to gather organic matter from surface Deposit Feeding modified prostomial appendages tentacles are hollow

36. Order Terebellida Family Pectinariidae Pectinaria californiensis, “ice cream cone worm” - selects sand grains of precise size for each region of tube

37. Order Sabellida Family Serpulidae Spirobranchus sp. “Christmas tree worm” - build calcareous tubes - often imbedded in rocks or coral heads - compound eyes on tentacles; shadows trigger rapid withdrawal

38. tubes encrusting a chiton’s shell valves Order Sabellida Family Spirorbidae Major fouling organism – rapidly colonize most marine surfaces with their tiny calcareous tubes have a large operculum, or stopper, to seal the opening of their tube after they withdraw their feeding tentacles