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Annelid Taxonomic Classes: Polycheta

Annelid Taxonomic Classes: Polycheta. Over 9000 spp., mostly aquatic many live in tubes. Clitellata. “ Earthworms ”. “ Bristle worms ”. “ Leeches ”. Annelid Taxonomic Groups: Previously considered sepearate phyla. Echiura. Sipuncula. Pogonophora. “. Annelida.

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Annelid Taxonomic Classes: Polycheta

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  1. Annelid Taxonomic Classes: Polycheta Over 9000 spp., mostly aquatic many live in tubes Clitellata “Earthworms” “Bristle worms” “Leeches”

  2. Annelid Taxonomic Groups: Previously considered sepearate phyla Echiura Sipuncula Pogonophora “

  3. Annelida • I. General Characteristics • Class Polychaeta • Basic Body Plan, Swimming, Reproduction and Development • Polychaete Adaptive radiation • III.Other Marine Annelids (derived polychaetes) • Family Siboglinida : Vent worms and whale worms • Echiura and Sipuncula • IV. Class Clitellata • A. Oligochaetes • B. Hirudinea

  4. Despite apparent differences the polychaetes and oligochetes share fundamental features Segmented body Metamerism Hydrostatic skeleton by a true coelom Complete digestive tract Closed circulatory system oligochete Leeches along with oligochetes; both are in the Class Clitellata Clitellum Coccoon No parapodia No head appendages polychete

  5. Class Polychaeta: marine bristle worms Prototype Errant (crawling-type) Nereis Prostomiumperistomium (Fig 15.4) segment Metameric condition

  6. Setae or Chetae (made of chitin) Parapodia acicula Parapodia capillaries ganglia nephridia Fig 15.1-3 Circulatory system

  7. Urine The excretory system consists of metanephridia that work by selective transport (fig 15.2)

  8. Types of Skeletons in Animals Endoskeleton Exoskeleton Hydrostatic skeleton In what ways are these three types of skeletons functionally similar?

  9. Polychaete swimming simulation

  10. Polychete Reproduction: Gametes form from cells that line the coelom Some copulate but most form Epitokes (Fig 17) In Fiji and Samoa, palolo worms swarm on the 7th night after the full moon that follows the autumnal equinox!! (October usually….) Odontosyllis enopla

  11. Hierarchical System of Controls - Day length cues seasonal reproduction Lunar Cycles synchronize local spawning events Meteorological phenomena are likely the final trigger to epitoky Complex Sex Pheromones synchronize nuptual dance and spawning

  12. Polychete Reproduction Is the trochophore a plesiomorphic (ancestral) character shared by molluscs, annelids and related phyla?

  13. Metameric body plan of Nereis and of other errants is the “basic” condition • Head prominent • Crawling parapods • Eversible pharynx • some spp. with • poison glands. fireworm

  14. Swimming Polychete: Tomopteris • Large parapods • Transparent body • Enormous eyes • Active predators Swim with paddle-like parapodia or for rapid swimming by increasingly rapid undulations of the body combined with parapodia

  15. Burrowing Polychaete: • Move by peristalsis • Head streamlined • Parapods reduced • Deposit Feeders • “earthworm-like”

  16. tube dwellers Feather duster Xmas tree Fan worms etc. --Tubes of Mucus Sand Parchment Calcite

  17. tube dwellers • Movement limited • Head reduced but • with tentacles • Parapods small • Passive and Active • suspension feeders • Filter Feeders

  18. Most specialized Tube dweller is Chaetopterus

  19. Marine annelid diversity Specialized Taxa

  20. Annelid Diversity: Polychaeta Family Siboglinidae SubFamily Vestimentifera SubFamily Frenulata Class Echiura Genus Osedax “

  21. Annelid Family Siboglinidae “... small but very intriguing group…” Includes Frenulate “spaghetti worms” that feed by absorbing nutrients Whale carcass worms: root system absorbs bacterial nourishment from bone marrow; & symbiotic bacteria Vestimentiferan giant cold seep and hot vent worms • Live deep in the ocean • No digestive system • Thrive in areas of high • methane or sulfur

  22. Sub Family Frenulata < 1mm diameter 10 - 74 cm long (spaghetti-like worms) opisthosoma 6-25 segments containing coelomic compartments that are isolated from each other by muscular septa; each segment bears chitinous setae Fig 13.12-13.14

  23. Sub Family Vestimentifera Large thick bodies, up to 2 m long vestimentum

  24. Whale fall time series Hagfish Sleeper sharks Polychaete worms (free living, bacterial grazers) Vigtorniella (Polychete) Whale carcass worms Osedax not considered Vestimentiferans

  25. A watercolor painting shows females and males from the new marine worm species. The female worms are illustrated both in their tubes and with a whalebone “cutaway,” to reveal their large ovisacs and extensive roots that invade the bone. The small males live in the tubes of the females and are shown as “blowups” with their relative positions in the tubes indicated by the dark lines. Top left: male Osedax rubiplumus. Top right: female Osedax rubiplumus. Bottom left: male Osedax frankpressi. Bottom right: female Osedax frankpressi.

  26. F. Siboglinidae Vestimentiferans vent worm Riftia plume heart V blood vessel trophosome tube Fig 13.15-16

  27. Read Research Focus 13.1 on Chemosynthesis Microbiologically analogous to Archean vent systems and may serve as models for the origin and evolution of life in Archean vents. Baross ad Hoffman (1985) in Origins of Life and Evolution of Biospheres …deep-sea hydrothermal vents may help advance the understanding of how early microbial life forms gained a foothold in hydrothermal systems on early Earth and potentially on other planetary bodies. (McCliment et al., 2005, Environmental Microbiology 8: 114-125) An alternative proposal to the “pre-biotic soup” theory…chemical conversions that involve “transition metal sulphide catalysts” create favorable environments for abiogenic acetate production that release energy… acetyl-coA is the most central carbon backbone in microbial metabolism Martin et al., 2008, Nature Reviews 6: 804-14

  28. The Newest Annelids Sipuncula Annelids (peanut worms) Echiura (inn keeper worms)

  29. The Sipuncula: - Fewer than 600 species; found primarily in shallow marine habitats; deposit/detritus feeders - Soft bodied, with very poor fossil record, but with distinctly protostomous embryological characters - Best known for having teleplanic larvae

  30. The Sipuncula Ecologically and functionally like Echiura Instead of a proboscis a fully retractable head region known (introvert) aids feeding

  31. The Echiura With scoop-shaped proboscis Main body is large coelom Muco-ciliary deposit feeders Live in sand, mud, crevices

  32. “Fat inkeeper” worm is best known representative

  33. Some Annelid (Echiura) vs Sipuncula Characteristics Annelid-like Characteristic Echiura Sipuncula Musculature outer circular and inner longitudinal Setae Present Absent Metamerism early juvenile Absent Coelom form. All have schizocoelous formation Cleavage All with spiral determinate cleavage Larval form The trochophore is the first larva

  34. Phylogeny of Annelida Among the Eumetazoa, within the lineage of Lophotrochozoa that includes molluscs Annelida monophyly is widely accepted Phylogeny within the Annelida in turmoil over last 15 yr, but a consensus is emerging

  35. 2007 Family Capitellidae Nuclear genes and rDNA sequence analyses Family Terebellidae Whither Polychaeta? Evolution of Clitellata? Family Nerididae Taxonomic Families traditionally considered to be polychaetes

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