Invertebrate Zoology Lecture 11 - Nemertea PDF
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2024
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Summary
This lecture covers the Phylum Nemertea, discussing defining characteristics, body systems, and reproduction. The lecture also touches on the feeding and movement strategies these invertebrates employ. It provides an overview for students studying invertebrate zoology.
Full Transcript
Invertebrates in the news… https://www.nytimes.com/2024/10/07/science/comb-jellies-fusing-bodies.html Invertebrate Zoology Lecture 11: 10/11/2024 Last time The Gnathifera: Phylum Rotifera, Phylum Acanthocephala This time Phylum Nemertea Next time Beast Profile...
Invertebrates in the news… https://www.nytimes.com/2024/10/07/science/comb-jellies-fusing-bodies.html Invertebrate Zoology Lecture 11: 10/11/2024 Last time The Gnathifera: Phylum Rotifera, Phylum Acanthocephala This time Phylum Nemertea Next time Beast Profiles: Sharon & Grace Phylum Mollusca, Part 1 Exam Review Phylum Nemertea “ribbon worms” Phylum Nemertea Defining Characteristic Muscular eversible proboscis house in a fluid-filled schizocoelous cavity (the rhynchocoel) Phylum Nemertea Nemertea – “unerring one” ~1300 species Mostly free living, benthic marine worms A few pelagic or fresh or terrestrial or parasitic (but rare) Found inside shells, under stones, in tangle of algae, burrow into mud & sand Long & thin, ribbon like (with slime) Largest 60m!!!! (mostly 2m or less) Often colorful Phylum Nemertea Triploblastic Acoelomate Bilaterally symmetrical Ciliated epidermis Reproduction Gonochoristic (mostly) Asexual via fragmentation & regeneration (only some species) Sexual: External fertilization ciliated larva “mini-me” (most common) Some have pilidium larva (metamorphosis required) Phylum Nemertea Gas Exchange Predominantly diffusion Circulatory System True blood vascular system (closed)!!!! No heart – body wall muscles Contractile vessels are modified coelomic spaces ?So maybe coelomates?? Distributes nutrients Phylum Nemertea Movement Glide on trail of slime (cilia) Muscular waves to crawl Undulation to swim Excretion Protonephridia with flame cells Nervous System 4-lobed “brain” w/ nerve cords More complex than flatworms Photoreceptors “eyes”, chemoreceptors, mechanoreceptors, some species have statocysts The “Gorgon Worm” Phylum Nemertea Digestion & Feeding Complete digestive tract with anus Extracellular and intracellular Carnivores mostly Eversible proboscis Not homologous with turbellarian pharynx RHYNCHOCOEL!!!!! [formed as split in mesodermal tissue] The Nemerteans Figure 11.5 Phylum Nemertea Class Anopla No stylet Class Enopla stylet
