October 2024 Pseudocoelomates Post-Notes (PDF)

1 OUTLINE Pseudocoelomates 1. Introduction 2. Phylum Nematoda 3.1 General characteristics 3.2 Parasitic strategies 2 INTRODUCTION Chord...

1 OUTLINE Pseudocoelomates 1. Introduction 2. Phylum Nematoda 3.1 General characteristics 3.2 Parasitic strategies 2 INTRODUCTION Chordates Arthropods Hemichordates Annelids Brachiopods Echinoderms Mollusks Bryozoans Nematodes Nemerteans Gastrotrichs ✓ Rotifers Flatworms ✓ Cnidarians ✓ Sponges Ancestral Metazoan ✓ Protozoa 3 INTRODUCTION Pseudocoelomates Possess a fluid (or gelatinous filled) pseudocoel Adaptive potential 1. space for development of more sophisticated organ systems 2. permits simple circulation of material throughout body 3. fluid storage area for waste Complete digestive tract build up prior to processing i.e. mouth-to-anus 4. hydrostatic support (skeleton) 4 PHYLUM NEMATODA- general characteristics Nematode worms are ubiquitous! - up to 4 million per square meter - good farmland topsoil estimated to contain billions/m2 5 GENERAL CHARACTERISTSICS Nematodes exhibit considerable uniformity of both internal and external anatomy A typical nematode: - is 1 - 2 mm long - shows no external segmentation - is tapered at both ends - is covered by a multilayered cuticle Cuticle: - non-cellular covering secreted by epidermis (may be lost in parasitic forms) - provides structural resistance for high pressure hydrostatic skeleton epidermis (syncytial)  6 GENERAL CHARACTERISTSICS Locomotion - internal hydrostatic pressure can be as high as 225 mm Hg (earthworm = 5 – 10 mm Hg) - epidermis does not possess cilia - nematodes possess longitudinal muscles but no circular muscles - movement achieved by undulating waves, dorsal non-contractile nerve cord driven by alternating contractions of muscle muscle cell bodies - muscle contraction controlled by nervous system - non-contractile extensions of muscle fibers contact dorsal and ventral nerve cords 7 Locomotion 8 Locomotion 9 PARASITIC STRATEGIES - NEMATODES - parasitic nematodes exist in every major animal group from sponges to mammals - nematodes also parasitize other nematodes as well as roots, stems, leaves and flowers of plants General Characteristics 1. economic importance - medical (humans), companion animals, livestock, crops 2. extensive migrations within vertebrate hosts 3. parasitic nematodes attain greater sizes than non-parasitic 4. reproductive capacities are enormous 10 PARASITIC INTESTINAL NEMATODES Necator americanus – American Hookworm Distribution - worldwide # people infected – 500 million (according to CDC) Size – Females 11 mm, males 9 mm Pathology – anemia, energy loss, respiratory problems, dermal larval migrans (ground itch) 1 hookworm can imbibe 0.6 mL blood/day Infections of 1000/host not uncommon = 600 mL blood loss/day 11 PARASITIC INTESTINAL NEMATODES respiratory problems dermal larval migrans 12 13 PARASITIC FILARIAL NEMATODES Wucheria bancrofti and Brugia malayi Distribution – W. bancrofti, tropical areas worldwide B. malayi, Asia # people infected – 250 million worldwide Size – Females 100 mm, males 50 mm Pathology – lymphatic dysfunction causing lymphedema* and elephantiasis** *Lymphedema - swelling of subcutaneous tissue caused by obstruction of lymphatic drainage **Elephantiasis – excessive growth of connective tissue in association with lymphedema 14 PARASITIC FILARIAL NEMATODES 15 16 17 NOT ALL NEMATODES ARE BAD! Parasitic species can be used to kill and/or reduce major agricultural pests and even mosquitoes Most nematodes are not parasitic and play a major role in nutrient cycling The nematode C. elegans is a very important model organism for scientific research 1 OUTLINE Phylum Mollusca 1. Introduction 2. Body Form and Function - simple body plan - Molluscan gills - buccal mass and radula - shell structure and formation 3. Reproduction & Development  INTRODUCTION Chordates Arthropods Hemichordates Coelomate Annelids Brachiopods Echinoderms Mollusks Bryozoans Nemerteans ✓ Nematodes Gastrotrichs ✓ Rotifers Flatworms ✓ Cnidarians ✓ Sponges Ancestral Metazoan ✓ Protozoa 2 INTRODUCTION Scaphopoda (1.0%) Mollusca represented by Polyplacophora (1.0%) approx. 93 000 species Cephalopoda (1.0%) Bivalvia (21.5%) Monop Aplaco % representation of Polypla extant molluscan classes Cephal Gastropoda *Monoplacophora Bivalvi (0.03%) *Aplacophora (0.40%) (Caudofoveata, Gastro Solenogastres)