Invertebrates

1. Invertebrates Chapter 33

2. Phylum Porifera • Sedentary suspension feeders, capturing food passed through the body • Water into spongocel, out thru osculum • Both vary in number • Sequential hemaphrodites • Eggs maintained in mesophyll, sperm out thru osculum • Motile larvae find substrate to develop • Celllular level of organization • Choanocytes, or flagellated collar cells, line interior of spongocel to move water in • Amoebocytestake food from water and choanocytes to digest it • Produce antibiotic related compounds

3. Classes of Porifera • Class Calcarea • Spicules, made by amoebocytes, of CaCO3 • E.g. Grantia • Class Hexacinellida • Spicules, made of silica • Referred to as ‘glass sponges’ • Class Demospongiae • Skeleton of silica spicules, flexible spongin, or both • Referred to as ‘bath spongs’ • E.g. Spongia

4. Phylum Cnidaria • Sessile and motile forms • Diplobalstic and radiallysymmetrical • Contain a gastrovascular cavity, from endoderm • Sac like body plan • Simplistic muscle and nerve tissues • Gastroderm contracts with closed mouth=shape change coordinated by nerve net • Arranged radially • Cnidocytes capture prey • Contain nematocysts, which penetrate, stick to, or tangle prey • Polyp or medusa body form • Some 1, other, or both in life

5. Classes of Cnidarians • Class Hydrozoa • Class Scyphozoa • Dominate medusa form and minor polyp stage • All marine • E.g. jellyfish • Class Cubozoa • Box-shaped medusa stage with complex eyes and potent venom • Class Anthozoa • Polyp stage only, mostly colonial and sessile • All marine • E.g. sea anemones and coral

6. Class Hydrozoa • Dominate polyp form and minor medusa stage • Most marine, some freshwater • Hydra • Freshwater species only exhibit polyp form • Can be motile • Obelia • Colony of chitinous covered polyps • Portugese man-of-war • Colony of polyps • Original is air bladder and rest for feeding and reproduction

7. Phylum Platyhelminthes • Bilateral, tribloblastic, acoelomates with sac body plan • Demonstrates cephalization and ladder like nervous system • Organ system variations • Hermaphroditic • No specialized circulatory or respiratory organs • Gastrovascular cavity branches throughout body to distribute material to cells • Excretory system of flame cells for osmoregulation • Reduced in parasitic forms

8. Classes of Platyhelminthes • Class Tubellaria • Most marine, some freshwater, some terrestrial • Specialized sense organs and nervous system • Eyespot, auricle, pharynx, and varies reproductively • E.g. planaria (Dugesia) • Class Trematoda • Parsitic, many with suckers to aid in attachment • Body mostly reproductive organs • Life cycle alters between sexual and asexual forms (intermediate host) • E.g. Schistosoma, blood flukes, evade detection by changing surface proteins • Class Cestoda • Parasitic in vertebrates with scolex to attach to intestines • Lack mouth and gastrovascular cavity, absorb through body • Chains of proglottids, sacs of sex organs that fill with eggs and exit in feces • Can form cyst stages to survive as larvae • E.g. Taenia (dog/cat tapeworm)

9. Phylum Nematoda • Non-segmented, pseudocoelomates, covered by a cuticle • Tube within a tube body plan characterized by an alimentary canal (mouth and anus) • Lack a circulatory system • Reproduce sexually with internal fertilization • Male and female species separate and distinct in size • Zygotes able to survive harsh conditions • Longitudinal muscles = whip-like movement

10. Nematode Examples • Trichinellaspiralis(trichinosis) • Juvenile worms encyst in pig muscle, humans consume • Adults burrow through intestines into lymph system • Caenorhabditiselegans (C. elegans) • Popular model for genetic research • Enterobiusvermicularis(pinworms) • Common childhood disease • Dinofilariaimmitis(dog heartworms) • Wucheriabancrofti(elephantiasis) • Transmitted by mosquitos and live in lymph systems • Necaturamericanus(hookworms)

11. Phylum Mollusca • Mostly marine, some freshwater or terrestrial • Soft-bodied, but secrete a shell of CaCO3 (some lost) • Coelomates with 3 part body plan • Foot: muscular organ for locomotion, attachment, or feeding • Visceral mass: contains internal organs • Mantle: suurounds visceral mass and may secrete shell; develops gills or lungs • Feed via a radula • Most separate sexes, but snails are hermaphrodites • Open circulatory system, blood not confined to vessels • Neural ganglia connected by nerve cord

12. Classes of Molluscs • Class Polyplacophora • Body of dorsal plates, but unsegmented; no head but radula • Class Gastropoda • Herbivore’s uses radula to scrape, carnivorous to bore thru prey • Developed head with eyes and demonstrates torsion • Some hermaphroditic, but require another individual • Class Bivalvia • Two part shells secreted by mantle and controlled by muscles • Can see growth rings; made of protein • Little cephalization, no head or radula • Gills for gas exchange, most suspension feeders • Separate sexes

13. Class Cephalopoda • Active predators with beak like jaws and poisoned saliva • Foot modified into a siphon to direct movement • Closed circulatory system, well developed sense organs, and a brain • Mantle covers visceral mass, but may be internal or missing • Nautiluses are last surviving ammonites, posses shells

14. Phylum Annelida • Segmented worms, separated by partitions called septa • Coelomates with a closed circulatory system • Solid ventral nerve cord, anterior brain, and a ganglia in each segment • Nephridia, coiled tubes for excretion in each segment • Digestive stystem with pharynx, stomach, and intestines • Some with setae, bristles, and parapodia, paddle-like appendages, for movement

15. Classes of Annelids • Class Polychaeta • Each segment with parapodia and setae • Marine animals that are mostly filter feeders, some predators • Defined cephalization with eyes, sense organs, and jaws • Class Oligochaeta • Moist environments to allow gas exchange • Include earthworms • Hermaphroditic, posses a clitellum to aid cross-fertilization • Class Hirudinea • Most freshwater, some marine and terrestrial • Invertebrate predators or parasites • Slit skin with jaws or dissolve hole with enzymes • Use anesthetic so undetectable and hirudin, an anticoagulant

16. Phylum Arthropoda • Specialized jointed appendages • Hard exoskeleton of chitin and protein • Sites for muscle attachment, protection, and stops desiccation • Limits growth so must molt = energetically expensive • Segmented bodies allows organ and system specializations • Developed nervous system for sight, smell, and touch • Open circulatory system • Respiratory systems vary between tubes, lungs, and gills

17. Subphyla of Arthropods Subphylum Crustacea Subphylum Chelicerata • Mostly marine with gills • Head with compound eyes & 5 appendage pairs • 2 pairs antennae • 1 mandible and 2 mandible for feeding • Walking legs on thorax • Includes Isopods, Copepods and Krill, Barnacles, and Decapods • Most collectively called arachnids • No antennae and simple eyes • Specialized appendages • 1 pair for feeding = chelicerae • 1 pair sensory function = pedipalps • 4 pair walking legs • Book lungs for respiration

18. Subphyla of Arthropods Subphylum Myriapoda Subphylum Hexapoda • 1 Pair of antennae, 1 pair of madibles, and 2 pairs maxillae • Class Diplopoda • Millipedes are herbivores with 2 pairs of legs a segment • Class Chilopoda • Centipedes are carnivorous with 1 pair of legs a segment; poison claws on first segment • Class Insecta • 1 or 2 pairs of wings from thorax, cuticle extensions not appendages • Advertize with colors , sounds, or odors for reproduction • Metamorphosis to reduce competition within a species • Complete (different and direct) or incomplete (similar and stages)

19. Phylum Echinodermata • Deuterostomes with a spiny endoskeleton covered by calcareous plates with spines • Water vascular system includes tube feet for locomotion, feeding, and gas exchange • Lack complex circulatory, respiratory, and excretory systems • Internal and external parts radiate from center of organism • Not true symmetry, larvae are bilateral and sieve plate offset in adult • Lack cephalization, nervous system is ring with radial nerves in each arm

20. Classes of Echinoderms • Can regrow lost arms, turns stomach inside out to eat • Long, flexible arms for movement • Mouth is a jaw like structure, tube feet in rows • Mouth faces up and arms for suspension feeding • Lack spines, tube feet around mouth for feeding • Armless with 5-sided organization, ringed by spines