Invertebrates

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Invertebrates

• Chapter 33

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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
• Amoebocytes take food from water and choanocytes
  to digest it
• Produce antibiotic related compounds

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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

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Phylum Cnidaria

• Sessile and motile forms
• Diplobalstic and radially symmetrical
• Contain a gastrovascular cavity, from endoderm
• Sac like body plan
• Simplistic muscle and nerve tissues
• Gastroderm contracts with closed mouthshape
  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

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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

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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

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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

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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)

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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

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Nematode Examples

• Trichinella spiralis (trichinosis)
• Juvenile worms encyst in pig muscle, humans
  consume
• Adults burrow through intestines into lymph
  system
• Caenorhabditis elegans (C. elegans)
• Popular model for genetic research
• Enterobius vermicularis (pinworms)
• Common childhood disease
• Dinofilaria immitis (dog heartworms)
• Wucheria bancrofti (elephantiasis)
• Transmitted by mosquitos and live in lymph
  systems
• Necatur americanus (hookworms)

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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

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Classes of Molluscs

• Class Polyplacophora
• Body of dorsal plates, but unsegmented no head
  but radula
• Class Gastropoda
• Herbivores 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

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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

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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

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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

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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

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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

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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)

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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

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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