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PROTOSTOMES

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Platyzoans—Phylum PlatyhelminthesCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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Protostomes

Spiralia

EcdysozoaLophotrochozoaPlatyzoa

• Flatworms are ciliated, soft-bodied animals

• Bodies are solid aside from an incomplete digestive cavity

• Many species are parasitic

• Others are free-living

• Marine, freshwater, moist terrestrial

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Flatworms

10 mm

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

© Tom Adams/Visuals Unlimited

• Only one opening to digestive cavity

• Muscular contractions in the pharynx allows food to be ingested

and torn into small bits

• Lack circulatory system

• Diffusion for gas transport

• Gut functions in digestion and food distribution

• Some particles digested extracellularly

• Cells engulf particles by phagocytosis

• Tapeworms (parasitic flatworms) lack digestive systems –

absorb food directly through body walls

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EyespotProtruding pharynx

Mouth

Testis

Oviduct

Sperm

duct

Circular

muscles

Longitudinal

muscles

Parenchymal

muscle

EpidermisNerve cord

Intestine

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Reproductive

System

Excretory

System

Nervous

System

Intestine

Nerve

cord

Testis

Ovary

Anterior

cerebral

ganglion


• Have an excretory and osmoregulatory system

• Network of fine tubules runs through body

• Flame cells located on the side branches

• Flagella move water and excretory substances into the

tubules and then to pores located between the epidermal

cells through which the liquid is expelled

• Metabolic wastes are excreted into the gut and eliminated

through the mouth

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• Simple nervous system

• Anterior cerebral ganglion and nerve cords

• Eyespot can distinguish light from dark

• Reproduction

• Most are hermaphroditic

• Undergo sexual reproduction

• Also have capacity for asexual regeneration

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• 2 major groups of flatworms

• Free-living Turbellaria

• Probably not monophyletic

• Dugesia – common planarian in bio labs

• Parasitic Neodermata

• Trematoda – flukes

• Attach within host body by suckers, anchors, or hooks

• Life cycle may have 2 or more hosts

• Clonorchis sinensis, oriental liver fluke

• Cercomeromorpha – tapeworms

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Metacercarial

cysts in fish

muscle

Metacercariae are

consumed by humans

or other mammals

Adult flukeMiracidium hatches after

being eaten by snail

Liver

Bile

duct

Egg containing

miracidium in feces

(into water)

Cercaria

Sporocyst

Redia

57 µm© Dwight R. Kuhn

• One of most important trematodes to human health are

blood flukes Schistosoma

• Afflict 5% of world’s population

• About 800,000 people die each year from schistosomiasis or

bilharzia

• Fertilized egg must break through the wall of the blood vessels

in intestine or the urinary bladder to get out

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125 µm

© The Natural History Museum/Alamy

• Cercomeromorpha – tapeworms

• Adult hangs onto inner wall of host intestine using scolex

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500 µm


© Dennis Kunkel/Phototake

• Most of tapeworm body is proglottids

• Complete hermaphroditic unit, containing both male and female reproductive

organs

• Formed continuously

• Beef tapeworm, Taenia saginata

• Frequent human parasite

• From eating uninspected rare beef 13

Scolex

Hooks

Sucker

Proglottids

Scolex attached

to intestinal wall

Uterus

Proglottid

Genital

pore


LOPHOTROCHOZOANS—PHYLUM MOLLUSCA

• Second in diversity only to arthropods

• Include snails, slugs, clams, octopuses and others

• Some have a shell, some do not

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Protostomes

SpiraliaEcdysozoa

LophotrochozoaPlatyzoa

a. b.

c. d.

a.

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a: © Marty Snyderman/Visuals Unlimited; b: © Alex Kerstitch/Visuals Unlimited; c: © Douglas Faulkner/Photo Researchers, Inc.; d: © agefotostock/SuperStock

• Range in size from microscopic to huge

• Giant clams may weigh 270 kg

• Evolved in the oceans, and most groups have remained there

• Important source of human food

• Economically significant in other ways

• Pearls are produced in oysters

• Mother-of-pearl is produced in the shells of abalone

• Pests – Zebra mussel (Dreissena polymorpha)

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MOLLUSK BODY PLAN

• Mantle

• Thick epidermal sheet

• Bounds mantle cavity

• Secrete shell (if there is one)

• Foot

• Primary means of locomotion for many

• Divided into arms or tentacles in cephalopods

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• Internal organs

• Coelom is highly reduced

• Limited to small spaces around the excretory organs, heart,

and part of the intestine

• Digestive, excretory, and reproductive organs are concentrated

in a visceral mass

• Ctenidia – gills in aquatic mollusks

• Also filter food in most bivalves

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Radula

Gut

Lung

Foot

Gastropods

Shell

Antenna

Radula

Mantle

Gut

Shell

Gill Foot

Chitons

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Gut

Gill

Gut

Gill

Foot Mantle

Shell

Cephalopods

Bivalves

Siphons

Siphon

EyeArmMantle

cavity

Adductor

muscle

Tentacle

• Shell

• Protects against predators and adverse environments

• Secreted by outer surface of mantle

• Clearly not essential – repeated loss or reduction

• Typical shell has 2 layers of calcium carbonate

• Internal layer may be mother-of-pearl or nacre

• Pearls are formed by coating foreign object with nacre to

reduce irritation

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• Radula

• Characteristic of most mollusks

• Rasping, tonguelike structure used in feeding

• Used to scrape up algae

• In predatory gastropods, modified to drill through clam shells

• In Conus snails, modifies into harpoon with venom gland

• Bivalves do not have a radula

• Gills used in filter feeding

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Esophagus

Radula tooth

Muscles

MouthRadulaMouth

25 µmBottom: © Eye of Science/Photo Researchers, Inc.

• Nitrogenous waste removal – nephridia

• Consist of cilia-lined openings called nephrostomes

• Tube to excretory pore to mantle cavity

• Circulatory system

• Open circulatory system

• Hemolymph sloshes around hemocoel

• 3-chambered heart

• Cephalopods have a closed circulatory system

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MOLLUSK REPRODUCTION

• Most mollusks are gonochoric

• A few are hermaphroditic

• Some oysters change sex

• Most engage in external fertilization

• Gastropods have internal fertilization

• Mollusk zygote undergoes spiral cleavage

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CLASSES OF MOLLUSKS

• There are 7 or 8 recognized classes

1. Polyplacophora – chitons

2. Gastropoda – limpets, snails, slugs

3. Bivalvia – clams, oysters, scallops

4. Cephalopoda – squids, octopuses, cuttlefishes, and chambered

nautilus

LOPHOTROCHOZOANS—NEMERTEA

• About 900 species of cylindrical to flattened very long

worms

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Protostomes

SpiraliaEcdysozoa


• Most are marine; a few species live in fresh water and humid

terrestrial habitats

• Lineus longissimus has been reported to measure 60 m in length –

the longest animal known!

• Body plan resembles a flatworm

• Has a complete gut

• Rhynchocoel – fluid filled coleomic cavity

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• Gonochoric with sexual reproduction

• Asexual reproduction through fragmentation

• Belong to lophotrochozoans because

• Blood flows entirely in vessels

• Rhynchocoel

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LOPHOTROCHOZOA

NSPHYLUM

ANNELIDA

• Segmented worms

• Body built of repeated

units

• Allows for specialization

• May not be monophyletic


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Protostomes

SpiraliaEcdysozoa


• Body plan

• Head has well-developed cerebral ganglion

• Sensory organs in ringlike segments

• Many species have eyes

• Segments divided internally by septa

• Each segment has a pair of excretory organs, a ganglion,

and locomotory structure

• Closed circulatory system

• Ventral nerve cord

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Brain

Dorsal blood

vessel

Septa

Intestine

Nephridium

Mouth

Pharynx

Esophagus

Clitellum

Setae

Ventral blood

vessel

Nerve cord

Female gonads

Male gonads

Segments

Hearts

• Each part of digestive tract specialized for different

function

• Locomotion

• Coelomic fluid creates a hydrostatic skeleton

• Alternating muscle contractions allows complex movements

• Chaetae – bristles of chitin found in most groups

• Closed circulatory system

• Gas exchange by diffusion across body surfaces

• Excretory system – nephridia similar to mollusks

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• Roughly 12,000 described species of annelids occur in many

habitats

• 2 classes

1. Class Polychaeta

• Monophyly not well established

2. Class Clitella

• Oligochaeta

• Hirudinea

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Protostomes

SpiraliaEcdysozoa


Phylum Nematoda

• Vinegar eels, eelworms, and other roundworms

• Members of this phylum are found everywhere – abundant and

diverse

• Marine, freshwater, parasites, free-living

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181.1µm


© Educational Images Ltd., Elmira, NY, USA. Used by Permission

• Bilaterally symmetrical and unsegmented

• Covered by a flexible, thick cuticle that is molted as they grow

• Digestive system well developed

• Stylets – piercing organs near mouth

• Pharynx – creates sucking action

• Anus

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Mouth

Dorsal nerve cord

Intestine

Testis

PharynxExcretory pore

Muscle

Pseudocoelom

Excretory duct

Intestine

Testis

Epidermis

Ventral nerve cord

Cuticle

Genital pore

AnusSpicules

• Sexual reproduction

• Most gonochoric

• Sexual dimorphism – male smaller with hooked end

• Internal fertilization

• Indirect development – egg, larva, adult

• Eutely

• Adults consist of a fixed number of cells

• Caenorhabditis elegans has only 959 cells

• Important in genetic and developmental studies

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• Lifestyles

• Many are active hunters, preying on protists and other small

animals

• Others are parasites of plants

• Still others live within the bodies of larger animals

• Largest known nematode, which can attain a length of 9 m,

parasitizes the placenta of sperm whales

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• About 50 species cause human diseases

• Hookworms

• Common in southern U.S.

• Produce anemia

• Trichinella causes trichinosis

• Forms cysts in muscles

• Infection from eating undercooked meat

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50 µm© Gary D. Gaugler/Photo Researchers, Inc.

• Pinworms, Enterobius vermicularis

• Infects 30% of children in U.S.

• Causes itching of the anus

• Ascaris lumbricoides – intestinal roundworm

• Infects 1 in 6 worldwide

• Adult female can be 30 cm long

• Rare in areas with modern plumbing

• Serious tropical nematode diseases

• Filariasis

• Elephantiasis

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ARTHROPODA

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Protostomes

SpiraliaEcdysozoa


• By far the most successful animals

• Well over 1,000,000 species (2/3 of all named species)

• Arthropods affect all aspects of human life

• Divided into four extant classes

• Chelicerata

• Crustacea

• Hexapoda

• Myriapoda

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3.4% Crustaceans

36.2%

Beetles

12.1%

Flies

12.1%

Butterflies,

moths

10.3%

Bees, wasps,

ants

8.6%

Other

insects12.1%

Other

arthropods

5.2% Arachnids

Arthropods are a successful group

About two-thirds of all named species

are arthropods. About 80% of all

arthropods are insects, and about half

of the named species of insects are

beetles

ARTHROPOD MORPHOLOGY

• Part of arthropod success explained by

1. Segmentation

• In some classes specialized into tagmata

• Head, thorax, abdomen

• Head and thorax may be fused into cephalothorax or

prosoma

2. Exoskeleton

• Made of chitin and protein

• Protects against water loss

• Must undergo ecdysis – molting

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3. Jointed appendages

• May be modified into antennae, mouthparts, or wings

• Can be extended and retracted48


Compound eye

Head

Thorax

Antenna

Mouth parts

Air sac

Malpighian

tubules

Abdomen

Rectum

Sting

Poison

sac

MidgutSpiracles

• Open circulatory system

• Nervous system

• Double chain of

segmented ganglia

• Ventral ganglia control

most activities

• Can eat, move, or

copulate with brain

removed

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Head Thorax Abdomen

Spiracles

Tympanum

Compound

eye

Ocellus

Antennae

BrainAorta Stomach Ovary

Heart Rectum

MouthCrop Gastric

ceca

Malpighian

tubules

Nerve

ganglia

a.

b.


• Compound eyes are found in many arthropods

• Composed of independent visual units called ommatidia

• Other arthropods have simple eyes, or ocelli

• May be in addition to compound eyes

• Have single lenses

• Distinguish light from darkness

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Ommatidium

Corneal lens

Crystalline

cone

Rhabdom

Retinular

cells

Pigment

cell

NervefiberOmmatidium

Optic nerve

Compound Eye

• Respiratory system

• Many marine arthropods have gills

• Some tiny arthropods lack any structure for gas exchange

• Terrestrial arthropods use tracheae

• Branch into tracheoles in direct contact with cells

• Connected to the exterior by spiracles

• Valves control water loss

• Many spiders use book lungs

• Leaflike plates

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Trachea

Spiracles

Tracheoles

Spiracles

• Excretory system

• In aquatic arthropods much of the waste diffuses out of gills

• Terrestrial insects and some others use Malpighian tubules

• Eliminates nitrogenous wastes as concentrated uric acid or

guanine

• Efficient conservation of water

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BrainAorta Stomach Ovary

Heart Rectum

MouthCrop Gastric

ceca

Malpighian

tubules

Nerve

ganglia

b.


PROTOSTOMES - Weeblymmsalemscienceteacher.weebly.com/uploads/2/3/3/6/... · 2017-02-09 ·...

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Transcript of PROTOSTOMES - Weeblymmsalemscienceteacher.weebly.com/uploads/2/3/3/6/... · 2017-02-09 ·...