Protostomes

Bio 2

Lophotrochoza clade

Spiral Cleavage embryonic development

most live in water

move using cilia or contractions of body musculature

Defining characteristics  of lophrotrochoza

Trochophore - a free living larva

Lophophore - a horseshoe - shaped crown of ciliated tentacles surrounds the mouth used in filter-feeding

Platyhelminthes Phylum

Flatworms

First animal with predatory lifestyle

Bilaterally symmetry with cephalization

lack specialized respiratory or circulatory system ( respire by diffusion)

Incomplete digestive system with gastrovascular cavity

Flatworms (animal)

simple bodies with no circulatory or respiratory systems, but complex reproductive system

Includes marine and freshwater planarians and parasitic flukes and tapeworms

ciliated and soft bodied

incomplete digestive cavity ( one opening)

many parasitic, some are free-living

marine, freshwater, and moist terrestrial environments

diffusion for gas transport

Tapeworms (parasitic) abosrb food directly through body walls

Flatworm excretion and osmoregulation

network of fine tubules runs through the body

Metabolic wastes are excreted into the gut and elimanted through the mouth

Flatworm nervous system and reproduction

simple nervous system,

Anterior cerebral ganglion and nerve cords

eyespot can distinguish light from dark

reproduction

Hermaphroditic ( both male and female reproductive organs)

sexual reproduction mostly but can do asexual

Trematoda - flukes

Attach to host by suckers, anchors, or hooks

life cycle have 2 or more hosts ( intermediate and definitive hosts)

includes the miracidium, sporocyst, redia, and cercaria stages

clonorchis sinessis, oriental liver fluke

schistosoma

schistoma

parastiic fluke life cycle: 

first ( intermediate) host usually mollusk

Final ( defintive) host is usually is a vertebrae

can be second or even a third intermediate host

blood flukes  schistomosa

cause schistomiasis

chronic inflammation and blockage of orgnas ( can be fatal)

Tapeworm

adult hangs on to host isntentine wall with scolex

most of tapeworms is proglottids

• complete hermaphtodiditc unit, both male and female reproductive organs

• formed consitnulsy

Beef tapeworm Taenia saginata

• Frequent human parasite

• from eating uninspected rare cooked beef

Cestode/tapeworm life cycle

require two differnet vertabrae species to being life cycle ( cattle or pigs)

another host required for developemt ( humans)

Scolex atttaches to host

proglottids develop thousands of eggs and continuously shed in feces

humans infected by eating undercooked infected meat

Rotifera phylum

Bilaterally symmetrical, unsegmented pseudocoelomates

highly developed internal organs

corona - wheel animals

• conspicuous ring of cilia at anterior end

• used for locomation and for sweeping food into mouth

Phylum Mollusca

second in diversity only to arthropods

includes snails, slugs, octopuses, squids, others

some have a shell (mantle) others don’t

Features of Mollusca

size from microscopic to huge

Evovled in oceans and most have remained in ocen

Improtant soruce of food for humans

Economcially significat

• pearls in oysters

• mother of pearl in abalone shells

• pests (invasive species) zebra mussel (Dreissena polymorpha)

Mollusk body plan: Mantle and foot

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

Mollusk body plan: internal organs

internal organs ( visceral mass)

• 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 the visceral mass

• Ctenida - gills in aquatic mollusks. Also filter food in most bilvalves

Mollusk body plan: shell

shell

• protects against predators

• secreted by the outer surface of the 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

  • Ocean acidification really impacts these animals (calcifiers) due to the loss of calcium carbonate

Mollusk body plan: radula

• rasping tongue-like structures used in feeding

• In predatory gastropods, modified to drill through clam shells

• In conus snails, it modifies into a harpoon with a venom gland

• Bivalves do not have a radula

Waste removal and Circulatory system

Nitrogenous waste removal - Nephridia

• consists of cilia-lined openings called nephrostomes

• tube to excretory pore to mantle cavity

Circulatory system

• open circulatory system

  • hemolymph sloshes around hemocoel

  • 3 chamebred heart

• Cephalopods have a closed circulatory system

Mollusk reproduction

• most are gonochoric ( individuals are either male or female)

  • a few are hermaphroditic

  • some oysters change sex

• most engange in external fertilization

  • gastropods have internal fertilization

• mollusk zygote undergoes sprial cleavage

Mollusk life stages

Trocophore

• free - swimming larval stage

Veliger

• second free-swimming larval stage

• only in bivalaves and most marine snails

Both forms drift widely in the ocean

Classes of mollusks

There are 7 or 8 recognized classes; four will be discussed

1. Polyplacophora - chitons

2. Gastropoda - limpets, snails, slugs

3. Bivalvia - clams, oysters, scallops

4. Cephalopoda - squids, octopuses, cuttlefishes, and chambered nautilius

Class Polyplacophora (chitons)

• marine mollusk that have oval bodies

• 8 overlapping dorsal calcareous plates

• body is not segmented under the plates

• most chitons are grazing herbiovres

Class Gastropoda

Limpets ( marine snail), snail, slugs, sea slugs ( nudibranchs)

primarly marine group - some freshwater and only terrestial mollusks

most have a single shell - some lost it

Heads typically have pairs of tentacles with eyes

Torsion

• Unique among animals

• Mantle cavity and anus are moved from the posterior to the front

Class Bivalves

Includes clams, scallops, mussels, oysters, and others

most marine, some freshwater

no radula or distinct head

have 2 shells ( valves) hinged together

• adductor muscles counter hinge ligament

water enters through inhalant siphon and exits through exhalant siphon

Class Cephalopoda

more than 700 marine species

active marine predators

only mollusk closed circulatory system

foot evolve into series of arms equipped with suction cups

• beak-like jaws, toxic saliva

largest relative brain sizes among invertebrates

highly developed nervous system

mouth with beaklike jaw surrounded by arms

natuliuses have retained external chambered cell

have been shown to be highly intelligent and can learn throuhg observation

closed circualtory system ( blood contains Hemocyanin)

Octopus cased study

octopuses trained to attack red or white ball using classical conditioning ( reward and punishment)

octopuses are color blind - so must see relative brightness of balls

Observer learned faster than original training

The Siphon and the Skin

Living cephalopods lack external shell

• except chambered nautilus

• squid and cuttlefish have internal shells

Jet propulsion using siphon

Ink can be ejected from siphon

Chromatophores allow for Changning skin color for camouflage or communication

Annelids ( Annelida)

Segmented worms

body built of repeated units

advantages

• repetition of vital strucutres provides backup ( if one segment is damaged, the organism can still survive)

• coelom can act as hydrostatic skeleton without distortion of body

• permits specialization

• locomotion more efficent

Annelid body plan

All annelids except leeches have setae on each segment

may be situated on fleshy parapodia (partial feet)

leecehs have suckers on anterior and posterior ends

Giant axons faciliate rapid response to simuli

double transport system

• cirucaltory system and coelomic fluid both carry nutrients, wastes and respiratory gases

Complete digestive system that is unsegmetned

Sexual reproduction inovlves two individuals ( sometimes seperate sexes, others hermaphroditic) with interal fertilization

• Asexual reproduction by fission

Annelid features

body plan

head has well developed cerbal ganglion

senory orgnas in ring like segementes

many species hvae eyes

segements divded internally by speta

closed circutlroy system

Ventral nerve cord

other feautes

Locomotion

coelomic fluid creates hydrostatic skeleton

althernating muscel contractions allow complex movemetns

chaetae - bristles of chitin found in most groups

closed circulatory system

has diffsuion across body surfaces

Closed circulaotry system

exectroy ssytem - nephridida sumilar to molluks

Major annelidian groups

Erranrtia

long setae on footlike parapodia

Sedebtaria

earthworms (condition soil through burrowing and feedings)

Leeches (freshwater, generally blood sucking , hiruidin protein ( anticoagulant)

Tube worms (marine, filter food from water with crown of tentacles)

Errantia,

Include Clamworms, scaleworms, lugworms, sea mice, tubeworms, and others

Have paired Parapodia on most segments

• for locomotion or gas excahnge

• Chaetae on parapodia

may have gonads in most segments or certain segments

• external fertiization

• trochopohre larva

Clitella clade

Citellum found in all members

Earthworms

• headwall not well differnetiated

• no parapodia

• few chaetae project from body wall

• hermaphroditic but cross-fetilize

• Clitellum secretes mucus cocoon

Earthworms

• 100 - 175 similar segments

• Chaetae project from body wall

• Head not well differnentiated 

• no parapodia

• no eyes

• can sense light, touvh, and also have chemorecpotrs

• citellum secrets mucus cocoon

• hermaphroditic but cross fertilizrers

Leeches

• most in freshwater

• flattened dorsoventrally

• hemraphorditic and cross-fertilization

• citellum only during the breeding season

• reduced coelom not divided into segments

• suckers at both ends of body

• No chaetae ( execptr for one species)

• Some eat detritus, others suck blood
  

Nemertea ( ribbion worms)

Super long worms ( 60M) 

Body plan resembles a flatworm

comeplet gut

Gonochoric with sexual reproductiomn

• asexual reproduction through fragmentation\

blood flows entirley in vessels

Ecdysozoa

• animals that molt

• exoskeelton

• two groups : Arthropods and Nematodes

Phylum Nematoda

Roundworms

• tough collagen cuticle covers body

• Not segmented and undergo ecdysis (molting)

• pseudocoelom acts as hydrostatic skeleton and circulatory system

• complete digestive tract

Additonal Nematode Charcteristics

• Bilaterally symmetrical and unsegmented

• covered by a flexibile, thick cuticle that is molted as they grow

• Digestive system well developed

  • stylets - piercing organs near mouth

  • Pharynx - creates sucking action

  • Anus

• Important in genetic and developmental studies

Nematode lifestlyes

• Many are active hunters, praying on protists and other small animals

• others are parasites of plants

• still others live within thte boides of larger animals

  • largest known Nematode, which can attain a lengt of 9 meters, parasitizes the placenta of sperm whales

Nematodes and human disease

hookworms

• common in southern U.S

• produce anemia

Trichinella causes trichinosis

• forms cysts in muscles

• infection from eating undercooked meat

Addtional Nematodes with Human Diesease

Pinworms

• infects 11% of U.S population

• causes itching of the Anus

Ascaris lumbricoides - intestinal roundoworms

• infects 1 in 6 worldwide

• adult female can be 30cm long

serious Nematode tropical disease

• filariasis

• elephantasis

Phylum arthropoda

1.2M species

affect all aspects of human life

four classes

• chelicerata

• crustacea

• hexapoda

• myriapoda

Arthropod segmenation and exoskeleton

segementation

• in some classes specialized into tagmata (tagmatization(

• head, throax abdomen

• head and thorax may be fused into cephalothorax or prosoma

Exoskeleton

• made of Chitin and protein

• protects against water loss

• must undergo ecdysis - molting

Jointed appendages

• may be modified into antennae, mouthparts, or wing

• can be extended and retracted

arthropod circualtory and nervous system

open circulaotry system

nervous system

• double chain of segmented ganglia

• ventral ganglia control most activites

  • can eat, move, or copulaate with brain removed

Arthropod eyes

compound eyes 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 singles lenses

• distinguish light from darkness

respiratory system

many marine arthopods have gills

some tiny arthopods lack any strucutes for gas excahnge

terrestial arthropods use trachae

• branch into tracheoles in direct contact with cells

• connected to exterior by spiracles

• valves control water loss

Many spiders use book lungs

Excetroy System

aquatic arthropods, waste diffuse out of gills

Terresital insect and some other use Malpighian tubules

• elimatnes nitrogenous wastes as concetrated as uric acid

• effcient concservation of water

Class Chelicerta

containes spiders,ticks,mits,scorpoions,horshoe crab

most anterior appendages called Chelicerae

• may function as pincers

body divided into 2 tagmata

• prosoma bearing all appendages

• pedipalps and 4 pairs of walking legs

  • posterior opisthosoma contains reproductive organs

order araneae ( spiders)

35k species

particulary important as predators

many spiders catch their prey in silk webs

• silk proetein forced out of spinnerets found on posterior of abdomen

other spiders actively hunt their prey

all spiders have poision glands with channels through their chelicerare

Order Acari

Contains Mites and ticks

predators and parasties

most mites are smalll

• cephalothorax and abdomen are fused into an unsegmeneted ovoid body

Ticks are larger

• blood - suckers

Can carry many disease

• rocku mountain spotted fever, Lyme disease

Class crustcea

largely marine, some freshwater

crabs, shrimps, lobsters, barnacles, crayfish, copepods, pill bugs, sand fleas

have three tagmata

• cephalon and thorax fused to form a cephalothorax

2 pairs of antennae, 3 pairs of appendages for chewing, and various pairs of legs

gas exchange through gills or across cuticle

Crustacean reproduction

all crustcean but barnacles have separate sexed

many kinds of copulation

Naupilus stage

• several stages before maturtiry

• evidence of common ancestor of diverse group

Decapod Crustcean

Ten feet with 5 pairs of thoracic appendages

includes: shrimps, crabs, and crayfish

exoskeleton usually enforced with CaCO3

Cephalothorax covered by carapace

lobsters and crayfish

• swimmerets used in reproduction and swimming

• uropods paddle on either side of telson

crab has small abdomen held under carapace

Order Cirripedia

Barnacles

sessile as adults

captures food with feathery legs

Hermaphroditic

Class Hexapoda 

insects are by far the largest group of animals

• number of species and number of individuals 

more than half of all named animal speices

approxiamtley 1 × 10^18 insecs are alive at any one time

Success of insects

• due to body segmentation

• exoskeleton

• jointed appendages

• flight

• different mouthpart adaptations

• waaterprood cuticle

• complex life cycle with short generations

external features

three body regions

• head

• thorax with three segments

• abdomen

Class Myriapoda

centipedes

have one pair of appednages

carnivours with poisionous fangs

millipedes

two pairs of appendages per segment

each segment is tagma of 2 segments

herbivores

defensive bad smelling fluid