Transcript Compound Eye

The Arthropods: Blueprint for
Success
Chapter 14
Zoology
What is the most abundant animal
on Earth?
• Answer: Copepods, a
type of marine
Arthropod.
• 1-2 mm planktonic
crustacean
• Basis of marine food
webs.
• One of the smallest
creatures is food to one
of the largest – blue
whales.
Number of Species by Phylum
Mollusca
Chordata
Platyhelminthes
Nematoda
Arthropoda
Porifera
Annelida
Echinodermata
Sarcomastigophora
Apicomplex
Ciliophora
What is an Arthropod?
• Arthro – joint + podas
– foot
• Crayfish, lobsters,
spiders, mites,
scorpions, and
insects.
• + 1 million species
described.
• Estimated to be 30 –
50 million
undescribed species.
• Most successful
Phylum in the Animal
Kingdom.
Arthropoda - Jointed Legs
Arthropods - Most Successful Animals
•
•
•
•
Number of species
Diversity
Distribution
Longevity
Reasons for Arthropod Success
• Versatile exoskeleton
• Segmentation
• Oxygen piped directly
to cells (terrestrial)
• Highly developed
sensory organs
(compound eye)
• Complex behavior
• Metamorphosis
General Characteristics of Arthropods
• Triploblastic Protostome
• Bilateral Symmetry
• Metamerism – segmented body with
tagmatization
• Jointed Appendages
• Exoskeleton
• Ecdysis or molting
• Ventral Nervous System
• Open Circulatory System
• Complete Digestive Tract
• Metamorphosis
Phylogeny of Arthropods
Arthropoda
Annelids
(worms)
Onychophorans
(worms w/legs)
Chelicerates
(spiders)
Crustaceans
(lobsters)
Trilobites
(extinct)
Worm-like
Ancestor
Insects
(butterflies)
Metamerism and Tagmatization
• Metamerism – segmented body (like
Annelida) but specialization of body regions
for specific functions – Tagmatization.
• Segmented externally, but no internal septa to
divide each segment; organ systems are not
divided.
• Internal metamerism is not needed;
exoskeleton replaces the hydrostatic
compartments of annelids for support.
Tagmatization
• Body regions are called tagmata - specialized
for feeding, locomotion, and visceral functions.
• Examples are: head, thorax, and abdomen
• Most internal organs are not segmented.
The Exoskeleton
• Arthropods enclosed in an external, jointed
skeleton – exoskeleton or cuticle.
• Provides: structural support, protection,
prevents water loss, attachment points for
muscle movement.
• It is a nonliving mixture of lipids, proteins and a
tough polysaccharide called – chitin.
• Made by a deeper layer of tissue – epidermis
or hypodermis.
Two Layers of The Exoskeleton
• Epicuticle – waxy,
outermost layer;
impermeable to
water, bacteria, and
pesticides.
• Procuticle – deeper,
thicker layer of chitin
and protein; outer
portion may darken
and harden by
sclerotization
(proteins) or with
calcium carbonate.
• Hard, but flexible
armor.
Hardened Procuticle
Softer
Procuticle
13
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Modifications of Exoskeleton
Soft and flexible at joints
for movement
Invaginations for
gas exchange
From A Life of Invertebrates, Copyright © 1979, W. D. Russell-Hunter.
Growth with an Exoskeleton
• Growing arthropods must periodically shed the
exoskeleton by molting – ecdysis.
• Triggered by hormones (ecdysone) – which
causes the old procuticle to breakdown and
separate from the epidermis.
• A new epicuticle and procuticle are made
underneath by the epidermis.
• Old exoskeleton splits open as the animal
stretches with air or water intake and wriggles
out of old exoskeleton.
How do Arthropods grow?
Ecdysis in my tarantula!
They grow up so fast!
Old Exoskeleton
New Exoskeleton
and Animal
Crawling Out
How big can something with an
exoskeleton get?
The Hemocoel
• An internal cavity for the open
circulatory system of arthropods; results
from no internal segmentation.
• Internal organs are bathed by body fluids
(hemolymph) for exchanges of nutrients,
wastes and gases.
• Because of an exoskeleton, the coleom is
no longer used as a hydorstatic skeleton.
Review of Circulatory Systems
Open Circulatory System
Ostia
Closed Circulatory System
Metamorphosis
• Changes in body form and physiology as
arthropods grow and develop.
• Immature stages (larvae) often are
radically different than adult forms.
• These differences reduce competition
between adult and young (different
body forms, behaviors, and habitats).
• Many types of metamorphosis
(discussed more with insects).
Metamorphosis
Metamorphosis in a Monarch Butterfly
Larva – Caterpillar
eats leafy vegetation
Chrysalis
Adult – Butterfly eats
nectar
Phylum Arthropoda Groups
• Subphylum Trilobitomorpha (trilobites)
• Subphylum Chelicerata
– Class Merostomata (horseshoe crabs)
– Class Arachnida (spiders,scorpions,ticks)
– Class Pycnogonida (sea spiders)
• Subphylum Crustacea
– Class Malacostraca (lobsters, crabs, shrimp)
– Class Branchiopoda (brine shrimp, water fleas)
– Class Maxillopoda (barnacles, copepods)
• Subphylum Hexapoda (insects)
• Subphylum Myriapoda (millipedes and centipedes)
Subphylum Trilobitomorpha
• Trilobites, dominant life form
that went extinct 345 million
years ago.
• Oval, flattened bodies divided
into 3 tagmata (head, thorax,
pygidium).
• All body parts could roll up
(like a rollie-pollie).
• Appendages – two lobes or
branches (biramous) – one as
a walking leg and the other for
digging or as a gill).
• Crawled on the bottom
feeding on annelids, molluscs,
and decaying matter.
Subphylum Chelicerata
• chele – “claw”; spiders,
mites, horshoe crabs,etc.
• Two Tagmata:
1. Prosoma (Cephalothorax)
- “head” for sensory,
feeding, locomotion; often
eyes but NEVER antennae.
2. Opisthosoma –
“abdomen” for digestion,
reproduction, excretion,
and respiration.
Prosoma has all the appendages!
• First two pairs of appendages for feeding:
1. Chelicerae – first pair that are pincerlike
(chelate) used in feeding; maybe hollow
fangs.
2. Pedipalps – second pair that are for
sensory, feeding, movement, or
reproduction.
3. Paired walking legs are posterior to the
pedipalps; number of legs varies.
Opisthosoma or
Abdomen
Prosoma or
Cephalothorax
Chelicerata Legs
1st Pair - Chelicerae
2nd Pair - Pedipalps
Posterior Pairs –
Walking Legs
Class Merostomata
• Ancient group of 4 species of horseshoe crabs and
giant water scorpions (extinct 280 mya).
• Horseshoe crabs are benthic scavengers and
predators.
• Hard, horseshoe-shaped carapace covers the
prosoma.
• Has cheilicerae, pedipalps and first three pairs of
walking legs are chelate – used in walking and
feeding.
• Last pair of legs for walking and digging – clams,
annelids, and other invertebrates.
Dorsal
Ventral
Opisthosoma of Horseshoe Crabs
• Long, unsegmented tail – telson – used to self-right the
animal.
• First Pair of Appendages – genital opercula - cover genital
pores.
• The remaining Five Pairs of Appendages – book gills –
platelike gills used in gas exchange between blood and
water.
Horseshoe Crab
•
Live up to 19 years; they are dioecious, may take 9-12 years to sexually mature.
•
Mates during spring and summer full and new moons, onto ocean beaches.
•
Females lay up to 30 thousand eggs, which males fertilize before burying them in
the sand
•
These eggs provide a major food source for migrating birds along the Atlantic
coast. Those that are not eaten hatch during the next high tide, and the tiny larvae
are carried away to sea.
Class Arachnida
• arachne – “spider”; includes mites, ticks and
scorpions.
• Some of the first terrestrial animals –
exoskeleton helps retain water; many other
adaptations for land.
• Have 4 pair of walking legs.
• 2 body segments (prosoma and opisthosoma)
– Except mites & ticks
• All are dioecious.
Digestion
• Most are carnivores.
• Some inject enzymes into prey with their
chelicerae (venomous) to help digest food.
• Suck digested material into pharynx.
• Gut tract is in three parts: foregut, midgut, and
hindgut- lined with cuticle so the lining is shed
as the exoskeleton.
Excretory Organs for Terrestrial
Arachnids
Excretion
• Arachnids use coxal glands and/or
Malpighian tubules to excrete waste and
reabsorb nutrients.
• Coxal Glands – paired, thin-walled sacs to
remove nitrogenous wastes; leave via
excretory pores at base of posterior
appendages.
• Uric acid is the main nitrogenous product of
land arachnids.
Malpighian Tubules
• In insects and other terrestrial arthropods,
Malpighian tubules
– Remove nitrogenous wastes from hemolymph and
function in osmoregulation Digestive tract
Rectum
Intestine
Midgut
(stomach)
Salt, water, and
nitrogenous
wastes
Malpighian
tubules
Feces and urine
Malpighian
tubule
Rectum
HEMOLYMPH
Hindgut
Reabsorption of H2O,
ions, and valuable
organic molecules
Anus
Malpighian Tubules
K+
Hemolymph
Water and K+
K+
Water and waste
K+
Na+/K+-ATPase
Hindgut
Conc. Waste
Respiration
• To reduce water loss, some arachnids have
book lungs – paried, leaf-like, infoldings on
the ventral surface.
• Air enters the book lung through slit opeing
and circulates between lamellae.
• Other arachnids have a tracheal system for
gas exchange.
• Exchange gases with the hemolymph fluid.
• Remember…no blood vessels!
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Arachnid Book Lung
Tracheal Systems in Insects
• The tracheal system of insects
– Consists of tiny branching tubes that penetrate the body
Air sacs
Tracheae
Spiracle
(a) The respiratory system of an insect consists of branched internal
tubes that deliver air directly to body cells. Rings of chitin reinforce
the largest tubes, called tracheae, keeping them from collapsing.
Enlarged portions of tracheae form air sacs near organs that require
a large supply of oxygen. Air enters the tracheae through openings
called spiracles on the insect’s body surface and passes into smaller
tubes called tracheoles. The tracheoles are closed and contain fluid
(blue-gray). When the animal is active and is using more O2, most of
the fluid is withdrawn into the body. This increases the surface area
of air in contact with cells.
• The tracheal tubes
– Supply O2 directly to body cells.
Body
cell
Tracheole
Air
sac
Trachea
Tracheoles
(b) This micrograph shows cross
sections of tracheoles in a tiny
piece of insect flight muscle (TEM).
Each of the numerous mitochondria
in the muscle cells lies within about
5 µm of a tracheole.
Body wall
Air
Mitochondria
Myofibrils
2.5 µm
Generic Arthropod Nervous System
• Ladder-like nervous system designed for a
segmented body plan – similar to annelids.
• Ventral longitudinal nerve cord.
NERVOUS SYSTEM
Lateral view of body showing
relative position of circulatory
(yellow), digestive (green), and
nervous (blue) systems.
Sense Organs
• Sensilla - modified
extensions of the
exoskeleton act as
receptors
(mechano- and
chemoreceptors).
• May be slits or
membraneous
drums.
Photoreceptors
• Arachnids have one or
more pairs of eyes.
• Detect movement, light
intensity or images
(hunting spiders).
• Two Types:
1. Simple or Pigment –
cup Ocelli – median
eyes.
2. Compound Eyes –
lateral eyes.
Pigment – cup Ocelli
• highly variable within the
arthropods.
• all the receptor units
(retina cells) share a
common lens.
• concavity of the cup is
oriented toward the light
source.
• pigment layer prevents
the entry of light from
any other direction.
Compound Eyes
• Most have one pair of
compound eyes.
• Each compound eye is made
of thousands of lightreceiving units called
ommatidia.
• Ommatidium is the
individual, self-contained,
independent light-detecting
unit.
• Each includes focusing
system (cuticular cornea and
crystalline cone)
Compound Eye
Lens
Crystalline cone
Pigment cells
Facet
Visual cells
Nerve fibers from visual cells
Ommatidia
Optic nerve
Compound Eye
Ommatidium Anatomy
Arachnid Reproduction
• All are dioecious
• Genital openings are ventral; sperm usually transferred
indirectly.
• Male may package sperm in a spermatophore which he
either places into the female or the female crawls over the
spermatophore and picks it up.
• May use modified pedipalps to transfer sperm. (spiders)
Order Scorpionida
• Scorpions
• Tropical and temperate
climates
• All are predatory
• Prosoma fused into hard
carapace
• Small chelicerae, but
enlarged pedipalps
• Opisthosoma is divided
into preabdomen and
postabdomen
• Sting and venomous gland
located on postabdomen
Scorpion Anatomy
3 Types of Birth in Scorpions
• Oviparous – females lay eggs that develop
outside of body.
• Ovoviviparous – young develop in large, yolky
eggs held internally in body, then are born,
fully developed.
• Viviparous – mother provides nutrients to
embryos; eggs develop in special chambers
close to female digestive tract. After birth,
young crawl onto mother’s back for about 1
month.
Viviparous Scorpion
Seeing is believing!
Order Araneae
• +34,000 species spiders; largest group of
arachnids
• Chelicerae are modified with poison and
fangs.
• Pedipalps are leg-like; males are modified for
sperm transfer.
• 6-8 eyes
• Spinnerettes at the posterior end that make
silk using silk glands.
Tarantula Feeding
What kinds of prey can they eat?
Latrodectus mactans
• Black widow spider
• Neurotoxin
Loxosceles reclusa
• Fiddle back spider
– Brown recluse
– Brown
– Violin
• Necrotoxin- causes
tissue death.
• Warning!!! The
following pictures
may be distrubing!
Loxosceles reclusa
• Necrosis of tissue
Day 3
Day 4
Day 5
Day 6
Day 9
Day 10
Order Acarina
• Mites and ticks
• Many are ectoparasites, others are
free-living.
• Most serious to human health
• Prosoma and opisthosoma are
fused and covered by a single
carapace.
• Chelicerae and pedipalps are
variously modified for piercing,
biting, etc. and have 4 pair of
walking legs.
Rocky Mountain Spotted Fever
•
•
•
•
•
Ticks are vector
High fever
Headache
Muscle pain
Rash
– BEGINS ON
EXTREMETIES
• 25% fatal without
antibiotics
Dermacentor variabilis
Dog tick
Dermacentor andersoni
Wood tick
Dermatophagoides
• Dust mite
• Allergies to fecal
products
• 1 gram of dust holds
250,000 droppings
Trombicula
•
•
•
•
Chigger mite
Larvae feed on skin
Dermatitis
Adults are feed on
insect eggs.
Sarcoptes scabiei, the human itch mite
See it in action!
Class Pycnogonida
• Sea Spider
• Marine arthropods- found
especially in the Mediterranean and
Caribbean Seas, as well as the Arctic and
Antarctic Oceans
• 1300 known species
• Walking legs is usually eight (four
pairs), but species with five and six pairs
exist.
• small size and slender body and legs, no
respiratory system is necessary for the
Sea Spiders, with gases moving by
diffusion.
Subphylum Crustacea
• Lobsters, shrimp, crayfish,
copepods, barnacles
• Have two pairs of
antennae
• Biramous appendages two distal projections
• Medial ramus –
endopodite
• Lateral ramus - exopodite
Class Malacostraca
• Crabs, lobsters,
shrimp; largest class
of crustraceans.
• Possess mandibles
and maxillae –
modified
appendages for
chewing and
grinding food.
Dorsal
Ventral
Internal Anatomy of Crustaceans
Excretory
Organs
Crayfish
87
Who cares about crustaceans?
The Krill
Some of the biggest aquatic
crustaceans!
Order Isopoda
Pillbugs- A terrestrial
crustacean.
A Strange Isopod Parasite!
Cymothoa exigua
See it in action!
Class Branchiopoda
• Branchio – gill + podos –
foot; fairy and brine
shrimp, water fleas;
freshwater.
• Flattened appendages for
respiration, filter-feeding,
and swimming.
• Females may reproduce
parthenogenetically.
Brine Shrimp
Class Maxillopoda
• Subclass Copepoda –
copepods; kope – oar +
poda – foot; most
abundant crustacean;
marine and freshwater.
• Cylindrical body and one
compound eye.
• First antennae are
modified for swimming
and no other appendages.
• Most are planktonic and
filter feeding.
Copepods
Class Maxillopoda
• Subclass Thecostraca – +1000 species of
barnacles; sessile marine crustaceans.
• Most are monecious.
• A larval form develops a bivalved
carapace and first antennae become used
for attachement.
• Gut tract becomes U-shaped and thoracic
appendages used for filter feeding.
• Attach to rocks, ships, whales
• Some are parasitic
Barnacle
Cirri
Testis
Penis
Anus
Mouth
Stomach
Ovary
Cement gland
Barnacles
The End?
Fig. 19.24a
100