IB-202-5
3-17-06
Cephalopods
• Class Cephalopoda includes squids and octopuses
– Carnivores with beak-like jaws surrounded by
tentacles. Foot modified to form siphon, tentacles
and head.
– Closed circulatory system
– Well developed eye similar to vertebrate eye (lens,
retina etc)
– Very active life style. Squid can feed on herring by
zipping through a school. Herring capable of rapid
swimming.
– Elaborate sex where male inserts packets of sperm
into mantle cavity of female.
– Ink gland for escape.
– Can teach octopus simple tasks. Can crawl out of
their tanks into another eat the crabs and return to
their own
• Most octopuses
– Creep along the sea floor in search of prey. Some
have toxin associated with their bite. Very good at
changing color so they are camouflaged in nature.
Figure 33.22a
(a) Octopuses are considered among the
most intelligent invertebrates.
• Squids use their siphon
– To fire a jet of water, which allows them to swim very
quickly
Figure 33.22b
(b) Squids are speedy carnivores with
beaklike jaws and well-developed eyes.
Wednesday, 15 Jan., 2003, 16:50 GMT
Giant squid Architeutis dux
'attacks French boat'
….De Kersauson says his squid was
three times as big
…..two of the tentacles were blocking
the rudder.
…. the squid must have been seven or
eight metres (22 to 26 feet) long.
…. we weren't going to attack it with our
penknives.
Wednesday, 28 September 2005, 05:42 GMT
Live giant squid caught on camera
Japan's Ogasawara Islands
8m-long Architeuthis
• One small group of `shelled cephalopods
– The chambered nautiluses, survives today
– Huge nautilus fossils in northern Africa
Figure 33.22c
(c) Chambered nautiluses are the only living cephalopods with an external shell.
Have rudimentary eye without lens like a pin hole camera. Shell is
chambered and put less dense ammonium chloride in chamber for flotation.
Less dense than seawater.
General Characteristics of
Phylum Arthropoda
• The diversity and success of arthropods.
• Find them in fresh water, the ocean and
the land and air.
– Are largely related to their segmentation,
hard chitinous exoskeleton, and the
specialization jointed appendages for
specific functions.
Common fossil trilobite
• Early arthropods, such as trilobites
– Showed little variation from segment to segment and
no specialized appendages
Figure 33.28
Specialization of appendages in
modern forms
• As arthropods evolved
–
The segments fused, and the appendages became more
specialized
• The appendages of some living arthropods
–
Are modified for many different functions as seen in the lobster
below (describe specialization)
Cephalothorax Abdomen
Antennae
(sensory
reception)
Head Thorax
Swimming
appendages
Walking legs
Figure 33.29
Pincer (defense) Mouthparts (feeding)
Thick exoskeleton
• The body of an arthropod
– is completely covered by the cuticle, an exoskeleton
made of chitin (polyglucoseamine). Hardened claws of
skeletons composed of protein, chitin and calcium
carbonate
• When an arthropod grows its soft body becomes
too large for its exoskeleton
– Thus it sheds or molts its exoskeleton in a process
called ecdysis. Then it grows a new one. Its
exoskeleton is very soft until the chitinous polymers
become cross linked which hardens the cuticle.
Physiological Systems
• Arthropods have an open circulatory system
– in which fluid called hemolymph is circulated
into the spaces surrounding the tissues and
organs. Tube like heart. Presence of oxygen
binding pigments (hemocyanin-blue)
• A variety of organs specialized for gas
exchange have evolved in arthropods
• Molecular evidence now suggests
–
That living arthropods consist of four major lineages that
diverged early in the evolution of the phylum (divided into
subphyla)
Table 33.5
Cheliceriforms
• Subphylum Cheliceriformes
– Are named for clawlike feeding appendages
called chelicerae
– Include spiders, ticks, mites, scorpions, and
horseshoe crabs
Horseshoe Crab
• Most of the marine cheliceriforms are extinct
– But some species survive today, including the
horseshoe crabs (laboratory experimental animal for
demonstrating osmotic conformity)
Figure 33.30
Scorpions, mites and spiders
• Most modern cheliceriforms are
arachnids
–
A group that includes spiders, scorpions,
ticks, and mites
50 µm
(a) Scorpions have pedipalps that are pincers (b) Dust mites are ubiquitous scavengers in (c) Web-building spiders are generally
specialized for defense and the capture of
human dwellings but are harmless except
most active during the daytime.
food. The tip of the tail bears a poisonous
to those people who are allergic to them
stinger.
(colorized SEM).
Figure 33.31a–c
Anatomy of a spider
• Arachnids have an abdomen and a cephalothorax
–
Which has six pairs of appendages, the most anterior of which
are the chelicerae (special structures)
Intestine
Digestive
gland
Stomach
Heart
Brain
Eyes
Poison
gland
Ovary
Anus
Book lung
Spinnerets
Figure 33.32
Silk gland
Sperm
Gonopore
(exit for eggs) receptacle
Chelicera
Pedipalp
Spiders digest there food outside
of their body
They stab prey with their fangs, inject toxins and
enzymes that digest tissues. Then they suck up
the partially digested material as a fluid. Some of
the enzymes are phospholipases that destroy cell
membranes.
Thus spider bites can develop into lesions and
tissue can become necrotic. Not sure why these
enzymes can have such a long half life (in case of
snakes give antivenom injections).
Subphylum Myriapoda
Includes millipedes and centipedes
• Millipedes, class Diplopoda
– have a large number of legs
• Each trunk segment
– has two pairs of legs-eats plant material and detritus
Figure 33.33
• Centipedes, class Chilopoda
– Are carnivores with jaw-like mandibles
– Have one pair of legs per trunk segment
– Poison claws on foremost trunk segment
Figure 33.34
Insects
• Subphylum Hexapoda, insects and their
relatives
– Are more species-rich than all other forms of
life combined
– Live in almost every terrestrial habitat,in
fresh water and a few on the surface of the
ocean.
– A few found in Antarctica where there are
only mosses to feed on.
Insect Anatomy
– Includes several complex organ systems
The insect body has three regions: head,
thorax, and abdomen. The segmentation
of the thorax and abdomen are obvious,
but the segments that form the head are fused.
Abdomen
Thorax
Head
Compound eye
Heart. The
insect heart
drives hemolymph
through an
open circulatory
system.
Cerebral ganglion. The two nerve
cords meet in the head, where the
ganglia of several anterior segments
are fused into a cerebral ganglion
(brain). The antennae, eyes, and
other sense organs are concentrated
on the head.
Antennae
Ovary
Figure 33.35
Malpighian tubules.
Anus
Metabolic wastes are
removed from the
Vagina
hemolymph by excretory
organs called Malpighian
tubules, which are outpocketings of the
digestive tract.
Tracheal tubes. Gas exchange in insects is
accomplished by a tracheal system of branched,
chitin-lined tubes that infiltrate the body and
carry oxygen directly to cells. The tracheal
system opens to the outside of the body
through spiracles, pores that can control air
flow and water loss by opening or closing.
Nerve cords. The insect
nervous system
consists of a pair of
ventral nerve cords
with several
segmental ganglia.
Dorsal
artery
Crop
Insect mouthparts are formed from
several pairs of modified appendages.
The mouthparts include mandibles,
which grasshoppers use for chewing.
In other insects, mouthparts are
specialized for lapping, piercing, or
sucking.
Insects very successful as a group
• Flight is obviously one key to the great success of insects
• An animal that can fly
–
Can escape predators, find food, and disperse to new habitats
much faster than organisms that can only crawl (example hords of
grasshoppers that strip vegetation in African lands from time to
time. Also in US, but we stop them with insect sprays.
Insect Reproduction
• Insects have internal fertilization. Lay eggs.
Development of many involve juvenile stages that
are very different from the adult
• Many insects
– Undergo metamorphosis during their development
• In incomplete metamorphosis, the young, called
nymphs
– Resemble adults but are smaller and go through a
series of molts until they reach full size
• Insects with complete metamorphosis
– Have larval stages specialized for eating and
growing that are known by such names as
maggot, grub, or caterpillar
• The larval stage
– Looks entirely different from the adult stage
Complete metamorphosis
• Metamorphosis from the larval stage to the adult
stage
– Occurs during a pupal stage
(a) Larva (caterpillar)
(b) Pupa
(c) Pupa
(d) Emerging adult
Figure 33.6a–e
(e) Adult
• Insects are classified into about 26 orders
ORDER
Blattodea
Coleoptera
Dermaptera
Diptera
Hemiptera
Hymenoptera
Isoptera
Figure 33.37
APPROXIMATE
NUMBER OF
SPECIES
4,000
350,000
1,200
151,000
85,000
125,000
2,000
MAIN CHARACTERISTICS
EXAMPLES
Cockroaches have a dorsoventrally flattened body, with legs
modified for rapid running. Forewings, when present, are
leathery, whereas hind wings are fanlike. Fewer than 40 cockroach species live in houses; the rest exploit habitats ranging
from tropical forest floors to caves and deserts.
German
cockroach
Beetles comprise the most species-rich order of insects. They
have two pairs of wings, one of which is thick and leathery, the
other membranous. They have an armored exoskeleton and
mouthparts adapted for biting and chewing. Beetles undergo
complete metamorphosis.
Japanese
beetle
Earwigs are generally nocturnal scavengers. While some
species are wingless, others have two pairs of wings, one of
which is thick and leathery, the other membranous. Earwigs
have biting mouthparts and large posterior pincers. They undergo incomplete metamorphosis.
Dipterans have one pair of wings; the second pair has become
modified into balancing organs called halteres. Their head is
large and mobile; their mouthparts are adapted for sucking,
piercing, or lapping. Dipterans undergo complete metamorphosis. Flies and mosquitoes are among the best-known dipterans,
which live as scavengers, predators, and parasites.
Hemipterans are so-called “true bugs,” including bed bugs,
assassin bugs, and chinch bugs. (Insects in other orders are
sometimes erroneously called bugs.) Hemipterans have two
pairs of wings, one pair partly leathery, the other membranous.
They have piercing or sucking mouthparts and undergo
incomplete metamorphosis.
Ants, bees, and wasps are generally highly social insects. They
have two pairs of membranous wings, a mobile head, and
chewing or sucking mouthparts. The females of many species
have a posterior stinging organ. Hymenopterans undergo complete metamorphosis.
Termites are widespread social insects that produce enormous
colonies. It has been estimated that there are 700 kg of
termites for every person on Earth! Some termites have two
pairs of membranous wings, while others are wingless. They
feed on wood with the aid of microbial symbionts carried in
specialized chambers in their hindgut.
Earwig
Horsefly
LeafFooted
bug
Cicada-killer wasp
Termite
ORDER
Lepidoptera
Odonata
APPROXIMATE
NUMBER OF
SPECIES
120,000
5,000
EXAMPLE
MAIN CHARACTERISTICS
Butterflies and moths are among the best-known insects. They
have two pairs of wings covered with tiny scales. To feed, they
uncoil a long proboscis. Most feed on nectar, but some species
feed on other substances, including animal blood or tears.
Swallowtail
butterfly
Dragonflies and damselflies have two pairs of large, membranous wings. They have an elongated abdomen, large, compound
eyes, and chewing mouthparts. They undergo incomplete metamorphosis and are active predators.
Dragonfly
Orthoptera
13,000
Grasshoppers, crickets, and their relatives are mostly herbivorous. They have large hind legs adapted for jumping, two
pairs of wings (one leathery, one membranous), and biting or
chewing mouthparts. Males commonly make courtship sounds
by rubbing together body parts, such as a ridge on their hind
leg. Orthopterans undergo incomplete metamorphosis.
Katydid
Phasmida
Phthiraptera
Siphonaptera
Thysanura
2,600
2,400
2,400
450
Stick insects and leaf insects are exquisite mimics of plants. The
eggs of some species even mimic seeds of the plants on which the
Insects live. Their body is cylindrical or flattened dorsoventrally.
They lack forewings but have fanlike hind wings. Their
mouthparts are adapted for biting or chewing.
Commonly called sucking lice, these insects spend their entire
life as an ectoparasite feeding on the hair or feathers of a single
host. Their legs, equipped with clawlike tarsi, are adapted for
clinging to their hosts. They lack wings and have reduced eyes.
Sucking lice undergo incomplete metamorphosis.
Fleas are bloodsucking ectoparasites on birds and mammals.
Their body is wingless and laterally compressed. Their legs are
modified for clinging to their hosts and for long-distance
jumping. They undergo complete metamorphosis.
Stick insect
Human
Body
louse
Flea
Silverfish are small, wingless insects with a flattened body and
reduced eyes. They live in leaf litter or under bark. They can also
infest buildings, where they can become pests.
Silverfish
Trichoptera
Figure 33.37
7,100
The larvae of caddisflies live in streams, where they make houses
from sand grains, wood fragments, or other material held together by silk. Adults have two pairs of hairy wings and chewing
or lapping mouthparts. They undergo complete metamorphosis.
Caddisfly
Class Crustacea
• While arachnids and insects thrive on land
– Crustaceans, for the most part, have
remained in marine and freshwater
environments
• Crustaceans, subphylum Crustacea
– Typically have biramous, branched,
appendages that are extensively specialized
for feeding and locomotion
• Decapods (10 walking legs) are all
relatively large crustaceans
– And include lobsters, crabs, crayfish, and
shrimp
(a) Ghost crabs (genus Ocypode) live on sandy ocean
beaches worldwide. Primarily nocturnal, they take
Figure 33.38a
shelter in burrows during the day. Note stalked eyes.
•
Planktonic crustaceans include many species of copepods. Plankton found
in surface waters of ocean either drifting or weakly swimming. Moved along
by the oceanic currents. Euphausids (krill) fed on my baleen whales (filter
out 5 cm long krill). Baleen is composed of horny strips in the mouth of
whales with fibers projecting from it to act as a filter. No teeth in these
whales although the fetus does have teeth but looses them during
maturation.
Figure 33.38b
(b) Planktonic crustaceans
known as krill are
consumed in vast
quantities by whales.
• Barnacles are a group of mostly sessile
crustaceans
– Whose cuticle is hardened into a shell composed
mostly of calcium carbonate.
– (Ships and whales-rocky intertidal full of barnacles)
Figure 33.38c
(c) The jointed appendages (modified legs)
projecting from the shells of these barnacles capture
organisms and organic particles suspended in
the water. Stand on their heads and glue
themselves to rocks with their antennae. Some form
Stalks like in picture, others not (example).
Phylum Echinodermata
(star fish, sea urchins and sea
cucumbers)
• Echinoderms and chordates are
deuterostomes
• At first glance, sea stars and other
echinoderms may seem to have little in
common with phylum Chordata, which
includes the vertebrates
Chordates and echinoderms share
characteristics of deuterostomes
– Radial cleavage
– Development of the coelom from the
archenteron (enterocoelus)
– Formation of the mouth at the end of the
embryo opposite the blastopore
Echinoderms
• Sea stars and most other echinoderms
– Are slow-moving or sessile marine animals
• A thin, bumpy or spiny skin
– Covers an endoskeleton of hard calcareous
plates
– Most have a water vascular system used for
movement
Anatomy of a Starfish
• Unique to echinoderms is a water vascular system
–
A network of hydraulic canals branching into tube feet that
function in locomotion, feeding, and gas exchange
A short digestive tract runs from the
mouth on the bottom of the central
disk to the anus on top of the disk.
Central disk. The central
disk has a nerve ring and
nerve cords radiating from
the ring into the arms.
Digestive glands secrete
digestive juices and aid in
the absorption and storage
of nutrients.
Figure 33.39
Radial canal. The water vascular
system consists of a ring canal in the
central disk and five radial canals,
each running in a groove down the
entire length of an arm.
Stomach
Anus
Spine
Gills
Ring
canal
Gonads
Radial
nerve
The surface of a sea star is
covered by spines that help
defend against predators, as
well as by small gills that
provide gas exchange.
Madreporite. Water can flow
in or out of the water vascular
system into the surrounding
water through the madreporite.
Ampulla
Podium
Tube
feet
Branching from each radial canal are hundreds of hollow, muscular tube
feet filled with fluid. Each tube foot consists of a bulb-like ampulla and
suckered podium (foot portion). When the ampulla squeezes, it forces
water into the podium and makes it expand. The podium then
contacts the substrate. When the muscles in the wall of the podium
contract, they force water back into the ampulla, making the podium
shorten and bend.
Why are echinoderms placed near
the chordates in view of their
radial anatomy???
• The radial anatomy of many echinoderms
(not symmetry) evolved secondarily from
the bilateral symmetry of ancestors
(madreporite off center).
• Living echinoderms are divided into six
classes
Table 33.6
Sea Stars
• Sea stars, class Asteroidea
– Have multiple arms radiating from a central
disk
• The undersurfaces of the arms
– Bear tube feet, each of which can act like a
suction disk
Figure 33.40a
(a) A sea star (class Asteroidea)
Brittle Stars
• Brittle stars have a distinct central disk
– And long, flexible arms
Figure 33.40b (b) A brittle star (class Ophiuroidea)
Sea Urchins and Sand Dollars
• Sea urchins and sand dollars have no arms
– But they do have five rows of tube feet that function
in movement (laboratory sea urchin reproduction)
Figure 33.40c (c) A sea urchin (class Echinoidea)
Crinoides (Feather stars)
– Move about slowly using their roots on the disc. Use
feathery arms to swim. Alternately pump them up
and down. Fossil forms were stalked crinoides.
Figure 33.40d
(d) A feather star (class Crinoidea)
Sea Cucumbers
• Sea cucumbers
–
–
–
Upon first inspection do not look much like other echinoderms
Have tube feet, but lack spines, and their endoskeleton is much
reduced.
Served as an expensive dinner food at Chinese banquetsgelatinous. Dried, rehydrated then braised in abolone sauce.
Figure 33.40e
(e) A sea cucumber (class Holothuroidea)
Sea Daisies
• Sea daisies were discovered in 1986
– And only two species are known live on water
soaked wood
Figure 33.40f
(f) A sea daisy (class Concentricycloidea)
Chordates
– Phylum Chordata
– Consists of two subphyla of invertebrates as
well as the hagfishes and the vertebrates
– Shares many features of embryonic
development with echinoderms
• A summary of animal phyla
Table 33.7