6. arthropods

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Transcript of 6. arthropods

Phylum Arthropoda

• “Jointed foot”

• Contains at least 75% of the described, living species of animals

• Almost 90% of the arthropods are insects

• Marine, fresh water, terrestrial and airborne

• Size range < 1mm mites to 4 m spider crabs

Phylum Arthropoda

• Exoskeleton (chitin)

• moult

• Jointed appendages

• Body divided into 2 or 3 sections

• Straight gut

• Brain and ganglia

• Open circulatory system

• Dioecious

Phylum Arthropoda

Metameric segmentation Tagmatizaion

Phylum Arthropoda

Insects Crustaceans Spiders & Scorpions

Cirripeds Copepods Isopods Amphipods Decapods

Phylum ArthropodaClass Crustacea

• 52,000 described

species, 10 to 100

times more

undescribed

• Most are free-living

and marine

• Two pairs of antennae

• Biramous limbs

• Nauplius larva

Phylum ArthropodaClass Crustacea Subclass Cirripedia

• Barnacles

• Classified as

molluscs until 1830

• First fully studied

and classified by

Charles Darwin

• ~ 1200 species

• e.g. acorn barnacle

Balanus sp

Phylum ArthropodaClass Crustacea Subclass Cirripedia

• Barnacles are

shrimp standing

on their head

(cemented to

the substrate)

and feeding with

their feet (called

cirri)

Phylum ArthropodaClass Crustacea Subclass Cirripedia

• e.g. Goose neck barnacles

Pollicipes sp

• Barnacles do not

have a true heart

• Do not have gills,

instead oxygen

diffuses through their cirri

• Sensitive to touch and have

a single eye

Phylum ArthropodaClass Crustacea Subclass Cirripedia

• Most Barnacles

are filter feeders

and use the water

currents for their

feeding

advantage.

Phylum ArthropodaClass Crustacea Subclass Cirripedia

Phylum ArthropodaClass Crustacea Subclass Cirripedia

• Barnacles are sessile

free living but some are

parasitic

(Rhizocephalans).

• Decapod host

• Only the larval form

resembles that of barnacles

• the adults lack appendages and internal

organs except for gonads

Phylum ArthropodaClass Crustacea Subclass Copepodia

• 13,000 described

species and half are

parasitic

• they form the largest

animal biomass on earth

• Main contributor to

secondary productivity

and the carbon sink of

the world oceans

Phylum ArthropodaClass Crustacea Subclass Copepodia

• Very small (1-2 mm)

• Mostly marine / planktonic

• Thin transparent cuticle

• One compound eye (red)

• No heart

• Lack gills (oxygen diffuses

thru the cuticle)

• Abdomen has no

appendages

Phylum ArthropodaClass Crustacea Subclass Copepodia

• Tide pool copepods e.g.

Tigriopus sp

• Can survive

freezing, high

temperatures, desiccation

and extreme salinity

changes

Phylum ArthropodaClass Crustacea Subclass Copepodia

• Copepods have bristle-like

setae that act as

mechanorecptors.

• An array of such sensors

allows detection of patterns of

water flow around the body

caused by approaching prey

or predator, and the copepod

can distinguish between the

two.

Phylum ArthropodaClass Crustacea Subclass Copepodia

• Copepods are

dioecious

• Planktonic copepods

use pheromones

emitted by the

swimming

female, which leaves a

trail in the water that the

male can follow to

locate the female

Phylum ArthropodaClass Crustacea Subclass Copepodia

• During mating

• Male grips the female

with his antennae, The

male then transfers

sperm to the female.

Eggs are sometimes laid

directly into the water, but

many species enclose

them within a sac

attached to female's body

until they hatch.

Phylum ArthropodaClass Crustacea Subclass Copepodia

• Eggs hatch into a nauplius

larvae

• The nauplius moults 5 or 6

times, before emerging as

a "copepodid larva".

• After a further five

moults, the copepod finally

takes on the adult form.

• Egg to adult can take one

week or one year

depending on species

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Isopoda

• Mostly free-living marine

e.g. Idotea sp

• Crawl rather than swim

• Terrestrial – pill bug

• Some parasitic

(fish, shrimp and crab

hosts)

• Biphasic molt

• Carapace – cephalic

shield

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Isopoda - Elongated flat and somewhat

arched bodies

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Isopoda• Females are brooders

• After female moults males

deposit sperm into the brood

pouch

• Eggs pass from the oviduct

into the pouch and are

fertilized on the way

• Isopods hatch from the eggs

as manca (adult like but last

pair of walking legs are

missing). Become juveniles 3

moults later

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Isopoda

• No free-swimming

larval stage

Endemism

Dispersal limited to the

crawling ability of the

individual

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Isopoda

• Excirolana

vancouverensis

Consume 53% of body

mass in 1 minute

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Amphipoda

• c-shaped bodies

flattened laterally

• Free living mostly

marine and freshwater

• Swim or hop

• Do not have a

carapace

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Amphipoda

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Amphipoda

• Females have a brood

pouch

• Hatch as miniature adults

• Development varies with

temperature

• For some, gender varies

with temperature (cold =

male, warm = female)

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Amphipoda

• Amplexus – large males

grasp onto females with

their gnathopods and

carry them for several

days

• Females moult before

they shed their eggs and

are vulnerable to

predation

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Amphipoda

• Females secrete a

pheromone in her urine

which triggers the

guarding behaviour in

males plus they lose the

desire to eat them

• After her eggs are

fertilized her exoskeleton

hardens and the male is

encouraged to leave

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Amphipoda

• Amphipods are difficult to

identify, due to their small

size, and the fact that they

must be dissected. As a

result, ecological studies and

environmental surveys often

lump all amphipods together

• Around 7,000 species of

amphipods have so far been

described

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Amphipoda

• Most planktonic

species are

symbionts with

gelatinous animals

sometime during

their lifecycle.

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Amphipoda

• Few are parasitic

– The whale lice - these are

dorso-ventrally flattened, and

have large, strong claws, with

which they attach themselves

to baleen whales. They are the

only parasitic crustaceans

which cannot swim during any

part of their lifecycle

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Amphipoda

• Caprellids

– Skeleton Shrimp.

• their body shape and

colour help them blend

with their surroundings and the gentle back and

forth sway resembles substrate within the water

current.

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• 15,000 species, half of

these are crabs, ¼ are

shrimp and the other ¼

are anomurans

• Most are marine but

some are freshwater

and a few are

terrestrial

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Deca = ten, pod = foot

• Appendages

– 5 pairs on the thoracic

segment, 1st usually a claw

– Three pairs, maxillipeds

(mouth parts)

– Each abdomen segment

has a pair of pleopods

– Tail fan telson and uropod

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• anatomy

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Shrimp vs Prawn

Lamellar gill vs

branched

– Two pairs of claws vs

three

– Brood eggs before

hatching vs doesn’t

brood

Phylum ArthropodaClass Crustacea Subclass

Malacostraca

Shrimp Prawna

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Infraorder Caridia

• Shrimps

– Adapted for swimming

– Bodies are laterally

compressed

– Slender legs and well

developed swimmerets

(pleopods)

– Rostrum

– Compound eyes

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Coonstripe or Dock Shrimp (Pandalus danae)

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Humpback or King Shrimp (Pandalus hypsinotus)

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Smooth or Ocean Pink Shrimp (Pandalus jordani)

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Pink Shrimp - Spiny (Pandalus borealis)

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Prawn or Spot Shrimp (Pandalus platyceros)

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Sidestripe or Giant Shrimp (Pandalopsis dispar)

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Infraorder Caridia

• Heptacarpus sp.

• Intertidal shrimps

• Transparent or a

variety of colours

• Hide during the

day, feed and are

easily seen at night.

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Infraorder Caridia

• Life cycle

– Spend 1st years as

males then switch to

females.

– Females brood their

eggs (50,000 – 1

million)

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Infraorder Caridia

• Life cycle

– Eggs hatch nauplii

larvae (yolk sac)

– metamorphosis into

zoeae (feed on algae)

– Metamorphisis into

myses (feed on algae

and zooplankton

– Metamorphosis into

young shrimp

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Infraorder Caridia

• Amazing shrimps

– The pistol shrimp

– The mantis shrimp

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Infraorder Anomura

• Differently tailed

• Have 5 pairs of

periopods but 1 pair is

internal and used to

keep their gills clean

• If you see a crab with

four legs then it is an

anomuran.

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Infraorder Anomura

• Squat Lobsters

• The body is usually flattened

• the abdomen is typically folded

under itself

• the first periopods are greatly

elongated and armed with long

chelae (claws).

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Infraorder Anomura

• Porcelain crab

– less than 15 mm (0.6 in) wide

– flattened bodies as an adaptation

for living in rock crevices

– readily lose limbs when attacked

– use their large claws for

maintaining territories

– They feed by using long setae

(feathery hair on the mouthparts

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Infraorder Anomura

• Heart crab

– Related to the Alaskan king

crab

– the asymmetry of the crab's

abdomen, which is thought to

reflect the asymmetry of

hermit crabs, which must fit

into a spiral shell (pleopods

are smaller on one side)

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Infraorder Anomura

• Hermit crabs

– Live in gastropod shells

usually.

– Spirally coiled soft

abdodmen

– Pleopod assymetry

– tip of abdomen is adapted

to clasp onto the columella

of the shell.

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Infraorder Anomura

• Hermit crabs

– vacancy chains: when a

new, bigger shell becomes

available, hermit crabs

gather around it and form a

queue from largest to

smallest. When the largest

crab moves into the new

shell, the second biggest

crab moves into the newly

vacated shell and so on.

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Infraorder Anomura

• Hermit crabs

• Symbiosis:

– with the sponge

– With anemones

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Infraorder Brachyura

• True crabs

• Eg. Hemigrapsus sp

reduced abdomen is

entirely hidden under the

thorax

Telson not

functional, uropods are

absent

Phylum ArthropodaClass Crustacea Subclass Malacostraca

• Order Decapoda

• Infraorder Brachyura

• True crabs

• New research suggests

that crabs not only suffer

pain but that they retain a

memory of it.

Pycnogonid – sea spider

• Body not divided into

distinct regions

• Very slow moving

• Appendages at the

head which are used

to groom the opposite

sex’s legs and are

used by the males to

carry fertilized eggs