arthropods

resilin

a protein that fleas use to jump

what do humans use resilin for?

artificial heart valves, spinal discs, tennis shoes

why are arthropods so diverse and abundant?

1) versatile exoskeleton2)jointed appendages and striated muscles3) oxygen is piped directly into tissues and cells4) highly developed sensory organs5) complex behavioural patterns6) metamorphosis

Arthropod characteristics

- Jointed limbs- Exoskeleton- Heart with Ostia- Trachea- Compound eyes- Malpighian tubules- Mandibles- No cilia at any life stage- Tagmatization: allows functional specialization of 'groups offused & modified segments'

exoskeleton layers

thin outer epicuticle and inner thicker procuticle

epicuticle

The outermost layer of the insect cuticle designed to prevent water loss. impermeable to water

procuticle

inner thick layer of an arthropod shell that consists primarily of layers of protein and chitin

chitin

tough and resilient but flexible

sclerotization

cross-linking of proteins which darkens the cuticle

ecdysis (molting)

Shedding of the cuticle and growing a new, larger cuticle after the body rapidly enlarges.

how many moults does it take before an animal becomes and adult?

4-7

Arthropods locomotion

because they are incased in a suit of rigid plates, the coelom fluid (haemocoel) plays NO major role in locomotion and is reduced- arthropods typically move by walking, swimming, or flying

arthropod circulatory system

open circulatory system- ostium

ostium

allows blood to enter heart from coelom but prevent it from leaving before it reaches the front

gills

outgrowths of the skin/modified appendages covered by thin, but permeable exoskeleton

book gill location

external

book lung location

internal, and connected by spiracles- maximizes gas exchange

tracheal system in a terrestrial arthropod

complex network of tubules that deliver oxygen directly to the animals tissues and cells

do arthropods carry their oxygen in haemolymp?

no, but vertabrates do .

spiracles

how the trachea is connected to the internal environment- can open and close to reduce water loss.

can velvet worms open and close their spiracles?

NO, they are always open.

do terrestrial arthropods transport oxygen in blood?

no. they lack haemolymph to bind oxygen

aquatic arthropod respiration

they use gills and transport oxygen in their blood, use hemocyanin

3 distinct regions in arthropod digestion

foregut, midgut, hind gut

foregut

highly muscular, breaks down food into small pieces to increase surface area

midgut

secretes enzymes to digest food and also absorbs nutrients

hind gut

reabsorbs water

arthropod excretion

solid wastes via anus

some aquatic arthropods excrete through

gills and digestive glands

some crustaceans have

green (antennal) glands- connected to pores under antennae

coxal glands

excretory organs of spiders

Malpighian tubules

found in most insects, arachnids, and myriapods

all arthropod muscles are:

striated

striated muscles

- allow for voluntary muscle movements.- are attached to skeleton- have more mitochondria

Why are striated muscle cells so important for arthropods?

- allows for much more rapid muscle contractions, this allows flight to be possible!

arthropod brain

supraesophageal ganglion

supraesophageal ganglion 3 regions

protocerebrum, deutocetebrum, tritocerebrum

protocerebrum

vision

deutocetebrum

processes sensory info from antennae

tritocerebrum

integrates sensory inputs from the protocerebrum and deutocerebrum

what's located immediately behind the arthropod brain?

subesophageal ganglion

subesophageal ganglion

part of the ventral nerve cord, it's connected to the brain
- controls sensory organs and muscles of the mouthparts and salivary glands.

how are anterior ganglia connected?

by a pair of ventral ganglionate nerve cord running along the length of the abdomen

why are spiders more centralized?

they have no ganglia in abdomen or terminal

Arthropod sensory

intricate mouthparts, statocysts, and antennae
sensitive hairs on body can detect touch, water currents, or chemicals

statocysts

sensory cells that help determine direction of gravity

arthropod vision

they use ocelli and compound eyes
insects usually have 2 compound eyes and 3 ocelli

ocelli

non image forming, can only detect direction of light

how many ocelli do arachnids have?

typically 8. a few species have good eye sight.

ommatidia

compound eyes- hexagonal visual units 10x loner than wide.

the cornea and crystalline cone, together focus the light onto the..

rhabdom

light energy absorbed by rhabdom is converted via..

photo receptor cells, into nerve signals the brain can understand.

\# of ommatidium

ranges from 15- several thousand

what animal has the most complex eyes?

the mantis shrimp.has at least 12 different photoreceptors.

earliest identifiable fossils of land animals...

arthropod fossils, 419ma

how did jointed exoskeleton and limbs make arthropods pre adapted for land?

provided protection against desiccation, support against gravity, and means of locomotion that wasn't dependant on water.

arthropod phylogeny

thought to be monophyletic

2 arthropod clades

chelicerate and mandibulata

Chelicerata key features

pointed, fang like appendages, lacks jaws; used to grasp food. considered a subphyla

mandibulata key feature

jaw like; used for chewing; divided into 3 extant subphyla

3 subphyla of mandibulata

myriapods, crustacea, hexapods

subphyla trilobita

extinct. no know descendants- had eyes of modern bees

examples of chelicerata

horseshoe crabs, spiders, ticks, mites, scorpions, sea spiders.

Chelicerata characteristics

- suck liquid from prey- no antennae-segmented (lost in acari)- no distinct head, 2 distinct portions the segments are organized into (tagmata)- 6 pairs of cephalothoracic appendages

2 distinct portions in chelicerata

- cephalothorax- fused head and thorax; called prosoma- abdomen (opisthosoma)

6 pairs of cephalothoracic appendages in chelicerata

1 pair of chelicerae (fang like appendages, adjacent mouth)1 pair of pedipalps (in front of head)4 pairs of walking legs.

what is the function of pedipalps in arachnids?

functions as an organ of touch and reproduction.

3 arthropod classes

merostomata (horse shoe crabs), pychnogonida (sea spiders), arachnida (spiders, scorpions, mites, ticks)

Merostomata Characteristics

long tail- used as rudder to help flip itself overbook gills- respiration. mouth between their legs- 10 eyes

2 subclasses of merostomata

eurypterida and xiphosurida

eurypterida

extinct form of giant water scorpions.- may be longest arthropod

xiphosurida

horseshoe crabs- not a crab or crustacean.- only 5 species left. behaviour based on mood and tidal cycles.- 10 eyes and can see uv light.

horseshoe crab feeding

small clams, crustaceans, worms.
- crush hard food between their legs before passing it to their mouth.

horseshoe crab eggs

- can lay 120 000 eggs a season. take 2 weeks to hatch.

how often do horseshoe crab larvae moult?

6 times during their first year. 18x before they reproduce.

when can horseshoe crabs reproduce.

at 9-11 years old

class pychnogonida

sea spiders- not true spiders or even arachnids.

class pychnogonida form

-mostly cephalothorax- abdomen reduced to a short stump.- variable number of walking legs

why is class pychnogonida proboscis unique?

it has chelicerae at terminal- allows them to suck juices from soft-bodied animals.

class pychnogonida speed

Very slow moving

class pychnogonida feeding

feed on immobile prey such as sponges and sea anemone

how many simple eyes in class pychnogonida ?

they have 2-4 simple eyes

in class pychnogonida, genitals and digestive system...

extend well into legs

class pychnogonida use their legs as gills and...

their guts ate hearts.

5 major orders of arachnids

1) araneae (spiders)
2)scorpionida (scorpions)
3)solpugida (sun or caramel spiders)
4)opiliones (harvestmen)
5)acari (ticks and mites)

in araneae, magmata are joined by a narrow...

pedicel

araneae feeding

ALL predaceous and largely feed on insects

araneae chelicerae

functions as fangs and bear ducts from venom glands.

araneae segmentation

MOST do no have external segmentation on abdomen

Liphistiidae

the araneae the does have segmentation

Araneae Excretion

- up to 4 pairs of coxal glands and Malpighian tubules for excretion

araneae respiration

have book lungs, trachea, or both.
( other arachnid orders use only trachea)

spinnerets

organ in spiders that contains silk glands

silk is stronger than

steel of the same diameter

not all spiders spin webs...

but ALL produce silk, it has many other uses
-acts as a balloon underwater for air.

red banded crab spider

awaits prey on flowers to which they are matched (they camouflage)

araneae reproduction

male spins web, deposits drop of sperm on it.- inserts a pedipalp into females genital opening- female fertilizes egg in silken cocoon which she might carry or attach to a plant

where is sperm stored in araneae

in his pedipalps

how many eggs in a araneae cocoon

hundres. they hatch in around 2 week

black widows are know for

cannibalizing their mates but this doesnt actually happen all the time