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Arthropods - Chelicerates C

Arthropods - Chelicerates C

- Chelicerates c.

to extract directly from air instead of water an ancient group with good record need moist thin surface protected inside body include horse shoe , sea , , ! several experiments: spiders, , , sea scorpions book tracheae most living are fairly small some can open and close spiracles

but some fossil sea scorpions () were d. modification of 5-6’long; a few up to 9’ for life on land (gravity) most members of the group are terrestrial strong muscles and strong support

!1st group of to successfully make transition to land e. change in sensory systems ! oldest known of terrestrial animals are chelicerate arthropods from 420 M ago () change from chemical (~; more reliable in water) to vision, vibrations of air & not water Transition to land (=sound), and airborne chemical senses (~smell)

f. required major adaptations: gametes must remain moist a. Ability to resist drying leads to anatomical changes for

already had waxy more elaborate rituals ! impermeable to water

b. improved excretory system g. must be protected from drying

must contain enough nutrients for early development for salt and water balance

or must bear live young conserve water by getting rid of N wastes as urea or uric

acid rather than as (most aquatic animals) h. ability to withstand extreme Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 1 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 2

temperatures contains:

or become inactive during temperature extremes feeding appendages; including

eg. diapause and

Distinctive Characteristics of Chelicerates: usually 4 pairs of

1. is fused to = cephalothorax chelicerates lack antennae

2. named after their main feeding Feeding &

! chelicerae (pincer-like or fang like) chelicerae are either pincher like or fang like used to grab or pierce or tear prey pedipalps are usually larger and also have most also have second feeding appendage “pinchers” = in some the pedipalps resemble the walking 4. only group without antennae legs

5. most have 4 pairs of walking legs Respiratory System

Body Plan aquatic species have book body consists of a cephalothorax and terrestrial species use book lungs or tracheae

cephalothorax book lungs consist of parallel air pockets extending into haemocoel no distinct head ! book lungs resemble book gills of head is fused with thorax to form a but are internal cephalothorax

Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 3 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 4 Senses = modified nephridia open at coxa of 1st and 3rd 1. Vision walking

aquatic species have simple and compound eyes dioecious terrestrial species generally have several pairs of simple eyes or ocelli some with elaborate rituals

2. mechanoreceptors some with considerable parental care

! sensory and bristles used for “touch”

some also can detect sounds; used for “hearing”

Circulation open as in all arthropods

body cavity a haemocoel in some, contains the blood to transport oxygen

Excretion excretory organ of most Chelicerates are malpighian tubules also have coxal glands at base of some legs Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 5 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 6

Classification of Chelicerates Merostomata

Class Merostomata (4 species) Eurypterids (Water Scorpions)

ancient. formerly diverse. group of aquatic chelicerates extinct group

today consist of 3 genera and 4 species of horse shoe crabs ! lived from to the Class Pycnogonida (~1000 species) (especially Silurian & )

sea spiders largest of all fossil arthropods Class Arachnida (>100,000 species) !some up to 6’ long spiders & scorpions, mites, ticks, etc is a blend between horseshoe crabs and scorpions

cephalothorax with simple and compound eyes, chelicerae & pedipalps

largest chelicerae of the

pedipalps resemble the 4 pr of walking legs

4 pr of walking legs

all but the last pair of walking legs had “pinchers”

last pair of legs have paddlelike structures for swimming

Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 7 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 8 segmented abdomen Horseshoe Crabs

spikelike [not “true” crabs which are ]

also an ancient group; but still survives today sluggish bottom dwellers ! almost unchanged for 300 million years marine, brackish and probably freshwaters can grow up to 2 feet in total length and weigh up to feeding: 6 lbs

they were the “killing machines” of the oceans females usually larger than males

probably mostly ate generally found on sandy bottoms in deeper water

one paleontologist: “ I’d much rather be in a pool with a can swim upside down above sediment 6’ shark than a 6’ ”

Body Form Eurypterids may have been the first animals to move

onto land large cephalothorax, abdomen & long telson

cephalothorax with compound and simple eyes

Feeding & Digestion

eats clams, snails and sandworms

mouth is in center of legs

! chews food with bases of legs = gnathobases have stiff spines

uses chelicerae to help get and break up food Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 9 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 10

Ecological and Human Impacts Respiration used by humans as cheap fertilizer for past 100 yrs, breaths by flat, leaflike book gills on underside of until 1970 when the last processing closed abdomen pharmaceuticals are also extracted from them the book gills can also be used for swimming today millions are taken to be used as bait for , Reproduction & Development conch and whelk in early summer (May & June) are the most important food source for loggerhead turtles nights of full and new moons they arrive by 1000’s on Atlantic beaches (100 years ago they arrived eggs are also a valuable food source for migrating by the millions) shore

female always dragging 1 & sometimes 2 or 3 !overharvesting of horseshoe crabs has males up onto the beaches with her correlated with a decline in shorebird numbers

the dramatic decline in shorebirds caused to female into sand to lay several 1000 eggs ban the collecing of horseshoe crabs recently, now at a time on beach subject to $10,000 fine

a horseshoe reserve has been recently created in may lay 120,000 eggs per season Bay where they are now permanently

protected one or more males deposit on the eggs then female covers them with sand today, the population has stopped declining

in 8-10 days, eggs hatch into larvae = “ a similar species is now almost extinct in Japan

”

horseshoe crabs live up to 20 years

Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 11 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 12 Class Pycnogonida Class Arachnida

(sea spiders) >100,000 species

1000 species most chelicerates belong in this class shallow coastal waters and deep oceans include spiders, scorpions, mites, ticks, & “daddy long-legs” common in all oceans, especially polar waters body with cephalothorax & abdomen also, often found on soft tissues of sponges, hydroids and soft corals, anemones, and clams cephalothorax with eyes, feeding appendages and 4 pairs of walking legs -like in appearance but with very small body and very long legs abdomen may or may not be segmented most with 8 legs; but some with 10 or 12 contains digestive, respiratory and reproductive systems many species have chelicerae and pedipalps Feeding & Digestion small head with 2 prs of eyes most are predators with fangs, , glands mouth at tip of long proboscis or are fluid feeders fangs = modified chelicerae

! feed on cnidaria and soft bodied animals claws = modified pedipalps gut branches and gonads extend throughout entire = last abdominal segments length of each leg generally predigest soft tissues then suck in no resp or excretory systems Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 13 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 14

predigested liquid with strong sucking Senses

Respiration most are predators , book lungs or both ! relatively simple eyes but very good vision book lungs consist of parallel air pockets extending into haemocoel main excretory organ in are malpighian oxygen diffuses from air into blood tubules

Circulation =closed end tubules that branch off the hindgut or rectum and float in haemolymph open circulatory system as in all arthropods unique organs of arachnids and dorsal tubular that moves fluid around internal organs also have coxal glands at the base of each leg hemocyanin is used to transport oxygen =modified nephridia

Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 15 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 16 Classification of Arachnida A. Scorpions

Order: Scorpionida (scorpions) (~2,000 sp) ~2000 living species : (vinegarroons or whip scorpions) (~100 sp) -book lungs -coxal glands & malphiggian tubules for excretion most ancient of all arachnids

Order: (short-tailed whip scorpions) (~230 sp) mainly in tropics and subtropics Order: (microwhip scorpions) (3,000 sp)

Order: Amblypygida (whip spiders) (~150 sp) but some temperate -no tail -short, wider, flat -whiplike pedipalps especially -common in South

Order: Pseudoscorpioida () (3,300 sp) secretive -very small, no tail -poisonous, active at night = nocturnal -widely distributed -tracheal system -coxal glands usually stay in underground burrows in day

Order: Solifugida (wind scorpions, sun spiders) (~1000 sp) -resemble spiders Texas has 18 species of scorpions -not poisonous but bite may become infected from bacteria Austin has 2 species -in dry areas, most nocturnal -SW US Body Form Order: (hooded tickspiders) (60 sp)

Order: Acarina (mites & ticks) (30,000 sp) cephalothorax & abdomen -large order -single prosomal , united epistosomal segments -pedipalps may be chelate or leg like cephalothorax (=prosoma) -smaller ones have no respiratory organs, larger ones have trachea short Order: Opilionida (daddy-long-legs, harvestmen) (6,300 sp)

Order: Aranea (true spiders) (40,000 sp) contains large median eyes

2-5 pairs of smaller lateral eyes Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 17 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 18

even death chelicerae and pedipalps a few are to humans

4 pair of walking legs ~25 of the 1500 species (2%)

abdomen (=) none in Texas

subdivided into a wider of 7 segments eg.

and a thinner tail-like of 5 segments found in Mexico

kills 100’s – 1000’s/yr in Mexico at tip of abdomen is recurved stinger effect of is very rapid Feeding & Digestion immediate drowsiness excessive salivation sluggish tongue come out at night to prey on spiders and insects severe contractions of jaw muscles fever to 104 or 105 detect prey by sensing vibrations in sand with hairs on may be hemorrhaging in , lungs and intestines legs and possibly pectines waves of convulsions cardiac irregularities large prey are subdued by injecting paralyzing venom breathing difficulties from stinger at tip of tail death usually occurs in <3hrs

rarely sting humans ! only if provoked if patient lives this long will probably

survive venom is a that causes paralysis

Reproduction & Development very painful but rarely fatal

scorpions have an elaborate courtship ritual and show in children the more poisonous species may cause convulsions parental care like spiders vomiting

Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 19 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 20 male and female hold each other by pinchers (chelae) at birth 1-100 babies are are born

touch chelicerae after birth, babies climb onto mom’s back and dance back and forth ! she carries them around for a week or so male then stings female before they set out on their own

! to subdue her aggression does not permanently harm her male deposits on ground (a solid packet of sperm) male maneuvers female until her genital pore is over the spermatophore she flips open lid of spermatophore releasing sperm into her genital opening in some species male then flees; in others he remains to be cannibalized ! provides food to nurture young development can take up to a scorpions are viviparous

! develop inside mom

development may take several months to a year

absorb nutrients from mom

born alive Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 21 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 22

B. Spiders then retracts like pocket knife large group; 40,000 species some spiders also use chelicerae to: carry prey Body Form grasp objects dig burrows two part body pedipalps help in manipulating food cephalothorax and unsegmented abdomen also sensory connected by small pedicel and to transfer sperm to female cephalothorax 4 pairs of walking legs simple eyes, no compound eyes, can detect movement with sensory setae

in some may actually form image ! tactile; cover legs and detect vibrations

yet some with very good vision in web and in air

eg. , , has eyes with spatial acuity abdomen better than most and birds (better than a cat or pigeon) unsegmented (but have only a few 1000 receptors; humans have ~200 M/eye) with and up to six glands for webmaking most have chelicerae modified into a

“switch-blade” like fang Feeding and Digestion

! extends and injects venom from poison all spiders are predators gland into prey

fang-like chelicerae inject venom into prey Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 23 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 24 eg. one African spider can liquefy a 2” or small venom can be: in <3 hrs

spider then uses pharynx and “pumping stomach” to 1. neurotoxin suck up liquefied prey

! affects nervous system and muscles spiders have very low metabolism: to cause paralysis or death most can live for long periods without eating

2. digestive eg. ! several months

eg. Black Widow ! 200 days ! digest to kill and liquify prey Spider Webs 3. pain inducing amines virtually every aspect of spider biology depends on its ! make prey unable to fight back ability to produce silk: after prey, spider backs off while kills or used to wrap prey paralyzes it silk is also used in web as “trip lines” many spiders wrap prey with silk to further males produce sperm webs immobilize it females weave coccoons and build nursery webs after prey has been subdued: juveniles use it to “balloon” to new

spider may mash it with chelicerae and spiders have six different kinds of silk glands regurgitate digestive enzymes over it !each produces a different kind of silk: or sperm web drag line if venom consisted of digestive enzymes injected coccoon into prey the spider sucks up liquified prey various parts of web

Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 25 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 26

silk is made of liquid proteins () that harden spider plucks web to determine where prey is located in as it is secreted from glands web

weight for weight is 20 x’s stronger than steel some other variations of web and silk use: silk is extruded from spinnerets eg. Bola Spiders

produce single sticky strand !tension of pulling out silk changes its structure from a liquid to a solid string they throw at flying insects (eg ) to catch them

eg. many spiders live in webs of other spiders after use it is eaten and amino acids are recycled into new silk eat host’s prey or host

3 basic types of webs: Reproduction

1. sheet webs when ready to reproduce, male stops feeding

most common constructs “sperm web”

leads to funnel shaped retreat in which spider awaits prey deposits drop of on it conspicuous on lawns after heavy dew picks up and stores semen in tip of pedipalp 2. cobwebs

loosely woven goes in search of a mate ()

depend on sticky threads to snare prey copulation is usually preceded by elaborate courtship rituals 3. orb webs

most well known ! to ensure the female doesn’t treat suitor as prey most intricate geometry

general pattern varies by species if successful, male inserts pedipalp with sperm into female genital opening Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 27 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 28 female stores sperm in seminal receptacle eg. Black Widow after mating male goes out in search of another has been found in all 50 states; common in central female Texas female remains in web and deposits 100’s or 1000’s of female is the most venomous eggs in egg web venom is a neurotoxin often lots of maternal care ! venom is 15x’s more toxic than that of a sexual is also common among spiders prairie rattlesnake

after mating female will pounce on male but so little that only ~1% of bites are fatal

fatherly meal improves hatching success for eggs native Americans of California rubbed arrows with mashed spiders for more effective hunting fishing spiders are so aggressive that some females pounce and eat the male suitor before causes synapses to release Ach causing: the nuptuals then lay unfertilized eggs that muscular spasms abdominal rigidity don’t develop cramps sweating Examples of Spiders salivation high blood pressure sometimes convulsions the two most dangerous spiders in US are Black Widow and eg. . Brown Recluse Brown Recluse. South Central US, including Texas both are common in Texas venom contains digestive enzymes both have a tendency to live in homes, outhouses and outbuildings Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 29 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 30

!its venom contains enzymes that destroy wander the jungle floor at night blood cells in day they hide inside mounds, under logs this induces WBC’s to attack surrounding and rocks or in and bromeliads tissues in some bites very little venom is released; creates large crater-like wounds that may in others a large amount is injected require months to heal bite can cause: its bite can be fatal to children intense pain eg. Phoneurtria sp. (Brazilian ) sweating

also called banana spiders but NOT the same as the relatively acute allergic reaction harmless , also called banana spiders uncomfortable penile enlargement - can lead to impotence most dangerous of all spiders (being studied as erectile dysfunction meds)

death (esp in children injected with large dose) ! most toxic venom eg. camel ‘spiders’ (=wind scorpions) species responsible for most deaths mideastern species Costa Rica and throughout South America east of have reputation as one of the nastiest arachnids but are the Andes relatively harmless

large spiders: 10-12 cm (4-5”) leg span it is said: they are bigger than a human hand extremely aggressive will climb onto the belly of a camel and eat the camel very aggressive alive

! will attack anything (including humans) who truth: they are as large as a 5 yr old child’s hand they can run up to 10 mph (fastest moving nonflying appear aggressive arthropod) they don’t eat camels or people

Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 31 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 32 C. Harvestmen (Daddy Longlegs; Harvestmen) feed as on inverts and plants ~6,300 sp. not predators most conspicuous in late summer (harvest time) cephalothorax has stink glands for protection easily distinguished from spiders Reproduction Body Form dioecious cephalothorax & abdomen internal fertilization broadly joined abdomen and cephalothorax rather than pedicel of spiders male has

cephalothorax lay eggs (oviparous)

no antennae Evolutionary Relationships

simple eyes new research shows they are more closely related to scorpions than to spiders no poison fangs

long thin legs

can be cast off to escape (=)

abdomen

unlike true spiders, abdomen is segmented

Feeding & Digestion

Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 33 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 34

D. Mites and Ticks after mating, the female broods the offspring inside her body

30,000 species described there may be up to 30 young, typically all are female except for one male ! most authorities believe unknown species outnumber known these offspring reach sexual maturity before they are even (est: 500,000 - 1 M undescribed species) born most economically important group of Chelicerates the lone male fertilizes all the females in the brood and dies before being “born”

Body Form the females are born pregnant with the next generation cephalothorax and abdomen completely fused the advantage to this bizzare life cycle is a very short generation time; 3-5 days no signs of eg. mites have projecting mouth region = capitulum mites usually < 1mm

contains mouthparts: ! some mites are so small they can only be identified with electron chelicerae for piercing or tearing food many species are freeliving Feeding & Digestion feed on decaying vegetation; some are blood sucking parasites some are predators Reproduction some are blood sucking parasites during all or some mites have a highly unusual reproductive part of their life cycles strategy; eg. Acarophenax

these mites are parasites of some mites have become adapted to live as internal parasites in the lungs and air sacs of

Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 35 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 36 , birds and mammals feed on dermal tissue of many a. follicle mites () including humans

mutualists with humans the irritation is largely due to sensitization to in the saliva that it injects to liquify found in hairs of face especially around nose, cells (not due to burrowing) and in ear wax 12-24 hrs after itching is at its worst ~ 1 in 5 people harbor them, proportion increases in older folks eg ticks usually symptomless ticks are much larger than mites in a few may cause redness or irritation all ticks are parasites during some part of in different species of same their life cycle cause feed on blood and lymph b. dust mites most infest mammals feces of dust mites sometimes causes many attack birds

eg. chiggers (redbugs) a few attack cold blooded vertebrates

“there is probably no creature on earth that some show host preference; others are can cause more torment for its size than a nonselective redbug” attracted by animal smells from a distance is actually a larvae: minute, reddish; of up to 50’ 0.2x0.15”; barely visible to eye ! tend to collect on game trails

Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 37 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 38

prodded by chemicals or heat some lay up to 12,000 eggs at a time best removed by gentle pulling ticks surpass all other arthropods in the numbers and variety of diseases that they can carry

they are vectors for some of the world’s main human diseases

second only to the in importance

transmit viral, fungal, & bacterial diseases

eg. deer ! lyme disease

eg. wood tick !rocky mtn spotted fever

eg. (rabbit fever)

their bite can be serious

anticoagulants are sometimes toxic

may cause fever and inflammation

wounds made by ticks are very likely to become infected

especially if “head” is torn off

may even result in blood poisoning

most ticks will not let go even if touched or

Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 39 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 40 excavate tortuous burrows in skin Human Impacts of Chelicerates: esp fingers, wrists, elbows, groin, back of knees mating occurs in burrows most arachnids, though feared, are actually harmless eggs hatch and larval excavates 2-3 mm/day to humans eg. chiggers “there is probably no creature on earth that can cause 1. spiders are directly beneficial as predators more torment for its size than a redbug” ! each kill 1000’s of crop pests red bugs are mite larvae that are very small and can easily go through clothing and in skin minute, reddish; 0.2x0.15”; barely visible to eye 2. large of some mites can damage food adults are not parasites and ornamental plants by sucking their juices chiggers don’t actually burrow into skin but secrete saliva to dissolve skin cells for food the irritation is largely due to sensitization to saliva 2. Venomous species ! a few are deadly and its enzymes 12-24 hrs after infection itching is at its worst eg. black widow

eg. follicle mites eg. brown recluse cause mange in dogs

in humans related species are commensals not eg. scorpions, esp Centruoides parasites

live in follicles esp eyebrows 3. Diseases and Parasites: 4. more serious impact on humans is as disease eg. ticks vectors: all ticks are parasites esp of birds and mammals eg. mites and ticks: feed on blood and lymph Rocky Mtn Spotted Fever some lay up to 12,000 eggs Lyme Disease the bite can be serious relapsing fever anticoagulants are sometimes toxic tularemia may cause fever and inflammation Cattle Diseases

eg. mites 5. Chinese herbal Medicine

eg. dust mite Black scorpions are sold for $12/lb feces in housedust causes dust allergies Future Applications eg. itch mite () Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 41 Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 42

6. scientists are experimenting with venom genes to use as biological control against insect pests

venom gene in virus ! infect & kill insect

7. spider silk is being investigated for a variety of possible uses.

(very similar to insect silk, eg silkworms)

20x’s stronger than steel

it does not trigger an immune response

can be easily produced at low temperatures and pressures compared to other similar polymers

is biodegradable

Animals: Arthropods-Chelicerates Ziser Lecture Notes, 2012.10 43

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