Phylum Arthropoda

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Arthropoda general facts, pt 1

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- largest phylum
- closest relative are Tardigrada (water bears) and Onycophora (velvet worms)
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Phylum Tardigrada

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- AKA "water bears"
- v small
- terrestrial, marine, freshwater; spaces between sand grains on a beach
- 4 pr legs - first time we've seen a real leg, tho unjointed
- in absence of water, forms a *tun*

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tun

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protective stasis capsule for Phylum Tardigrada. resistant to high/low temperature, near-total vacuum, and very, very high radiation levels.

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Phylum Onyncophora

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- AKA "velvet worms"
- true legs, no joints
- tropical forests
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Onycophora: BAsics

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- dermal pappillae and velvet-like scale covering
- oral papillae secrete mucus which is used to capture prey
- little cephalization, cuticle similar to arthropods
- some body part segmentation

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The success of Arthropoda: Why?

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Four characteristics contribute:
Metamerism/Tagmatizaiton
Exoskeleton
- Hemocoel
- Metamorphosis

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Matamerism/Tagmatization in Arthropoda

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External segmentation not reflected in internal
- Permits specialization of body regions for specific fxns

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Arthropoda: Cuticle/Exoskeleton

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- provides attachment sites for muscles internal organs
- Protection against physical injury or invasion by pathogens
- Slows water loss This allows for more/different territory than previously-covered species
- an external and jointed
- usu made of chitin except in marine, where CaCO3
- ARTICULAR MEMBRANES cover joints and are more flexible than chitin

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Arthropoda:
Exoskeleton limitations

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- does not allow for growth of the organism. For growth to happen, molting must occur
- molt leaves the animal very vulnerable for a period of time during which it's largely undefended from any & all comers
- constraints maximum body size

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Arthropoda:
Hemocoel

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- Internal cavity used in circ system
- DOES NOT arise from coelom
- organs in hemocoel, bathed in HEMOLYMPH (blood functionary), as excretory, nutrient, and gas exchange method
- coelom exists but only around gonads, excretory organs

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Arthropoda:
Metamorphosis

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A substantial change in body form between juveniles and adults
- Adults and juveniles often live in different habitats, and have different behaviors, feeding habits, etc.
- This can reduce competition between adults and immature stages
- It can also aid in dispersal (larvae)
- Not all arthropods go through metamorphosis, however

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Arthropoda: Basic Anatomy

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- Paired, jointed appendages
- Ventral nervous system
- Complete digestive system
- Most are dioecious

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Arthropoda: Subphyla

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- Chelicerata
- Crustacea
- Myriapoda
- Hexapoda

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Subphylum Chelicerata

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- AKA "horseshoe crabs"
- usu terrestrial but some marine, freshwater
- wide size range <1 mm to 5m
- majority are carnivores, some are parasites

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Chelicerata: External anatomy

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- PROSOMA or CEPHALOTHORAX - sensory organs, feeding, and locomotion
- ABDOMEN or OPISTHOSOMA - digestive, reproduction, excretory, respiratory organs

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Chelilcerata:
External Anatomy II

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6 pr of appendages, last 4 the walking legs. 1st pr the CHELICERAE, 2d pr the PEDIPALPS (multi-use - sensory, feeding, locomotion, reproduction)
- No antennae

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Chelicerata, Class Merostomata

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- ancient grp, 4 spp
- 1st 3 walking legs are CHELATE (pincherlike)
- BOOK GILLS are resp. system
- spikelike tail called TELSON
- eats annelids, other inverts

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Cryptobiosis

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- Tardigrada's encapsulation to resist water-deficient death
- highly resistant to extremes of temp and radiation.

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Chelicerata, Class Arachnida

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- walking legs are NOT chelate
- Chelicerae modged for piercing or chewing
- pedipalps variable in appearance
- Resp sys= BOOK LUNGS (likely modded from book gill) or TRACHEAE

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Tracheae

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respiration for some of Arachnida
- consist of SPIRACLES, an entry pt of air, which circulates between page-like LAMELLAE

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Arachnida
common names

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- spiders,
-ticks/mites
- scorpions

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Arachnida
Gen'l Characteristics

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Variety sensory structures (sensilla, setae) for chemoreception
- Most 1 or more pr eyes
- almost exclusively dioecious, often sexually dimorphic (female>male)
- Males repro uses SPERMATOPHORES (oacket of sperm) to transfer sperm to females
- Many tend developing eggs.
- NO METAMORPHOSIS

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Arachnida:
Excretion

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- excrete URIC ACID from 1 of 2 organs
- COXAL GLANDS are sacs bathed by HEMOLYMPH that collect wastes and excrete through pore at base of posterior appendages
-MALPHIGIAN TUBULES are blind-ending tubules of the gut tract; collect nitrogenous wastes, excrete them with digestive wastes

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Arachnida, Order Scorpiones

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- all terrestrial
- most nocturnal
- carnivore on other invertebrates
- pedipals modded to lg pinchers
- Posses PECTINES on ventral side (comblike sensory organs, chemoreceptors and pick up vibrations)
- Opisthosomadivided into MESOSOMA (abdomen) & METASOMA (tail)
- METASOMA tipped with TELSON (stinger) & venom glands

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Scorpiones:
Reproduction

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- Oviviparous (eggs dev inside female) or Viviparous (nourishment inside mother)
- Offspring born alive, carried on mom's back till 1st molt

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Arachnida, Order Aranaea

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- chelicerae modded into fangs usu w poison glands
- pedipalps leg-like tip expanded in males for reproduction
- all carnivores, diff hunting modes
- SPINNERETS on abdomen

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Order Aranaea:
Reprodction

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- males weave sperm web, lay sperm in tip of pedipalp
- females lay eggs in an egg sac
- some females carry or guard offspring after birth, no livebearing spiders
- spiderlings may disperse by ballooning

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Arachnida, Order Opiliones:
Harvestment, Daddy Longlegs

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- resembles v long legged spiders
- all terrestrial
- carnivores, omnivores
- NO venom glands
- oviparous, dep eggs in/on ground

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Arachnida, Order Acari:
Mites & Ticks

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- primarily terrestrial,some freshwater or marine
- small to v small (<1 mm)
- Chelicerae & pedipalps mod for piercing, biting, anchoring, & sucking. Might be fused for piercing structure
- + ectoparasites of vertebrates or invert
- others, herbivore, scavengers or carnivores
- undergo slight metamorphosis in parasitic lifestyle
- may lack 1 or more pr of legs
- Prosoma and Opisthosoma are fused

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Acari:
Parasites

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- some spread disease (Lyme, Rocky Mtn. Spotted Fever)
- Follicle mites live in hair follicles
- Commonparasites of dogs, cats, other animals associated w humans
- 6-legged larvae of ticks called "seed ticks". Get 8 legs in 1st or 2nd molt.

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Other chelicerates

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Pseudoscorpion, vinegaroon/whip scorpion, solfugid/camel spider, amblypygid/whipspider

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Arthropoda Subphylum Crustacea:
Shrimp, Crabs, Lobsters, Crayfish, Barnacles, & Relatives

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- primarily aquatic some terrestrial
- most carnivorous, some parasitic, some filter feeders
- 2pr antennae
- BIRAMOUS (branched) appendages
- MANDIBLES are main mouthpart

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Crustacea: Class Malacostraca

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- primarily marine
- some laterally compressed & swim, some dorsoventrally compressed & usu crawl
- ALL HAVE GILLS

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Malacostraca
Body Form

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2 regions - cephalothorax and abdomen, which is segmented
- CARAPACE shield-like, protects soft bits of cephalothorax
-muscular tail flexible, for swimming
- in chelicerates, appendages attached to cephalothorax. Not necessarily so in Malacostracans

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Malacostraca:
Appendages

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- paired in both body regions, 18 pr in most species
- MANDIBLES and MAXILLAE (1st two pr.s of appendages) used for feeding, usu have gills
- 5 pr Walking legs and 5 pr swimmerets
- CHELIPEDS are lg pinchers that are modded walking legs
in males swimmeret might be modded for sperm production

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Malacostraca:
Gas exchange, circulation

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- respiratory pigment carries gases, uses Cu, not Fe to carry O, with a muscular heart
- gills attached base of appendages, exchange gases,blood in gill chamber under carapace
- Dorsal & ventral blood vessels connect hemocoel sinuses

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Malacostraca:
Nervous System

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- ventral nervous sys w fused ganglia in ea segment, lgest ganglion in head region
- antenna are primary chemoreceptors
- many other receptors on appendages; compounds eyes on stalks, simple eyes, chemoreceptors, tactile receptors
- statocyst with cemented sand grains

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Malacostraca:
Excretion and Reproduction

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- excrete ammonia from antennal glands or maxillary glands (structurally similar to coxal glands)
- gill surfaces important for osmoreg
- dioecious w copulation, sexual dimorphism (female>male)
- females brood eggs till hatching
- You resemble adults in some, but planktonic in others

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Crustacea, Class Branchipoda:
Brine Shrimp, Cladocerans

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- mostly freshwater, some marine
- Most sm, planktonic thofairy & some bring shrimp relatively lg
- Dioecious, monoecious, or parthenogenic
- many adapted to life in ephemeral pools

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Crustacea, Class Maxillopoda:
Copepods

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- all aquatic, marine & fresh
- V tiny may be plankonic or BENTHIC (live on sediments)
- May be most abundant amimals on earth
- mostly filter feeder, some predatory, parasitic
- reduced # appendages - none on abdomen
-resemble rotifers but no corona, have "arms"
- Carry eggs inside like rotifers
- Parasitic copepods are parasitic on fish esp shark eyeball

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Crustacea, Class Maxillopoda:
Barnacles

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- planktonic larvae that a little resemble copepods, sedentary as adults
- attach rocks, ships, docks, animals
- adults have calcareous plates that resemble mollusc shells
- filter feed, some few parasitic
- exclusively marine
- most monoecious, w extensible penis

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Subphylum Myriapoda:
Millipedes, Centipedes, & ALlies

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- all terrestrial
- Carnivorous (centipedes) or herbivorous (millipedes)
- 2 body regions, head & trunk
- 1 pr antennae
- mandibles
- TEN TO >750 PR LEGS
- all walking legs. mandibles only other appendage

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Myriapoda, Class Diplopoda:
Millipedes

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-usu 30+ pr legs, TWO PR/SEGMENT
- Body usu round in cross section or oblong
- Mandibles modded to chew
- + have REPUGNANTORIAL GLANDS that make foul-smell liquid for defense, along w tasting REALLY BAD. Also poop in defense
-often found in leaf litter, under decaying logs, etc.
- slow-moving; diurnal or nocturnal
- Dioecious; females lay eggs
- Males may use spermatophores or GONOPODS

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Myriapoda, Class Chilopoda:
Centipedes

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- usu 15+ pr legs, 1 PAIR/SEGMENT
- body usu flattened in cross sxn
- 1st pr appendages modded to FORCIPULES or POISON CLAWS (usu not dangerous to human)
- found leaf litter or under debris; house centipedes often inside bldgs
- FAST-moving; nocturnal
- dioecious, females may brood eggs & young
- males produce a spermatophore

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Subphylum Hexapoda:
Insects & Relatives

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- >1M descrived sp, est >5-30M
- Most terrestrial, some aquatic
- many sp aquatic as juveniles, terrestrial as adults
- 3 body regions: head, thorax, abdomen
- MANDIBULATE MOUTHPARTS often v modded
- canivores, herbivores, omnivores, or parasite
- 3 pr legs on THORAX
- 1 pr antennae
- Wings! If it has wings it's an insect and an arthropod

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Class Insecta:
Flight

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-1st animals to develop, allows migration, new food sources or mvoe to find more, escape predatorrs
- Wings have thickened, hollow VEINS for strength & nutrient transport to wings
- Most can fold wings over back except mayflies (Order Ephemeroptera) & damselflies (Order Odonata)
- many wings v maneuverable, some can hover
- wings ma be modded reduced or absent
- wings ONLY in adults except in mayflies, where next to last stage has nonfxnal wings

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Insecta:
Types of flight

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- INDIRECT or ASYNCHRONOUS FLIGHT - spastic, multiple flaps v fast, one nervous impulse for several wing beats
- caused by muscles attached to exoskeleton, changing shape of the body and snapping the wings to make thrust
- DIRECT or SYNCHRONOUS FLIGHT - one nervous impulse per wing beat, cause by muscles attached to wings contracting for downward thrust

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Insecta:
Appendages

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- insects may run, walk, jump, swim, burrow, or skate on water surface
- b/c of this, many have hily modded limbs
- lags may also be modded for catching prey, such as RAPTORIAL LEGS in mantids

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Insecta:
Feeding & Digestion

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-4 types mouthparts: labrum, maxilla, labium (move food around) and mandible (chew)
- Long, straight digestion system typical of all arthropods made of FOREGUT (muscular pharynx & crop), MIDGUT (digestion & absorption), and HINDGUT (instestine, reabsorbs water)
- foregut & hindgut lined in cuticle, which is shed in molt

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Insecta:
Gas Exchange

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- TRACHEAE in body open to outside cia SPIRACLES
Direct O2 exchange into plasma
- Most insects have methods for ventilating tracheae to outside, not just passive airflow
- aquatic have gills or diffuse gas across body walls, or carry bubbles underwater

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tracheae

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In Insecta, chitin-lined tubes that open to the outside via spiracles (holes in the exoskeleton)

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Insecta:
Circulation & Excretion

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Open circ system. Less developed than, but similar to other arthropods - blood not used in gas exchange, O2 is carried in plasma called hemolymph
-some insects generate heat by rapid contraction of flight muscles w/o flight, called SHIVERING THERMOGENESIS
- Malpighian tube excrete uric acid

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Insecta:
Nervous System

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Similar to annelids and other arthropods
- + have 2 enlarged ganglia in the head - BRAIN and SUBESOPHAGEAL GANGLION (associated with mouthparts)
- segmental gangliaoccur along ventral nerve cord
- some insects capable of learning & memory

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Insecta:
Chemical Regulation

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- Have ENDOCRINE GLANDS thatrelease HORMONES, which may control many biological processes like molting, growth, etc.
- PHEROMONES are released chemicals that cause behavioral changes in other individuals (sex, alarm)

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Insecta:
Reproduction

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- + have complex mating behaviors & internal fertilization
-pheromones, visual signals, or auditory signals may be involved in displays
- Females of many sp deposit eggs w an ovipositor
- Male member, itiagus, and the female genital opening can be a species-exclusive arrangement called a "lock and key mechanism."

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Types of Development in Insecta

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-Ametabolous Development (least common)
-Hemimetabolous Development
-Holometabolous Development

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Ametabolous Development

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-immature stages are sm adults
-no metamorphosis
- only change is dev of adult repro structures
- Found on in more primitive *wingless* hexapods

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Hemimetabolous Development

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-immature stages, "nymphs," usu look like sm adults
- as age juveniles develop wings, adult repro structures
- sometimes called "simple metamorphosis"

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Holometabolous Development

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Larvae, immature stages, don't resemble adylts
- Larvae often worm/grublike
- larvae go thru resting stage, "pupa"
- Pupae often (not always) encased in cocoon
- Inside pupa, larva retransformed into an adult
- called "complete metamorphosis"

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Insecta:
Social Insects

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- all ants & termites, some bees & wasps have hi'ly develeloped social systems
- refered to as EUSOCIAL insects
- individuals form large colonies (which acts as a "superorganism"), almost entirely female, with castes (division of labor w body appropriate to position/job)
- 1 or a handful for breeding, the queens
- Other females are sterile; they're workers, foragers, or soldiers
- Males are usu called drones and just for mating
- Termites mix this up, can have queen & king, workers are m & f, tho usu juveniles.

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Most damaging organism to humans

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the mosquito