Phylum Arthropoda PDF

Phylum Arthropoda  Phylum Anthropoda Segmented animals that shed an external exoskeleton, & ecdysis. Defining characteristics: Exoskeleton made of chitin, jointed legs (appendages); Protostomes, triploblastic, bilateral, coelomates; m...

Phylum Arthropoda  Phylum Anthropoda Segmented animals that shed an external exoskeleton, & ecdysis. Defining characteristics: Exoskeleton made of chitin, jointed legs (appendages); Protostomes, triploblastic, bilateral, coelomates; molting (Ecdysozoa); Eight main taxa: Class Arachnida, Merostomata, Pycnogonida, Chilopoda, Diplopoda, Hexapoda, Malacostraca, Thecostraca; Marine, freshwater, terrestrial and many can fly; General Body Plan Segmented with fused / modified body regions for specialized functions (tagmatization); Exoskeleton of chitin that must be shed by ecdysis; Internal body cavity is a hemocoel, like in mollusks; Complete digestive system; Complex muscular system; Well developed sensory organs; Respiration by body surface, gills, trachea or book lungs; Respiratory system Land arthropods —> tracheal system of air tubes deliver oxygen directly to tissues and cells. Trachea open to the outside through openings called spiracles. Aquatic arthropods —> no trachea, they breath mainly by gills. Ecdysis: the Hemocoel: a body process of cavity that contains shedding the old blood or hemolymph and functions as part skin or casting off of the circulatory the outer cuticle system Me Me Different body regions called tagmata  Exoskeleton: cutícula Exoskeleton Structure resistente, mas flexível, Epidermal cells secrete the exoskeleton que cobre o corpo de Two main regions: muitos animais e Epicuticle (outer) – waxy lipoprotein protistas, fornecendo a proteção para os órgãos Procuticle (inner, makes up the majority) – chitin internos. Me Not all exoskeletons are calcified, special layer in the procuticle. Hardening the exoskeleton Crustaceans = add Ca2CO3 into the procuticle; All arthropods = tanning; Protein cross-links form spontaneously in the procuticle immediately after it is secreted by epidermal cells Ecdysis To increase in body size, the entire exoskeleton must be shed at once; Arthropods molt many times before reaching adulthood, and some continue to molt after that. Old exoskeleton is degraded by enzymes and split open by allowing water or air in to “inflate” it; Under neural and hormonal control; Y-organ in the head Prothoracic glands in the thorax Produces ecdysteroids to trigger moulting Nervous system Complex brain and sensory structures in head region; Ventral nerve cord with metamerism (ganglia associated with body segments); Circulation Open/closed hybrid system; Blood leaves heart through closed vessels; Blood enter the heart via holes directly from the hemocoel (main body cavity); Visual systems Two levels of complexity: Ocelli (small cup with light sensitive surface); Compound eye (filled with many stacks of lenses and receptor cells organized into units called ommatidia); -Can detect UV and polarized light! Reproduction Almost exclusively sexual, some asexual, some parthenogenesis; Mix of internal and external fertilization; Many larval forms;  Subphylum CHELICERATES Defining characteristics: Only arthropods with no antennae, body in two sections with no distinct head, chelicerae (first pair of appendages); Spiders, scorpions, horseshoe crabs, sea spiders; Body divided into two regions: prosoma (head + tórax), opisthosoma (abdomen); Appendages NO antennae, no mandible - Clawed appendages called chelicerae on either side of the mouth for food ripping and predation; Food manipulators with blunt ends called pedipalps; Walking legs (4 pairs). Segments Segments 1-6 = Prosoma 1 = Chelicerae 2 = Pedipalps 3-6 = Paired walking legs Segments 7-20 = Opisthosoma Heavily modified or lost  Class Merostomata - Horseshoe Crabs Defining characteristics: Appendages on opisthosoma are flattened into ‘book gills’, final segment modified into long spike; Only 4 living species, remained relatively unchanged for 450MY; All marine; They are at risk because their blood has the blue pigment hemocyanin and is an essential ingredient in biomedical research; They are important ecologically; They are known as “book gills” because their abdomen resembles it; Gas exchange occurs in water, and it is limited in air; A chill predator of clams and worms Horseshoe Crab Opisthosoma (abdomen) is the posterior part of the body in some Anthropods, behind the prosoma (cephalotorax). Me  Class Arachnida Defining characteristics: Varied opisthosoma appendages from book lungs (internal) to spinnerets; Mainly terrestrial; Spiders, scorpions, mites, ticks; Spiders Solitary carnivores, usually only interact to mate; Scorpions Mainly nocturnal, solitary carnivores, cannibalism common; Mites / ticks Parasitism common, may live on or in association with hosts. Appendages Modifications Chelicerae = preset in all, may be hollowed out for delivery of venom (spiders mainly); Pedipalps = Modified into claws in scorpions, blind end appendages in the other groups —> 4 pairs of walking legs Specialized Abdominal Appendages Opisthosoma often separated from prosoma by narrow stalk (pedicel) in spiders; Spiders also have abdominal appendages called spinnerets near the anus for release of silk; Scorpions have modified final abdominal segment into a stinger.  Scorpions are cannibals, they can kill and eat other scorpions, and they are not immune to their own venom. Scorpions have two methods to capture prey: Brute force (large body, big pedipalps), Venom (small body, small pedipalps). Respiration Book gills have been modified to sit inside the abdomen as book lungs; Air gets in via holes call spiracles and is piped via tracheae tubes to the lungs for gas exchange  Class Psycnogonida All > ege - Defining characteristics: No clear tagmata, extendible proboscis around mouth, variable pairs of walking legs; Marine, often deep sea; Sea spiders. Lifestyle Carnivorous and scavengers, mainly on sessile inverts like sponges, anemones; They use their long proboscis to “fish around” inside of prey and pull out the good stuff. -x General anatomy No clear prosoma or opisthosoma, body is reduced to a stubby trunk; “All legs”; Appendages Chelicerae are present as well as palps; 3rd pair of appendages is special = ovigers —> Unique to this group; 4-6 pairs of walking legs. CHELICERATES SUMMARY Body regions —> Tagmata = 2 Characteristics appendages —> Chelicerae Pairs of walking legs = 4 Spiders, scorpions, horseshoe crabs, sea spiders  Subphylum - MYRIAPODS Defining characteristics: No unique synapomorphies but have many many legs! Ancestors were likely some of the first terrestrial animals; Centipedes, millipedes; Lifestyle Mainly detritovores in moist terrestrial environments; Some predators (centipedes); General features Two tagmata = head and trunk Trunk is comprised of elongated thorax and reduced abdomen; Segments Segments 1-5 = Head 1 = Antennae 2 = Lost during development 3 = Mandibles (jaws) 4 = Maxilla 1 (flappy mouth parts) 5 = Maxilla 2 (stringy mouth parts) Segments 6 onwards = Trunk 6 = Maxillipeds (centipedes) Paired walking legs (10s to 100s) Mouth Parts Flappy primary maxillae form the lower lip; Mandibles / jaws are inside the mouth; Respiration Openings to the outside = spiracles; Connected to the inside via tracheal system that delivers O2 to the tissues Excretion Malpighian tubules = tubules extending from the back of the gut; Absorb solutes and wastes from hemolymph; Passes solid nitrogenous waste to the gut for excretion. Class Chilopoda Centipedes One pair of walking legs per segment, spiracles on the top or side of the body; All venomous; Predatory. Appendages Modifications 1st pair trunk / thoracic appendages (maxillipeds) modified for venom delivery Important Predators Large centipede in the South Pacific feeds on seabird chicks; —> Important for nutrient cycling to transfer “marine” nutrients to a terrestrial ecosystem. -  Class Diplopoda Millipedes Two pairs of walking legs per segment, spiracles on the bottom of the body; Produce noxious chemicals as a defense; Detritovores. Appendage Modifications Segments of the trunk are fused together in pairs, resulting in two sets of walking legs per trunk segments; Defense Mechanisms Unlike centipedes, millipedes can’t bite and are slow moving; Option 1 = defense coil; Option 2 = release noxious chemicals through holes along the side of their bodies; —> Including cyanide! MYRMECOPHILY Some species of millipedes live in close association with ants; Symbiotic and commensal; Used by the ants to clear nest space in some cases! However, sometimes this can turn to a toxic relationship, and if ants are too hungry, they can eat them. MYRYAPODS SUMMARY Body regions —> (Tagmata) = 2 Characteristic appendage(s) —> None Pairs of walking legs —> Many Centipedes, millipedes  CRUSTACEANS Defining characteristics: Shared DNA features, similar compound eye structures; Hexapoda, Malacostraca, Thecostraca; General Features —> Insects Three tagmata = head, thorax, and abdomen; Organs specialized for respiration, if present, are in the forms of gills; Malpighian tubules are absent; Appendages Antennae ( 1 set) Segments (Insects) Walking legs (3 pairs) Segments 1-5 = Head Wings ( 2 pairs) 1 = Antennae 3 = Mandibles (jaws) 4-5 = Maxillae (mouth parts) Segments 6-8 = Thorax 6-8 = Paired walking legs, Wings on 7 and 8 Segments 8-19= Abdomen Significantly reduced, could be reproductive or sensory structures General Features —> Non-insect crustaceans (decapod crustaceans) Two tagmata = cephalothorax and pleon; Cephalon is the head; Pereon is the thorax; Pleon is the abdomen. Appendages Antennae (2 pairs) Short maxillipeds to move food around Claws (chelipeds, 1 pair) Walking legs (4 pairs) Swimmerets (in lobsters and shrimps, not in crabs) Segments Segments 1-5 = Cephalon 1 = Antennae 1 (short and branched) 2 = Antennae 2 (long and unbranched) 3 = Mandibles (jaws) 4-5 = Maxillae (mouth parts) Segments 6-14 = Pereon 6-8 = Maxillipeds 9-14 = Cheliped (claw) and Paired walking legs Segments 15-19 = Pleon 15-18 = Pleopods (swimmerets) 19 = Uropod Subphylum Hexapoda Class Insecta Defining characteristics: 3 pairs of waking legs Found everywhere; All feeding modes. 1 milhão of species, 1500 families. Complete digestive system Insect Ecology They are important community members: Decomposers Carnivores Herbivores Pollination = Mutualism Entomophily, pollination by insects helps 80% of plants world-wide complete their life cycles; Bees and other pollinators see flowers differently —> UV light, they can see colours differently  Class Malacostraca Crabs, Shrimps, Lobsters, Prawns Defining characteristics: Decapoda have 5 pairs of walking legs of which the first is often modified to form pincers (chelae); 20 body segments, compound eyes placed on movable stalks; All environments; Largest class of crustaceans and the most diverse collection of body plans (>40K living species). How to sex your crabs ?  Class Thecostraca Barnacles Defining characteristics: Encrusting organisms with flat calcified plates; Marine, some free-living, others parasitic; Head end attached to the rock (really!) and use legs to kick food into their mouths. Feed on small planktons using feathery appendages called cirri, complete loss of walking legs. They can go to great lengths to reproduce. They use scapulas to reproduce with their neighbors, Internal fertilization. Bamacle molt - CRUSTACEANS SUMMARY Body regions (Tagmata) = 3 (insects), 2 (non-insect crustaceans) Characteristic appendage(s) —> None Pairs of walking legs = 3 (insects), 4 (crabs, lobsters), lost in barnacles Hexapoda, Malacostraca, Thecostraca