BIOL 1030 – TOPIC 14 LECTURE NOTESTopic 14: Ecdysozoans: Nematodes, Arthropods, & some minor groups (Ch. 33)I. Ecdysozoa (clade)A. defined primary by molecular evidenceB. synapomorphy is ecdysis, or molting, of cuticle1. cuticle is a (relatively) tough external coat that is often chitinous and often serves as an exoskeleton2. growth requires partial dissolving and then shedding of the cuticle (ecdysis) and depositions of a new cuticle3. process of molting (ecdysis) usually controlled by molting hormone, or ecdysone4. new cuticle is relatively soft and expandable for a while• animal usually “puffs up” to expand new cuticle, then grows into it• animal is vulnerable while the new cuticle hardensC. clade includes the following phyla and organizational taxons that we will cover:1. Scalidophora• Phylum Priapulida (clade)• Phylum Loricifera (clade)• Phylum Kinorhyncha (clade)2. Nematoida• Phylum Nematoda (clade)• Phylum Nematomopha (clade)3. Panarthropoda• Phylum Onychophora (clade)• Phylum Tardigrada (clade)• Phylum Arthropoda (clade)1 of 16BIOL 1030 – TOPIC 14 LECTURE NOTESII. ScalidophoraA. clade of three phyla: Priapulida, Loricifera, and KinorhynchaB. basal branch within EcdysozoaC. all are pseudocoelomate or acoelomateD. have spiny, evertable proboscis that is used for feedingIII.Phylum Priapulida (clade) – penis wormsA. marine; 16 living species, all with phallic appearanceB. range from near microscopic to about 20 cm in lengthC. fossil record back to the Cambrian period, were likely major predators during CambrianD. named for Greek fertility god PriaposIV.Phylum Loricifera (clade)A. ~100 living speciesB. live in marine sedimentC. tiny (less than 3 mm long)D. can telescope most of body into lorica, a protective 6-plate pocketV. Phylum Kinorhyncha (clade)A. ~150 living speciesB. live in marine sedimentC. tiny (less than 1 mm long)D. segmented body, with head, neck, and trunk with 11 segmentsVI. NematoidaA. clade containing two phyla: Nematoda and NematomorphaB. sister group to Panarthropoda2 of 16BIOL 1030 – TOPIC 14 LECTURE NOTESC. pseudocoelomateVII.Phylum Nematoda – roundworms or nematodesA. "If all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable…we should find its mountains, hills, vales, rivers, lakes, and oceans represented by a thin film of nematodes." -N.A. Cobb, 1914, Yearbook of the United States Department of AgricultureB. ~25,000 living species (maybe as many as 500,000)C. most soil-dwelling and microscopic (< 1 mm)D. covered with flexible, thick cuticleE. muscles extend along length (longitudinal), not aroundF. feeding:1. many are parasites2. mouth often has stylets for piercing3. muscular chamber in throat (pharynx) used for sucking up foodG. many are important plant parasitesH. about 50 species parasitize humansI. Trichinella - causes trichinosis, females in digestive tract of pigs produce young which make their way to muscle tissue where they form cysts - cook well and you are fine, but 2.4% of people in U.S. carry the worm (don’t eat raw pork!)J. Caenorhabditis elegans – important lab animal; adult has exactly 959 cells; complete developmental cellular anatomy knownK. no cilia or flagellae, even on spermL. reproduction – sexual, with separate sexes (dioecious) VIII.Phylum Nematomorpha – horsehair worms or nematomorphsA. ~320 living speciesB. similar to nematodes in physiology3 of 16BIOL 1030 – TOPIC 14 LECTURE NOTESC. adults average ~1 meter longD. all are parasitic1. famous example – the cricket brain takeover2. larva develops within Orthopteran host3. when the nematomorph reaches adulthood, it causes the host to drown itself4. adult emerges and lives the rest of its life in waterIX. PanarthropodaA. clade containing three phyla: Tardigrada, Onychophora, and ArthropodaB. all have legs, claws, ventral nervous system, and segmented bodyC. all have coelom, but it is mostly associated with gonads; main cavity is instead the hemocoelD. all have open circulatory system with hemolymph (associated with hemocoel)X. Phylum Onychophora – velvet wormsA. ~150 described living speciesB. once marine, forms living today are all terrestrialC. mostly limited to humid forests in the Southern hemisphereD. (segmented) worms with legs1. many repetitious body segments, some similarity to caterpillars2. legs are internally hollow and not jointed; sac-like3. 13-43 pairs of legsE. average 5 cm long as adults; some as long as 20 cmF. thin, chitinous cuticleG. predatory, mainly on arthropods and mollusks1. often squirt fast-drying glue-like slime to catch and trap larger prey2. toxic saliva injected into victim to kill it and begin digestionXI.Phylum Tardigrada – water bearsA. over 1000 living species4 of 16BIOL 1030 – TOPIC 14 LECTURE NOTESB. aquatic or on other organisms; easiest to find on lichens and mosses1. many feed on plants or algae2. some feed on bacteria3. some hunt smaller animalsC. mostly microscopicD. body with head, then 4 segments1. covered by a chitinous cuticle 2. 4 pairs of lobe-like legs with claws3. rounded, stubby appearance and slow, lumbering gaitE. very hardy animals; able to enter a state of dormancy where they can1. can survive extreme cold or heat2. can survive very high radiation doses3. can survive up to a decade without waterXII.Phylum Arthropoda - arthropodsA. includes spiders, insects, lobsters, and others B. very diverse and important group1. ~1 million named species (about 2/3 of all named species)2. probably at least 10 million living species still unnamed3. dramatic impact (for good and bad) on environment4. major impact (for good and bad) on economy and human healthC. characteristics1. jointed appendages (arthros – jointed, podes – feet); may be modified as mouth parts, antennae, and legs2. exoskeleton – cuticle composed primarily of chitin• provides protection• strong but brittle; must be thicker for larger insects• insects cannot be too large because the exoskeleton would be too heavy5 of 16BIOL 1030 – TOPIC 14 LECTURE NOTES3. segmented – often fused into sections or tagmata (tagmatization important in arthropod evolution)4. all have a distinct head with a brain; sometimes head and thorax are fused into a cephalothorax, and sometimes several segments fused into an abdomenD. four subphyla with living members1. Cheliceriformes or Chelicerata (spiders, horseshoe crabs, sea spiders, etc.)• cephalothorax and abdomen• have