Chapter 12 Smaller Ecdysozoans

2 Ecdysozoans As a group: –Ecdysis the body has a cuticle that keeps enlarging and has to be shed periodically Molting regulated by a hormone known as ecdysone No common body plan –Acoelomates, psuedocoelomates and coelomates All but the arthropods in this chapter

3 Phylum Kinorhyncha “motion” “snout” (179 species) Marine in the mud Less than 1 mm cuticle is divided into 13 or 14 segments called zonites –Head, neck and trunk spines called scalids go down the body used to burrow in the mud dioecious

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8 Phylum Loricifera “corset” “ to bear” (100 species) 0.25 mm in size Live in the small grains of marine gravel oral styles, scalids lorica body can be pulled into this covering

9 Figure 15.15

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12 Phylum Priapulida “phallus” (16 species) Marine worms, burrow in sand cold water cm proboscis which is introvertable posterior trunk has rings and spines caudal appendages Dioecious, external fertilization

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15 Phylum Nematomorpha “thread” (320 species) Horsehair worms, Gordian worms Live anywhere—as long as it is wet cm long adults are free living (water) juveniles are all parasitic in arthropods (crabs, beetles, etc.) Adults absorb nutrients dioecious

16 life cycle: after copulation eggs are deposited in the water egg hatches into larvae stage (has spines) where it must quickly enter the host arthropod when the host is near water the mature worm leaves.

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21 Phylum Onychophora “bear” “claws” (70 species) Velvet worms or walking worms 0.5 to 15 cm long Rain forest/ tropical, leafy habitats Long fossil record Soft cuticle Pair of antenna pairs of unjointed legs with claws Tracheal system to breath – body pores Most dioecious –Viviparous (placental) –Ovoviviparous (develop inside—no placenta) –Ovoviparous (lay eggs)

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26 Phylum Tardigrada “slow” “step” (900 species) Water bears Microscopic < mm Four pairs unjointed legs with claws Nonchitinous cuticle No circulatory or respiratory organs Cryptobiosis – hibernates in a suspended state that has virtually no metabolism –Extreme temperatures, ionizing radiation, lack of oxygen, lack of water Parthenogenesis or sexual reproduction –Lay eggs in old cuticle

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30 Phylum Nematoda – “thread” (12,000 species) Round worms - found EVERYWHERE and in EVERYTHING! less than mm to 1 meter Parasites every animal and most plants Worm like shape Lips surrounding mouth with spines or teeth Cuticle made of 3 layers Longitudinal muscles Dioecious –Male smaller with copulatory spicules –Internal fertilization

31 Important human nematodes: 1. Ascaris lumbricoides – (intestinal roundworms) 1.27 BILLION infected around world life cycle: (2 months) –eggs in soil from feces (200,000/day) –eaten –juveniles hatch in intestine then burrow through wall into blood stream –go to the heart and lungs cause pneumonia –get into pharynx and to stomach Causes abdominal problems Wander out orafices: ears, mouth, anus, etc. –where eggs will be released –cycle begins again

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34 2. Necator americanus – hookworms –Life cycle: eggs in soil through feces burrow through exposed skin –have a special plate on mouth that can cut through skin go to lungs and intestines –Suck blood Shelled embryos leave body Juveniles hatch in soil –can cause anemia, mental and physical retardation

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40 3. Trichinella spiralis – –Worms encyst in the muscle of pigs, dogs, rats, bears, lions, etc. –T. spiralis found in many carnivorous and omnivorous animals worldwide T. britovi found in carnivorous animals in Europe and Asia T. pseudospiralis found in mammals and birds worldwide T. nativa found in arctic mammals T. nelsoni found in African mammals T. murrelli found in wild animals in the U.S

–Humans eat improperly cooked pork –Causes trichinosis first phase (intestinal) causes diarrhea, and nausea that begins two days after eating infected meat second phase (muscle) causes muscle aches, itching, fever, chills, and joint pains that begin about two to eight weeks after ingestion Can cause death 41

42 Trichina worm and cyst

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44 4. Enterobius vermicularis – pin worms Probably the most common worm parasite in the world adults live in the colon Haplodiploidy – males are haploid; females are diploid Females lay eggs at night Itching results in eggs being transmitted to hands and bed sheets Swallowed and it begins again Scotch tape method

45 Pinworms

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49 5. Filarial worms (8 types) –Wuchereria bancrofti: –live in the lymphatic system –where they block vessels and fluid builds up –Adults will copulate in lymph producing larvae (microfilariae) which will be released into the blood stream. Mosquitoes feed on blood Mosquito becomes infective The infective mosquito then feeds on a new host

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53 Elephantiasis

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6. Dracunculus medinensis –Longest nematode infecting humans Female 800 mm, male 40 mm –Dracunculiasis or Guinea worm disease –Become infected drinking unfiltered water with copepods that have the D. medinensis larva –Copepods die in stomach and release larvae –Female will migrate along subcutaneous tissue –Year later female forms blister on skin (allergic reaction) causes intense burning pain 55

Blister will break open Emerge from body usually foot, head, buttocks, genitalia, arms, etc. Patient seeks water for relief Female worm emerges and releases her larvae Larvae ingested by copepods Starts over again! Control worm by controlling water 85 percent reduction in past years 56

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Blister 58

Female worm emerging 59

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62 Loa Loa filaria

63 Dirofilaria immitis

64 Keys to prevention of nematodes: 1. Properly cook meat (pork) 2. Good sanitation 3. Wear shoes outside 4. Mosquito control, and 5. Watch who you sleep with!