Phylum: Nematoda Phylum: Nematoda “Round Worms”“Round Worms”

Mr. “I Got Worms” ChapmanMr. “I Got Worms” Chapman

Phylum: NematodaPhylum: Nematoda Some of the most abundant animals Some of the most abundant animals

on earthon earth In each acre of fertile garden there In each acre of fertile garden there

are how many nemtaodesare how many nemtaodes 5 Billion 5 Billion Believe to be 16,000 to 500,000 Believe to be 16,000 to 500,000

speciesspecies Most are parasiticMost are parasitic

NematodesNematodes Examples:Examples: PinwormsPinworms Hook WormsHook Worms Guinea wormsGuinea worms AscarisAscaris Soil NematodesSoil Nematodes

Micrograph of hookworm headMicrograph of hookworm head Cutting teeth of hookwormCutting teeth of hookworm

Symbiotic RelationshipsSymbiotic Relationships Mutualism:Mutualism: When both organisms benefit. Ex. When both organisms benefit. Ex.

Clownfish and anenome.Clownfish and anenome. Parasitism:Parasitism: When one benefits (parasite) and the When one benefits (parasite) and the

other is harmed (host).other is harmed (host). Commensalisms:Commensalisms: When one benefits and the other is not When one benefits and the other is not

affected. Example: Rino’s and birdsaffected. Example: Rino’s and birds

Phylum: NematodaPhylum: Nematoda Important role in Important role in

recycling nutrients recycling nutrients in soilin soil

Lack cilia (except Lack cilia (except for sensor for sensor structures)structures)

CharacteristicsCharacteristics Triploblastic, bilateral, unsegmented, Triploblastic, bilateral, unsegmented,

and pseudocoelomate.and pseudocoelomate.

Covered by a cuticleCovered by a cuticle– Has to molt to growHas to molt to grow

Complete digestive tractComplete digestive tract

CharacteristicsCharacteristics Body wall has only Body wall has only

longitudinal muscles longitudinal muscles with a ganglion at with a ganglion at anterior end.anterior end.

Has Eye spotsHas Eye spots

Tapered at both Tapered at both ends (comes to ends (comes to point)point)

FeedingFeeding CarnivoreCarnivore HerbivoreHerbivore OmnivoreOmnivore SaprobesSaprobes

– Feeds on decomposing organismsFeeds on decomposing organisms– Blood and tissue fluidsBlood and tissue fluids

Digestive SystemDigestive System Have mouth with teethHave mouth with teeth Muscular pharynxMuscular pharynx Long tubular intestinesLong tubular intestines

– Where digestion and absorption occursWhere digestion and absorption occurs

ReproductionReproduction Most are Dioecious and DimorphicMost are Dioecious and Dimorphic DioeciousDioecious – having male and females – having male and females

sexessexes DimorphicDimorphic – two different forms, so – two different forms, so

males and females look differentmales and females look different

Males are smaller than femalesMales are smaller than females

ReproductionReproduction Female – has ovaries, tubular uterus, Female – has ovaries, tubular uterus,

Male – single testis, tube that Male – single testis, tube that connects to cloaca.connects to cloaca.

Cloaca – one opening used for Cloaca – one opening used for reproduction and excretory. reproduction and excretory.

Important EvolutionImportant Evolution High reproductive potentialHigh reproductive potential Life cycles (different from flatworms)Life cycles (different from flatworms)

– Increases likelihood of transmission from Increases likelihood of transmission from one host to anotherone host to another

Enzyme-resistant cuticleEnzyme-resistant cuticle Resistant eggResistant egg