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Including the Phyla: Rotifera, Nematoda, Rhynchocoela, and Platyhelminthes Also called Nemertinea Commonly referred to as ribbon or bootlace worms Over 900 different species They live in marine habitats including: sand, mud, or under shells and rocks Mostly ocean dwelling Often brightly colored Can reach lengths of 1-100 feet long Carnivorous Uses proboscis to capture prey ▪ Eats segmented worms, and crustaceans Simplest animal with a circulatory system Contains Nervous system Sensory nerve cells located in epidermis Respiration occurs through epidermis Reproduce asexually or sexually When sexual, fertilization occurs externally, forming a larvae called pilidium When asexual, ribbon worms regenerate themselves The larvae pilidium develops into adult Common name Roundworm Has a bilaterally symmetrical body, surrounded by a cuticle Characterized by pseodocoelom Moves by contraction of muscles, producing a back and forth motion Muscles run in a longitudinal direction, along with nerve cords Can be decomposers, predators, or parasites Inhabit a wide variety of places, from beer coasters to mud, from humans to the placentas of sperm whales Extremely abundant, about 12,000 known species An rotting apple could have 90,000 individuals living on it 236 species could live in a few cubic centimeters of mud Sexual Males fertilize eggs by using copulatory spines to open a females reproductive tracts, and inject sperm into them Sperm do not have flagellae, it uses pseudopodia to move around ▪ Eggs develop directly into adult Roundworms infest half of the worlds humans Hookworms Worms that cause trichinosis Pinworms A worm whose eggs can be transmitted in household dust Filarial worms Can cause filariasis and onchocerciasis Rotifer: Latin for “Wheel bearer” The cilia round the mouth resembles a wheel Microscopic Found in marine environments Can vary in length from 200-500 micrometers, to one millimeter Omnivorous Sometimes cannibalistic ▪ Eats things from decomposing materials, to algae and phytoplankton Many Rotifers use parthenogenesis Asexual reproduction Two types of parthenogenesis The formation of only females The formation of males and females, where males are degenerate ▪ Condition is know as sexual dimorphism Males in the second type of parthenogenesis survive only long enough to produce sperm to fertilize eggs ▪ Eggs that are formed either hatch and release into water, or stay attached to the posterior end of the rotifer until enough water is available for it to hatch Lack both circulatory and respiratory systems Not necessary because of cells located near the animal’s exterior No body cavity About 20,000 species Consists of three major classes Turbellaria Trematoda Cestoda A common flatworm that can be found worldwide, is the Dugesia, otherwise known as the planarian Over 3,000 species in its class Live in marine environments Body resembles a piece of tape Moves by flexing its body, producing a wavelike motion that propels it through water Produce asexually All are predatory, feeding upon: bacteria, algae, protozoans and invertebrates Over 6,000 species in its class Mostly parasitic Also known as flukes Flukes can be endoparasites, or ectoparasites ▪ Endoparasites are covered by a tegument Simple bodies, due to parasitic lifestyle Contain multiple suckers to attach to hosts Reproduce asexually, allows for an exponential population growth Some flukes can be found in the blood, liver, or intestinal wall Common fluke found in humans: Clonorchis Sinensis (Liver fluke) About 1,500 species Parasitic Commonly referred to as tapeworms Cestoda attach themselves permanently to intestinal walls of hosts, absorbing food through their skin Grown in sections called proglottids May grow to reach a length of 40 feet. Imagine that in your intestine! About a dozen types of tapeworm infect humans, one of them being Taenia Saginata (beef tapeworm) They are hermaphrodites, but cannot reproduce asexually Each proglotid produces sperm and eggs
