aquatic worms phylums: platyhelminthes nematoda annelida nemertea
TRANSCRIPT
Aquatic Worms
Phylums:Platyhelminthes
NematodaAnnelida
Nemertea
General Characteristics of Worms
• Long, slender soft bodies• Bilateral Symmetry
• Classified according to the shapes of their bodies– Phylum Platyhelminthes--flatworms– Phylum Nematoda--roundworms– Phylum Annelida--segmented worms– Phylum Nemertea--ribbon worms
Phylum Platyhelminthesa.k.a. Flat Worms
Phylum Platyhelminthes
• Dorsoventrally flattened- flat back and belly• Simplest animals that contain tissues and
organ systems• Acoelomates: no body cavity• Triploblastic: three fundamental cell layers
– Epidermis– Mesoderm (parenchyma tissue), which becomes
muscle tissue– Gastrodermis
Nervous System– Auricle: used to
sense surroundings– Eyespot: cluster of
light-sensitive cells– Ganglia: cluster of
nerves that send impulses along two ventral nerve cords to the rest of the body; found near eyespots (primitive brain)
– Ladder-like nerve cord
http://images.google.com/imgres?imgurl=http://cas.bellarmine.edu/tietjen/Laboratories/Bio%2520Pix%25204%2520U/Image37.gif&imgrefurl=http://cas.bellarmine.edu/tietjen/images/platyhelminthes.htm&usg=__mEw33qCB-6EekFvYb4ymy1Km9t8=&h=648&w=1016&sz=36&hl=en&start=13&um=1&tbnid=0Segtrs_6xQguM:&tbnh=96&tbnw=150&prev=/images%3Fq%3Dturbellaria%2Bnervous%2Bsystem%26hl%3Den%26rlz%3D1T4GZHZ_enUS223US223%26sa%3DN%26um%3D1
Digestive System
– Sac-like: one opening; mouth/anus- Intestines distribute food throughout the body
• No circulatory or respiratory system:– Their flat thin bodies allow diffusion to occur
through skin and cells
• Excretory system:– Flame cells connected to excretory ducts
http://io.uwinnipeg.ca/~simmons/lb6pg6.htm
Phylum Platyhelminthes
• Both aquatic (freshwater and marine) and parasitic species
• Classes:– Turbellaria (flatworms)– Trematoda (flukes)– Cestoda (tapeworms)
Class Turbellaria
• Most are free-living carnivores• Most are marine• Some have toxins for protection• Exhibit warning coloration• Characterized by beautiful colors and
patterns, many have frilly edges
Class Turbellaria
Class Turbellaria
• Movement:– Benthic: glides along the bottom using well
developed muscles and cilia• Reproductive system:
– Asexual• stretch its body and break in half; each half can regenerate
– Sexual• Hermaphroditic--have both sets of gonads and ducts• Internal fertilization, but NOT self-fertilization• Exchange of egg and sperm from different organisms must
occur
Class Turbellaria
Planaria• Can you see the eyespots and intestines?
Class Turbellaria
Class Trematodaa.k.a Flukes
• All are parasitic• Most adults parasitize vertebrates• Common parasite in fishes, seabirds and
whales• Over 6,000 species
Class Trematoda
• Characterized by having one or two holdfast devices (suckers)
• The life cycle of a fluke has two hosts (digenic)• First host is usually a snail, second host is
usually a vertebrate.• Examples
– Liver flukes– Blood flukes (schistosomes)
common liver flukeFasciola hepatica
Class Cestodaa.k.a. Tapeworms
• Adult lives in a host’s intestines, head attaches to the walls by hooks or suckers.
• Absorb nutrients from their hosts’ guts directly across their body wall (diffusion)
• No digestive system of their own• No respiratory organs• Have both sex organs in segments called
proglottids which are released in the host’s feces.
Class Cestoda• Longest tapeworm
recorded was found in a sperm whale it was 15 m long (50 ft)!
Phylum Nematodaa.k.a. Roundworms
Phylum Nematoda a.k.a Round worms
• Largest phylum of worms• Cylindrical body shape with tapered ends• No circulatory or respiratory system• Hydrostatic Skeleton• Complete digestive system• Some are parasitic and live in the intestines of
other organisms others free living
Phylum Nematoda
Anisakis (Why I don’t eat sashimi)
Hookworms
Guinea Worm infection - Roundworm
1.5 billion people worldwide were infected in 2002
Ascaris
Wuchereria bancrofti
causes elephantaisis
Phylum Annelida
Phylum Annelidaa.k.a. Segmented worms
• Segmentation: body consists of similar compartments (rings of an earhtworm)
• Triploblastic• Found in freshwater, saltwater and soil• Coelomates; coelom: fluid filled cavity that
surrounds the gut and serves as the hydrostatic skeleton
Phylum Annelida• Digestive system:
– Complete, one way• Circulatory system:
– Closed (blood does not leave the vessels)– Hemoglobin: binds oxygen
• Respiration:– Gills in some species– Diffusion across epidermis is most
• Excretory system:– One pair of nephridia per segment (nephridia is an organ =
to our kidneys)– Removes waste from coelom and bloodstream
Phylum Annelida
• Muscular system:– Circular and longitudinal muscles
• Nervous system:– Pair of cerebral ganglia (brain) connected to a nerve cord
that extends the length of the body– Nerve cord is connected to lateral nerves in each segment– Has sensory cells for touch, taste and perception of light
• Reproductive system:– Can have separate sexes or can have both sex organs– Some species can reproduce asexually by budding
Classes of the Phylum Annelida
• Class Polychaeta– Almost all marine annelids are in this class– Each body segment has a pair of flattened
extensions, parapodia, with setae (bristles)– Name means many bristled worms
Class Polychaeta
• Nereis: sandworm• Carnivore• Proboscis and jaws to capture prey
Class Polychaeta
• Fanworms and Feather-duster worms• Feathery tentacles covered with cilia used to
filter feed• Tubes are made from calcium carbonate or
bits of particles semented together with mucus
Class PolychaetaTube worms
Class Polychaeta
Riftia pachyptila Giant Tube Worms
Giant Tube Worm
Vestimentiferans
Class Polychaeta
• Giant tube worms: Vestimentiferans• Live near hydrothermal vents• 3 meters in length (10 ft)• Bright red tentacles contain hemoglobin• No mouth, stomach or gut• Symbiotic bacteria perform chemosynthesis
and provide nutrition to the worm.
Class Polychaeta» Hesionidae Onuphidae
» Eurythoe complanata
Class Polychaeta
• Tomopteris– A bioluminescent polychaete– Lives in abyssal environments– When attacked, they release luminescent particles
from their legs to confuse the predator and get away unnoticed
Class Polychaeta
• Chaetopterus pugaporcinus Yes, it means pig butt worm!
– Lives in abyssal environments– This species is so new...they don’t know if this is the
adult or larval stage...but they haven’t found sex organs yet...what do you think?
Classes of the Phylum Annelida• Class Oligochaeta
– Earthworms and other aquatic relatives, found in the mud
– Feed on organic matter– Lack parapodia– Name means few bristles
• Class Hirudinea a.k.a leeches– Freshwater or moist ground– Sucker at one end– Feed on fish and marine invertebrates– Leeches
Class Oligochaeta» Branchiura sowerbyi
» Earthworms » Lumbricus terrestris
http://www.scienceimage.csiro.au/index.cfm?event=site.image.detail&id=6391
Class Hirudinea
Phylum Nemertea
Phylum Nemerteaa.k.a. Ribbon Worms
• Most are marine, usually in shallow waters,
• Digestive system:– Complete– Long flexible proboscis to capture food
• No respiratory system: diffusion of gases across the skin
• Circulatory system: primitive, two pulsating vessels
Phylum Nemertea
• Examples:– Lineus longissimus
Has been recorded at 30 meters long, some scientists estimate they may reach up to 60 meters in length while still being only a few millimeters wide
Phylum Nemertea