Aquatic Worms Phylums: Platyhelminthes Nematoda Annelida Nemertea

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