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Back to Chapter 7. The Marine Worms. So far, this chapter…. Marine animals without a backbone Vertebrates vs. invertebrates Vertebrates have a backbone (a row of bones called vertebrae) 97% of all animal species are invertebrates Animals Multicellular Cannot manufacture own food. - PowerPoint PPT PresentationTRANSCRIPT
Back to Chapter 7The Marine Worms
So far, this chapter…
• Marine animals without a backbone• Vertebrates vs. invertebrates– Vertebrates have a backbone (a row of bones
called vertebrae)• 97% of all animal species are invertebrates• Animals – Multicellular– Cannot manufacture own food
Porifera - Sponges
• Sessile• Filter feeders• No true tissues or organs• Suspension feeders(eat food
particles suspended in water)
• Filter feeders )actively filter food particles
Types of Symmetry (Body Types)
Cnidarians: Radial symmetry
• Phylum Cnidaria• Also called coelenterates• Oral surface and aboral surface• Nematocysts (stinging structures
found in cnidocysts)• Two forms: polyp and medusa• Two layers of cell form a body wall– Epidermis external– gastrodermis lines gut
• with gelatinous mesoglea in between
Types of Cnidarians
• Hydrozoans –sessile, feathery or bushy colonies of tiny polyps
• Siphonophores – hydrozoans that form drifting colonies of polyps
• Scyphozoans – larger jellyfish– Large bell, swim with rhythmic
contractions of the bell• Anthozoans –lack a medusa stage– Sea anemones, corals, gorgonians
Ctenophora
• Comb jellies• Radial symmetry• Eight rows of ciliary
combs• Capture prey using two
long tentacles– Sticky cells named
colloblasts
Worms, Worms, Worms!
What are worms?
• Commonly, animals with long, thin bodies and no legs
• Bilaterally symmetrical invertebrates
Why bilateral symmetry?
• Allows animals to be more active– To capture prey– To develop sophisticated behaviors
• Implies development of an anterior end with a head, brain, and eyes.
Main groups of marine worms:• Flatworms• Ribbon worms• Nematodes - roundworms• Segmented worms :
• Annelids• Polychaetes• Oligochaetes• Leeches
• Peanut worms• Echiurans• Arrow worms – chaetognaths• Acorn worms
Flatworms: Platyhelminthes
• Dorsoventrally flattened• Simplest animal with
tissues organized into real organs and organ systems
• Brain and central nervous system
• Only one opening to gut• No body cavity
Flatworms
Flatworms
• Flukes or trematodes– All are parasitic– In fish, seabirds, whales
• Tapeworms or cestodes– Body in repeated units– Lack a mouth or gut– Found in sperm
whales,fish
Parasites in local fish
http://www.dfg.ca.gov/marine/parasites.asp
Ribbon worms: Nemertea
• More complex than flatworms
• Complete digestive tract– Gut with mouth and anus
• Closed circulatory system• Proboscis– Used to entangle prey– Secretes toxins, may have a
spine• 5mm- 30 m in length!
Nematodes• Roundworms• Pseudocoelem
– Tube-within-a-tube body plan
• In sediments • Some parasitic
– Seals, dolphins– Risk in sashimi, ceviche
• Small, slender, cylindrical bodies
• Gut, ends in anus– Lies within a body cavity
• Hydrostatic skeleton
Roundworm life cycle
Body cavity development
Flatworms
Roundworms
True coelom
• Segmented worms • Humans
• Gut lies in the coelom
Segmented worms: Annelida• Earthworms and marine worms• Body consists of similar segments• Gut goes through all segments• Gut lies in coelom• Hydrostatic skeleton• Longitudinal and circular muscles
– Efficient crawlers and burrowers– Longitudinal muscles lengthen and shorten segments– Circular muscles increase or decrease diameter.
• Closed circulatory system• Respiration by diffusion
bristleworm
Polychaetes• All marine annelids are polychaetes• Each body extension has a pair of parapodia– Flattened extensions– May be stiff, sharp bristles or setae
Annelida, Christmas tree worm
Polychaete variety
• May burrow• May crawl• May live in tubes • May be planktonic– Palolo worm
• Swarming• Timed by moon cycle• Bottom half of body breaks off and swims to surface to
spawn.
• Trochophore – planktonic larval stage
Leeches
• Blood sucking parasites that attach to marine fish and invertebrates
NOT Worms?
• Larval stages: grubs, caterpillars, maggots• Legless amphibians and reptiles• Insects • Centipedes
Anguis, or slow worm
Grubs: beetle larvae centipede
Marine Worms• Annelida (segmented worms) • Chaetognatha (arrow worms) • Gnathostomulid (jaw worms) • Hemichordata (acorn/tongue worms) • Nematoda (roundworms) • Nematomorpha (horsehair worms) • Nemertea (ribbonworms) • Onychophora (velvet worms) • Phoronida (horseshoe worms) • Platyhelminthes (flatworms) • Priapulida (phallus worms) • Sipuncula (peanut worms)
Sipuncula – peanut worms
•Some burrow in mud or rock•Some live in crevices•Shaped like a peanut•Unsegmented. •Intestine forms a loop•Retractable forward section, called the introvert•No circulatory or respiratory systems•1-35 cm long
EchiuraSoft, unsegmented, sausage-likeLike sipunculans, except for a non-retractable, spoon-like or forked proboscisDeposit feedersProboscis gathers organic material
The “fat innkeeper” lives in mud in a U-shaped tube.
Arrow worms - Chaetognatha•All marine.•Planktonic.•Transparent.•Fish-like tail and fins.•Head with eyes, grasping spines and teeth.•4mm-10cm in length.•Hermaphrodites.•Remain motionless and then dart rapidly toward prey.
Acorn worms - Hemichordata•Evolutionary link between Echinoderms and Chordata•Dorsal, hollow nerve cord•Openings along the anterior of the gut, gill slits,•Body in three parts•Worm-like deposit feeders•Live free or in U-shaped tubes•Use a thick, muscular proboscis to collect organic material from sediment
• Sea worm is a general term that may refer to a number of phyla of animals, or may refer specifically to:• Acanthocephala, parasitic worm • Annelida, segmented worms • Chaetognatha, arrow worms • Cycliophora, lobster worms • Entoprocta • Echiura, spoon worms • Gastrotricha, microscopic • Gnathostomulida, microscopic • Hemichordata • Kinorhyncha • Loricifera • Micrognathozoa, microscopic • Nematoda, round worms • Nematomorpha, parasitic worms • Nemertea, ribbon worms • Phoronida, horseshoe worms • Platyhelminthea, flatworms • Priapulida • Sipuncula, peanut worms • Xenoturbellida
Summary of distinguishing features
Annelida[3]Recently merged into Annelida[5] Closely-related Similar-looking phyla
Echiura[16] Sipuncula[17] Nemertea[18] Arthropoda[19] Onychophora[20]
External segmentation Yes no no Only in a few
species Yes, except in mites no
Repetition of internal organs Yes no no Yes In primitive forms Yes
Septa between segments In most species no no No No No
Cuticle material collagen collagen collagen none α-chitin α-chitin
Molting
Generally no;[13] but some polychaetes molt their jaws, and leeches molt their skins[21]
no[22] no[22] no[22] Yes[15] Yes
Body cavity
Coelom; but this is reduced or missing in many leeches and some small polychaetes[13]
2 coeloms, main and in proboscis
2 coeloms, main and in tentacles
Coelom only in proboscis Hemocoel Hemocoel
Circulatory system Closed in most species
Open outflow, return via branched vein
Open Closed Open Open