polychaetes Flashcards

1
Q

name the unsegmented Marine worms

A

Flatworms (Phylum Platyhelminthes)
Ribbon worms (Phylum Nemertea)
Round worms (Phylum Nematoda)

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2
Q

name the segmented Marine worm

A

annelids (Phylum Annelida)

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3
Q

Phylum Platyhelminthes characteristics (flatworms)

A

Flukes, tapeworms and turbellarians
- dorsoventrally flattened
- Gas exchange via diffusion (big enough body surface)
- Well-developed reproductive system in most
- brain = clusters of nervous tissue in head

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4
Q

Phylum Nematoda characteristics (Round worms)

A
  • Extremely abundant in interstitial spaces of marine + freshwater sediments and soil water
  • tapered at both ends with a thick, tough cuticle
  • important in decomposition + nutrient cycling
  • Significant parasites of humans, plants, animals
  • Can be very difficult to identify species
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5
Q

Phylum Nemertea characteristics (Ribbon worms)

A
  • free living, mostly marine
  • Dorsoventrally flattened
  • Ciliated epidermis
  • Complete digestive system with mouth and anus
  • Circulatory system
  • Predators - eat other invertebrates e.g. worms and crustaceans
  • Proboscis = long fleshy tube - used to entangle prey or inject venom via a stylet
  • Prefer shallow, coastal waters
  • Mostly < 20 cm; can be much longer (e.g. bootlace worm over 30 m)
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6
Q

Phylum Annelida characteristics

A
  • Well-developed nervous system (with brain)
  • Segmented internally + externally
  • Bristles setae / chaetae in most (except leeches) – rods formed from scleritosed chitin that extend from each segment
  • Closed circulatory system + haemoglobin
  • Bilateral symmetry
  • Traditionally divided into 3 classes: Hirudinea, Oligochaeta and Polychaeta
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7
Q

Sipunculans (Peanut worms) characteristics

A
  • all marine, relatively common
  • Live in shallow waters - either in sediment or in discarded shells
  • Some bore into solid rocks to make a shelter for themselves
  • Deposit feeders
  • Anterior retractable appendage, introvert= multi-lobed or tentacled with mouth at end
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8
Q

Clitellata characteristics

A
  • Branchiobdella - formerly in Hirudinea
  • Class Hirudinea + Oligochaeta
  • Form cacoons
  • Hemaphrodites
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9
Q

what classes are apart of Clitellata

A

Hirudinea + Oligochaeta

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10
Q

class Hirudineans (Leeches) characteristics

A
  • Marine species = parasitic - prey on other invertebrates or fish
  • Anterior and posterior suckers to hold prey
  • Dorsoventrally flattened
  • Segmentation not as distinct as in other annelids
  • No setae
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11
Q

Class Oligochaetes characteristics

A
  • burrow in soft sediments
  • Deposit feeders
  • Terrestrial earthworms are also in this group
  • Mainly found in shallow coastal waters
  • Hermaphroditic
  • Few chaetae (oligo)
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12
Q

Class Polychaetes (bristle worms) characteristics

A
  • Largest + most of the diversity of annelids
  • Paraphyletic
  • Gonochoristic
  • Often many chaetae (poly)
  • Distinct head
  • Trochophore larvae
  • Varied morphologies and feeding mode
  • Coelom (true body cavity) - important for hydrostatic skeleton
  • can regenerate lost segments
  • May have natural break points if grabbed by predators (autotomy)
  • 2 clades = Errantia and Sedentaria
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13
Q

explain Parapodia in polychaetes

A
  • fleshly lobes supported by chaetae on the side of each segment
  • important for identification of species
  • vascularized parapodia often used for movement
  • Act as primary respiratory surfaces
  • can be thought of as kinds of external gills that are also used for locomotion
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14
Q

what is the Errantia clade in polychaetes

A
  • include free-living crawlers like nereidids (ragworms) and phyllodocids (paddleworms)
  • include flattened worms protected with shield-like dorsal scales like thempolynoids (scaleworms) e.g. sea mouse
  • include predatory swimming worms with giant eyes like the alciopids
  • Gonochoristic - gametes released into the coelom
  • Many species reproduce en masse at night (broadcast spawning)
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15
Q

what is epigamy

A

worm transforms into a swarming epitoke - rises into the water column to shed its eggs + sperm (sexual reproduction)- worm dies after reproduction (e.g. Nereids)
- most metamorphose to become night-time swimmers (epitokes) to meet their mates - timing of swarmings synchronised with the phases of the moon

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16
Q

what is Schizogamy

A

sexual forms bud from posterior or parapodia

17
Q

what is the Sedentaria clade in polychaetes

A
  • Stationary form
  • “Biogenic reefs” - individual organisms live in each hole
  • do not have well- developed sense organs or jaw – but may have specialized gills or tentacles used for respiration + deposit / filter feeding
  • Include colonial, reef-building forms with fans of head tentacles like the serpulids and sabellariids
  • biofouling organisms – problem for boat owners
  • Important for bioturbation e.g. Arenicola Marina – eats sand, digests material, produces cleaner sand
  • Get extremely beautiful filter feeder forms – giant axons make them retract quickly
  • Very interesting e.g giant tube worms in hydrothermal vents
18
Q

what’s the name of the family in the Sedentaria clade in polychaetes

A

Family Siboglinidae
- family of tube dwelling worms found throughout the worlds oceans
- organ trophosome replaces digestive system (they have no gut or mouth) - becomes filled with chemosynthetic bacteria
- Bacteria in the trophosome fix the chemicals leaving the vents

19
Q

what is a prototroch

A

a ring of cilia used for locomotion in larvae