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Annelida hydrostatic skeleton

Zoology 212 Lecture notes on Annelida Hydrostatic Skeleton
Course

Zoology (BIOL 212)

28 Documents
Students shared 28 documents in this course
Academic year: 2022/2023
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Saginaw Valley State University

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1 Phylum Annelida [little rings] contains the true worms. Annelid bigmac: •protostomes •segmented •schizocoelous coelomates •spiral cleavage •closed circulatory system •cutaneous respiration via skin, gills, parapodia •complete digestive system •organ-system level of organization •coelom is a hydrostatic skeleton & 2  transport [circulatory] system. 1 2 They are ‘true’ worms, because they display segmentation [metamerism]: the repetition of body parts. Segments form anterior to the pygidium [last piece containing the anus]. Thus, segment number varies with species, not age, since the segments form during the same developmental interval. McEuen et al. 1983 2 →

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Spiral

ions *

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mesoderm 3 groups ¥¥Ñn _ pepitah of body parts all same Ge true segments pro

# -

developmental pathway = metamerism

  • blood never leaves vessels

É

  1. Pan arthropods ( insects)
  2. Chor data (you) 1 type of endoskeleton
  • Trip 10 blasts
  • open circulatory system - hemolymph " fluid " segments added infront of pygidium

Coelom vs Pseudo coelom - - → both 2 ' body cavities → 0h14 Occur in trip/ oblasts redodf?oderm ✗ ✗ × × ✗ ✗ ✗ × , ✗ ✗ ✗ ✗ ✗ ✗ Ex ✗ ✗ × ✗ + ✗ ✗ ✗ × ✗ ✗ ✗ × X T ✗ I ✗ ✗ ✗ ✗ **¥ ✗ # ✗ ✗ *✗ ** ¥ bound via mesoderm apoptosis ↓ Programed cell death

5 The digestive system is not coiled, so a typhlosole increases surface area. The typhlosole is the indented/folded intestinal wall. lumen Gut lacking typhlosole lumen Typhlosole [red] jobilize//course/section/annelid-diversity-mollusks-and-annelids-by-openstax Same idea, different view: intestine [green] in situ is U-shaped Circumference is 33% larger in this example! 5 6 Locomotion is via muscular contractions against a hydrostatic skeleton. Since fluid in the coelom can not escape an individual segment, each segment changes shape relative to its neighbor. Contraction waves image.slidesharecdn/locomotioninannelid s-141204235026-conversion-gate02/95/locomotion- in-annelids-26-638?cb= classconnection.s3.amazonaws/126/fl ashcards/134126/jpeg/url-31360911137112 Setae anchor worm to prevent sliding backwards Similar compression of segments in polychaete worms using parapodia 6

  • groove in Intestine

/

On dorsal side

  • flexibility

7 Annelids are often categorized by 1 of 2 body types: polychaete versus oligochaete. clitellum setae: chitinous bristles Parapodia: leglike appendages anus Polychaete body plan Many setae Parapodia present Clitellum absent Oligochaete body plan Few or no setae Parapodia absent Clitellum present 7 8 Errantia are dioecious, primarily marine, active predators, that do not form tubes but with a polychaete body plan. Alitta virens En.wikipedia Cross-section of parapodium. It functions in respiration [via diffusion] and locomotion. “polychaete” is a grade to describe annelids with similar features but not necessarily related to each other! Nick Hobgood Evertible ”jaws”. Note the sensory tentacles and palps. Cosmic73. CC BY-SA 4. 8 differentiate setae Parapodia C Helium ← grade

  • Shared set of ↓ featured < " Jaws " move via parapodium Increase of SA. Oxygen diffusion through skin
  • thin & Moist

11 Most leeches occur in fw habitats. Parasitic species attach to the host using a sucker. Traits are feeding adaptations for large blood meals. annuli Feeding adaptations: Anticoagulants – host blood does not clot. heparin? Cutting jaws – cut skin of the host Suckers – holdfast and locomotion Loss of septa and expandable gut – body swells to hold more blood Annuli – extra external grooves that are not segments Pumping pharynx – keeps blood meal moving Medicinal leeches at the site of internal bleeding. 11 12 Like earthworms, they are monoecious [simultaneous hermaphrodites]. annuli Adult protecting cocoons RM Overstreet One difference is that leeches have internal fertilization via a protrusible penis or hypodermic injection. Some species carry cocoons, thus providing parental care! 12 (lithium only

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during reproduction liquid , meals gets rid of

  • ring externally → expansion & safer contractions

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parental

care

spiralia Rotifers

  • Water currents = motion
  • free living in
fw/-elicpseudocoeiomates

Coronal> at sexual maturity # of cells in animals doesn't change Acanthocephalans

  • derived from rotifers
  • 2nd body cavity not sister groups mesoderm & Proboscis w/ hooks
  • endoparasites w/ vertebrae
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Annelida hydrostatic skeleton

Course: Zoology (BIOL 212)

28 Documents
Students shared 28 documents in this course

University: Saginaw Valley State University

Was this document helpful?
9/19/20
1
1
Phylum Annelida [little rings] contains the true worms.
Annelid bigmac:
•protostomes
•segmented
•schizocoelous coelomates
•spiral cleavage
•closed circulatory system
•cutaneous respiration via skin, gills,
parapodia
•complete digestive system
•organ-system level of organization
•coelom is a hydrostatic skeleton &
2transport [circulatory] system.
1
2
They are ‘true’ worms, because they display segmentation
[metamerism]: the repetition of body parts.
Segments form anterior to the
pygidium [last piece containing
the anus].
Thus, segment number varies with species, not age, since the
segments form during the same developmental interval.
McEuen et al. 1983
2
→
󲰜☒"
Spiral
ions
*
*⑧
'
mesoderm
3
groups
¥¥Ñn󲰜
_
pepitah.cn
of
body
parts
all
same
Ge
true
segments
pro
#
-
developmental
pathway
=
metamerism
-
blood
never
leaves
vessels
É
2.
Pan
arthropods
(
insects
)
3.
Chor
data
(
you
)
1
type
of
endoskeleton
•
Trip
10
blasts
•
open
circulatory
system
-
hemolymph
"
fluid
"
segments
↳
added
infront
of
pygidium

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