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Biology of Invertebrates-Lectures > Cnidarians > Flashcards

Cnidarians Flashcards

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1
Q

Unique characteristics of cnidarians

A
  1. Release complex intracellular organelles called cnidae or nematocyst
  2. Presence of larvae stage called planula
  3. Among simplest living animals with true tissues
  4. All members lossess tentacles surrounding the mouth
  5. Mouth is the only opening to the gut
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2
Q

Cnidarians

  • habitat
  • examples
A
  • 99% marine, 0.2% freshwater (all aquatic)
  • most live attached (sessile)
  • manh live colonialy (coral colony)
  • jellyfish, sea anemones, corals, sea fans, sea whips
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3
Q

What is more complex- cnidarians or sponges

A

Cnidarians

Though still simple

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4
Q

Symmetry of cnidarians

A

Radically

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5
Q

Body layers of cnidarians

A

Diploblastic (2 enbryonic layers of living tissue)

  • epidermis
  • gatrdodermis

Mesoglea is a nin living jelly-like layer between the elidermis and the hypodermis

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6
Q

Despite non living, the mesiglea may hold living cells from the embryonic ectoderm called_____

A

Amoebocytes

-coukd functioj in digestion, nutritien transport, repair abd defend agaisnt bacteria

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7
Q

Body forms of Cnidarians

A
  • members exhibit polymorphism (2 kr more body forms)
    1. Medusa (jellyfish): have unbrella shaped inverted mouth (facing down) often, thuck jelly-like layer in body wall as in jellyfish. Move by contractions of “bell”-free floating, pelagic planktonic
    2. Polyp (hydroid): tubular body, ysually sessile/attached, mouth sureounded by tentacles
  • in most species, these body forms are present at different stages of lifecycle; while both occur at the same tine individually
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8
Q

Cnidae

A

Stinging thread

Unique organelle produced by cells called cnidoblasts (nematoblasts) and released with explosive force for defence, food collection, and locomotion

-may be specialized for attachement to surfaces, wrapping small objects, penetrating surfaces or secreting toxins made of proteins (highky toxic)

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9
Q

Cnidae release may be triggefed by

A

Osmotic oressure, chemical and tactile stimuli usually detected by group of specialized cilia (cnidocil)

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10
Q

Cnidarians have no gills or respirsti organelles so they…

A

Gaseous exchange via diffusion through exposed epidernak and gastrodernal surfaces

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11
Q

Cnidarians only have one opening that serves as both..

A

The mouth and anus

Digestive cavity leads to single opening

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12
Q

Gonad development of cnidarians

A

Occurs in the dugestive cavity and embryos released through the mouth

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13
Q

Cnidarian Feeding

A

Memebrs are mainily carnivorous, fee feed on phytoplanton (soft coral), few are symbiotic with unicellular photosynthetic algae in their tissues (endosymbionts)

-most have one or more rings of tentacles surrounding mouth armed with cnidocytes (stinging cells) for capturing prey

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14
Q

Cnidarians posess both ____ and ____

A

Nerves abd muscles

However lack CNS, nervous control invokves network of neurons (nerve cells) and their processes (nuerites)

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15
Q

Cnidarians lack ____ and ____ systems

A

Respiratory and excretory

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16
Q

Life span of cnidarians

A

Sea andmone can for 80+ years

Jellyfish up to 10

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17
Q

Cnidarian reproduction

A

Both asexual and sexual

Asexual: budding, fission (sea anamones)

Sexual: most are dioecious (separate sexes); geberaly sperm are shed in water

Alteration of generations in some soecues; polyp produces asexually abd medusae reproduxe sexully

-some can switch genders (males are scarce)

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18
Q

Larvae stage in marine cnidarians is comminly called a

A

Planula

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19
Q

Cnidarians are classifed into 2 subphyla

A
  1. Medusozoa

2. Anthozoa

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20
Q

The two subphyla are then broken into whicb classes

A

Mudosoza-

  1. Scyphozoa
  2. Cubozoa
  3. Hydrozoa

Anthozoa

  1. Hexacorallia
  2. Octociallia
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21
Q

Class scyphozoa

A
  • inverted cup shaped cnidarians commonly known as jellyfishes
  • over 200 species
  • all madine
  • large sized
22
Q

General characteristics of scyphozoa

A
  • mesoglea is thick gelatinous layer
  • mouth us bourne through an opening called the manubrium
  • Gastrovascular canal
  • ability to process sensory info
  • vertical migration in water
23
Q

Scyphozoa gastrovascular canal

A

Fluid filled canal leading to the outside through the manubrium
-function in oxygen and carbon dioxide circulation and nutriebt distribution following digestion

24
Q

Schyphozoa may form endosymbiotic relationships with

A

unicellular green algae (zooxanthallae) living inside the jellyfish

25
Q

Sensory receptors of scyphozoa

A

Possess slighkt advanced sensory receptors with ability to process and integrate sensory signals:

  • organ of balance (statocysts)
  • simple light receptors (ocelli)
  • some have touch receptors (sensory lappets)
26
Q

Rholalia

A

Club-like structures housing the ocelli and staocyst, arranged around the swimming bell

27
Q

Schphozoan reproduction

A
  • separate sexes
  • fusion of egg and sperm results in planula larvae (non feeding and attached)
  • planula changes into a polypoid scyphistoma
  • scyphiztoma grows and undergo budding asexually
  • then strobilation: transverse division of the body into many modules (ashtrays) called ephrya
  • ephrya develop to adult
28
Q

Under unfavouravke lab condititions adult scyphozoans can…

A

Differentiate back to the ephryae

29
Q

2 orders of scphozoans

A
  1. Semaeostomeae
    - aurelia species (moon jellyfish) and cyanea (lion mane jellyfish); produces the largest known medusae
  2. Rhizostomeae
    - lack central mouth, but has many small oral openings leading jntk a complex canal system
    - rhizostoma, cassiopea, stomolophus
30
Q

Class cubozoa (cube like animals)

A
  • body of memebrs are box like
  • known as cubomedusa
  • few members
31
Q

Rhopalia of cubozoa

A

Compelx with lensed eyes

Decelops nervous systems with compelx eyes

32
Q

Do cubozoans strobilate

A

No

33
Q

Characteristics of cubozoa

A
  • 4 tentacles or clusters of 4 around the edges of the bell, close to the 4 rhopalia
  • giid swinmers
  • body highly transparent
  • 2cm dismter with 30cm tentacles
  • tentacles are highky armed with toxic nematocysts called sea wasps
34
Q

Habitat of cubozoans

A

Mainly tropical and subtropical waters with seasonal abundance

35
Q

Food of cubozoans

A

Small fishes, crustaceans, annelids, but could kill animals larger than itself, even humand after injections with the toxins

-most venomous animal toxin (cubomedusae)

36
Q 
Class Hydrozoa (water animals) 
Characterisrics
A
  • possess more polyp form than medusa
  • gastroderm lacks nematocyst
  • nematocyst only around epidermis
  • smaller than scyphozoans (<2cm) and possess velum
  • mesoglea lack cells
  • mostly marine
  • form symbiotic relationships with other hydrozoans and invertebrates like fish, sponges
37
Q

Velum

A

Extended tissue which invaginates from the edge of the swimming bell to the manubrium

38
Q

Hydrozoan reproduction

A
  • fertilized eggs develop into planula larvae
  • planula metamorphose into sessule polypoid form without statocysts and ocelli
  • polyp form are typically more functionality and structurally complex than scyphozoan
  • unique freshwater slecies (hydra) produce single and independnt polyp
  • medusa form is absent
39
Q

Some hydra soecies harvour symbiotic unicellular ____

A

Green algae (zoochloellae) in their tissues

40
Q

Hydrozoan subclasses

A
  1. Hydriodolina (95%)

2. Trachylina (5-10%)

41
Q

Hydriodolina

A

Mostly marine

Mainly Surface water dweller

42
Q

3 orders of Hydriodolina

A
  1. Anthomedusae (sarsia, hydra, tubularia)- bell shaped free living medusa when present
  2. Leptomedusae (Obelia, clytia, sertularia): medusa not when present are flat, never bell shaped, 100% marine, may form assiciaition with molluscs, living in the mantle cavity of oysters, bivalves, and mussles
  3. Siphonophora (portugese man of war)- marine and contain nematocyst for killing prey that is toxic to humans
43
Q

Subclass Tachylina

A

Marine abd pellagic (mainly in warm open water) ex: liriope species

44
Q

Tachylina orders

A
  1. Narcomedusae
  2. Limnomedusae
  3. Trachymedusae
  4. Actunulida
45
Q

Subphylum Anthozoa (flower animals) unique characteristics

A
  • lack medusa form
  • lack operculum and corals
  • mDNA is circular like eykaryotes but unique in cnidarians
  • possess ciliated groove (siphonoglyph) in the pharyngeal wall leading from the mouth.
  • distinct sheets of tissue (septa) separate the coelenteron

Ex: sea anemines and corals

46
Q

What is the most abundant group of cnidarians

A

Anthozoans (70%)

-15 orders and 6000 species

47
Q

Anthozoan habitat

A
  • all marine
  • mostly colonial (corals)
  • some live solitary (sea anemones)
48
Q

Anthozoan members can secrete

A

Skeleton composed of calcium carbonate or protein

49
Q

Anthozoan reproduction

A

Asexually vis transverse or longitudinal fission by pedal laceration; portioj of foot (pedal disc) breaks off from the adukt Nd differentiates into a new individual.

50
Q

Subclasses of anthozoan

A 
1. Zoantharia 
Common orders:
-Actinaria 
-Corallinorpharia 
-Scleractinaria
  1. Alcyonaria
    - Stolonifera
    - Gorgonacea
    - Pennatulacea
    - Alcyonacea
51
Q

Acontia

A

Located in gastrovascualr cavity of anemones (anthozoans), thread like tissue containing numerous stinging threads

52
Q

Which mesentery of anthozoans have nematocysts?

A

Incompelte mesenteries to secrete digestive enzymes and cells that phagocytize bacteria

Biology of Invertebrates-Lectures (10 decks)

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