IB-202-2 3-10-06
Jan 03, 2016
IB-202-2
3-10-06
Chapter 33
Invertebrates
Sponges
• Overview: Life Without a Backbone
• Invertebrates– Are animals that lack a backbone– Account for 95% of known animal species
Figure 33.1
• A review of animal phylogeny
Ancestral colonialchoanoflagellate
Eumetazoa
Bilateria
Deuterostomia
Po
rife
ra
Cn
ida
ria
Oth
er
bila
teria
ns
(incl
ud
ing
Ne
ma
tod
a,
Art
hro
po
da
,M
ollu
sca
, a
nd
An
ne
lida
)
Ech
ino
de
rma
ta
Ch
ord
ata
Figure 33.2
• Sponges are sessile and have a porous body and choanocytes
• Sponges, phylum Porifera– Live in both fresh and marine waters– Lack true tissues and organs
• Sponges are suspension feeders– Capturing food particles suspended in the
water that passes through their body
Azure vase sponge (Callyspongia plicifera)
Osculum
Spicules
Waterflow
Flagellum
CollarFood particlesin mucus
Choanocyte
Phagocytosis offood particles Amoebocyte
Choanocytes. The spongocoel is lined with feeding cells called choanocytes. By beating flagella, the choanocytes create a current that draws water in through the porocytes.
Spongocoel. Water passing through porocytes
enters a cavity called the spongocoel.
Porocytes. Water enters the epidermis through
channels formed by porocytes, doughnut-shaped cells that span the body wall.
Epidermis. The outer layer consists of tightly
packed epidermal cells.
Mesohyl. The wall of this simple sponge consists of
two layers of cells separatedby a gelatinous matrix, themesohyl (“middle matter”).
The movement of the choanocyte flagella also draws water through its collar of fingerlike projections. Food particles are trapped in the mucus coating the projections, engulfed by phagocytosis, and either digested or transferred to amoebocytes.
Amoebocyte. Amoebocytes transport nutrients to other cells ofthe sponge body and also produce materials for skeletal fibers (spicules).
5
6
7
4
3
2
1
Figure 33.4
• Choanocytes, flagellated collar cells– Generate a water current through the sponge
and ingest suspended food
• Most sponges are hermaphrodites
• Meaning that each individual functions as both male and female
Experiment: If a sponge is forced througha fine mesh screen and the cells put in aBeaker, within a few days they will reassembleand form an intact sponge. What does thismean? Do sponge cells communicate with each other?
Variations in Form or Shapes of Sponges
Sponges come in a variety of shapes, sizes and Colors!
Since sponges are an aggregation of cells and not organized into tissues, how do they achieve this variability in structure and color??? Something to think about!
The Shape of Life
Episode 1- Origins (Sponges)The Story of Science.
Video
• One hypothesis of animal phylogeny based mainly on molecular data
Figure 32.11
Ca
lcar
ea
Sili
care
a
Cte
no
ph
ora
Cn
ida
ria
Ech
ino
de
rmat
a
Ch
ord
ata
Bra
ch
iop
od
a
Ph
oro
nid
a
Ect
op
roc
ta
Pla
tyh
elm
inth
es
Ne
me
rte
a
Mo
llu
sca
An
nel
ida
Ro
tife
ra
Ne
ma
tod
a
Art
hro
po
da
“Radiata”
“Porifera” Deuterostomia Lophotrochozoa Ecdysozoa
Bilateria
Eumetazoa
Metazoa
Ancestral colonialflagellate
• One hypothesis of animal phylogeny based mainly on morphological and developmental comparisons
Figure 32.10
Po
rife
ra
Cn
ida
ria
Cte
no
ph
ora
Ph
oro
nid
a
Ect
op
roc
ta
Bra
ch
iop
od
a
Ech
ino
de
rmat
a
Ch
ord
ata
Pla
tyh
elm
inth
es
Mo
llu
sca
An
nel
ida
Art
hro
po
da
Ro
tife
ra
Ne
me
rte
a
Ne
ma
tod
a
“Radiata” Deuterostomia Protostomia
Bilateria
Eumetazoa
Metazoa
Ancestral colonialflagellate
Phylum Cnidaria• Cnidarians have radial symmetry, a
gastrovascular cavity, and cnidocytes
• All animals except sponges– Belong to the clade Eumetazoa, the animals
with true tissues
• Phylum Cnidaria– Is one of the oldest groups in this clade
• Cnidarians– Have diversified into a wide range of both
sessile and floating forms including jellies, corals, and hydras
– But still exhibit a relatively simple diploblastic, radial body plan
• The basic body plan of a cnidarian– Is a sac with a central digestive
compartment, the gastrovascular cavity
• A single opening– Functions as both mouth and anus
• There are two variations on this body plan– The sessile polyp and the floating medusa
Mouth/anus
TentacleGastrovascularcavity
Gastrodermis
Mesoglea
Epidermis
Tentacle
Bodystalk
Mouth/anus
MedusaPolyp
Figure 33.5
Tentacle
“Trigger”
Nematocyst
Coiled thread
DischargeOf thread
Cnidocyte
Prey
Figure 33.6
• Cnidarians are carnivores– That use tentacles to capture prey
• The tentacles are armed with cnidocytes– Unique cells that function in defense and the
capture of prey
• The phylum Cnidaria is divided into four major classes
Table 33.1
– Hydrozoa, Scyphozoa, Cubozoa, and Anthozoa
(a) These colonial polyps are members of class Hydrozoa.
(b) Many species of jellies (classScyphozoa), including thespecies pictured here, are bioluminescent. The largest scyphozoans have tentaclesmore than 100 m long dangling from a bell-shaped body up to 2 m in diameter.
(c) The sea wasp (Chironex fleckeri) is a member of class Cubozoa. Its poison,which can subdue fish andother large prey, is more potent than cobra venom.
(d) Sea anemones and othermembers of class Anthozoaexist only as polyps.
Figure 33.7a–d
Hydrozoans• Most hydrozoans
– Alternate between polyp and medusa forms
Feeding polyp
Reproductivepolyp
Medusabud
ASEXUALREPRODUCTION(BUDDING)
GonadMedusa
MEIOSIS
FERTILIZATION
SEXUALREPRODUCTION Egg Sperm
Developingpolyp
Portion ofa colonyof polyps
Maturepolyp
Planula(larva) Key
Haploid (n)Diploid (2n)1 mm
Zygote
Figure 33.8
A colony ofinterconnected
polyps (inset,LM) results
from asexualreproductionby budding.
1
Some of the colony’s polyps, equipped with tentacles, are specialized for feeding.
2 Other polyps, specialized for reproduction, lack tentacles and produce tiny medusae by asexual budding.
3
The medusae swim off, grow, and reproduce sexually.
4
The zygote develops into a solid ciliated larva called a planula.5 The planula eventually settles
and develops into a new polyp.6
Scyphozoans
• In the class Scyphozoa– Jellies (medusae) are the prevalent form of
the life cycle
Cubozoans
• In the class Cubozoa, which includes box jellies and sea wasps. Nematocysts full of
• toxic venom– The medusa is box-shaped and has complex
eyes unlike scyphozoa
Anthozoans
• Class Anthozoa includes the corals and sea anemones– Which occur only as polyps