Echinoderms undergo a complex metamorphosis during development, starting as free-swimming larvae. There are five main larval forms: dipleurula, bipinnaria, brachiolaria, ophiopluteus, and echiniopluteus. These larvae have ciliated bands that help them swim and feed. As they develop arms and other features, they transition into their respective adult body plans through metamorphosis and settlement. The common larval features indicate a shared evolutionary ancestry among the classes of echinoderms.

1. Larval forms in echinoderms
KANAK BALI
20-zoo-21
University of Jammu

2. Echinoderms
• Marine spiny skinned animals
• Unique water vascular system
• Triploblastic, coelomate, unsegmented
• Head absent; body differentiated into oral and aboral
surfaces
• Adults show radial symmetry (usually pentamerous)
• Complex metamorphosis in course of development
• DevelopmentDeuterostomous fashion
• Direct/indirect
• Divided into 5 classes

4. DIPLEURULA LARVA
peri-oral band
adoral band
First larval stage
Two ciliary wavy bands
Found in all
echinoderms
lies inside mouth
Helps in collecting food particles
Actively feeds on diatoms etc.
Swims near the surface and rotates clock wise with the help of cilia of
peri-oral band

5. class Asteriodea eg. asterias
pre-oral region – elongated
post-oral region– broad
possesses two ciliated bands
Preoral ciliated band which surround the preoral lobe of
larva
Postoral ciliated band which appear to be longitudinally
placed and forms a complete ring between the mouth
and anus .
The arms are provided with muscles and
are contractile in nature
larva feeds on diatoms etc .
Inside the body occurs alimentary canal

6. bipinnaria larva Brachiolaria larva
BRACHIOLARIA LARVA
Has 3 short arms at preoral lobe---brachiolar arms (1
median ;2lateral)
adhesive cells at their tips
adhesive glandular area at base acts as sucker
Arms ---- long slender and ciliated larval arms
swims and feeds like bipinnaria larva
ciliated arms---- help swimming in the water.
The digestive system is completely developed with
definite stomach and intestine
after swimming --->settle-on a solid object and gets
attached to it by its adhesive arms.
slowly the larva metamorphosis into an adult.
postoral arm

7. OPHIOPLUTEUS LARVA
Class ophiuroidea
Posterolateral arms longest;
directed forward
Ciliated bands along edges
arms are supported by
calcareous rods
arms are directed upwards
Preoral loop is reduced
Ciliated band is undivided
postero-lateral arms are very
long and they are directed
forwards
digestive system is developed

8. ECHINOPLUTEUS LARVA
‡ Class Echinoidea
‡ Six arms—preoral ,anterolateral,
anterodorsal, postoral ,posterodorsal
posterolateral(very short/absent)
‡ Fully developed echinopluteus 5or 4
pairs of arms instead of 6
‡ Tips are pigmented
‡ arms supported by calcareous
skeletal rods
‡ Locomotion by ciliated bands may
become thickenedepaulettes
‡ The digestive system is developed
which shows mouth and anus.
.

9. AURICULARIA LARVA
• Class Holothuroidea
• Arms are absent
• Ciliated bands are well-developed
• The body is provided with single longitudinal
ciliated band which forms a pre oral loop around
the mouth and anal loop encircling anus.
• These help in swimming
• the pre oral lobe is very well formed .
• there are no calcareous rods being replaced by
spheroids star shaped or wheel like bodies
• the interior of larva is occupied by the curved gut
with saccular stomach hydrocoel and right and
left stomocoels
• the hydrocoel is produced into primary tentacles
and communicates with the hydropore by canal .

10. DOLIOLARIA LARVA
• Class Crinoidea
• body has 4 or 5 ciliated bands
• apical sensory plate at anterior end
provided with a bunch of cilia
• On the mid ventral line near apical
plate,adhesive pit is present over the 1st
ciliated band
• Between 2nd & 3rd ciliated band—
stomodaeum/vestibule
• After swimming develop a stalk. It is
called Pentacrinoid larva.
• attach to the substartum.
• The internal organs rotate at 90°
• It develops into an adult
.

11. 1.Common origin of classes :
 larval forms of all classes in Echinodermata shows general resemblance (bilateral symm. , flattened body
,longitudinally looped ciliated bands ,gut and enterocoelic coelom) except crinoidea larva.
 same ancestor ->coelomate, bilaterally symmetrical and free swimming.
 Dipleurula and pentactula larvahypothetical ancestors
 All modern echinoderms originated from them
2.Relationship with chordates:
 Auricularia larva & Tornaria larva shows resemblance.
 Cleavage is indeterminate and mesoderm and coelom have similar origin in echinoderms & lower
chordates
 Thus Echinoderm & chordates are phylogenetically related
3.Aid in dispersal and feeding:
 adults are sluggish ; larvae—dispersive phase
 Different feeding habits—no competition
4.Retrogressive metamorphosis:
 Adult Echinoderms are primitive than larvae
 radial symmetry, absence of head, lack of
anterior and posterior ends
Significance of Echinoderm larva :

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