one of the free
swimming larval stages of sponges and numerous
coelenterates. The elongated oval body consists of
flagellate ectodermal cells and a mass of
entodermal cells (parenchyma). In sponges, the
parenchymula settles to the bottom and becomes
attached; in coelenterates, it changes into the
Amphiblastula larva is found in some of the sponges.
It is a free-swimming larva with the front half having
flagellated cells and the other half having cells
A larval stage of some hydrozoans
that has tentacles and a mouth;
attaches and develops
into a hydroid in some species, or
metamorphoses into a medusa.
planula, plural planulae, free-swimming or crawling
larval type common in many species of the
phylum Cnidaria (e.g., jellyfish, corals, and sea
anemones). The planula body is more or less cylindrical
or egg-shaped and bears numerous cilia (tiny hairlike
projections), which are used for locomotion.
cydippid larva A free-swimming, larval
stage of a ctenophorid (Ctenophora)
which resembles adults of the order
Müller's larva or Mulleria is a larva of
some Polycladida.[It has 8-fold symmetry and is
somewhat like a ctenophore.[Müller’s larva is ciliated
and has several paired and unpaired lobes.
The Miracidium is the second stage in the life cycle of
trematodes. When trematode eggs are laid and come into
contact with fresh water, they hatch and release
miracidium. In this phase, miracidia are ciliated and free-
A cercaria (plural cercariae) is the larval form of
the trematode class of parasites. It develops
within the germinal cells of the sporocyst or
redia.] A cercaria has a tapering head with large
penetration glands. It may or may not have a long
swimming "tail", depending on the species.
An oncomiracidium is the ciliated and free-
living larva of a monogenean, a type
of parasitic flatworm commonly found on fish. It is
similar to the miracidium of Trematoda, but
has sclerotised (hardened) hooklets not found in the
The free-swimming hat-shaped
larva of various nemertean worms
in whose interior the young worm
Trochophore, also called trochosphere, small,
translucent, free-swimming larva characteristic
of marine annelids and most groups of mollusks.
Trochophores are spherical or pear-shaped and are
girdled by a ring of cilia (minute hairlike structures),
the prototroch, that enables them to swim.
The smallest Amphisamytha larvae fall in the size range
of the nectochaetes and have a similar number of
chaetigers. Nectochaete larvae have a ciliary band behind
the head and are generally thinner for their length
The cyphonautes larva is the planktonic propagule of
benthic bryozoans. Usually found in shallow-water and
can be common in some seasons.
In crustaceans the larva, called nauplius, does not differ
substantially in mode of life or means of locomotion from
the adult but has fewer appendages than the adult. A
typical crustacean nauplius has three pairs of legs and an
unpaired simple eye. Additional pairs of appendages and
paired compound eyes appear in the course of a
sometimes prolonged development.
•It is the larvae of Sacculina, Balanus and Lepas.
•It develops from nauplius
•It is a free swimming larva.
•It is triangular in shape with bivalent shell.
•The larva has seven pairs of appendages, namely a pair of
antennules and six pair of thoracic appendages.
•A median eye is present.
•The larva contains a mass of germ cells.
•It undergoes a remarkable series of metamorphoses to
become the sessile adult form.
A free-swimming planktonic larval form of many
decapod crustaceans and especially crabs that has a
relatively large cephalothorax, conspicuous eyes, and
fringed antennae and mouthparts.
•In true crabs, the zoaea larva or metazoaea larva passes
through successive moults into the post larval megalopa
•It has a broad and crab-like unsegmented
•The carapace is produced anteriorly into a median
•The eyes are large, stalked and compound.
•All the thoracic appendages are well formed of which
the last 5 pairs are uniramous.
•The abdomen is also well formed, straight and bears
•In the rock- lobster (Palinurus), the newly hatched larva is
called the phyllosoma larva or glass- crab
•It is a greatly modified mysis stage.
•It is a remarkable for its large size, extremely flattened and
leaf- like delicate form and glassy transparency.
•A narrow constriction demarcates the head from thorax.
•A large oval carapace covers the head and the first two
•The eyes are compound and borne by large stalks.
•Only anterior 6 pairs of thoracic appendages are present in the
newly hatched larva.
•The first thoracic appendages or maxillipedes are rudimentary
(Palinurus) or absent (Scyllarus) and the second are uniramous;
succeed by 4 pairs of very long and biramous legs with
•Last two pairs of thoracic appendages are usually absent.
•Abdomen, though indistinctly segmented is very small and
•Phyllosoma undergoes several moults before reaching the
•It is the larva of Apus.
•It is the second larval stage which develops from the
•The body has an anterior oval cephalothorax, an
elongated trunk-region and an abdomen terminating in a
caudal fork provided with setae.
•The anterior end has a pair of frontal sense organs.
•Dorsal shield of the head grows back to form carapace.
•The larvae has three pair of appendages just as in
nauplius, it also develops the rudiments of 4 pairs of
appendages, which later become the maxillae and 2 pairs
of maxillipedes of the adults.
•In Penaeus, the zoaea larva, instead of
converting into the megalopa stage, moults into
the post larval mysis larva.
•It has 13 pairs of appendages. All the thoracic
appendages are biramous. Even the 5 pairs of
posterior thoracic legs are biramous with
flagellar exopodites which take up the
•The abdomen develops similar to that of the
adult form, with 5 pairs of biramous pleopods
and a pair of uropods and a telson.
•The mysis larva metamorphosis in to the adult
prawn by the loss of the exopodites on the
•Sea urchins; the small and spiny creatures
found in the oceans of the world.
•Planktonic larva is called pluteus larva.
A hypothetical bilaterally symmetrical
echinoderm larva sometimes regarded
as a common ancestor of echinoderms
2: a larval echinoderm (such as a
bipinnaria or an echinopluteus) —not
A bipinnaria is the first stage in the larval development of
most starfish, and is usually followed by a brachiolaria stage.
Movement and feeding is accomplished by the bands of cilia.
Starfish that brood their young generally lack a bipinnaria
stage, with the eggs developing directly into miniature adults
The bipinnaria is free-living, swimming as part of
the zooplankton. When it initially forms, the entire body is
covered by cilia, but as it grows, these become confined to a
narrow band forming a number of loops over the body surface.
A brachiolaria is the second stage
of larval development in many starfishes. It follows
the bipinnaria. Brachiolaria have bilateral symmetry,
unlike the adult starfish, which have a pentaradial
The brachiolaria develops from the bipinnaria larva
when the latter grows three short arms at the
underside of its anterior end. These arms each bear
sticky cells at the tip, and they surround an adhesive
The larva of echinoderms of the class Ophiuro
idea. An ophiopluteus has four pairs of long pr
ocesses, or arms, enclosing calcareous rods.
These arms, which are covered with a strip of
ciliate epithelium, enable the larva to swim. Th
ree pairs of coelomic sacs extend from the int
estine; the left anterior sac opens to the outsid
e through an interstitial canal. The adult form
develops from the anterior part of the larva onl
A tornaria is the planktonic larva of some species
of Hemichordata such as the acorn worms.It is very
similar in appearance to the bipinnaria larvae
of starfishes, with convoluted bands of cilia running
around the body. It is an oval shaped, transparent
larva. The diameter of the body is about 3 mm. It
has an apical plate, which is a thickened region
provided by a tuft of cilia and a pair of eye spots.
The larva has a complete alimentary canal. The
ciliary band stretches throughout the anterior and
posterior region, and also the postoral region.