Transcript CRUSTACEAN DEVELOPMENT I: Life Cycle

CRUSTACEAN
DEVELOPMENT I:
Life Cycle
Bambang Irawan
1 Oktober 2009
ANAMORPHIC AND
EPIMORPHIC DEVELOPMENT
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Crustacean may be either anamorphic (indirect)
or epimorphic (direct)
In anamorphic development a larva hatches from
egg with its embryonic development still
incomplate and only a portion of the adult
complement of segments and appendages
In direct development there are no larval stages,
the eggs hatch as immature having the adult
complement of segments and appendages
Anamorphic development
• The individual undergoes development and then leaves
the egg at a hatching stage typical for the taxon.
• The hatching stage is characterized by a specific number
and segments
• Those characteristics referes to a specific larval name
such as nauplius and zoea.
• After hatching, larvae undergo postembryonic
development, in which new segments proliferate at the
anterior margin of the telson
• In the course of successive molts, additional segments
and appendages are gradually acquired until the adult
condition is achieve
• Anterior segment and their appendages are added first.
CRUSRACEAN LARVAE
 Crustacean taxa have many larval stages,
which tend to have different names in each
taxon
 The basic crustacean larvae are: nauplius,
zoea, and megalopa
 Some authors differentiate the zoeal stage base
on its development: protozoea, zoea, mysis.
 In some taxa there is metanauplius between
nauplial and zoeal stage.
Nauplius
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In Greek mythology Nauplius is the name of the son
of Poseidon and Amymone,
Nauplia is the name of a descendant of Nauplius
In Biology nauplius the name of a stage in
crustacean larval development, the first laval stage
Nauplius is singtular case, the plural case is nauplii
It also a generic name in sunflower family
(Asteracea)
Nauplius characters
 It consists of a head and a telson
 The telson is unarmed in the early nauplii, but by the end of
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the naupliar phase it usually bears spines or setae whoese
number and arrangement may provide useful taxonomic
characters
A prominent characteristic of nauplii is that they have only one
compound eye, which will divide in two in later stages
Nauplii have three pairs of cephalic appendages with which
they swim; in the adult these become the antennules, the
antennae, and the mandibles
The name nauplii properly refers to crustacean larvae that use
appendages that stem from the head (antennules and
antennae) as their mains means of swimming.
It is common for the nauplius to suppressed by the embryo so
that the hatching stage is more advanced larva with additional
segments and appendages
More simply
Nauplius structural charactyeristic:
 Have no functional thoracopods
 Have no compound eyes
 Usually have simple median eye
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NAUPLIUS
Metanauplius
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Metanauplius stage follows the nauplius
phase
Have only three pairs of functional
appendages
Have additional segments and nonfunctional
appendages
Nauplius Paraleptastacus brevicaudatus; Nauplius I–VI
(Dahms, dkk. 1990. J.of Crustacean Biology, 10(2):330339).
Zoea
 The zoea is a free-swimming larval stage of
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crustaceans.
It follows the nauplius stage, and precedes the postlarva.
Zoea larvae swim with their thoracic appendages
It often has spikes on its carapace which may assist
these small organisms in maintaining directional
swimming
In many decapods, due to their accelerated
development, the zoea is the first larval stage
In some cases the zoea stage is followed by the
mysis stage and in others by the megalopa stage,
depending of the crustacean group involved.
Zoeal characters
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No functional pleopods
At least one pairs of biramous
locomotory thoracopods
Usually have a pair of compound eyes
Zoeal
development in
Uca tangeri
Dorsal view of abdomen and
telson od the zoea and megalopa
(Uca tangeri)
Dissodactylus nitidus; Zoea I – IV.
(Pohle. 1989. J. of Crustacean Biology, 9(2):278-296).
Pagurus vetaultae; Zoea I – IV dan megalopa
(McLaughlin, dkk. 1991. J. of Crustacean Biology,
11(2):277-291).
Protozoea
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Follows metanauplius
Addition in segments and appendages
Thoracic somites are formed
Complate set of head appendages and
first two maxillipeds
Upon acquiring its functional thoracic
appendages, the protozoea becomes a
zoea
Mysis
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Do not confuse with mysid (Mysidacea)
The Mysidacea is a group of small, shrimp-like creatures.
Mysid is a zoea with functional pereopods
All of thoracopods have large exopods, which become
locomotory appendages
The larvae now swim backwards
Body vertical with the telson up
Slowly spinning on the vertical axisThe carapace more closely
and covers most of the thoracic somits
The antennae have lost their locomotion function
Post larva
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Complete complement of segments and
appendages, including the abdomen and
pleopods
Still small, does not closely resemble the
adult, and is not sexually mature
Megalopa
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Complate set of head, thoracic, and
abdominal appendages and segments
Mostly benthic
Macroscopic and more like the adult
The most significant charater is in
having at leat one pair of natatory
pleopod
Uca tangeri megalopal stage
The modes of development in Crustacea
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3.
Egg
Egg
Egg
nauplius protozoea zoea
mysis juvenil
protozoea zoea mysis juvenil adult
protozoea zoea
megalopa juvenil adult
General modes in shrimps
Egg Nauplius Zoea Juvenil
General modes in crabs
Egg Zoea Megalopa
Juvenil
Adult
Adult
adult