1. CRUSTACEAN DEVELOPMENT I: Life Cycle
Bambang Irawan
1 Oktober 2009

2. ANAMORPHIC AND EPIMORPHIC DEVELOPMENT
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

3. 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.

4. 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.

5. Nauplius
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)

6. Nauplius characters It consists of a head and a telson
The telson is unarmed in the early nauplii, but by the end of 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

7. More simply Nauplius structural charactyeristic:
Have no functional thoracopods
Have no compound eyes
Usually have simple median eye

8. NAUPLIUS

9. Metanauplius Metanauplius stage follows the nauplius phase
Have only three pairs of functional appendages
Have additional segments and nonfunctional appendages

10. Nauplius Paraleptastacus brevicaudatus; Nauplius I–VI (Dahms, dkk J.of Crustacean Biology, 10(2): ).

11. Zoea The zoea is a free-swimming larval stage of crustaceans.
It follows the nauplius stage, and precedes the post-larva.
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.

12. Zoeal characters No functional pleopods
At least one pairs of biramous locomotory thoracopods
Usually have a pair of compound eyes

13. Zoeal development in Uca tangeri

14. Dorsal view of abdomen and telson od the zoea and megalopa (Uca tangeri)

15. Dissodactylus nitidus; Zoea I – IV. (Pohle. 1989. J
Dissodactylus nitidus; Zoea I – IV. (Pohle J. of Crustacean Biology, 9(2): ).

16. Pagurus vetaultae; Zoea I – IV dan megalopa (McLaughlin, dkk. 1991. J
Pagurus vetaultae; Zoea I – IV dan megalopa (McLaughlin, dkk J. of Crustacean Biology, 11(2): ).

17. Protozoea 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

18. Mysis 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

19. Post larva
Complete complement of segments and appendages, including the abdomen and pleopods
Still small, does not closely resemble the adult, and is not sexually mature

20. Megalopa
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

21. Uca tangeri megalopal stage

22. The modes of development in Crustacea
Egg nauplius protozoea zoea mysis juvenil adult
Egg protozoea zoea mysis juvenil adult
Egg protozoea zoea megalopa juvenil adult
General modes in shrimps
Egg Nauplius Zoea Juvenil Adult
General modes in crabs
Egg Zoea Megalopa Juvenil Adult