CRUSTACEAN DEVELOPMENT I:

Life CycleBambang Irawan

1 Oktober 2009

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

Anamorphic developmentAnamorphic 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

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

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 thoracopodsHave no compound eyesUsually have simple median eye

NAUPLIUS

Metanauplius

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):330-

339).

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.

Zoeal characters

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 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 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 appendagesThe 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 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

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

1. Egg nauplius protozoea zoea mysis juvenil adult

2. Egg protozoea zoea mysis juvenil adult

3. Egg protozoea zoea megalopa juvenil adult

General modes in shrimps

Egg Nauplius Zoea Juvenil Adult

General modes in crabs

Egg Zoea Megalopa Juvenil Adult