Presentation on theme: "CRUSTACEAN DEVELOPMENT I: Life Cycle Bambang Irawan 1 Oktober 2009."— Presentation transcript:
CRUSTACEAN DEVELOPMENT I: Life Cycle Bambang 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 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 thoracopods Have no compound eyes Usually have simple median eye
Metanauplius Metanauplius stage follows the nauplius phase Have only three pairs of functional appendages Have additional segments and nonfunctional appendages
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 J. of Crustacean Biology, 9(2): ).
Pagurus vetaultae; Zoea I – IV dan megalopa (McLaughlin, dkk J. of Crustacean Biology, 11(2): ).
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 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 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