Presentation on theme: "CRUSTACEAN DEVELOPMENT I: Life Cycle"— Presentation transcript:
1 CRUSTACEAN DEVELOPMENT I: Life Cycle Bambang Irawan1 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 appendagesIn 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 segmentsThose 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 telsonIn the course of successive molts, additional segments and appendages are gradually acquired until the adult condition is achieveAnterior segment and their appendages are added first.
4 CRUSRACEAN LARVAECrustacean taxa have many larval stages, which tend to have different names in each taxonThe basic crustacean larvae are: nauplius, zoea, and megalopaSome authors differentiate the zoeal stage base on its development: protozoea, zoea, mysis.In some taxa there is metanauplius between nauplial and zoeal stage.
5 NaupliusIn Greek mythology Nauplius is the name of the son of Poseidon and Amymone,Nauplia is the name of a descendant of NaupliusIn Biology nauplius the name of a stage in crustacean larval development, the first laval stageNauplius is singtular case, the plural case is naupliiIt 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 charactersA prominent characteristic of nauplii is that they have only one compound eye, which will divide in two in later stagesNauplii have three pairs of cephalic appendages with which they swim; in the adult these become the antennules, the antennae, and the mandiblesThe 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 thoracopodsHave no compound eyesUsually have simple median eye
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 appendagesIt often has spikes on its carapace which may assist these small organisms in maintaining directional swimmingIn many decapods, due to their accelerated development, the zoea is the first larval stageIn 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 thoracopodsUsually have a pair of compound eyes
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 formedComplate set of head appendages and first two maxillipedsUpon 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 pereopodsAll of thoracopods have large exopods, which become locomotory appendages The larvae now swim backwardsBody vertical with the telson upSlowly spinning on the vertical axisThe carapace more closely and covers most of the thoracic somitsThe antennae have lost their locomotion function
19 Post larvaComplete complement of segments and appendages, including the abdomen and pleopodsStill small, does not closely resemble the adult, and is not sexually mature
20 MegalopaComplate set of head, thoracic, and abdominal appendages and segmentsMostly benthicMacroscopic and more like the adultThe most significant charater is in having at leat one pair of natatory pleopod