Farming freshwater prawns

FIGURE1The external features of Macrobrachium rosenbergiiNOTE: OTHER CARIDEAN PRAWNS HAVE SIMILAR CHARACTERISTICS BUT SOME (E.G. PANDALUS, CRANGON, PALAEMON) ARE MARINEcephalothorax (‘head’)abdomen (‘tail’)rostrumABCDeyepleuraEtelsonFLuropodschelaeGJKpleopodsMantennagills are belowthis portion ofthe carapaceI2nd abdominalsomite (segment)(see also Figure 7)Hpereiopods (walking legs)SOURCE: EMANUELA D’ANTONIthe adult male has very long second chelipeds in which all segments are elongate andhave blunt spines;the movable finger of the second chelipeds of the adult male is covered by a dense velvet-likefur (except the extreme tip) but this fur is absent from the fixed finger andthe rest of the cheliped; andit is the largest known of all Macrobrachium species, adult males having been reportedwith a total body length of up to 33 cm, and adult females of up to 29 cm.1.2 The shape (external morphology) and othercharacteristics of freshwater prawnsThe following information deals with the general external anatomy of the freshwaterprawn M. rosenbergii, and provides some notes on the function of various major parts ofthe body. Internal morphology (circulatory, respiratory, digestive, excretory, reproductiveand nervous systems) is not covered in this manual, which concentrates on farming, butfurther information is available in the references cited in the introduction to this section.Freshwater prawn eggs of this species are slightly elliptical, with a long axis of 0.6-0.7 mm, and are bright orange in colour until 2-3 days before hatching when they becomegrey-black. This colour change occurs as the embryos utilize their food reserves.Most scientists accept that the larvae go through 11 distinct stages (Uno and Kwon1969) before metamorphosis, each with several distinguishing features which are describedand illustrated in Annex 1. However, from stage VI onwards their size is variable, whichhas led to some workers, notably Ling (1969) to describe only eight stages. Stage I larvaeCHAPTER 13