Farming freshwater prawns A manual for the culture of ... - eXtension

FIGURE3
How to sex juvenile Macrobrachium rosenbergii
NOTE: EXAMINE THE VENTRAL SIDE OF THE FIRST
SOMITE (SEGMENT) OF THE ABDOMEN; MALES
HAVE A LUMP OR POINT IN THE CENTRE OF
THE SOMITE WHICH CAN BE FELT WITH
THE FINGER
1. ventral view of 1
A
st
abdominal somite of
male and female
2. B ventral view of 2 nd
abdominal somites
C3. towards the head
D
D4. cross section of male
1 st abdominal segment
C
C
A
A
B
B
SOURCE: EMANUELA D’ANTONI, AFTER MARIO PEDINI
Figure 4
Notice that the
abdominal pleura
of the two
females with
this BC male
Macrobrachium
rosenbergii are
enlarged to
accommodate
eggs (Brazil)
to younger juveniles, the prawns are much older. The third type of males are known as
orange claw males (OC). OC males have golden coloured claws, which are 30 to 70% shorter
than the claws of BC males. The three major types of males can generally be distinguished
by sight. However, more reliable ways of determining which type males are can be
found in Karplus, Malecha and Sagi (2000). As mentioned, a number of intermediate male
forms have also been recognized, including weak orange claw (WOC), strong orange claw
(SOC) and transforming orange
claw (TOC) males. The relationship
and transformation of these
various male types, and their
importance in size management is
covered later in this manual
(Annex 8).
Many people find it hard to
distinguish between Macrobrachium
and penaeid (marine) shrimp,
once they have been harvested
and the heads have been removed.
If the ‘tail’ still retains its shell
there are, in fact, two easy ways of
distinguishing them (Fincham
and Wickins, 1976). Firstly,
SOURCE: EUDES CORREIA
CHAPTER 1
7