Morpho-genetic characterization of morphotypes of the giant freshwater prawn, Macrobrachium rosenbergii

Abstract

Different morphotypes of Macrobrachium rosenbergii show variations in growth. The
objective of the study is to characterize the morphological and genetic variations in M.
rosenbergii male and female morphotypes. Juveniles of M. rosenbergii (average body wt.
5.33±0.72 g) were stocked in an earthen pond at a stocking density of 20,000 per hectare and
reared for five months using shrimp quality feed. After harvesting, males were characterized into
three morphotypes such as blue- and orange-clawed males (BC and OC, respectively) and small
males (SM) based on color and claw length. Here, morphometric characteristics of the BC
morphotype demonstrated significantly higher (p<0.05) values followed by OC, SM, and
females. Likely, the proportion of CL and BL were found to be highest in the OC morphotype
(1.25±0.01) followed by BC (1.16±0.10), SM (0.84±0.10), and female morphotypes
(0.64±0.16). For the genetic variation study, four allozyme enzymes were screened that were
encoded by six loci (Ldh-1*, Mdh-1*, Mdh-1*, Pgm*, Gpi-2*, and Gpi-2*). Two loci, Gpi-1*
and Pgm* showed polymorphism (p<0.05) in all morphotypes. The observed (Ho) and expected
(He) heterozygosities were higher in the BC morphotype followed by OC, female and SM. In the
UPGMA dendrogram, the BC morphotype made a one cluster and was differentiated from other
morphotypes by the genetic distance D=0.0047. The results suggest that considerable
morphogenetic variations existed in BC, OC and SM morphotypes even though they were
siblings.