Interspecies hybrids were produced by artificial insemination of Penaeus monodon females with P. esculentus males. Successful spawnings (those in which some eggs hatched) were achieved from nine of the 17 P. monodon x P. esculentus matings attempted (53%). Mean egg numbers produced ranged from 158,000 to 438,000 but hatch rates were low (< 4% in all cases). Cumulative survival of the hybrids and both parental species was similar, and around 30% at 4 weeks. There was no indication of hybrid vigour for growth. However, growth rate of hybrid larvae (0.048 g day(-1)), was the same as those of pure P. monodon (0.047 g day(-1)) and significantly greater than that of P. esculentus larvae (0.033 g day(-1)). The relative growth rate among parental species and the hybrids was determined accurately by rearing progeny of pure and hybrid matings in parallel under controlled conditions. The colour pattern of the hybrids was intermediate between that of P. monodon and P. esculentus. Sex ratio was significantly skewed in favour of males in the hybrids (proportion of males was 0.86 compared with 0.56 in the parental species), possibly suggesting females are the heterogametic sex in penaeids. The hybrids had the fast growth rate of P. monodon, and some of the attractive colour pattern of P. esculentus. Crown Copyright (C) 2001 Published by Elsevier Science B.V. All rights reserved.
