DEVELOPMENT AND CHARACTERIZATION OF GENETIC STOCKS AND THEIR HYBRIDS IN Macrobrachium rosenbergii: PHYSIOLOGICAL RESPONSES AND LARVAL DEVELOPMENT RATES

Abstract

ABSTRACTSeveral genetic stocks of Macrobrachium rosenbergii were examined with respect to their physiological responses to different laboratory culture environments as juveniles and their development rates as larvae. Results indicate that physiological genetic differences exist between these genotypes and that these differences may be important for genetic improvement. Early growth rates for Thai, Sarawak, and Australian stocks were compared to those for the Anuenue stock (originally brought from Malaysia) at 19, 23, and 29°C. Growth at 19°C was very poor for all genotypes. At 23 and 29°C the Anuenue strain grew faster than the Thai and Australian strains and about equal to the Sarawak strain.Growth of Anuenue, Australian, Thai and Sarawak strains at 0, 5, and 10 ppt salinities was also compared. The Anuenue and Thai strains grew as well at 5 ppt as in freshwater while 10 ppt significantly depressed growth. In the Australian and Sarawak groups growth was depressed in both 5 and 10 ppt treatments.Temperature tolerance was found to increase with age for all strains although the Anuenue strain appeared to be the most tolerant to low temperatures. The prawns were tested just after metamorphosis at two weeks post‐metamorphosis and one month post‐metamorphosis.Tolerance to high pH was tested for the Anuenue and found to increase with age. Mortality at a pH of 9.5 at 29°C went from 80% for newly metamorphosed juveniles to 43% for two‐week‐old animals and 50% for one‐month‐old animals.Among the “pure” strains only the Australian strain showed significantly faster development times in replicated trials. The first Australian postlarvae appeared after an average of 15.5 days and 95% metamorphosed after 20.5 days compared to 24 and 32 days for the Anuenue strain. In unreplicated trials involving hybrids between Anuenue stocks and over two dozen other stocks only the Australian‐Anuenue hybrid showed faster larval development times with time to 95% settling at 35 days compared to 47 days for the Anuenue controls.