Effects of a diatom Thalassiosira spp. supplements on nursing of blue swimming crab (Portunuspelagicus) larvae from zoea I, II, III and IV stages. The results showed that average survival rates of crab larvae fed with Thalassiosira spp. + zooplankton (rotifers, Branchionus sp. and Artemia nauplii) were 93.33 ± 4.04, 79.66 ± 17.24, 72.66 ± 6.65 and 59.66 ± 2.08 %, respectively. The average duration of larval development from zoea I to IV stages was 8.3 ± 0.5 days. Their average survival rates and larval development were compared with those crab larvae fed with Chlorella sp. and Chaetoceros spp. + zooplankton. Results showed that average survival rates and larval development of crab in each treatment were not significant difference (P > 0.05). The results clearly showed that a diatom Thalassiosira spp. could be used for nursed blue swimming crab larvae.