A 50-day growth trial was conducted to evaluate the efficacy of Chlorella vulgaris (Beijerinck) as an ingredient in the diets of giant freshwater prawn Macrobrachium rosenbergii (De Man) postlarvae (PL30). Immune response (total haemocyte count and prophenoloxidase activity) was also assessed by subjecting postlarvae to a challenge test against Aeromonas hydrophila (Chester) for 14 days. Isonitrogenous and iso-lipidic test diets were prepared using a fishmeal-based-positive control diet (D0) and four basal diets with inclusion levels of 2% (D2), 4% (D4), 6% (D6) and 8% (D8) C. vulgaris. Postlarvae of M. rosenbergii were randomly stocked (mean initial body weight of 0.19 AE 0.02 g) in 30-L tanks in three replicates per dietary treatment for evaluation of growth performance. Another set of postlarvae (mean initial body weight of 1.25 AE 0.02 g) was randomly distributed in 95-L tanks in three replicates per dietary treatment for the assessment of immune response. Results showed that specific growth rate was significantly higher (P < 0.05) in postlarvae fed D4 and D6. Variations in values for carcass protein, lipid, moisture and ash were also evident. Postlarvae fed diets with Chlorella showed increased prophenol oxidase activity and total haemocyte counts. Moreover, survival rate after challenge with A. hydrophila was significantly increased (P < 0.05). Inclusion of C. vulgaris in diets enhanced immune response and resistance of M. rosenbergii postlarvae against A. hydrophila infection.

A feeding trial was conducted to evaluate the effects of Spirulina (Arthrospira platensis) inclusion in experimental diets of juvenile Nile tilapia (Oreochromis niloticus). Iso-nitrogenous and iso-lipidic diets were prepared using a positive control diet (S0) and four basal diets with A. platensis at 30 % (S30), 45 % (S45), 60 % (S60), and 75 % (S75) inclusion levels. Experimental diets were randomly assigned to tanks (13.35 kg m −3 ) with initial body weight of 0.89±0.02 g in triplicates.The results of the feeding trial demonstrated significantly improved (P < 0.05) growth performance and hepatosomatic and viscerosomatic indices of fish fed S30. Blood chemical profile also indicated desirable values in fish fed A. platensis diets as compared to fish fed S0. On the contrary, fish fed S75 exhibited significantly reduced fish growth. Blood chemical analysis showed significant difference (P<0.05) in levels of plasma triglyceride. Results of the present work indicate that 30 % A. platensis inclusion is deemed the optimal level of dietary replacement for increased growth performance, improved feed utilization efficiency, and enhanced overall health status of Nile tilapia juveniles.

An entomopathogenic nematode, Heterorhabditis H39, was found in Darwin, Australia. Based on morphological and morphometric similarities, and molecular characterisation, it is an isolate of Heterorhabditis bacteriophora. Males, hermaphrodites, females and juveniles showed important similarities on most characters that define H. bacteriophora. The morphometrics of the infective juvenile of Heterorhabditis H39 are similar to those of H. bacteriophora, including average body length (562 (537-587) vs 570 (520-600) µm), maximum body width (21 (19-22) vs 24 (21-31) µm), distance from the anterior end to the EP (96 (87-104) vs 104 (94-109) µm) and tail length (101 (94-111) vs 91 (83-99) µm). The morphology of the spicules and gubernaculum of male Heterorhabditis H39 are indistinguishable from those of H. bacteriophora. The biology and life cycle of Heterorhabditis H39 are similar to those of other Heterorhabditis species. The Neighbour-Joining Tree based on 475 nucleotides of the SSU rRNA gene showed that Heterorhabditis H39 formed a monophyletic group with other H. bacteriophora isolates with a bootstrap value of 100. Thus, phylogenetic study of SSU sequence data provided strong evidence that Heterorhabditis H39 is an isolate of H. bacteriophora. This is the first record of H. bacteriophora in northern Australia.