The entomopathogenic nematode-bacterium complex Heterorhabditis bacteriophora-Photorhabdus luminescens is used in commercial biocontrol of insect pests. Tolerance and activity of the nematodes at extreme environmental conditions can limit the shelf life, quality and field performance of nematode-based products. To overcome these limitations, the potential for genetic improvement of the heat tolerance and the activity at low temperature was investigated. Heat tolerance and cold activity are quantitative traits, influenced by several genes and environmental factors. The breeding success for such traits depends on the genetic proportion on the phenotypic variability, the heritability, which was determined by recording the variability within and between homozygous inbred lines. The heritability for heat tolerance was 0.68 and for activity at low temperature 0.38. To increase heat tolerance, 4 selection steps were carried out, which increased the mean tolerated temperature from 38.5 to 39.2°C. The mean temperature at which the dauer juveniles of H. bacteriophora were active, could be reduced from 7.3 to 6.1°C during the first 5 selection steps. However, for unknown reasons, it increased during the following 5 steps to 7.1°C. A screening among different P. luminescens isolates for growth at low temperature resulted in several cold-adapted strains from North America, which reached considerable cell density at 6°C.

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The nematode Panagrolaimus sp. was tested as live feed to replace Artemia nauplii during first larval stages of whiteleg shrimp Litopenaeus vannamei. In Trial 1, shrimp larvae were fed one of four diets from Zoea 2 to Postlarva 1 (PL1): (A) Artemia nauplii, control treatment; (NC) nematodes enriched in docosahexaenoic acid (DHA) provided by the dinoflagellate Crypthecodinium cohnii; (N) non-enriched nematodes; and (Algae) a mixture of microalgae supplemented in C. cohnii cells. In Trial 2, shrimp were fed (A), (NC) and a different treatment (NS) with nematodes enriched in polyunsaturated fatty acids (PUFAs) provided by the commercial product S.presso ® , until Postlarva 6 (PL6). Mysis 1 larvae fed nematodes of the three dietary treatments were 300 μm longer (3.2 ± 0.3 mm) than control larvae. At PL1, control shrimp were 300 μm longer (4.5 ± 0.3 mm) than those fed DHA-enriched or PUFAs-enriched nematodes. No differences were observed in length and survival at PL6 between control larvae and those fed DHA-enriched nematodes (5.1 ± 0.5 mm; 33.1%-44.4%). Shrimp fed microalgae showed a delay in development at PL1. This work is the first demonstration of Panagrolaimus sp. suitability as a complete substitute for Artemia in rearing shrimp from Zoea 2 to PL6. K E Y W O R D S Crypthecodinium cohnii, docosahexaenoic acid enrichment, Litopenaeus vannamei, nematode, Panagrolaimus sp., shrimp feeding How to cite this article: Seychelles LH, Happe S, Palacios E, et al. Successful rearing of whiteleg shrimp Litopenaeus vannamei larvae fed a desiccation-tolerant nematode to replace Artemia. Aquacult Nutr. 2018;24:903-910. https://doi.