Asian seabass (Lates calcarifer) larval rearing using cyclopoid copepod (Apocyclops royi) live feed: A new approach

Abstract Background The Apocyclops species are gaining importance as suitable live feed for augmenting growth and survival of marine finfish larvae. In the present study, as a new approach Apocyclops royi is mass cultured using monoalgal diet (Chloroidium saccharophilum) and its nutritive value is assed and used as supplementary diet in the Asian seabass Lates calcarifer larval rearing. Results Mass culture of A. royi with C. saccharophilum diet reached population density of 12,700 ± 454 ind./L on 21 days culture period. A. royi showed high ratio of DHA:EPA and EPA: ARA. Rearing experiments of the Asian seabass (Lates. calcarifer) 11 DPH larvae with copepod, Artimia nauplii and their combination diets recorded faster growth and maximum survival (90%) with A. royi + Artemia nauplii diet compared to A. royi and Artemia nauplii lone feeds. Seabass larval length and weight gain showed significant (p < 0.05) difference among the three dietary treatments. Significantly high content of essential fatty acids in the L. calcarifer larvae have been reported in A. royi + Artemia nauplii fed seabass larvae compared to individual A. royi and Artemia nauplii fed larvae. Conclusions Our finding highlights the importance of incorporating A. royi as a supplementary feed for seabass larvae, which will bring improvement in their growth and survival leading to sustainable seed production of this fish

Efficacy of Apocyclops royi (Cyclopoida, Copepoda) Nauplii as Live Prey for the First Feeding Larvae of Silver Pompano, Trachinotus blochii (Lacepède, 1801)

In the rearing of first exogenous feeding, marine finfish larvae availability of live prey with suitable size and nutritive content is vital for their growth and survival. Copepods represent an important alternative food to present traditional live feed organisms used in marine fish hatcheries. Use of copepods is known to improve survival, growth, and development of fish larvae. The silver pompano, Trachinotus blochii (Lacepède, 1801) is one of the suitable candidate species for aquaculture due to its fast growth, good meat quality and high market demand. The present study aimed to investigate the efficacy of Apocyclops royi nauplii in the rearing of first feeding larvae of T. blochii. The feeding experiments were conducted from 3 to 7 Day Post Hatch (DPH) using A. royi nauplii and Brachionus plicatilis (s type) diets. Higher growth of T. blochii larvae was evident with A. royi nauplii than that of rotifer diet. The A. royi nauplii fed experimental group of T. blochii larvae showed significantly different length (p &lt;0.05) compared to rotifer fed larvae and the specific growth rate recorded was 29.42% and 24.28% in A. royi and rotifers fed experimental groups, respectively. On 7 DPH, A. royi nauplii fed T. blochii larvae showed higher mortality than rotifer fed group. With A. royi feed T. blochii larvae produced higher pigmentation which gradually started on the head and dorsal surface of the body from 3 DPH onwards and spread all over the body and became intense as the larvae grew to 7 DPH. Our results suggest the A. royi nauplii are suitable live prey for the T. blochii larvae during the initial feeding phase for better growth and pigmentation

What Determines Successful Colonization and Expression of Biocontrol Traits at the Belowground Level?

Editor: Antonieta De Cal, Paloma Melgarejo, Naresh Magan.Plants and their associated microbial communities are continuously interacting. The consequences of this complex, multi-actor dialogue are of utmost relevance for the health and development of the plant holobiont. The plant-associated microbiota is a natural source of microorganisms with plant growth-promoting abilities, including biological control agents (BCA). Plant roots are the main entrance for soilborne phytopathogens, which are also components of the belowground plant-associated microbiota. Successful root colonization by BCA is thus key for effective biocontrol against these pathogens. Colonization and biocontrol are complex processes influenced by many (a)biotic factors. Upon colonization of the target niche, effective biocontrol is then the result of diverse modes of action that BCA may display, thereby eliminating pathogens’ propagules, reducing their number, or alleviating their deleterious effects. These mechanisms are not mutually exclusive and can operate either individually or in combination, varying in time and space. Inconsistencies usually observed in biocontrol effectiveness is a consequence of numerous (a)biotic and environmental factors affecting BCA performance. A more comprehensive knowledge of colonization processes and biocontrol modes of action of BCA, and that of the diverse factors influencing them, is now possible with the support of the currently-available -omics approaches. They will definitively offer a more holistic perspective that will help to overcome the lack of success sometimes observed when implementing biocontrol measures, particularly at the field scale.Our work is currently supported by grant AGL2016-75729-C2-1-R from the Spanish Ministerio de Economía, Industria y Competitividad/Agencia Estatal de Investigación, co-financed by the European Regional Development Fund (ERDF), and by the Horizon 2020 Project ‘Microbial Uptakes for Sustainable Management of Major Banana Pests and Diseases’ (MUSA; grant number 727624)