Optimization of weaning strategy in the climbing perch (Anabas testudineus, Bloch 1792) larvae on growth, survival, digestive, metabolic and stress responses.

A 30-day experiment was carried out to know responses of different weaning approaches to the growth and survival of Anabas testudineus larvae. A total of 10800 larvae (Avg. weight 0.016 ± 0.03 mg; 3DPH) were randomly distributed in nine treatments (triplicates), including two controls. The strategies are as follows: C1 (Control I): feeding with live food (LF) for 30 days and C2 (Control II): feeding with microparticulate diet (MPD) for 30 days; T1: LF for 5 days and MPD for next 25 days; T2: LF for 10 days and MPD for next 20 days; T3: LF for 15 days and MPD for next 15 day; T4: LF for 20 days and MPD for next 10 days; T5: LF for 25 days and MPD for next 5 days; T6: LF for 5 days, then 25% LF replacement by MPD for next 5 days, 50% LF replacement by MPD for next 5 days, 75% LF replacement by MPD for next 5 days, and 100% LF replacement by MPD for last 10 days; and T7: LF for 10 days, then 25% LF replacement by MPD for next 5 days, 50% LF replacement by MPD for next 5 days, 75% LF replacement by MPD for next 5 days, and 100% LF replacement by MPD for last 5 days. Significantly (p < 0.05) higher WG and SGR were recorded in T2 (213.17 ± 0.32, 23.98 ± 0.02) followed by T6, whereas the lowest was found in C2. Significantly higher (p < 0.05) percentage survival was manifested in the T7 (31.83 ± 0.22), followed by T2 (24.75 ± 0.13), and the lowest survival was observed in the C2. The digestive enzyme activities were found to be non-significant (p > 0.05) between different treatment groups. The alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and malate dehydrogenase (MDH) were reported to be significantly higher (p < 0.05) in C2 (68.52 ± 0.08, 19.55 ± 0.10, 21.79 ± 0.04, and 0.044 ± 0.01) followed by T1; however, their reduced level was observed in C1. The activity of superoxide dismutase (SOD), catalase (CAT), glucose, and cortisol levels was observed significantly (p < 0.05) higher in C2 and lower in C1 and T2. As per the finding, it can be recommended that the appropriate weaning time for A. testudineus larvae is from 13 DPH onwards, in which larvae can be fed an initial ten days LF afterward MPD and the best weaning strategy can be adopted as in the T7 group for higher survival percentage.

Feedback regulation of crystal growth by buffering monomer concentration.

Crystallization is a ubiquitous means of self-assembly that can organize matter over length scales orders of magnitude larger than those of the monomer units. Yet crystallization is notoriously difficult to control because it is exquisitely sensitive to monomer concentration, which changes as monomers are depleted during growth. Living cells control crystallization using chemical reaction networks that offset depletion by synthesizing or activating monomers to regulate monomer concentration, stabilizing growth conditions even as depletion rates change, and thus reliably yielding desired products. Using DNA nanotubes as a model system, here we show that coupling a generic reversible bimolecular monomer buffering reaction to a crystallization process leads to reliable growth of large, uniformly sized crystals even when crystal growth rates change over time. Buffering could be applied broadly as a simple means to regulate and sustain batch crystallization and could facilitate the self-assembly of complex, hierarchical synthetic structures.