The limb bud Shh-Fgf feedback loop is terminated by expansion of former ZPA cells

Vertebrate limb outgrowth is driven by a positive feedback loop involving Sonic Hedgehog (Shh), Gremlin, and Fgf4. By overexpressing individual components of the loop at a time after these genes are normally down-regulated in chicken embryos, we found that Shh no longer maintains Gremlin in the posterior limb. Shh-expressing cells and their descendants cannot express Gremlin. The proliferation of these descendants forms a barrier separating the Shh signal from Gremlin-expressing cells, which breaks down the Shh-Fgf4 loop and thereby affects limb size and provides a mechanism explaining regulative properties of the limb bud.     

Differential rescue of light- and food-entrainable circadian rhythms

When food is plentiful, circadian rhythms of animals are powerfully entrained by the light-dark cycle. However, if animals have access to food only during their normal sleep cycle, they will shift most of their circadian rhythms to match the food availability. We studied the basis for entrainment of circadian rhythms by food and light in mice with targeted disruption of the clock gene Bmal1, which lack circadian rhythmicity. Injection of a viral vector containing the Bmal1 gene into the suprachiasmatic nuclei of the hypothalamus restored light-entrainable, but not food-entrainable, circadian rhythms. In contrast, restoration of the Bmal1 gene only in the dorsomedial hypothalamic nucleus restored the ability of animals to entrain to food but not to light. These results demonstrate that the dorsomedial hypothalamus contains a Bmal1-based oscillator that can drive food entrainment of circadian rhythms.     

Regulation of blood and lymphatic vascular separation by signaling proteins SLP-76 and Syk

Lymphatic vessels develop from specialized endothelial cells in preexisting blood vessels, but the molecular signals that regulate this separation are unknown. Here we identify a failure to separate emerging lymphatic vessels from blood vessels in mice lacking the hematopoietic signaling protein SLP-76 or Syk. Blood-lymphatic connections lead to embryonic hemorrhage and arteriovenous shunting. Expression of slp-76 could not be detected in endothelial cells, and blood-filled lymphatics also arose in wild-type mice reconstituted with SLP-76-deficient bone marrow. These studies reveal a hematopoietic signaling pathway required for separation of the two major vascular networks in mammals.     

The effect of dosing with sodium hydroxide (NaOH−) on water pH and growth of Haliotis midae in an abalone serial-use raceway

Abalone culture systems are characterised by high water exchange rates as abalone are sensitive to changes in water quality. To reduce the costs of pumping, serial reuse systems have been tested. As water pH can decline in these systems, this study determined the effect of raising pH through the addition of sodium hydroxide (NaOH^?) on weight gain, length gain and feed conversion ratio of H. midae in a serial-use raceway. Dosing with NaOH^? increased pH by 0.3, 0.27 and 0.21 units at positions 1, 2 and 3 of a serial-pass system, respectively. Weight gain (Wg) and length gain (Lg) were correlated with pH (Wg: F _{1, 16} = 16.35, P = 0.0009, r ² = 0.51; Lg: F _{1, 16} = 16.16, P = 0.0009, r ² = 0.50), and using pH, dissolved oxygen and free ammonia nitrogen as independent variables suggested that water pH was the best predictor for abalone growth.     

Evaluation of limb autotomy as a promising strategy to improve production performances of mud crab (Scylla olivacea) in the soft‐shell farming system

Soft‐shell crab, a newly moulted crab having non‐calcified and hydrated soft exoskeleton, farming has been increasing tremendously in recent years throughout the world due to its high market price and consumer preferences. However, high aggressiveness and cannibalistic behaviour of mud crab limit its culture to an individual chamber system which ultimately makes the soft‐shell mud crab farming space and labour‐intensive. Therefore, the aim of this study was to improve the efficiency of soft‐shell crab production by autotomy of the claw and/or walking legs to reduce the moulting duration and intensify the culture system through double stocking in the existing individual chamber culture system. To achieve our objectives, a series of experiment were conducted at both indoor and on‐farm levels by removing the claw and/or walking legs of Scylla olivacea for two consecutive moulting cycles. Results showed that both claw ablation significantly (p < .01) shortened the moulting duration and increased the carapace width, weight gain, specific growth rate, feeding efficiency and yield parameter compared to the non‐ablated crabs more prominently at 1st moulting than the 2nd moulting in both indoor and on‐farm trials. Ablation of all walking legs while keeping the claw intact did not significantly influence (p > .05) the moulting duration and carapace width, but significantly (p < .01) improved the specific growth rate, weight gain, feeding efficiency and yield parameters at 1st moulting compared to the non‐ablation and unilateral three walking leg ablation groups. However, ablation of all appendages (both claw and walking legs) showed significant (p < .01) improvements of carapace width, weight gain, specific growth rate, feeding efficiency and yield parameters, and shortened the moulting duration up to 23 days from 34 days during 1st moulting and up to 27 days from 40 days at 2nd moulting. The survivals of different autotomized mud crabs were statistically non‐significant (p > .05) to the non‐autotomized crabs in various indoor and on‐farm trials. Besides improving the production performances, ablation of bilateral claw and all appendages allowed to double the stocking density in the existing individual chamber‐based soft‐shell crab farming that enhanced the production about threefold higher than the existing individual chamber‐based culture system. Finally, our results suggest that autotomy could be a promising technology for the commercial farming of soft‐shell mud crab in near future.     

Intercohort cannibalism and parturition-associated behaviour of adult swordtail, Xiphophorus helleri Heckel (Pisces: Poeciliidae)

The post‐parturition behavioural patterns of adult Xiphophorus helleri (Heckel) were described and quantified by recording their duration and/or frequency in glass tanks. All births occurred in the dark. Female behaviour might increase the chance of newborn juvenile survival: at the top of the tank, where juveniles are more vulnerable to predation, the females gave birth in the artificial refuge, while no parturition took place in the refuge at the bottom. Birth‐giving females were no less cannibalistic than males and other females. There was a reduction in cannibalism and the frequency of secondary attacks with time, even though the number of juveniles in the tank continued to increase due to ongoing parturition. Most adults were found at the bottom of the water column during the first 500 min of parturition, after which they were distributed equally in the water column. The movement of adults, away from the bottom and consequently away from the juveniles corresponded with an increase in feeding on alternative food and a reduction in cannibalism. Thus, cannibalism in swordtail might be opportunistic predation.     

Metabolism of the 1,2,4-triazolylmethane fungicides,triadimefon, triadimenol,and diclobutrazol,by Aspergillus niger (van Tiegh.)

Metabolism of the triazolylmethane fungicides triadimefon, triadimenol, and diclobutrazol by Aspergillus niger was studied using a replacement culture technique and ¹⁴C substrates. Components of metabolite mixtures were characterized by TLC, GLC, radio-GC, and GC-MS analyses of the free materials and their trifluoroacetate and trimethylsilyl ether derivatives. The three compounds underwent a common metabolic change involving oxidation of C(CH₃)₃ to C(CH₃)₂CH₂OH. In this work the isopropyl analog of triadimefon, previously reported as a metabolite, was an artifact and resulted from nonbiological oxidation of the corresponding primary alcohol. The fungus also reduced triadimefon to triadimenol, giving a mixture of 1R2S, 1S2R and 1R2R, 1S2S diastereoisomers. The less fungitoxic 1R2S, 1S2R triadimenol predominated, so that this conversion may be directly associated with the relative insensitivity of A. niger to triadimefon. Implications of oxidative and reductive metabolism of these fungicides are suggested with particular reference to the differing fungitoxicities of diastereoisomers and enantiomers.