非洲桃花心木国内外研究现状与发展建议

文章从引种、种子贮藏与繁殖技术、林木遗传改良、人工林培育、木质产品和非木质产品的利用、病虫害防治等几个方面,总结了国内外非洲桃花心木研究的现状,并对中国发展非洲桃花心木提出了几点建议。     

不同种源非洲桃花心木苗期抗寒能力和生长节律研究

2008年1月上旬至2009年7月下旬,对非洲引进的3个桃花心木种源的幼树进行每周1次的观测.结果显示:种源间抗寒能力、树高生长和地径生长以及速生期都存在明显差异.种源3-1324与4-1325在苗期表现出一定的抗寒性,种源1-1320苗期对低温敏感.总体上,非洲桃花心木幼树1年抽梢4～7次,1～2月为树高生长休眠期,...     

非洲桃花心木大树移植的生长效应研究

大树移植是现代城市园林植物景观建设中常见的栽培措施.对不同移植年龄的非洲桃花心木大树移植后的生长情况、受寒害程度以及寒害后的恢复生长情况进行研究.结果表明,非洲桃花心木的生长在不同移植年龄有显著差异;不同移植年龄的1～2年生平均粗度在14.5～19.5 mm的枝条均受到寒害而枯,受伤枝条平均长度范围为0.79～0.88 m;寒害后,不同株间的萌芽数差异较大,但各个方向的枝条生长无显著差异,不同季节间的枝条生长存在极显著差异,且春夏的粗度、长度极显著大于秋冬的粗度、长度.     

The whole amino acid profile as indicator of the nutritional condition in cultured marine fish larvae

The effect of variations in the amount or quality of food provided on the amino acid profile of larvae, was tested in two marine fish species, the Senegal sole (Solea senegalensis) and the sea bass (Dicentrarchus labrax). The objective was to assess whether such nutritionally suboptimum dietary patterns, which simulate situations that may occur in hatcheries, result in variations in the concentration of one or more amino acids that could be used as indicators of nutritional condition of larvae. Restriction in the normal food ration by 60% had no clear effect on the amino acid profile of sea bass, while the concentration of some amino acids (Arg, Ala and Phe) showed significant variations in sole. Feeding on artificial diets, which have shown their inadequacy a priori, resulted also in no significant effect on the profile of sea bass, but in a dramatic modification of the amino acid profile in sole. In addition, changes in the amino acid profiles considered as a whole were evaluated using the cluster analysis instead of paired comparisons between amino acid concentrations in each treatment. The analysis clearly separated profiles of larvae fed restrictedly or inadequately from their controls, irrespective of the species. This demonstrated the potential value of evaluating whole changes in amino acid profile as nutritional indicator. Besides, it was demonstrated that sensitivity of larvae to nutritional changes that may be reflected in the amino acid profile is greatly conditioned by the species and developmental stage.     

Tolerance response to water pH in larvae of two marine fish species, gilthead seabream, Sparus aurata (L.) and Senegal sole, Solea senegalensis (Kaup), during development

Gilthead seabream, Sparus aurata (L.) and Senegal sole, Solea senegalensis (Kaup) are two fish of primary importance in Mediterranean aquaculture. In the present study, the larvae of these species were exposed to different rearing‐water pH during 24 h to examine their tolerance. The 24‐h pHL50 values were calculated with low and high pH values at 7, 20 and 32 days after hatching (DAH) in S. senegalensis larvae, and 12, 20 and 52 DAH in S. aurata larvae. Low 24‐h pHL50 values ranged between 4.88 and 5.76, whereas high 24‐h pHL50 values ranged between 8.94 and 9.57 in S. senegalensis larvae. S. aurata larvae showed values of low 24‐h pHL50 that ranged between 4.82 and 5.55, whereas values of high 24‐h pHL50 ranged between 8.66 and 9.26. Both species showed similar tolerance response at all the tested ages. The high 24‐h pHL50 values found were close to pH values that eventually can be reached in the rearing tanks. The pH should be carefully controlled in rearing water during the first development stages of both species.     

Cholecalciferol-induced bait shyness in possums (Trichosurus vulpecula)

Cholecalciferol (vitamin D₃) is used in a variety of bait formulations to control populations of the brushtail possum (Trichosurus vulpecula), an introduced pest that seriously damages and threatens primary production and native biota in New Zealand. In cage trials, possums readily ate sublethal baits containing either an estimated LD₁₅ or LD₄₀ dose of cholecalciferol, leading to a depression of appetite that lasted for 7-15 days. When lethal quantities of baits were presented 21-30 days after the initial LD₁₅ or LD₄₀ baits, 40 and 88% of possums survived, respectively, compared with a 21% survival rate among naive possums, and bait consumption was also reduced among survivors of the initial baits. Subsequent switching of the bait base to a gel was partially successful in overcoming bait shyness, killing 40% of one group (formed by pooling the original groups), while switching both the bait type (to gel) and the toxicant (to 1080) resulted in a 63% mortality rate in a second group. By comparison, 95 and 100% of naive groups were killed by cholecalciferol and 1080 gel respectively. Practical measures are identified for both avoiding and overcoming bait shyness based on the use of alternative bait types and toxicants.     

Superoxide dismutase and catalase activities in Photobacterium damselae ssp. piscicida

The ability of a set of Photobacterium damselae ssp. piscicida strains isolated from different fish species to produce different superoxide dismutase (SOD) and catalase enzymes was determined. Unlike other bacterial pathogens, P. damselae ssp. piscicida is not able to produce different isoforms of SOD or catalase containing different metal cofactors when cultured under oxidative stress induced by hydrogen peroxide or methyl viologen, or under iron depleted conditions. However, iron content of the growth medium influenced the levels of SOD and catalase activity in cells, these levels decreasing with iron availability of the medium. Comparison of virulent and non-virulent strains of P. damselae ssp. piscicida showed similar contents of SOD, but higher levels of catalase were detected in cells of the virulent strain. Incubation of bacteria with sole, Solea senegalensis (Kaup), phagocytes has shown that survival rates range from 19% to 62%, these rates being higher for the virulent strain. The increased levels of catalase activity detected in the virulent strain indicates a possible role for this enzyme in bacterial survival.     

Growth, stress response and free amino acid levels in Senegalese sole (Solea senegalensis Kaup 1858) chronically exposed to exogenous ammonia

Stressful husbandry conditions are likely to affect growth and amino acid metabolism in fish. In this study, chronic ammonia exposure was used to test the effects of a stressor on growth and amino acid metabolism of Senegalese sole juveniles. The fish were exposed for 52 days to 11.6 mg L⁻¹ [low‐TAN (L‐TAN)] or 23.2 mg L⁻¹ [high‐TAN (H‐TAN)] of total ammonia nitrogen (TAN), or to 0 mg L⁻¹ (Control). Growth in L‐TAN groups was slightly but significantly different from the Control groups [relative growth rate (RGR=0.35±0.13 and 0.52±0.23% day⁻¹ respectively)]. In H‐TAN groups, growth was severely affected (RGR=0.01±0.13% day⁻¹). Stress parameters (plasma cortisol and glucose) showed slight or no significant differences between treatments. Plasma free amino acid (FAA) concentrations were affected after H‐TAN treatment. Increases in glutamine and aspartate concentrations in H‐TAN fish suggest alterations in amino acid metabolism related to nitrogen excretion processes. Some of the changes in FAA concentrations also suggest mobilization to energy supply and synthesis of metabolites related to stress response. Therefore, Senegalese sole seem to adapt to the L‐TAN concentration tested, but the H‐TAN concentration reduced growth and affected amino acid metabolism.     

Selenium supplementation changes glutathione peroxidase activity and thyroid hormone production in Senegalese sole (Solea senegalensis) larvae

Dietary selenium (Se) influences the glutathione peroxidase (GPx) activity and the thyroid hormone system in vertebrates, but these relations are poorly described in fish. The present study aimed to evaluate the effect of Se supplementation on Senegalese sole larvae, focusing on GPx activity and thyroid status. Two groups of larvae were fed on either control (C) or Se‐enriched live feed, from 2 days after hatch (DAH) until 34 DAH. Senegalese sole larvae fed Se‐enriched live feed significantly increased their whole‐body Se, compared to larvae from C group. The activity of GPx was higher in larvae from Se group, suggesting that the levels of this mineral were suboptimal in the control diet. TH levels were also higher in larvae fed Se‐enriched live feed, suggesting that Se may have a positive influence on the TH production in early life stages of marine fish larvae.     

Thyroid gland development in Senegalese sole (Solea senegalensis Kaup 1858) during early life stages: A histochemical and immunohistochemical approach

A key to success in the culture of marine fish species is the mass production of high quality fry, a process largely dependent on successful first feeding and normal development and growth of fish larvae. In this regard it is important to examine the structural and functional development of the endocrine system (pituitary, thyroid, interrenal glands) during early ontogeny of marine fish. Particularly, the thyroid hormones, thyroxine (T₄) and triiodothyronine (T₃), influence numerous metabolic processes, such as growth, differentiation, metamorphosis, reproduction, respiration, migratory behaviour, central nervous system activity, seasonal adaptation, etc. Therefore the aim of this study was to describe the development of the thyroid gland and the ontogeny appearance of the thyroid hormones in Solea senegalensis larvae by means of histological and immunohistochemical techniques. The first thyroid follicle was present at 4 days-post-hatch (dph) coinciding with first feeding. During metamorphosis (12–20 dph) the follicles increased in both number and size, and by 30 dph presented the same characteristics as that seen in adult fish. Tissue immunostaining of both thyroid hormones decreased during the endogenous larvae development to nearly undetectable levels at the completion of yolk-sac absorption. During larvae exogenous phase, T₃ and T₄ immunostaining was first detected by 6 dph and an increase of specific staining for both hormones was detected between 12 and 20 dph, during metamorphosis phase.