Potential of Cactoblastis cactorum as a Vector for Fungi Pathogenic to Pricklypear, Opuntia inermis

In Australia, fungi associated with larvae of the biological control agent Cactoblastis cactorum may contribute to the control of the exotic weed pricklypear (Opuntia inermis). C. cactorum larvae were assessed for their ability to vector pathogenic fungi into O. inermis by the infestation of larvae with fungal suspensions. Six fungal isolates caused disease after being carried into the host on external surfaces of larvae, and propagules of one isolate (UQ5109) initiated disease after being transferred from the cladode epidermis into the host by larvae feeding on the plant. Scanning electron microscopy revealed extensive hyphal growth on the external surfaces of larvae infested with several of the isolates. Fungi isolated from field-grown O. inermis cladodes were tested for pathogenicity to this plant in an in vivo plant assay. In total, 152 isolates were screened, 22 of which infected the host in pathogenicity tests. Only 1 (UQ5115) infected undamaged host tissue, whereas the remainder required the host to be wounded before infection could proceed. The majority of isolates were only weakly pathogenic, even when inoculated via wounds, suggesting that most were either saprophytes or weak parasites. This study demonstrates that it is possible for larvae of C. cactorum to transmit fungal pathogens into O. inermis tissue and it has provided a sound basis for future field work to determine the contribution that fungi make to the control of O. inermis.     

无芒雀麦种子产量因子与产量的相关和通径分析

采用多因素正交试验设计,通过大样本相关、通径和逐步回归分析后表明,无芒雀麦5个种子产量因子对种子产量的直接贡献大小排序为:生殖枝数/m 2＞种子粒数/小穗＞小花数/小穗＞单粒种子重＞小穗数/生殖枝;提高小花数/小穗和种子粒数/小穗可最有效提高无芒雀麦的种子产量,其次是提高生殖枝数/m2.     

Plasma and ovarian thyroxine levels in relation to sexual maturation and gestation in female Sebastes inermis

Plasma T₄ (L-thyroxine) concentrations in the viviparous rockfish Sebastes inermis showed a peak (119·3±27·8 ng ml⁻¹) during the development of embryos. Ovarian T₄ concentrations increased during vitellogenesis and final maturation and decreased during embryogenesis.However, total T₄ content within the ovary increased continuously up to the larval stages. Plasma oestradiol-17β, (E₂) concentrations peaked at the final maturation stage and then recovered to the level seen during the non-reproductive periods. Plasma testosterone (T) concentrations showed a peak (5·33±1·08 ng ml⁻¹) at the embryo stage and high levels were maintained throughout the gestation period. Plasma T₄ concentrations during the embryo stage and ovarian T₄ content during vitellogenesis were much higher than the levels reported in oviparous fishes. These data suggest that in viviparous rockfish, T₄ may be required for sustaining gestation or embryo development within the maternal body. In addition, the high content of total T₄ in the ovary implies that there probably does exist a maternal-embryo relationship during gestation as well as during vitellogenesis.     

Do benthic and planktonic diatoms produce equivalent effects in crustaceans?

Hippolyte inermis Leach 1814 is a benthic shrimp characterized by a peculiar mechanism of sex reversal influenced by diatom foods. In fact, the appearance of primary females in spring is due to an apoptotic early disruption of the androgenic gland and of the male gonad, triggered by still unknown compounds present in diatoms of the genus Cocconeis. The influence of diatoms on the reproductive ecology and life cycle of planktonic crustaceans has been demonstrated previously: some planktonic diatoms produce aldehydes inducing apoptosis in the embryos and in the larvae of marine copepods, reducing their viability. Both benthic and planktonic diatoms therefore produce compounds having an apoptotic effect on some tissues of target crustaceans, although the ecological significance of the two processes is different: deleterious for copepod populations, regulative for shrimps associated with Posidonia oceanica. In the present article we experimentally administered specific planktonic diatoms, their fractions and compounds known to induce apoptosis in planktonic copepods, to H. inermis postlarvae, to check whether the apoptotic effect is due to an identical family of diatom compounds, and to establish whether the processes observed in the plankton and in the benthos, respectively, are analogous or homologous, from an ecological point of view. Our results indicated that diatom compounds acting in the two systems are different, since both planktonic diatoms and their aldehydes had negligible effects on the sex ratios of cultured shrimps.     

Asymmetric Somatic Hybridization Between Wheat (Triticum aestivum) and Bromus inermis

Asymmetric hybridization was conducted between wheat and Brorrats inermis keyss which is a distanfiy related intergeneric plant (belonging to different tribe) of wheat and possesses some favorable traits, such as resistant to cold, drought and disease. Protoplasts isolated from young embryo-derived calli of common wheat ( Triticura aestivum L., tv. 99P, (AABBDD), 2n = 42) were fused with UV-treated protoplasts isolated from young embryo-derived calli of Bromus inermis by PEG method. Three clones (No. 1 ~ No. 3) were regenerated from the fusion products and differentiated into albino seedlings. The clones and the seedlings were all verified as hybrids by chromosome counting, isozyme and RAPD analysis. Their isozyme and RAPD pattern contained the characteristic bands of both parents as well as new band(s). The chromosome numbers of albino were in the range of 42~54 with small chromosomes of Bromus inerm/s and chromosome fragments. The above results confirmed that hybrid albinos were obtained.     

盐城獐种群生存力的初步分析

本文采用Ｖｏｒｔｅｘ６．０计算机程序对盐城獐（Ｈｙｄｒｏｐｔｅｓｉｎｅｒｍｉｓ）种群的生存力进行了分析。结果表明：若无狩猎和海潮侵袭的影响,在能容纳５００头獐的栖息地中,盐城獐可长期生存。如狩猎死亡率达５％和１０％,拥有１００～２００头獐的种群分别在３２～５０年和１５～２７年内灭绝率超过５％;拥有３００～５００头的现存种群分别在９０～９５年和２９～４２年内灭绝率超过５％。在有海潮侵袭的栖息地中,不管现存种群多大,在未来２５年左右的时间内种群灭绝率大于５％,在５０年内种群绝灭的可能性超过５０％。根据该地的实际情况,建议在无海潮侵袭的堤内选择至少能容纳２００头獐的栖息地和在相临的堤外选择能容纳５００头獐的栖息地建立保护区,才能保证盐城獐种群长期生存。     

苔藓植物耐旱机制研究进展

耐旱藓类快速脱水并存活的能力可由快速建立起来的对环境变化的耐受机制来反映,保护细胞完整性的组成型机制与修复细胞损伤的诱导机制协同作用使苔藓植物渡过干旱胁迫.再水化时光合系统原初恢复非常迅速;ABA处理可显著改变PSⅡ的生理特征;基因表达的变化主要由翻译调控引起;脱水组织中贮存mRNPs既保护了mRNAs,又加快了再水化修复速度.山墙藓(Tortula ruralis)是耐旱研究较多的一个种,已建立了表达序列文库(EST),将会成为耐旱研究的重要模式植物.     

獐在吉林省的重新发现

獐(Hydropotes inermis)在历史上曾广泛分布于中国的辽东半岛、华北平原及长江两岸,在1949年以后的多篇文献中没有发现对吉林省獐分布的记载。2017年12月至2018年3月,利用红外相机于吉林省白山市(原浑江市)白山原麝国家级自然保护区拍摄到獐有效照片21张,有效视频时长总计600 s。在后续的野外调查中,研究者现场拍摄到獐幼崽活体及大量獐的活动痕迹,确认獐在吉林省重新发现。     

江苏盐城保护区獐的栖息地选择

1999年3月至2000年9月期间在江苏盐城保护区对獐的栖息地选择进行了研究。共记录了123个栖息地利用样方和300个任意样方,在样方中测定了5种生态因子(植被类型、植被高度、植被覆盖度、距水源距离和人为干扰距离)。不同季节獐对植被类型、植被高度和距水源距离的利用有显著差异,对植被覆盖度和人为干扰距离的利用有极显著差异。春季獐偏好选择白茅草滩、大穗结缕草滩、芦苇地和獐毛草滩;夏季主要选择碱蓬地、芦苇地和盐蒿草甸;秋季倾向于选择獐毛草滩、盐蒿草甸、藨草滩和大米草滩。在春、夏、秋季,獐都倾向于选择高度在90-110cm的植被。在不同季节獐都偏好选择植被覆盖度>90%的栖息地,主要选择距离水源200-599m之间的栖息地。     

舟山群岛獐的食性研究

利用野外观察、粪便显微组织学分析和投喂实验等方法对舟山群岛獐的食性进行了研究。结果表明,研究地的獐所食植物共有137种,隶属于6l科l15属,其中豆科植物在取食种类和取食频次上均多于其它科植物。尽管獐对植物科和种的选择在四季间没有显著差别,但取食科和种的数量依然从春天到冬天呈递减趋势,并且冬天与其它3个季节差别较大。獐的食物中,每个季节都含有非禾草类草本植物、禾草类草本植物、木本植物和蕨类植物,且其食物组成在季节间亦无显著差异;除木本植物外,獐对其它3类植物的选择在季节间有显著差异。獐在冬天较多选择木本植物,而其它季节较多选择草本植物,但木本植物和非禾草类草本植物在四季食物组成中均占较高比例,而禾草类植物所占的比例很小。因此,笔者认为舟山群岛的獐应该偏向于嫩食者。