May Rare Metallophytes Benefit from Disturbed Soils Following Mining Activity? The Case of the Crepidorhopalon tenuis in Katanga (D. R. Congo)

Cuprophytes are plants that mostly occur on Cu‐rich soil. In South Central Africa, these species are threatened by intensive mining exploitation destroying their habitats. Crepidorhopalon tenuis (Scrophulariaceae) is a tiny annual cuprophyte endemic to the Zambesian center of endemism and is particularly abundant in the Lubumbashi area. We investigate here the ecological niche of C. tenuis through the analyses of its abundance and distribution in relation to soil factors, plant community composition, and anthropogenic perturbations. Soil and vegetation data were collected in seven sites (five metalliferous and two nonmetalliferous). The current study shows that C. tenuis has its ecological optimum on copper‐rich soil and can be referred to as an elective pseudometallophyte. This species is rare in primary steppic savanna on natural metalliferous soil. Its frequency and abundance peak in pioneer communities on bare soil. In particular, the species showed a surprising ecological plasticity as it was able to benefit from anthropogenic disturbance and to colonize the large areas of bare, contaminated soil left over by mining activities. Our results strongly suggest that C. tenuis was a very rare species in natural metalliferous communities, restricted to patchy areas of open soil in steppic savanna. Recent anthropogenic habitats may have conservation value for some rare metallophytes with colonizing traits and low competitive ability.     

Physiological tolerance to hyperthermia and hypoxia and effects on species richness and distribution of rockpool fishes of Loggerhead Key, Dry Tortugas National Park

Rockpools on Loggerhead Key in the Dry Tortugas National Park experience cyclic tidal changes in water quality and physical dimension resulting in ichthyofaunal assemblages that differ markedly from the adjacent coral reef. Within the beach rock formations and areas transitioning to the nearby reef, we observed 45 fish species; however, only four species - schoolmaster, Lutjanus apodus, French grunt, Haemulon flavolineatum, cocoa damsel, Pomacentrus variabilis, and frillfin goby, Bathygobius soporator - were found in all rockpools. All fishes were transient juveniles except for frillfin goby, which was a pool resident. High temperature tolerance, (Critical Thermal Maxima), and low oxygen tolerance, (Critical Oxygen Minima) for schoolmaster, French grunt, cocoa damsel, and frillfin goby were 40.9, 36.2, 37.6, 40.9 °C and 0.56, 0.77, 0.50, and 0.27 mg/L, respectively. All four species demonstrated thermal and hypoxia tolerance values similar to those published for species traditionally noted as abiotic specialists. Although fish distribution patterns in rockpools were likely influenced by structural complexity and spatial limitations, the relationship between pool morphology and species richness was weak, suggesting that physiological tolerance to high temperature and low oxygen among reef fishes may be more influential in determining which species inhabit the rockpools. Harsh thermal and oxic conditions that cannot be exploited by less tolerant species may be beneficial for some Loggerhead Key reef fishes in providing refuge from predators, foraging grounds, or potential nursery areas.     

Field studies on the bionomics of the free-living stages of St. Lucian Schistosoma mansoni.

Densities of Schistosoma mansoni miracidia and cercariae in natural habitats in three St. Lucian valleys were monitored over a 3-year period by exposure of sentinel snails, Biomphalaria glabrata, and a cercariometric technique, supplemented by sampling of field snails. Separate measures for control of S. mansoni transmission were under evaluation in two of the valleys. Sentinel snails became infected sporadically and their infection rates per valley ranged from 0·12% to 4·99%. S. mansoni miracidial inoculation rates ranged from 1 to over 4 per infected sentinel snail. Combined rainfall of more than 3 in on the day before any day of sentinel snail exposure interfered with miracidium-snail interaction. Densities of S. mansoni cercariae ranged from 0·05 to 21 per litre of water sampled. The number of cercariae detected in a habitat by cercariometry was directly proportional to the number of infected field snails. Sentinel snail infection rates exhibited a downward and an upward trend, respectively, in the controlled and uncontrolled areas, although the changes were not significant statistically.     

Spontaneous mutation in a thermoacidophilic archaeon: evaluation of genetic and physiological factors

We used direct selection of pyrE and pyrF mutants to estimate the rates of spontaneous mutation in Sulfolobus acidocaldarius as a function of genetic background and culture conditions. Fluctuation tests were applied to several genetically marked strains, including one isolated as a putative mutator strain, and to cultures grown over a wide range of temperature and other physiological conditions. The results suggested some impact of auxotrophic markers on the apparent rate of mutation, but no obvious pattern of effect of growth conditions, including those that gave evidence of being physiologically stressful. Received: 27 May 1997 / Accepted: 2 September 1997     

被遗忘的城市“生境”:重庆市墙体自生植物调查分析

被称为“钢筋水泥森林”的现代城市存在大量的墙体,包括建筑外墙、独立围墙、挡土墙等类型。通常情况下,这些完全硬质化的界面不会被认作为生境或栖息地。以典型山城重庆市为例,探索城区范围内墙体成为城市生境的可能性。于2017年9—11月对重庆主城区共120块墙,包含359个4×1 m小样方,调查墙面上自生植物的物种、覆盖度等信息;记录墙体4类特征共22个因子作为生境影响因素;并采用方差分解和典范对应分析(CCA)排序法研究影响因素与自生植物组成和分布的关系。结果表明:(1)市区墙境自生植物丰富,共记录到70科149属193种,以菊科植物种类最丰富,其次是禾本科和荨麻科。优势种包括蜈蚣草(蕨类)、井栏边草(蕨类)、构树幼苗(乔木)、贯众(蕨类)和黄葛树幼苗(乔木)。相比平面环境的自生植物以旱生为主,墙体上喜阴湿的蕨类植物占明显优势,反映出墙体作为生境的独特性,可以作为城市生态空间的有效补充。(2)墙体4类特征共解释自生植物组成与分布变化的14.4%,植物传播、定植与构建是一个综合复杂的过程,受各种随机因素影响;此外,本文所选因素也未考虑更大尺度的周边景观等因素。所有因子中,墙体高度、藤蔓覆盖度和墙体遮阴率是影响植物变化的主要因子,且与CCA排序第1轴相关性最强。这些因子均与墙体自身湿度有关,表明水分在决定墙面植物组成与分布起主要作用,植物在墙面沿水分呈梯度分布。讨论了本研究对现代城镇绿化的启示,从自然做功的角度提升城市生态系统服务,为城市生态设计与低成本管理提供科学依据。     

Microplastics affected black soldier fly (Hermetia illucens) pupation and short chain fatty acids

Microplastics (MPs) are microscopic particles that are now found in almost all ecosystems where they may exert adverse effects on various organisms, including insects. In this study, 20 black soldier fly (Hermetia illucens) larvae (BSFL) were exposed to MPs, in the form of polypropylene (PP-MPs; 55 ± 4 µm) at 0.22% (26,972,507 particles/kg), versus a control (no added MPs) in triplicate for two weeks. After two weeks, final lengths, weights, percentage of pupation, fatty acid composition of BSFL and substrate reduction percentage were measured. Survival, lengths/weights and percentage substrate reduction in the PP-MP group were not significantly different from the control. However, percentage of pupation was significantly lower in the PP-MP treatment (at 65.2%) compared to the control (at 83.8%). Among the measured fatty acids, only propionic and butyric acid changed, and these short-chain fatty acids (SCFAs) significantly increased from 0.12% and 0.17% to 0.14 and 0.19%, respectively, in the PP-MP-exposed group. This study indicates that exposure to environmentally relevant levels of PP-MPs can substantially delay development, while the increase in the SCFA may indicate a change in the gut microbiota.