Larval alarm pheromones as a potential control for invasive cane toads (Bufo marinus) in tropical Australia

Novel approaches to control invasive species are urgently needed. Cane toads (Bufo marinus) are large, highly toxic anurans that are spreading rapidly through tropical Australia. Injured toad larvae produce an alarm pheromone that elicits rapid avoidance by conspecifics but not by frog larvae. Experiments in outdoor ponds show that repeated exposure to the pheromone reduced toad tadpole survival rates (by >50%) and body mass at metamorphosis (by 20%). The alarm pheromone did not induce tadpoles to seek shelter, but accelerated ontogenetic differentiation. Perhaps reflecting mortality of weaker individuals during larval life, growth rates post-metamorphosis were higher in animals emerging from the pheromone exposure treatment than from the control treatment. Nonetheless, body size differentials established at metamorphosis persisted through the first 8 days of post-metamorphic life. We will need substantial additional research before evaluating whether the alarm pheromone provides a way to reduce cane toad recruitment in nature, but our field trials are encouraging in this respect.     

Assessing the Potential Impact of Cane Toads on Australian Snakes

Abstract:   Cane toads ( Bufo marinus ) are large, highly toxic anurans that were introduced into Australia in 1937. Anecdotal reports suggest that the invasion of toads into an area is followed by dramatic declines in the abundance of terrestrial native frog-eating predators, but quantitative studies have been restricted to nonpredator taxa or aquatic predators and have generally reported minimal impacts. Will toads substantially affect Australian snakes? Based on geographic distributions and dietary composition, we identified 49 snake taxa as potentially at risk from toads. The impact of these feral prey also depends on the snakes' ability to survive after ingesting toad toxins. Based on decrements in locomotor (swimming) performance after ingesting toxin, we estimate the LD₅₀ of toad toxins for 10 of the at-risk snake species. Most species exhibited a similar low ability to tolerate toad toxins. Based on head widths relative to sizes of toads, we calculate that 7 of the 10 taxa could easily ingest a fatal dose of toxin in a single meal. The exceptions were two colubrid taxa (keelbacks [  Tropidonophis mairii ] and slatey-grey snakes [  Stegonotus cucullatus ]) with much higher resistance to toad toxins (up to 85-fold) and one elapid (swamp snakes [  Hemiaspis signata ]) with low resistance but a small relative head size and thus low maximum prey size. Overall, our analysis suggests that cane toads threaten populations of approximately 30% of terrestrial Australian snake species.     

Effects of azadirachtin on mortality, fertilization, and swimming speed in larvae of the cane toad, Bufo marinus (Anura: Bufonidae)

Experiments were conducted to assess the effects of azadirachtin (AZ) on survival capacity, fertilization success, and swimming speed in larval stages of the cane toad, Bufo marinus . LC50 values (96-hr) for various larval stages exposed to 0.50 mg/l AZ were as follows: 5.35 (stage 12), 5.77 (stage 16), 787 (stage 20), 13.43 (stage 24), and 21.54 (stage 30). Tadpoles did not exhibit any apparent disorientation or production of mucous in response to AZ concentrations ranging from 0.3 to 0.5 mg/l. Mortality was significantly higher at 0.50 mg/l AZ than at lower concentrations. At 0.50 mg/l, mortality rate decreased significantly from 36% for stage 12 tadpoles, to 24% for stage 20 tadpoles. Mortality for early stages (stage 12) dropped significantly, from 36% at 0.50 mg/l, to 21% at 0.40 mg/l AZ There were no significant differences in percent mortality for any developmental stage at an AZ concentration of 0.3 mg/l, or for controls (no AZ). Exposure of gametes to 0.30 mg/l AZ did not reduce fertilization success as compared to controls (89.8 vs. 83.7%). At 0.40 mg/l, percent fertilization decreased significantly (68.8%). This effect was even more pronounced at 0.50 mg/l. No significant difference was found in swimming speeds between controls and subjects exposed to 0.30 mg/l AZ. However, at a concentration of 0.40 mg/l, tadpoles required a significantly longer period of time to swim a distance of 140 cm as compared to controls. The potential impact of AZ on amphibian populations is discussed.     

Distribution of shallow-water epibenthic macrofauna in Moreton Bay,Queensland, Australia

The distribution of epibenthic penaeid prawn postlarvae has previously been shown to relate to the degree of marine influences in the flora, sediment and water conditions in littoral and infralittoral habitats in Moreton Bay. The postlarvae are part of a complex faunal assemblage of approximately 400 mobile epibenthic species. Samples of the assemblage from stations situated throughout Moreton Bay were analysed by multivariable methods, to detect whether the environmental influences volated to the distribution of penaeid prawns, were related to the fauna as a whole. This was found to be so. The fauna occurred in two groups in areas of either less marine or more marine influences. Animals in the first group were less diverse, with distributions unrelated to depth or presence of seagrasses, but related to the level of marine influences between geographical areas sampled. Animals in the second group were closely related to depth and presence of seagrasses, but no overall differences were attributable to marine influeces apart from those attributable to depth. Temporal changes in species composition were smaller than spatial changes, and changes in relative abundance were, in both groups, related to differences between (i) summer and winter, and (ii) spring and the rest of the year.     

毛棉杜鹃地理分布及其开发利用

毛棉杜鹃为常绿灌木或小乔木,具有很高的观赏价值,介绍我国毛棉杜鹃的地理分布,生态学特性,阐述其优良特性以及开发利用的应用领域.结果表明:毛棉杜鹃具备优良的观赏特性和生态学特性,是一种极具发展潜力的园林植物材料.图2,表1,参8.     

Trace Metal Distribution and Enrichment in Benthic, Estuarine Sediments: Southport Broadwater, Australia

The distribution and enrichment of selected trace metals (Cd, Cr, Cu, Ni, Pb, Sn, Zn) in benthic sediments of the Southport Broadwater, a semi-enclosed coastal body of water adjacent to the Gold Coast city, south-eastern Queensland, Australia, was studied with the objective of assessing the extent and degree of sediment contamination. Sediment samples from the 0–10 cm and 10–20 cm depth intervals of 32 sites within the Southport Broadwater and surrounding residential canals were analysed for particle size distribution, pH, organic C and ‘near-total’ major (Al, Ca, Fe, Mn) and trace (Cd, Cr, Cu, Ni, Pb, Sn, Zn) metal contents. Sediment contamination for each trace metal was assessed by (1) comparison with Australian sediment quality guidelines, (2) calculation of the index of geoaccumulation based on regional background values, and (3) geochemical normalisation against Al (i.e. the abundance of alumino-silicate clay minerals). Based on this approach, the results indicate that submerged sediments in the study area are not presently enriched with Cd, Cr or Ni, with the spatial distribution of these metals being very well explained by the abundance of alumino-silicate clay minerals. However, several sites were strongly enriched with Cu, Pb, Sn and Zn, arising from sources related to either urban runoff or vessel maintenance activities. The study indicates that several varying approaches are needed for a satisfactory assessment of contaminant enrichment in estuarine sediments.     

外来入侵假臭草在中国分布区的预测

假臭草原产南美洲,上世纪80年代首次记载传入中国,是潜在的恶性杂草.为提供其在中国分布区的预测资料,采用397个采集数据和已有的146个分布点数据,利用生态位模型(GARP)和Domain模型对分布区进行预测分析,并通过AUC与MaxKappa进行模型评价.结果显示:近十年,假臭草入侵记录增多,入侵扩散加剧;太阳辐射、水汽压、极端高温、霜日频率和水流方向对假臭草的分布限制较小,雨日频率、坡向、坡度、海拔、年降水、年均温、地形指数和极端低温等8个环境因子对其分布影响显著;入侵的主要植被类型是农田、灌木或草类覆盖嵌合区,常绿、落叶灌木地带,栽培植被及相关联地带等.模型评价表明两种模型预测能力为较好及以上,预测结果显示:假臭草在西藏(除东南小块区域)、新疆、青海、内蒙古、宁夏,陕西和山西北部地区,黑龙江、吉林、辽宁(除辽东半岛小块区域)是不宜生长区;最易入侵广东、广西、海南等地区,其中华中部分省份、华北平原为适生区,还未见有假臭草入侵的报道,相关部门应引起重视,严防入侵.     

云南地区种子植物东亚分布成分的地理分布格局

植物区系分析是理解植被起源、性质和分布的基础.本研究利用大尺度的区系分布信息,结合地理信息系统平台和统计分析方法,探讨了云南地区种子植物东亚分布成分的地理分布格局以及"田中线"的生物地理意义.结果表明,东亚分布成分及其亚型所占比重均随着纬度的升高呈递增趋势.在经度梯度上,中国-日本植物分布亚型所占的比重从东到西呈递减趋势,而中国-喜马拉雅分布亚型所占比重的经度格局则与此相反.东亚分布成分在云南地区的扩散方向以由北到南为主,其次为经度梯度上的双向迁移.与过去的研究不同,本研究结果表明,东亚分布成分在云南地区的起源中心更可能为滇西北.我们未能证实"田中线"对中国-喜马拉雅分布亚型的分布具有限制意义,但对东亚分布成分(总体)和中国-日本分布亚型在云南地区的分布具有严格的限制意义.     

Distribution and community structure of midwater fishes in relation to the subtropical convergence off eastern Tasmania,Australia

Midwater fishes were sampled at night to a depth of 400 m in oceanic waters east of Tasmania, Australia, in May/June of 1992, 1993 and 1994. We examined whether there were differences in the distribution and density of these fishes in relation to the subtropical convergence (STC) separating East Australia Current (EAC) water from subantarctic water (SAW) to the south. A total of 23999 fishes from 107 taxa and 43 families were identified. Four new records were identified from the study area. Myctophids and stomiatoids were the main fish taxa captured. We found no evidence of increased density of the combined fish catch in any particular area. However, differences between areas in the density of individual species were noted, although no species was confined to any one area. Ceratoscopelus warmingi, Lobianchia dofleini and Vinciguerria spp. were most abundant in the EAC, whereas Lampichthys procerus was most abundant in the SAW. Only Diaphus danae was found in significantly higher numbers in the STC. Multivariate analysis revealed that community structure in the EAC was significantly different from that of the SAW but not from the STC. Further, when separated by depth, the shallow EAC group was significantly different in all group comparisons bar that with the shallow STC. Our data indicated that the thin EAC layer above 200 m could be distinguished by its fauna from the SAW. However, we could not detect a separate community in the STC. We conclude, therefore, that the STC is not an area of increased micronekton abundance, nor does it contain a distinct community, during the Australian autumn/winter.     

基于MaxEnt的加拿大一枝黄花在中国的潜在分布区预测

基于采样后的加拿大一枝黄花(Solidago canadensis)在北半球的分布数据,以温度和降水作为预测的环境因子,以MaxEnt模型作为物种适生性预测模型,预测加拿大一枝黄花在我国的潜在分布。结果表明:加拿大一枝黄花在我国有广泛的潜在分布区,目前的实际分布远未达其最大潜在分布范围,仍有可能继续扩散。加拿大一枝黄花主要适生区包括上海、江苏、浙江、安徽、山东、河南、湖北、湖南、江西、福建、重庆、贵州、四川省东部、广东和广西2省北部、云南省东北部、山西和陕西2省南部地区。必须采取有效措施阻止加拿大一枝黄花扩散蔓延。     

Biochemical composition and energy reserves in the larvae and adults of the four british periwinkles Littorina littorea,L. littoralis,L. saxatilis and L. neritoides

The biochemical composition of the adult body tissue is similar in Littorina littorea, L. littoralis, L. saxatilis and L. neritoides. In the newly crawling metamorphosed young of L. littoralis and L. saxatilis, the biochemical composition is similar to that of the mature adults. The newly released planktonic veliger larvae of L. littorea and L. neritoides, which represent and earlier stage of development than the newly crawling young, have a neutral lipid level (mean, 16.5% of ash-free dry flesh weight) approximately three times the level (5.4%) in the newly crawling young of L. littoralis and L. saxatilis. Otherwise the biochemical composition of free-swimming larvae is similar to that of newly crawling young and adults. Neutral lipid is apparently utilised by L. littoralis and L. saxatilis larvae during larval development and metamorphosis. It is suggested that neutral lipid is the major energy reserve of Littorina veliger larvae whereas in the adults, as exemplified by L. littorea, both lipid and carbohydrate are important as energy reserves.     

Vertical distributions and photosynthetic action spectre of two oceanic picophytopianlcters,Prochlorococcus marinus andSynechococcus sp.

Two picophytoplankters,Prochlorococcus marinus andSynechococcus sp., were isolated from the bottom of the euphotic zone (150 m depth) in the western Pacifie Ocean. The concentration ofP. marinus at this depth was more than 10⁴ cells ml^–1 while that ofSynechococcus sp. was less than 10² cells ml^–1. TheP. marinus isolate has a high divinyl-chlorophylla:b ratio similar to that of the Mediterranean strain, while theSynechococcus sp. isolate is of the phycourobilinrich type. The growth rate ofP. marinus was higher thanSynechococcus sp. when both were cultured under weak blue-green to blue-violet light (ca. 2 E m^–2 s^–1). While the chlorophyll-specific absorption spectra showed higher values inSynechococcus sp., the photosynthetic action spectre revealed thatP. marinus was able to use blue-violet light, whereasSynechococcus sp. was able to use blue-green light, more efficiently for photosynthesis. The photosynthetic quantum yield ofP. marinus was higher than that ofSynechococcus sp. at any wavelength between 400 and 700 nm. The calculated in situ photosynthesis rates per Gell volume forP. marinus were estimated to be higher than forSynechococcus sp. at 50 and 150 m depth. These results indicate thatP. marinus photosynthetically surpassesSynechococcus sp. in the blue-light-rieh environment of the oceanic euphotic zone. This may be why the former predominates at depths in temperate to tropical open ocean waters.     

Population dynamics and production of the planktonic copepods in a eutrophic inlet of the Inland Sea of Japan. IV. Pseudodiaptomus marinus, the egg-carrying calanoid

Population dynamics and production of the egg-carrying calanoid copepod Pseudodiaptomus marinus were studied for a year in Fukuyama Harbor, a eutrophic inlet of the Inland Sea of Japan. This species was perennial, with a large numerical peak in June and small peaks in September/October and November/December. During the study period, at least 11 generations could be detected. For each generation, the stage-specific survival from egg to Copepodite Stage (C) V was determined; it was very high during early life stages (egg to NIII), and gradually decreased beyond. On average, 94% of eggs recruited into NIII, which is strongly contrasted with very high (>ca. 90%) mortality during the corresponding stages for free-spawning copepods, i.e. Acartia omorii, Centropages abdominalis and Paracalans sp. This demonstrates that the egg-carrying strategy has a great advantage to reduce mortality in egg stage. The biomass of this species showed marked seasonal variations largely in parallel with numerical abundance. The instantaneous somatic growth rate increased linearly with temperature. The population production rate was estimated as the sum of somatic growth of larval stages and egg production of adult females; the annual integration was 51.0 mg C m⁻³ yr⁻¹ or 0.38 g C m⁻² yr⁻¹. Received: 11 November 1996 / Accepted: 7 December 1996     

The tunicate Salpa thompsoni ecology in the Southern Ocean. I. Distribution, biomass, demography and feeding ecophysiology

Distribution, density, and feeding dynamics of the pelagic tunicate Salpa thompsoni have been investigated during the expedition ANTARKTIS XVIII/5b to the Eastern Bellingshausen Sea on board RV Polarstern in April 2001. This expedition was the German contribution to the field campaign of the Southern Ocean Global Ocean Ecosystems Dynamics Study (SO-GLOBEC). Salps were found at 31% of all RMT-8 and Bongo stations. Their densities in the RMT-8 samples were low and did not exceed 4.8 ind m⁻² and 7.4 mg C m⁻². However, maximum salp densities sampled with the Bongo net reached 56 ind m⁻² and 341 mg C m⁻². A bimodal salp length frequency distribution was recorded over the shelf, and suggested two recent budding events. This was also confirmed by the developmental stage composition of solitary forms. Ingestion rates of aggregate forms increased from 2.8 to 13.9 μg (pig) ind⁻¹ day⁻¹ or from 0.25 to 2.38 mg C ind⁻¹ day⁻¹ in salps from 10 to 40 mm oral-atrial length, accounting for 25–75% of body carbon per day. Faecal pellet production rates were on average 0.08 pellet ind⁻¹ h⁻¹ with a pronounced diel pattern. Daily individual egestion rates in 13 and 30 mm aggregates ranged from 0.6 to 4.8 μg (pig) day⁻¹ or from 164 to 239 μg C day⁻¹. Assimilation efficiency ranged from 73 to 90% and from 65 to 76% in 13 and 30 mm aggregates, respectively. S. thompsoni exhibited similar ingestion and egestion rates previously estimated for low Antarctic (~50°S) habitats. It has been suggested that the salp population was able to develop in the Eastern Bellingshausen Sea due to an intrusion into the area of the warm Upper Circumpolar Deep Water     

Effects of Landscape Composition and Wetland Fragmentation on Frog and Toad Abundance and Species Richness in Iowa and Wisconsin, U.S.A.

Abstract: Management of amphibian populations to reverse recent declines will require defining high-quality habitat for individual species or groups of species, followed by efforts to retain or restore these habitats on the landscape. We examined landscape-level habitat relationships for frogs and toads by measuring associations between relative abundance and species richness based on survey data derived from anuran calls and features of land-cover maps for Iowa and Wisconsin. The most consistent result across all anuran guilds was a negative association with the presence of urban land. Upland and wetland forests and emergent wetlands tended to be positively associated with anurans. Landscape metrics that represent edges and patch diversity also had generally positive associations, indicating that anurans benefit from a complex of habitats that include wetlands. In Iowa the most significant associations with relative abundance were the length of the edge between wetland and forest ( positive) and the presence of urban land (negative). In Wisconsin the two most significant associations with relative abundance were forest area and agricultural area ( both positive). Anurans had positive associations with agriculture in Wisconsin but not in Iowa. Remnant forest patches in agricultural landscapes may be providing refuges for some anuran species. Differences in anuran associations with deep water and permanent wetlands between the two states suggest opportunities for management action. Large-scale maps can contribute to predictive models of amphibian habitat use, but water quality and vegetation information collected from individual wetlands will likely be needed to strengthen those predictions. Landscape habitat analyses provide a framework for future experimental and intensive research on specific factors affecting the health of anurans.     

Distribution of Juvenile,subadult and adult Scylla serrata (Crustacea: Portunidae) on tidal flats in Australia

In Deception Bay, northern Australia, during 1979–1981, a study was made of the distribution of Scylla serrata (Forskal) in an area having a broad intertidal zone. Juveniles (20 to 99 mm carapace width) were resident in the mangrove zone, remaining there during low tide. The majority of subadult crabs (100 to 149 mm) migrated into the intertidal zone to feed at high tide and retreated to subtidal waters at low tide. Adults (150 mm and larger) were caught mainly subtidally and only small numbers were captured in the intertidal at high tide. Few crabs were captured in the coolest months (May to August). Adults were captured on the flats mainly in the warmest months (January to April), but subadults could be captured over the entire summer (September to March). Juveniles were found in the upper intertidal throughout the year.