Effects of irradiance on photosynthetic characteristics and growth of <Emphasis Type="Italic">Mosla chinensis</Emphasis> and <Emphasis Type="Italic">M. scabra</Emphasis>

Photosynthetic and growth characteristics of Mosla chinensis and M. scabra were compared at three irradiances similar to shaded forest understory, forest edge, and open land. At 25 % full ambient irradiance, M. chinensis and M. scabra had similar photosynthetic characteristics, but saturation irradiance, compensation irradiance, and apparent quantum yield of M. chinensis were higher than those of M. scabra at full ambient irradiance and 70 % full ambient irradiance. At the same irradiance treatment, specific leaf area and leaf area ratio of M. chinensis were lower than those of M. scabra. Photon-saturated photosynthetic rate and water use efficiency of M. chinensis, however, were not significantly higher than those of M. scabra, and the leaf area and total biomass were lower than those of M. scabra. As a sun-acclimated plant, the not enough high photosynthetic capacity and lower biomass accumulation may cause that M. chinensis has weak capability to extend its population and hence be concomitant in the community.     

Periodic movement,recruitment and size-related distribution of the sea cucumber Holothuria scabra in Solomon Islands

Field studies of the sea cucumber Holothuria scabra conducted in Kogu Veke, Solomon Islands, showed monthly recruitment of newly-settled juveniles on seagrass and indicated that size distribution was a function of substratum type and depth. Adults >250 mm body length were found mainly on sand, with <5% organic matter (OM), at depths of >1–3 m. Individuals >10–250 mm were found mostly in 30–120 cm of water, on mud and muddy sand with OM content between 5 and 10%. Specimens >40–150 mm were also found in the intertidal zone, sometimes burrowed on exposed sandflats at low tide. Holothuria scabra avoided substrata of fine silt or shell and coral pebbles, and sediment with an organic content 30%. Juveniles 100 mm burrowed at sunrise and surfaced at sunset, whereas individuals >100 mm burrowed and surfaced a few hours earlier. Holothuria scabra tended to burrow when salinity decreased, whereas increased water temperatures reduced normal burrowing behaviour. Spatial distribution, observed during tank experiments, suggested that adult H. scabra aggregated prior to spawning and in response to the lunar cycle. The formation of pairs, trios or larger groups increased during the new moon and was most common just before the full moon. Newly-settled juveniles up to ca. 9 mm were found on seagrass leaves. Typically, maximum densities and smallest recruits were observed a couple of weeks after the full moon, lower densities and slightly larger recruits were found a few days later. Juveniles with a mean length around 65 mm released on sand moved less and grew faster than juveniles released in seagrass beds or on substrata of shells and crushed coral.     

Ammonia Excretion in Snails Viviparus bengalensis (LAMARCK) and Pila globosa (SWAINSON) during Active and Dormant Periods

The quantities of ammonia excreted over a period of 24 h by two prosobranch snails Viviparus bengalensis and Pila globosa were measured at 30 day intervals to compare their excretion during the active and dormant phases of their life. The aquatic snail V. bengalensis excreted 0.5-1.0 μmole of ammonia per day and snail throughout the year. The ammonia excretion rate of this snail was 40-50% lower in winter than in the monsoon and summer period. In the amphibious snail Pila globosa excretion of ammonia was limited to only four months of its active life i. e. during July-October. Also the rate of ammonia excretion in P. globosa (0.2-0.3 μmole per day and snail) was very low compared with V. bengalensis.     

Effects of earthworms, nematodes, cultivations and host plants on Verticillium wilt of peach and cherry

Verticillium dahliae but not V. albo-atrum Berth was isolated from eight out of twenty-one stone fruit orchards surveyed for Verticillium wilt disease in western New York. Wilt incidence was related to the cultivation of tomato or legumes as previous or inter-crop with stone fruit trees. A limited cross species inoculation using isolates of V. albo-atrum and V. dahliae from woody and herbaceous plants showed that peach and cherry were susceptible to both species. The effect of V. dahliae on growth of cherry seedlings in the presence of Tylenchorynchus claytoni, Pratylenchus penetrans and Meloidogyne hapla was compared. P. penetrans and M. hapla produced more severe growth reduction than T. claytoni. The adverse effect of Verticillium on the growth of cherry seedlings was greater acting together with any one of the three nematodes than acting alone. V. dahliae was shown to be capable of passage through earthworms without loss of infectivity.     

Stylosanthes sp. aff.S. scabra: a putative diploid progenitor ofStylosanthes scabra (Fabaceae)

Stylosanthes sp. aff.S. scabra is an undescribed taxon showing affinities with the allotetraploid speciesS. scabra, but distinct in a number of attibutes. Several collections show potential as forage for clay soils in northern Australia. Twelve accessions have been analysed using STS (sequence-tagged-sites) as genetic markers, and they all displayed STS phenotypes of typical diploid species. Taking into account their morphological similarities, the STS analysis provides strong evidence thatStylosanthes sp. aff.S. scabra might be a diploid progenitor of the allotetraploidS. scabra. This speculation was supported by cytological examinations. Somatic chromosome numbers of two of these accessions were counted and both were found to be diploid (2n = 20). The level of polymorphism among the 12Stylosanthes sp. aff.S. scabra accessions, estimated using randomly amplified polymorphic DNA (RAPD) as markers, was 7.8%, and the dissimilarity value betweenStylosanthes sp. aff.S. scabra andS. viscosa (the other putative progenitor ofS. scabra) was 89%.     

COMPARATIVE ANATOMY OF SOME PARENTS AND HYBRIDS OF THE HAWAIIAN MADIINAE (ASTERACEAE)

Comparative leaf morphology and anatomy was examined in five species and four hybrids involving three genera of Hawaiian Madiinae (Asteraceae). The comparisons included Argyroxiphium grayanum, Dubautia ciliolata subsp. ciliolata, D. knudsenii subsp. knudsenii, D. scabra subsp. leiophylla, D. scabra subsp. scabra, and Wilkesia gymnoxiphium, and the hybrids A. grayanum × D. scabra subsp. leiophylla, D. ciliolata subsp. ciliolata × D. scabra subsp. scabra, D. knudsenii subsp. knudsenii × D. scabra subsp. leiophylla, and W. gymnoxiphium × D. scabra subsp. leiophylla. Foliar morphology, leaf tissue organization, and various characters of stomata and trichomes were compared, using epidermal peels, cross and paradermal sections, and clearings of leaves. Pronounced anatomical differences among these closely related taxa were characterized, and effects of hybridization on the expression of anatomical features were documented. Most comparisons of parents and hybrids revealed statistically significant differences in leaf size, distribution of adaxial and abaxial stomata, and marginal and surface trichomes. In most instances hybrids demonstrated intermediate status in their foliar characters, indicating that these features are inherited from both parents. However, differences in foliar characters were usually of sufficient magnitude to allow recognition of hybrids as well as parents.     

High mortality and sex ratio imbalance in a critically declining Oriental White-backed Vulture population (Gyps bengalensis) in Pakistan

Populations of Oriental White-backed Vulture (Gyps bengalensis) and Long-billed Vulture (Gyps indicus) declined dramatically by 95–100% on the Indian subcontinent in during the mid-1990s. The study reported here was conducted in Pakistan to compare the population size, breeding success, patterns of mortality and sex ratios among dead vultures and newly hatched nestlings of G. bengalensis and G. indicus at Toawala (TW) and Nagar Parkar (NP), respectively, during the breeding seasons 2005/2006 and 2006/2007. At TW, diclofenac poisoning was most likely responsible for the high mortality and sex ratio imbalance among dead G. bengalensis, where vulture counts and breeding success declined quickly during the study period. However, at NP no significant difference in population size, breeding success and annual mortality of G. indicus was recorded during the study period. A sex ratio imbalance was detected among nestlings of G. bengalensis, with 68% males and 32% females. In contrast, the sex ratio did not differ significantly in G. indicus.     

Life at the edge: an experimental study of a poleward range boundary

Experimental studies of biogeographic processes are important, but rarely attempted because of the logistical challenges of research at large spatial scales. I used a series of large-scale transplant experiments to investigate the mechanisms controlling species abundance near a poleward range boundary. The intertidal limpet Collisella scabra experiences a 100-fold decline in abundance over the northernmost 300 km of its range. Temperature and food supply both strongly influenced individual survival, growth, and maturation. Regression analysis also revealed significant interactions among these conditions: the effect of one could not be predicted without knowing the level of the other. But these relationships could not explain geographic abundance patterns. Instead, individual limpets were highly successful at sites with relatively low abundance. These results suggest that, even though temperature is important to the success of individual C. scabra populations, the primary effect of warming temperatures under climate change may not be a shift in geographic distribution.     

Cytogenetics of new Guizotia Cass. (Compositae) interspecific hybrids pertaining to genomic and phylogenetic affinities

 The following crosses were made using four recognized species/subspecies and a new population of Guizotia, referred to as Chelelu after the name of the locality in Ethiopia from which it was collected: G. scabra subsp. schimperi × Chelelu, Chelelu × G. scabra subsp. scabra, G. zavattarii × G. arborescens and Chelelu × G. zavattarii (all accessions with 2n=30). Plant morphology as well as mitotic and meiotic chromosome analysis confirmed the hybrid nature of the obtained progeny. At metaphase I of meiosis, the F₁ hybrid plants (2n=30) showed a mean of about 95%, 31%, 63% and 0.50% of the pollen mother cells with 15 bivalents, and a mean of about 14.95, 13.75, 14.40 and 7.86 bivalents per cell, respectively. The respective mean pollen stainability was about 67%, 19%, 31% and 2%. From the results it was concluded that Chelelu is more closely related to G. scabra subsp. schimperi than to G. scabra subsp. scabra but more to the latter than to G. zavattarii. Guizotia zavattarii and G. arborescens are closely related to each other. Based on the cytological observations made, the probable basic chromosome number for the genus is discussed. Received November 5, 1999 Accepted August 21, 2001     

蔓赤车叶绿体基因组结构及系统进化分析

蔓赤车(Pellionia scabra)属于荨麻科赤车属,是一种具有高营养价值的优质野菜。本研究以蔓赤车为材料,基于高通量技术方法完成叶绿体基因组测序、组装注释、结构解析及构建系统发育树,以此深入研究蔓赤车叶绿体基因组特征。结果表明,蔓赤车叶绿体基因组大小为153220 bp,GC含量为36.4%,属于典型的四分体结构。共注释到130个基因,其中85个蛋白编码基因,37个转运RNA基因,8个核糖体RNA基因;其中,有15个基因包含1个内含子,2个基因包含2个内含子,rps12存在反式剪接情况。蔓赤车叶绿体基因组可分为光合作用(43个)、自我复制(64个)、其他编码蛋白(7个)以及未知功能(4个)4大类基因。蔓赤车叶绿体基因组共检测出51073个密码子,其中编码亮氨酸(Leu)的密码子占比最大,密码子偏向使用A和U两种碱基。检测到72个简单重复序列位点,其中有58个单核苷酸、12个二核苷酸、1个三核苷酸和1个四核苷酸4种不同类型的简单重复序列(simple sequence repeats,SSRs)。蔓赤车IRb/SSC边界存在ycf1基因扩张现象。系统进化树显示,蔓赤车(Pellionia scabra OL800583)与庐山楼梯草(Elatostema stewardii MZ292972)、盘托楼梯草(Elatostema dissectum MK227819)、光叶楼梯草(Elatostema laevissimum var.laevissimum MN189961)亲缘关系最密切。基于蔓赤车叶绿体基因组的研究,旨在为蔓赤车物种鉴定、遗传进化及基因组学研究奠定理论基础。     

Laboratory evaluation of a toxicant-sterilant, alpha-chlorohydrin, for the control of Indian mole rat Bandicota bengalensis

A toxicant-sterilant, alpha-chlorohydrin, was evaluated against the Indian mole rat Bandicota bengalensis and the ship or house rat Rattus rattus. It caused 100% mortality of B. bengalensis at 100 mg/kg but no mortality was observed in R. rattus even at 300 mg/kg. The acute oral LD₅₀ for B. bengalensis was found to be 82 mg/kg. The survivors of B. bengalensis, which received 60 - 90 mg/kg of alpha-chlorohydrin by oral intubation, showed dose-dependent decreases in testicular weight, and cauda epididymal sperm concentration, live sperm count and sperm motility. The values of these parameters indicated that mole rats receiving the above doses would be sterile. In contrast, these changes were observed in R. rattus only at doses of 200 and 300 mg/kg. The toxic and antifertility effects of alpha-chlorohydrin observed on B. bengalensis suggest that it should be evaluated for the management of this species under held conditions.     

Patch use behaviour of Elephantulus myurus and Micaelamys namaquensis: the role of diet,foraging substrates and escape substrates

We investigated the role of diet and substrate features in the coexistence and habitat affinities of the rock elephant shrew, Elephantulus myurus, and the Namaqua mouse, Micaelamys namaquensis. We measured giving‐up densities at experimental food patches that varied in foraging substrate, escape substrate surrounding the food patch and food type. In terms of food consumption, E. myurus favoured pebble (63% total harvest) over sand and sawdust, whereas M. namaquensis favoured foraging in sand (48% total harvest) over sawdust (29%) and pebbles (23%). Mealworms comprised most of E. myurus’s harvest, and M. namaquensis harvested seeds the most, followed by alfalfa and mealworms. In terms of escape substrates, M. namaquensis had significantly higher GUDs when the food patch was surrounded by tussocks of sedge (average 28.11 seeds/patch) than rock surfaces (17.41) or by bush/crevice (14.36). In conjunction with morphologic adaptations, E. myurus detects and recovers food using its snout and long tongue, and M. namaquensis digs and handles foods with its forepaws. The different foraging preferences of E. myurus and M. namaquensis suggest that the interaction of substrates with food types characterize their niches and promote coexistence. Elephantulus myurus travelled greater distances, whereas M. namaquensis was selective for microhabitats offering refuge or traction.     

Intraguild dietary overlap and its possible relationship to the coexistence of mesocarnivores in intensive agricultural habitats

The stone marten (Martes foina) and the pine marten (M. martes) are closely related mammalian carnivores potentially subject to exploitative competition. The recent expansion of the pine marten into the intensively cultivated plain of the River Po (NW Italy), where previously only stone marten occurred, offered an interesting opportunity to analyse their relationships. We studied the distribution and diet of Martes species and trophic niche overlap between martens and red foxes (Vulpes vulpes) in two study areas, each with two pseudoreplicates, by analysing genotyped faeces. Our results seem to confirm the displacement of the stone marten from one study area, the pine marten being the only Martes species occurring where previously the stone marten had been reported. We found a large food niche overlap between red fox and both stone and pine martens, but with evidence of size-related differences in the consumption of some food items. We hypothesised that, due to the poor prey-base of the environment, highly altered by intensive crop cultivation, intense interspecific competition originally occurred between the red fox and stone marten. The heightening of interspecific competition caused by the entry of the pine marten in the predator guild may have caused the displacement of the stone marten, at least temporarily. The mechanism of such displacement needs to be clarified through further surveys in areas where the three species occur sympatrically.     

Behavioral thermoregulation in a tropical gastropod: links to climate change scenarios

Tropical species are vulnerable to global warming because they live at, or near to, their upper thermal threshold limits. Therefore, the predicted increase in the frequency of warming events in the tropics is expected to be critical for the survival of local species. This study explored the major environmental variables which were thought to be correlated with body temperatures (BTs) of the tropical snail Littoraria scabra at the niche level. A correlation between BT and substrate temperature (ST) was detected from field observations which suggests a possible causal relationship between both substrate and BTs. In contrast, there was no correlation between BT and air temperature. Field observations suggest that 33.4 °C may be L. scabra upper limit of substrate surface temperature, although further experiments are needed to assess if the upper limit of physiological tolerance is actually different. As L. scabra individuals were free to choose their substrata, the observed distribution pattern at the niche level is related to L. scabra's behavior. Additionally, substrate surface temperatures were very heterogeneous at centimeter scale (i.e. from 22.5 to 53.1 °C) and L. scabra was shown to select specific STs (i.e. between 22.5 and 33.4 °C) rather than microhabitat type. Therefore, L. scabra did not seem to behaviorally thermoregulate through microhabitat selection nor aggregation. In contrast, behavioral experiments showed that L. scabra has the ability to actively select a thermally favorable site over short temporal scale (i.e. individual average speed of 1.26 cm min^?1) following exposure to high temperatures above 33.4 °C. Hence, this study supports the crucial need to integrate intertidal invertebrate behavioral responses to thermal constraints in climate change studies.     

Influence of peat substrate on the distribution and behaviour patterns of sand shrimp, Crangon septemspinosa, under experimental conditions

Peat harvesting is a lucrative industry in New Brunswick, Canada, and is for the most part located along the coast. Current methods of mining peatlands are such that high levels of peat fibers are transported by runoff into fresh and marine waters. To understand better the influence of peat substrate on aquatic organisms living in peat‐impacted habitats, the sand shrimp (Crangon septemspinosa) was used as a bioindicator. A series of laboratory experiments was conducted in which shrimp were provided with a choice between sand and peat. Long‐term studies on starved shrimp confirmed that whereas foraging activities took place on both substrates, shrimp display an overall preference for sand (73% of all shrimp observed were on sand, n=60). When food was deposited on each of the substrates, shrimp generally opted to feed on sand (75% of all shrimp observed were on sand, n=60). After all food on sand was consumed, shrimp tended to move to peat. This was followed by a short period of foraging on both sand and peat with an eventual return to sand in most instances. The presence of food on both substrates did not influence their preference for sand. However, shrimp will move onto a peat substrate to forage if food is present only there. This observation suggests that, although there is a marked preference for sand, peat is not completely repellent to them. Finally, histological investigations of the shrimp digestive system revealed that peat was ingested with food particles and processed in the gastric mill. There was, however, no discernible discrimination between the two substances during ingestion. Finally, starved shrimp on peat substrate did not ingest peat fibers, suggesting that peat is not perceived as an alternative food source.     

Degradation of n-alkanes by Candida parapsilosis and Penicillium frequentans immobilized on granular clay and aquifer sand

Summary The immobilization intensity of cells of Penicillium frequentans and Candida parapsilosis on materials such as granular clay, granular clay + aquifer sand and aquifer sand alone, was followed by scanning electron microscopy (SEM). The results demonstrate that the granular clay was the best adsorbent for both organisms, followed by the mixture of both granular clay and aquifer sand. Poor adhesion of cells was detected on using aquifer sand alone with C. parapsilosis.The highest degree of degradation of the alkane mixture (C₁₂–C₁₈) used was achieved by cells immobilized on granular clay, followed by those cells adsorbed on clay and sand. The weakest degradation was observed with cells immobilized on the sand alone.     

Nitrogen Requirements of Microtus rossiaemeridionalis

Total nitrogen requirements in the small herbivorous rodent Microtus rossiaemeridionaliswere studied. When provided with two kinds of standard laboratory food (about 20% and 0% digestible protein, respectively) ad libitum(cafeteria diet), the voles chose a diet of 14% protein. The total daily (with urine and faeces) nitrogen losses were, in this case, determined as 3.65 ± 0. 60 mg N/ g of body mass. When provided with a protein-free diet alone, the animals lost 0.90 ± 0,05 mg N/ g body mass per day, comprising about 3% of their body mass daily. It was proposed that the consumption of a low-fiber diet (about 4% in both kinds of food) could affect the gastrointestinal bacterial flora and, thus, lead to changes in the primarily herbivorous nitrogen metabolism.     

Feed‐through insecticides for the control of the sand fly Phlebotomus argentipes

Three rodent feed‐through studies were conducted to evaluate the efficacy of insecticides to control Phlebotomus argentipes (Diptera: Psychodidae). The initial test evaluated diflubenzuron, eprinomectin, fipronil and ivermectin as feed‐through treatments in Rattus rattus (Rodentia: Muridae). In the preliminary trial, all four insecticides yielded 100% mortality of P. argentipes larvae within 20 days of exposure to treated rodent faeces. Based upon the initial results, fipronil was evaluated further as a feed‐through utilizing Bandicota bengalensis (Rodentia: Muridae). The B. bengalensis trial evaluated fipronil against both adult and larval sandflies at 250 p.p.m., 100 p.p.m. and 50 p.p.m. The results showed the fipronil treatment to have 100% efficacy against larvae up to 20 days post‐treatment and over 74% efficacy against adult sandflies presented with B. bengalensis faeces up to 10 days post‐treatment at all three dosage levels. The results of the three studies suggest that all four insecticides may be useful tools with which to control Leishmania vector populations.     

Gut contents and diel feeding rhythm in dominant copepods in the ice-covered Weddell Sea,March 1992

Zooplankton was sampled at a diurnal station during the drift of the Ice Station Weddell-1 in the western Weddell Sea in March 1992. Gut contents of Metridia gerlachei, Calanoides acutus, Calanus propinquus and Rhincalanus gigas were studied. Calanoides acutus was trophically inactive, but 18%, 33% and 45% of Calanus propinquus, R. gigas and M. gerlachei, respectively, contained food in their guts. Diel changes in gut levels and percentage of individuals with full guts with maximum during the dark period were observed in M. gerlachei copepodite stage V and females. The possible reasons for observed differences in foraging patterns of the four copepod species are discussed.     

Temporal and developmental aspects of diet-induced food preferences in larvae of the tobacco hornworm, Manduca sexta

Diet‐induced changes in food preferences in an oligophagous caterpillar were studied in order to characterize the conditions under which this induction occurs. The time course of acquisition and extinction of induced food preferences by larvae of the tobacco hornworm, Manduca sexta (Johan.) (Lepidoptera, Sphingidae), was examined by varying the food and duration of larval food experience. Larvae were given feeding experience with the host plant tomato, Lycopersicon esculentum (Mill.) (Solanaceae), or the acceptable non‐host plant cowpea, Vigna unguiculata (Walp.) (Fabaceae), or switched from one to the other during different instars. Food preferences for V. unguiculata by the fourth or fifth instar larvae were measured individually in two‐choice tests with discs of V. unguiculata and moist filter paper. The acquisition or extinction of an induced food preference for V. unguiculata was indicated by larvae preferring V. unguiculata to filter paper or the reverse, respectively. Results showed that: (1) the period required for the acquisition of induced preference for V. unguiculata can be short (36 h), (2) food experience in either the third or fourth instar period is sufficient, and (3) the most recent feeding experience appears to be important. In contrast, the period required for extinction of induced preference for V. unguiculata appeared to be longer (1–3 instars), and both the most recent feeding experience and total duration of larval experience with the inducing food seem to play a role. Experience is not restricted to a particular instar period to acquire or extinguish such an induced food preference. The induced food preference for V. unguiculata was not very rigid and could be reversed by having one instar of feeding experience on L. esculentum. The findings indicate that diet‐induced food preferences in M. sexta contains elements of habituation and associative learning, but do not support food imprinting and induction of oligophagy.