Effects of Hunger on Foraging Behavior of Age-0 Smallmouth Bass in a Heterogeneous Environment

We examined how hunger affected habitat use by juvenile smallmouth bass, Micropterus dolomieu, as they moved among a variety of habitat patches. Hungry and satiated fish were placed in an artificial stream that contained three types of habitat patches: pools with uniform depth and low water velocities, mazes with uniform depth and moderate water velocities, and riffle-pool complexes with varying depth and the highest water velocities. Food was only available in the riffle-pool complexes. Hungry fish spent more time in the riffle-pool complex than satiated fish did. However, hungry and satiated fish did not differ in the time it took to exit the pool they were initially placed in, the number of patches entered, or the number of times they moved among patches. Both hungry and satiated fish frequently entered other patches after foraging successfully in the riffle-pool complexes. There was wide variation in foraging behavior among individuals in both treatment groups, and we consistently observed individuals that did not alter their foraging behavior in response to the difference in food availability among patches.     

The effects of supplemental food on reproduction in parental male smallmouth bass

Synopsis We provided supplemental food for parental male smallmouth bass,Micropterus dolomieu, to determine if food supply limits the reproductive performance of nesting males as measured by care duration, reproductive success and survival of adult males. Although supplementing the diet of parental males had a positive effect on all three reproductive measures, the experiment generated contrasting results in different years. In the first year, supplemental feeding only improved the survival of fed males versus unfed males. In the second year, supplemental feeding increased care duration and reproductive success of fed males but reduced their survival relative to unfed males. Our supplemental feeding improved current or future measures of reproductive performance, but not both simultaneously. The results appear to demonstrate phenotypic plasticity in the extent to which energy from supplemental feeding can be allocated to present or future reproduction.     

Contributions of Robert (Bob) J. O’Neil to the field of predaceous Heteroptera

Predaceous Heteroptera are important components of natural and managed habitats. The extent of predatory habits among taxa ranges from those that are totally (or nearly totally) predaceous to those that are nearly totally phytophagous, but occasionally feed on arthropod prey. Because of that variability in predatory habit, the contributions of heteropteran taxa to management of pest species will vary greatly. The late Robert (Bob) J. O’Neil (1955–2008) added significantly to understanding the roles of and benefits from facultatively predaceous Heteroptera. His focus on behavioral and physiological attributes that permitted facultatively predaceous species to persist in agricultural habitats demonstrated that facultative predators could help prevent pest outbreaks, but were less effective at reducing numbers of species already considered above economic thresholds.     

Size structure and substitutability in an odonate intraguild predation system

Interactions between different size classes of predator species have the potential to influence survival of prey species in intraguild predation (IGP) systems, but few studies test for these effects. Using a substitutive design in a field setting, I measured the effects of two size classes of IG predators (large and small larvae of the dragonfly Anax junius) on the mortality of IG prey (larvae of the dragonfly Pachydiplax longipennis). I also examined whether combinations of large A. junius and P. longipennis and small A. junius and P. longipennis had substitutable effects on shared prey (larvae of the damselfly Ischnura verticalis). The presence of both size classes of A. junius, when alone and in combination with P. longipennis, significantly increased mortality of I. verticalis. In the presence of P. longipennis, large and small A. junius had similar effects on the mortality of I. verticalis, and effects of size-structured assemblages of A. junius were similar to the effects of each size class alone at the same density. The effects of the two size classes of A. junius on P. longipennis differed, and P. longipennis mortality was lower when exposed to size structured assemblages of A. junius than when exposed to only large A. junius at the same density. Results were similar to those in a laboratory study, although the effect of P. longipennis on I. verticalis was much lower in the field setting. These results demonstrate that interactions between different size classes of IG predators promote the survival of IG prey and highlight the importance of within-species size structure as a characteristic that may promote the coexistence of predators in IGP systems.     

Distribution and diet of Suwannee bass and largemouth bass in the lower Santa Fe River,Florida

Synopsis Suwannee bass,Micropterus notius, and largemouth bass,Micropterus salmoides, were collected by electrofishing in six habitats in the lower Santa Fe River, Florida during May 1981–March 1982. Both bass species were collected concomitantly in all habitats and habitat segregation was not evident. Crayfish (Procambarus spp.) were the primary food of Suwannee bass. Fish were the primary food of largemouth bass, but crayfish were common in the diet of largemouth bass ≥300 mm long. Suwannee bass have a greater throat width and consumed longer and wider forage than did largemouth bass of equal length. Available evidence suggests that Suwannee bass exhibit a positive selection for crayfish and a diverse forage resource, including abundant crayfish, is necessary for a Suwannee bass to coexist with a largemouth bass. This is Journal Series Number 6034 of the Florida Agricultural Experiment Station.     

Diet of the black-headed heron Ardea melanocephala during the breeding season in South African grasslands

The diet of the black-headed heron was studied using analysis of pellets and prey remnants (225 prey items identified) collected from four sites in South African Highveld Grassland, transformed into cultivated fields. Small vertebrates comprised the staple food of chicks. Rodents were the most important vertebrate prey. Otomys irroratus comprised ca. 50% of the total biomass of vertebrate prey consumed. The diet was supplemented by small lizards, snakes, frogs and fishes. Grasshoppers, beetles, crabs and other arthropods were occasionally preyed upon.     

鰤诺卡氏菌对大口黑鲈头肾巨噬细胞的侵染过程

【背景】鱼类诺卡氏菌病潜伏期和病程较长,感染率和死亡率较高,给水产养殖业带来较大的经济损失,其病原鰤诺卡氏菌(Nocardia seriolae)是胞内寄生菌,侵入细胞后引起慢性感染是主要的致病机制。【目的】构建鰤诺卡氏菌侵染大口黑鲈(Micropterus salmoides)头肾巨噬细胞体外模型,观察鰤诺卡氏菌侵染巨噬细胞的过程并探究鰤诺卡氏菌对巨噬细胞的凋亡作用。【方法】采用密度梯度离心法分离巨噬细胞,通过特异性染色和PCR扩增巨噬细胞表达基因mpeg1对细胞进行鉴定,并通过CCK-8法和氧呼吸暴发活性测定检测巨噬细胞的活性;通过倒置荧光显微镜和流式细胞术观察侵染过程中细菌与细胞的形态与数量变化;通过双荧光流式细胞术检测、乳酸脱氢酶(lactate dehydrogenase, LDH)释放试验及线粒体膜电位检测,探究鰤诺卡氏菌对巨噬细胞的凋亡作用。【结果】从大口黑鲈头肾分离获得纯度高的巨噬细胞,经染色和PCR法鉴定为巨噬细胞;筛选出最优的体外培养条件为1640培养基+1%青霉素链霉素+1%胎牛血清。在脂多糖刺激后,巨噬细胞的氧呼吸暴发能力显著提高(P<0.05)。GFP-鰤诺卡氏菌侵染细胞2 h后细菌被细胞吞噬,4 h细胞变圆且贴壁率降低,6 h细菌大量繁殖并包围细胞,8 h后细胞大量死亡。凋亡相关实验结果表明,侵染初期巨噬细胞凋亡率增加,LDH释放增加,线粒体膜电位下降;随着侵染时间延长,细胞凋亡率下降、LDH释放量及线粒体膜电位下降减少,说明鰤诺卡氏菌对巨噬细胞起先促进后抑制凋亡的作用。【结论】通过密度梯度离心法成功分离大口黑鲈头肾巨噬细胞,并通过鰤诺卡氏菌侵染细胞后初步摸清鰤诺卡细菌在细胞水平的致病机理,建立了鰤诺卡氏菌侵染大口黑鲈头肾巨噬细胞的体外模型;证实了鰤诺卡氏菌可侵染巨噬细胞并抑制细胞凋亡,从而达到在巨噬细胞内存活,为进一步开展鰤诺卡氏菌与巨噬细胞相互作用并阐明鰤诺卡氏菌的致病机制奠定了研究基础。     

Initial mortality of radio-tagged Atlantic salmon (Salmo salar L.) smolts following release downstream of a hydropower station

The fate of radio-tagged hatchery-reared salmon smolts (Salmo salar L.) was investigated in the tailrace of a hydropower station in the Danish River Gudenaa during 2 years. Seventeen and 27 smolts were tagged and released in late May 1996 and during April 1999, respectively. Out of the total of 44 smolts, only two were recorded to leave the river and enter the estuary. In both years of study, electrofishing was used to sample tagged smolts. In 1996, these attempts were unsuccessful, while in 1999, 19 (70% of total) transmitters were retrieved in the stomachs of pikeperch (Stizostedion lucioperca (L.)) and pike (Esox lucius L.), and in grey heron (Ardea cinerea L.) nests. The present study demonstrates that the physical condition of the watershed, with respect to spawning and rearing, may not be the only crucial determining factors of the success of reintroduction of Atlantic salmon. Hydropower plants not only block the free movement of migratory fish, hence preventing the utilisation of spawning and rearing areas, but also form the basis of areas with increased mortality.     

Carotenoids in fish. XXVIII. Carotenoids in Micropterus salmoides (Lalépéde) Centrarchidae

The occurrence and contents of carotenoids in different body parts were investigated by column chromatography and TLC in Micropterus salmoides (Lalép).The following carotenoids were found: -carotene, -cryptoxanthin, -cryptoxanthin, echinenone, canthaxanthin, lutein, zeaxanthin, neothxanthin, tunaxanthin, -doradexanthin, -doradexanthin, idoxanthin, astaxanthin, astaxanthin ester, mutatochrome and mutatoxanthin.Their total contents varied within the range of 0.071–1.691 µg/g wet weight.     

加州鲈源鰤鱼诺卡氏菌的分离鉴定及致病性

[背景] 鰤鱼诺卡氏菌（Nocardia seriolae）是一种严重危害水产养殖业的病原菌,可引起以体表溃疡、出血及组织器官形成结节为特征的鱼类慢性肉芽肿疾病,目前尚无有效的防治方法。[目的] 明确引起安徽省临泉县某养殖场加州鲈（Micropterus salmonoides）结节病的病原菌,探讨其致病性,为该病的有效防治提供科学依据。[方法] 取肝脏结节病灶接种于TSB培养基分离优势细菌,利用表型检查结合分子生物学方法鉴定分离菌株。进一步通过检测分离菌株的毒力基因、测定其对加州鲈的半数致死量（LD₅₀）以及所感染加州鲈的组织病理学变化与组织载菌量,分析其致病性。[结果] 从病鱼体内分离到一株优势菌株NI,综合NI分离株的表型特性、16S rRNA基因序列与鰤鱼诺卡氏菌参考株相应序列的一致性以及特异性PCR扩增结果,确定其为鰤鱼诺卡氏菌。鰤鱼诺卡氏菌NI分离株携带毒力基因gapA、ibeA和mip,人工回归感染后加州鲈出现与自然病例相似的症状,其对加州鲈的LD₅₀为2.58×10⁶ CFU/尾。组织病理学观察到头肾、心脏、肝脏、胃和脾脏均出现慢性肉芽肿病变,肠管肌层疏松、肠绒毛脱落,肌肉组织中肌纤维疏松、间隙增宽。qPCR检测结果显示,组织中鰤鱼诺卡氏菌载量由高到低依次为头肾、心、肝、胃、脾、肠和肌肉。[结论] 鰤鱼诺卡氏菌是引起此次加州鲈结节病的病原菌,对该菌致病性的研究为加州鲈诺卡氏菌病的防控提供了理论依据。     

Can polyphagous predators control the bird cherry-oat aphid (Rhopalosiphum padi) in spring cereals?: A simulation study

Predation by two carabid species,Bembidion lampros (Herbst.) andPterostichus cupreus L., on the cereal aphid,Rhopalsiphum padi L., was described using a discrete event simulation model. The results were incorporated into an aphid population growth model. The aphid model was run using actual temperatures,R. padi emigration rates, field densities and distributions from three years with distinctly different aphid population levels. Predation was incorporated at different time periods. Predation during the arrival of emigrants and establishment of aphid populations had approximately the same effect as predation over the entire aphid period, whereas predation during the 20 days prior to peak had very little effect on resulting peak populations. We conclude that a) yearly levels ofR. padi infestation are mainly determined by the volume and intensity of emigrants; b) peak levels are sensitive to changes in predator density; and c) in some cases an outbreak ofR. padi may be prevented by the action of spring active polyphagous predators alone.     

A comparison between predation effects on zooplankton communities by Neomysis and Chaoborus

Community level effects of predation by two invertebrate predators, the opossum shrimp (Neomysis intermedia), and the larva of the phantom midge (Chaoborus flavicans) were studied and compared. N. intermedia appeared abundantly in the shallow eutrophic Lake Kasumigaura and had a significant impact on the zooplankton community. The predation pressure by Neomysis was highest on cladocerans, followed by rotifers, and finally copepods. At high densities (maximum nearly 20 000 individuals m^–2), Neomysis excluded almost all cladocerans, rotifers and copepods from the lake.Zooplankton communities were established in experimental ponds, into which C. flavicans was introduced. The predator's density was around 1 individual l^–1, and was probably controled by cannibalism. Although Chaoborus larvae feed on various zooplankton species, their predation impact on zooplankton populations was markedly selective. They eliminated medium- and small-sized cladocerans and calanoid copepods from the ponds, but rotifers increased.Although the feeding selectivities of Neomysis and Chaoborus individuals were similar, the predation effects on zooplankton communities by the two predators were different.     

Delineating the effects of a plant trait on interactions among associated insects

Plant traits can affect ecological interactions between plants, herbivores, and predators. Our study tests whether reduced leaf wax in peas alters the interaction between the pea aphid ( Acyrthosiphon pisum), a foliar-foraging predator (a lady beetle, Hippodamia convergens) and a ground-foraging predator (a ground beetle, Poecilus scitulus). We performed a 2×2×2 factorial experiment in which wax level, presence of H. convergens, and presence of P. scitulus were manipulated. Experimental arenas consisted of a cage surrounding three pea plants. One plant in each cage was stocked with 15 pea aphids. In greenhouse and field cage experiments, we assessed the effect of each factor and their interactions on aphid density. As in previous studies, H. convergens foraged for aphids more effectively on reduced wax peas than on normal peas. Other interactions among H. convergens, P. scitulus , and A. pisum were the same on both types of peas. We consider how aphid movement, plant growth, and a high frequency of predation by P. scitulus on H. convergens influenced pea aphid density.     

Relations between hydrological variables and year-class strength of sportfish in eight Florida waterbodies

Hydrological variables have influenced fish recruitment in lakes, reservoirs and rivers. We evaluated how annual and seasonal hydrological variables were related to year-class strength (i.e., residuals from catch curves) of sportfish across eight Florida waterbodies (four rivers and four lakes). Multiple regression equations computed for black bass Micropterus spp. were combined across rivers and year-class strength was negatively related to spring median flow rates and in some cases positively related to winter median flow rates (all p0.10). Conversely, Lepomis spp. residuals combined from the rivers indicated that year-class strength was positively related to median flow rates in the fall prior to spawning and negatively related to post-spawn fall median flow rates (all p0.10). Fish recruitment combined across lakes were not related to water levels in this study, although within lake relationships did occur in some instances. Ecological implications of this work include regulations such as minimum flows and levels (MFLs) regarding sportfish species. Impacts of hydrology on year-class strength of sportfish were stronger in rivers than in lakes for these Florida systems. High flows at least once every 3years in the fall may allow inundation of floodplain habitat, providing favorable environmental conditions for Lepomis spp. reproduction. Setting MFLs during periods of drought (i.e., 3years or more) should consider impacts to short-lived species such as Lepomis spp.     

Phenotypic variation and vulnerability to predation in juvenile bluegill sunfish (<Emphasis Type="Italic">Lepomis macrochirus</Emphasis>)

Bluegill sunfish (Lepomis macrochirus) are known to diversify into two forms specialized for foraging on either limnetic or littoral prey. Because juvenile bluegills seek vegetative cover in the presence of largemouth bass (Micropterus salmoides) predators, natural selection should favor the littoral body design at size ranges most vulnerable to predation. Yet within bluegill populations, both limnetic and littoral forms occur where vegetation and predators are present. While adaptive for foraging in different environments, does habitat-linked phenotypic variation also influence predator evasiveness for juvenile bluegills? We evaluate this question by quantifying susceptibility to predation for two groups of morphologically distinct bluegills; a limnetic form characteristic of bluegills inhabiting open water areas (limnetic bluegill) and a littoral form characteristic of bluegills inhabiting dense vegetation (littoral bluegill). In a series of predation trials, we found that bluegill behaviors differed in open water habitat but not in simulated vegetation. In open water habitat, limnetic bluegills formed more dense shoaling aggregations, maintained a larger distance from the predator, and required longer amounts of time to capture than littoral bluegill. When provided with simulated vegetation, largemouth bass spent longer amounts of time pursuing littoral bluegill and captured significantly fewer littoral bluegills than limnetic fish. Hence, morphological and behavioral variation in bluegills was linked to differential susceptibility to predation in open water and vegetated environments. Combined with previous studies, these findings show that morphological and behavioral adaptations enhance both foraging performance and predator evasiveness in different lake habitats.     

大口黑鲈白皮病病原菌的分离鉴定及药物敏感性试验

【背景】近年,广东、广西等多地养殖的大口黑鲈(Micropterus salmoides)在苗种期间极易暴发白皮病,并且与已报道的症状不同,严重危害大口黑鲈苗种的生产。【目的】确定大口黑鲈苗种白皮病的病原,通过分析生长特性、毒力因子、致病性、组织病理与敏感药物筛选试验,为该病的研究与防控提供科学参考。【方法】从患白皮病大口黑鲈的病灶处分离细菌,结合形态观察、生理生化指标、16S rRNA基因和gyrB基因序列分析等鉴定菌株;绘制菌株的生长曲线,分析温度、盐度及pH对生长的影响;采用平板法检测菌株毒力因子活性,PCR方法检测携带毒力基因的情况;通过浸泡感染试验验证菌株的致病性及其组织病理特征;采用微量稀释法测定菌株对水产常用的10种抗菌药物和6种消毒剂的敏感性。【结果】从患病的大口黑鲈白皮处肌肉分离纯化到优势菌株ZJS18004,经形态特征、生理生化特性、16S rRNA基因和gyrB基因序列分析,鉴定为维氏气单胞菌(Aeromonas veronii);菌株ZJS18004的最适生长温度为30°C,最适pH值为8.0,最适盐度为5‰;在30°C时的生长曲线显示0-1 h是迟缓期,1-5...     

Negative dietary effects of Colorado potato beetle eggs for the larvae of native and introduced ladybird beetles

Aphidophagous ladybird beetles (Coleoptera: Coccinellidae) are attracted to and feed heavily on aphids, but many species will also feed opportunistically on other prey that they encounter. In potatoes (Solanum tuberosum L.) in Washington State, USA, coccinellids feed on both green peach aphids (“GPA,” Myzus persicae Sulzer) and eggs of the Colorado potato beetle (“CPB,” Leptinotarsa decemlineata Say). The guild of aphidophagous ladybirds includes two native species, Hippodamia convergens Guérin-Méneville and Coccinella transversoguttata Brown. Recently, an introduced species, Coccinella septempunctata L., has invaded and apparently displaced its native congener. A second exotic, Harmonia axyridis Pallas, has colonized the area and is becoming more abundant. We compared larval development of each species on a monotypic diet of GPA, a monotypic diet of CPB eggs, or a mixed diet of both GPA and CPB eggs. Our goal was to answer two questions: (1) do larvae of the four ladybird species benefit from including CPB eggs in their diet and (2) do the four ladybird species differ in their ability to utilize CPB eggs as prey? No larva of any species completed development on a pure diet of CPB eggs, and survivorship was highest for all species when they fed on a pure diet of GPA. One native species, H. convergens, and one exotic species, H. axyridis, exhibited significantly lower survivorship on a mixed diet of both CPB eggs and GPA, compared to a pure GPA diet; H. axyridis also took longer to develop from egg to adult when both prey were provided. Survivorship of the two Coccinella spp. was not altered by the inclusion of CPB eggs with GPA, although CPB eggs lengthened the development time of C. transversoguttata. Adult size was not consistently affected by diet for any of the coccinellids. Overall, no ladybird species benefited from the inclusion of potato beetle eggs in its diet. The two Coccinella species responded similarly to the inclusion of CPB eggs, and so we would not expect any difference in the success of coccinellid larval development in potato fields following the replacement of C. transversoguttata by C. septempunctata. Hippodamia convergens and H. axyridis, the two species whose survivorship was depressed by combining CPB egg and aphid prey, were also the two species that consumed the greatest number of CPB eggs during successful larval development. A comparison of total egg consumption by each species cohort suggested that displacement of the other species by H. axyridis would not alter CPB biological control, because the higher per capita feeding rate by H. axyridis larvae compensated for individuals’ greater mortality risk on a diet including CPB eggs.     

Food and growth relations of the marine microzooplankter,Synchaeta cecilia (Rotifera)

The trophic interactions of the marine rotifer Synchaeta cecilia were investigated by determining its feeding and growth rates on a wide variety of marine phytoplankton and by determining its susceptibility to predation by the calanoid copepod, Acartia tonsa. Reproduction of S. cecilia was sustained in four-day feeding trails by 13 of 37 algal species tested. Growth-supporting species included species of Cryptophyceae, Dinophyceae, Chlorophyceae and Haptophyceae in sizes from 4 to 47 μm. Within these taxa, other species in the acceptable size range failed to support growth. No species of Cyanophyceae, Bacillariophyceae, or Chrysophyceae supported growth of the rotifer. S. cecilia can be maintained on unialgal cultures of Cryptophyceae but growth is enhanced by a combination of two or three species; a mixture of Chroomonas salina (Cryptophyceae), Heterocapsa pygmaea (Dinophyceae), and Isochrysis galbana (Haptophyceae) has sustained laboratory stocks of S. cecilia for over four years. The expected response of S. cecilia to food quantity was observed: as food concentration was increased from 58 to 1154 μg C 1⁻¹, the population growth constant increased from 0.17 to 0.60 d⁻¹ at 20°C. This is equivalent to population doubling times of 4.0 and 1.1 days at H. pygmaea densities of 500 and 10⁴ cells ml⁻¹, respectively. The susceptibility of S. cecilia to predation was investigated by determining its rate of capture by the omnivorous marine copepod Acartia tonsa. At prey densities of 5 to 35 μg C 1⁻¹ (0.3 to 1.9 individuals 1⁻¹), A. tonsa readily ingested S. cecilia at rates up to 3 μg C copepod⁻¹ day⁻¹.