POPULATION DYNAMICS OF ZEBRA MUSSELS DREISSENA POLYMORPHA (PALLAS, 1771) DURING THE INITIAL INVASION OF THE UPPER MISSISSIPPI RIVER, USA

The aim of this study was to document and model the populationdynamics of zebra mussels Dreissena polymorpha (Pallas, 1771)in Pool 8 of the Upper Mississippi River (UMR), USA, for fiveconsecutive years (1992–1996) following their initialdiscovery in September 1991. Artificial substrates (concreteblocks, 0.49 m² surface area) were deployed on or aroundthe first of May at two sites within each of two habitat types(main channel border and contiguous backwater). Blocks wereremoved monthly (30 ± 10 d) from the end ofMay to the end of October to obtain density and growth information.Some blocks deployed in May 1995 were retrieved in April 1996to obtain information about over-winter growth and survival.The annual density of zebra mussels in Pool 8 of the UMR increasedfrom 3.5/m² in 1992 to 14,956/m² in 1996. The average May–Octobergrowth rate of newly recruited individuals, based on a von Bertalanffygrowth model fitted to monthly shell-length composition data,was 0.11 mm/d. Model estimates of the average survivalrate varied from 21 to 100% per month. Estimated recruitmentvaried substantially among months, with highest levels occurringin September–October of 1994 and 1996, and in July of1995. Recruitment and density in both habitat types increasedby two orders of magnitude in 1996. Follow-up studies will benecessary to assess the long-term stability of zebra musselpopulations in the UMR; this study provides the critical baselineinformation needed for those future comparisons. (Received 5 November 2004; accepted 30 September 2005)     

迁飞过程中昆虫的行为:对风温场的适应与选择

本文综述了昆虫在迁飞过程中对大气物理环境的各种行为反应,有边界层气象的理论重新审视迁飞种群的时空分布,提出了“边界层顶现象”的概念。即边界层顶的低空逆温和低空急流为迁飞种群提供了最适宜的风温场,迁飞种群在边界层顶集聚成层,并通过定向理一步修饰其位移方位,表现出对风温场的主动选择能力和对大气结构和运动的高度复杂的适应性反应。进一步深化对“边界层顶现象”的认识,对迁飞性害虫的异地预测具有重要的理论意义     

三平正并殖吸虫成虫、童虫和后尾蚴扫描电镜的观察

本文是在原光学镜观察的基础上,用扫描电镜对三平正并殖吸虫模式标本产地广东产的本种并殖吸虫进行形态学观察。发现幼虫及成虫期的腹吸盘体壁及成虫排泄孔体壁上均有单个或两个以上的群(簇)生棘排列。并证实在不同宿主体内(犬和猫),不同虫龄期(172和90天)的形态基本相符。讨论申提示不同地域的虫体形态有差异,可能存在地域株的问题。     

THE REACTION OF WHEAT VARIETIES TO LOOSE SMUT AS DETERMINED BY EMBRYO, SEEDLING, AND ADULT PLANT TESTS

The possibility of using an embryo test as a means of determining the reaction of wheat varieties to loose smut ( Ustilago tritici (Pers.) Rostr.) has been investigated. Fifty-seven varieties were inoculated with two physiologic races by the partial vacuum method and the embryos, seedlings, and adult plants were examined for infection. Most of the varieties were fully susceptible to one or both races, and only ten showed real resistance to any one race. Braun R and Molinel proved almost immune to infection. The resistance in other varieties which showed no infection in the field was expressed as embryo susceptibility, i.e. the embryo became infected in much the same way as in field-susceptible varieties.
In the latter varieties infection passes from the embryo into the growing point of the young seedling. In the embryo-susceptible field-resistant varieties, infection does not pass from the scutellum and the growing point is therefore uninfected.
The reaction of most of the varieties tested was straightforward resistance or susceptibility, but in a few varieties a small proportion of the grains reacted differently from the majority. These reactions are discussed.     

THE COURSE OF ROD DARK ADAPTATION AS INFLUENCED BY THE INTENSITY AND DURATION OF PRE-ADAPTATION TO LIGHT

An increase in the degree of light adaptation causes a decrease in the slope of the subsequent rod dark adaptation function and a displacement of the function to the right on the time axis. Over a wide range, these changes occur to the same extent whether the increase in the degree of light adaptation is produced by raising the intensity or by prolonging the exposure. Within these limits, the Bunsen-Roscoe reciprocity law applies to the intensity and duration of pre-exposure. Over a still wider range, dark adaptation has the same course following brief exposure to a bright light as it has following prolonged exposure to a dim light, provided the degree of light adaptation is the same in both instances (as indicated by identical initial dark adaptation thresholds).     

GROWTH AND TOXICITY OF PRYMNESIUM PARVUM (HAPTOPHYTA) AS A FUNCTION OF SALINITY,LIGHT, AND TEMPERATURE1

The growth rate, stationary cell concentration, and toxicity of Prymnesium parvum N. Carter were measured using a strain isolated from Texas inland waters. We used a multifactor experimental approach with multiple regression analysis to determine the importance of environmental factors, including temperature, light, and salinity to these algal measurements. Exponential growth rate was unimodal in relation to temperature, salinity, and irradiance, with an estimated maximal growth of 0.94 d^?1 occurring at 27°C, 22 practical salinity units (psu), and 275 μmol photons·m^?2·s^?1. Stationary cell concentrations also had unimodal responses to temperature and salinity but increased with irradiance. Maximal cell concentrations were estimated to occur at 26°C and 22 psu. Both maximum growth rate and highest stationary cell concentrations were measured at levels of each factor resembling warm, estuarine conditions that differ from the conditions under which blooms occur in inland waters in the southwestern United States. Acute toxicity to fish was highest at the lowest salinity and temperature levels, conditions not optimal for exponential growth but similar to those under which blooms occur in inland waters. Our results imply that summer blooms could occur in inland waters of the southwestern United States. Generally, they have not, suggesting that factors other than those investigated in this research influence bloom dynamics.     

INTERPOPULATION VARIATION IN JUVENILE SURVIVAL AND GROWTH RATES OF LYMNAEA PEREGRA (GASTROPODA: PULMONATA); TEMPERATURE AT RECRUITMENT AS A SELECTION PRESSURE?

Three neighbouring populations of Lymnaea peregra had recruitmentin the summer (June and July), but one population (Sheaf) hada second recruitment in September and October. We hypothesizedthat juveniles of the Sheaf population would be subject to selectionunder both ‘summer’ and ‘winter’ conditions,and thus should be more resistant to low-temperature stressthan juveniles of the other populations. The hypothesis wassupported by the findings that Sheaf juveniles survived andgrew better over a wider range of temperatures (2, 10, 15 and20°C )while juveniles of the other two populations wereadapted only to higher temperatures (15 and 20°C). Therewas evidence that some of these traits were genetically fixed. ^*Present address: Department of Applied Science, City Polytechnicof Hong Kong, Mongkok, Kowloon, Hong Kong. (Received 15 September 1988; accepted 16 December 1988)     

光照强度对中华鳖稚鳖摄食和生长的影响

在３０００，１０００，３００和１０１ｘ的光照强度下，测定了中华鳖稚鳖的最大日摄食量和特定生长率。结果表明，光照强度对中华鳖稚瞥珠最大日摄食量影响显著，随着光照强度的减弱，中华鳖稚鳖的最大日摄食量逐渐增加，二者之间呈线性负相关。     

ACTION OF A JUVENILE HORMONE ANALOGUE,ALTOSID®, INSECT GROWTH REGULATOR,ON THE MORPHOGENESIS AND ADULT ECLOSION OF THE FLESHFLY,SARCOPHAGA BULLATA

Topical application of a juvenile hormone analogue, Altosid, onto the larvae of the fleshfly, Sarcophaga bullata, inhibited adult eclosion. While the head and thorax were resistant to the hormone analogue, the abdomen was highly sensitive. Depending on the dose of the compound applied, various morphogenetic effects were noticed on the abdomen such as failure of rotation of male genitalia, reduction in the number of bristles and microtrichiae, irregular orientation of bristles and inhibition of differentiation of genitalia.The affected flies were examined histologically. The muscles of the genitalia and abdomen failed to develop, while thoracic muscles exhibited dystrophic changes. The significance of these muscular effects is discussed in relation to the inhibition of adult eclosion of Altosid treated insects.

---

Résumé L'application topique d'un analogue de l'hormone juvénle, l'Altosid, sur les larves de la mouche de la viande Sarcophaga bullata, inhibe l'éclosion imaginale. Tandis que la tête et le thorax sont résistants à cet analogue de l'hormone, l'abdomen y est très sensible. Selon la dose du produit appliquée, différents effets morphogénétiques ont été observés au niveau de l'abdomen, tels que l'absence de rotation des genitalia du mâle, la réduction du nombre des soies et microtriches, l'orientation irrégulière des soies et l'inhibition de la différenciation des genitalia.Les mouches traitées ont été examinées histologiquement. Les muscles des genitalia et de l'abdomen ne se sont pas développés cependant que les muscles thoraciques montraient des dystrophies. La signification de ces effets sur les muscles est discutée en rapport avec l'inhibition de l'élosion imaginale chez les insectes traités par l'Altosid.

     

THE RESPONSE TO SELECTION FOR FAST LARVAL DEVELOPMENT IN DROSOPHILA MELANOGASTER AND ITS EFFECT ON ADULT WEIGHT: AN EXAMPLE OF A FITNESS TRADE-OFF

A selection experiment using Drosophila melanogaster revealed a strong trade-off between adult weight and larval development time (LDT), supporting the view that antagonistic pleiotropy for these two fitness traits determines mean adult size. Two experimental lines of flies were selected for a shorter LDT (measured from egg laying to pupation). After 15 generations LDT was reduced by an average of 7.9%. The response appeared to be controlled primarily by autosomal loci. A correlated response to the selection was a reduction in adult dry weight: individuals from the selected populations were on average 15.1% lighter than the controls. The lighter females of the selected lines showed a 35% drop in fecundity, but no change in longevity. Thus, there is no direct relationship between LDT and adult longevity. The genetic correlation between weight and LDT, as measured from their joint response to selection, was 0.86. Although there was weak evidence for dominance in LDT, there was none for weight, making it unlikely that selection acting on this antagonistic pleiotropy could lead to a stable polymorphism. In all lines, sex differences in weight violated expectations based on intrasex genetic correlations: Females, being larger than males, ought to require a longer LDT, whereas there was a slight trend in the opposite direction. Because the sexual dimorphism in size was not significantly altered by selection, it appears that the controlling loci are either invariant or have very limited pleiotropic effect on developmental time. It is suggested that they probably control some intrinsic, energy-intensive developmental process in males.