Temporal dynamics of inducible anti‐herbivory defenses in the brown seaweed Ascophyllum nodosum (Phaeophyceae)1

Anti‐herbivory defenses support persistence of seaweeds. Little is known, however, about temporal dynamics in the induction of grazer‐deterrent seaweed traits. In two induction experiments, consumption rates of the periwinkle Littorina obtusata (L.) on the brown seaweed Ascophyllum nodosum (L.) Le Jolis were measured in 3‐d intervals. Changes in palatability of directly grazed A. nodosum were tested every 3 d with feeding assays using fresh and reconstituted seaweed pieces. Likewise, assays with fresh A. nodosum assessed changes in seaweed palatability in response to water‐borne cues from nearby grazed conspecifics. Consumption rates of L. obtusata varied significantly during the 27‐d induction phase of each experiment. Direct grazing by L. obtusata lowered palatability of fresh and reconstituted A. nodosum pieces to conspecific grazers after 15 d as well as after 6 and 12 d, respectively. After 12, 18, and 24 d, fresh A. nodosum located downstream of L. obtusata‐grazed conspecifics was significantly less palatable than A. nodosum located downstream of ungrazed conspecifics. Changes in L. obtusata consumption rates and A. nodosum palatability during both induction experiments suggest temporal variation of grazer‐deterrent responses, which may complicate experimental detection of inducible anti‐herbivory defenses.     

Parasite-induced alteration of odour responses in an amphipod–acanthocephalan system

Odour-related behaviours in aquatic invertebrates are important and effective anti-predator behaviours. Parasites often alter invertebrate host behaviours to increase transmission to hosts. This study investigated the responses of the amphipod Hyalella azteca when presented with two predator chemical cues: (i) alarm pheromones produced by conspecifics and (ii) kairomones produced by a predatory Green Sunfish (Lepomis cyanellus). We compared the responses of amphipods uninfected and infected with the acanthocepalan parasite Leptorhynchiodes thecatus. Uninfected amphipods reduced activity and increased refuge use after detecting both the alarm pheromones and predator kairomones. Infected amphipods spent significantly more time being active and less time on the refuge than uninfected amphipods, and behaved as if they had not detected the chemical stimulus. Therefore, L. thecatus infections disrupt the amphipods’ anti-predator behaviours and likely make their hosts more susceptible to predation.     

A cytological study on the development of the different types of visual cells in the chicken (Gallus domesticus)

The formation of visual cells and their intracellular organelles was studied in the embryonic chicken (Gallus domesticus) between stage 36 and hatching. Cilia formation was observed at stage 30 and by stage 42, outer segment formation from the cilia was evident. The inner segments appeared as buddings at stage 36. By stage 37, the buddings of double cones were observed clearly and such buddings elongated by stage 42. Both the single cones and rods appeared as buddings by stage 38 and elongation of the buddings was seen by stage 42. Oil droplets initially appeared by stage 39 in accessory cones and were observed in other cones by stage 42. Glycogen bodies were demonstrated firstly in rods and accessory cones at stage 43 and their development was completed by stage 45. In essence, all the essential elements of the visual cells were fully developed by hatching.     

Melanic moths and charges in epiphytic vegetation in north-west England and north Wales

In 1973 the appearance and epiphyte cover of tree trunks was examined along a 125 km cline of melanic frequency in the peppered moth in NW England and N Wales. The sampled sites were resurveyed in 1986. There has been a marked increase in the crustose lichen Lecanora conizaeoides at the eastern end of the transect, an increase in lichen diversity in the middle of the transect and a possible decline in large foliose forms at the western end. These changes are discussed in relation to the eastward shift of the cline in melanic frequencies in the moth.     

When assumptions on visual system evolution matter: nestling colouration and parental visual performance in birds

Comparative studies in visual ecology of birds often rely on several assumptions on the evolution of avian vision. In this study, we show that when these assumptions are not upheld, conclusions may be strongly affected. To illustrate this purpose, we reanalysed the data of Avilés & Soler (J. Evol. Biol. 22 : 376–386, 2009) who demonstrated that nestling gape colouration in altricial birds is associated with visual system. We show that a slight change in analysis methodology leads to opposite conclusions. Such conflicting result raises the problem of applying powerful methods developed for continuous variables to a small sample and a small number of independent events of qualitative visual system shift in comparative analyses. Further, we show that the current trend to assume strong phylogenetic inertia of avian visual systems is contradicted by data and that the sequencing of the SWS1 opsin gene should be considered as an alternative approach.     

Relationships among male sexually selected traits in the bean bug,Riptortus pedestris (Heteroptera: Alydidae)

Current concepts of sexual selection suggest that male reproductive success is determined by multiple sexual traits. As expression and production of multiple sexual traits are frequently associated with each other, positive or negative correlations among multiple sexual traits ensue. These relationships among traits associated with male reproductive success may be crucial in the evolution of male reproductive strategies. Here, we investigate phenotypic relationships among sexually selected traits in the armed bean bug Riptortus pedestris. In this insect, males with a larger body and weapon are more likely to win male–male competitions, and males with a larger weapon or higher courtship rate are more attractive to females. There was a significant positive correlation between body size and weapon size, whereas the courtship rate had significant negative correlations with body size and weapon size. Our results suggested that there was a phenotypic trade‐off between courtship rate and male morphology. In this insect, smaller males may make more effort in courtship behavior as an alternative mating tactic.     

多尺度植物色彩表征及其与人体响应的关系

色彩是人们对植物外观的第一印象,与植物视觉特征和人体响应关系密切,因此,对森林美景度提升和公众适宜性契合具有重要作用。结合色彩学形成的历史关键节点和1个世纪以来植物色彩的研究动态,将植物色彩研究的发展历程划分为萌芽、形成、发展和繁荣等4个阶段,并简介了各阶段的主要特点。同时,从植物器官、植物个体、植物群体(涵盖种群和群落)、整体景观等4个视觉尺度以及审美、生理与心理等3个影响层面,阐述与评价了植物色彩传达机制与人体响应关系的相关研究。在此基础上,围绕植物色彩特征提取中存在的色彩要素定量、特征因子选取、色彩量化方法等方面的不足之处,对未来研究方向进行展望,提出植物色彩尺度与公众响应关系剖析、较大尺度色彩评价因子的深入挖掘、色彩量化方法的多学科融入、公众对植物色彩响应关系综合比对、森林景观美景度提升实践等5个方向的发展趋势,以期为全面地了解植物色彩的传达机制与影响、科学地开展不同精度和尺度下的植物色彩研究提供参考。     

Comparing entire colour patterns as birds see them

Colour patterns and their visual backgrounds consist of a mosaic of patches that vary in colour, brightness, size, shape and position. Most studies of crypsis, aposematism, sexual selection, or other forms of signalling concentrate on one or two patch classes (colours), either ignoring the rest of the colour pattern, or analysing the patches separately. We summarize methods of comparing colour patterns making use of known properties of bird eyes. The methods are easily modifiable for other animal visual systems. We present a new statistical method to compare entire colour patterns rather than comparing multiple pairs of patches. Unlike previous methods, the new method detects differences in the relationships among the colours, not just differences in colours. We present tests of the method's ability to detect a variety of kinds of differences between natural colour patterns and provide suggestions for analysis.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 86 , 405–431.     

Tuning in to multiple predators: conflicting demands for shell morphology in a freshwater snail

1. We examined the response to chemical cues from fish and crayfish, two predators with contrasting feeding modes, and their single and combined effect on shell morphology in the freshwater snail Radix balthica. 2. Snails were subjected to four treatments: tench (Tinca tinca), signal crayfish (Pacifastacus leniusculus), a combination of tench and signal crayfish and no predators (control). Shell shape, crushing resistance and shell thickness were quantified. We also analysed whether shape or shell thickness contributes most to crushing resistance. 3. Chemical cues from the fish induced a rounder shell shape in R. balthica, a thicker shell and a higher crushing resistance, whereas crayfish chemical cues had no effect on shell morphology, shell thickness or crushing resistance. Shell shape contributed more to crushing resistance than shell thickness. 4. The combined predator treatment showed an intermediate response between the fish and crayfish treatments. Shell roundness was reduced compared with the fish treatment, but the reduced crushing resistance that comes with a less rounded shell was compensated by an increased investment in extra shell material, exceeding that of the fish treatment. 5. Our study extends previous studies of multipredator effects on phenotypically plastic freshwater snails by showing that the snails are able to fine‐tune different elements of morphology to counter predator‐specific foraging modes.