Handedness in fiddler crab fights

Asymmetric weapons are common in bilateral animals and, in some species, they can occur on either the left- or the right-hand side of the body (lateralization). Fiddler crabs (Uca spp, Decapoda: Ocypodidae) have an enlarged claw that is used in male–male combat over territories and in courtship displays. Males can be either right- or left-handed, and most species have a 1:1 ratio. Past studies have found little effect of handedness on fighting success, fight duration or other measures of combat. Here we show that, while handedness per se, does not affect fighting, handedness matching has a significant effect. In Uca mjoebergi, fights between different-handed males were more likely to escalate to grappling, suggesting that it is harder for the combatants to determine the winner. We suggest that the positioning of the claws during fighting creates distinct forces that result in different outcomes for same- versus different-handed fights. This can represent a strong selective pressure in populations with an uneven handedness distribution where the handedness minority will often engage in different-handed fights. We discuss these results in light of the selective forces that may act on handedness distribution in fiddler crabs

An evaluation of a two year cognitive intervention programme in technology education for Key Stage 4

We reported (in Vol. 1 No 2 1996) an interim evaluation of the effects of a small-scale cognitive intervention programme in technology. The subjects in this study were 120 Year 10 students (15+) attending a girls comprehensive school in an inner London. Education Authority. The students were randomly placed in eight all ability classes according to the normal school practice and policy. Three experimental classes (45 students) and five control classes (75 students) were identified. The new head of design and technology had targeted this year group in order to try to raise achievement of a group of students in a domain which had not previously performed as effectively as had been expected. The teacher would be taking the three experimental groups designated 10.1, 10.2, 10.5. Two other teachers would have the responsibility of teaching the five control classes. Unfortunately we were unable to establish a control group being taught by the teacher of the experimental groups.The model that was adopted for the study utilised principles from Cognitive Acceleration through Science Education (CASE) (the five pillars), from Instrumental Enrichment and from the Somerset Thinking Skills project. The essential feature of the study was to concentrate on enhancing the students' thinking, reasoning and problem solving capability with the teacher acting as a mediator and director of the activities and of the discussion that occurred. (For details see pp 121-124 Vol. 1 No 21996). The results suggested that the intenention was having a positive but modest effect in technology achievement on the experimental classes, but that there was little or no effect in other areas of the curriculum that we were investigating. This article is a follow-up to the original paper and presents further data showing the effects of the inteNention after the full two years of the programme. The subjects, design and methodology adopted throughout this project are described in the original paper (Hamaker et al 1996).The established groups with their corresponding teachers are summarised in Table 1. Each of the experimental classes had one core technology lesson replaced by an inteNention lesson each fortnight. Class 10.2 had a further graphical communication option replaced by an intervention lesson each fortnight. The five control classes received a normal allocation of technology core and option lessons. The tests and measures used for analyses are similar to that already described (Hamaker et al 1996). Further clarification on the nature of these tests and measures can be obtained from the authors of this article

The role of claw color in species recognition and mate choice in a fiddler crab

Many animal signals are brightly colored and convey information about species identity as well as information about individual conspecifics. Colorful bird and lizard signals have received much attention, and many studies have related specific spectral properties of these signals to variation in mating success and territory defense. Far less attention has been given to invertebrates even though there are spectacularly colorful species. The enlarged claw of the male banana fiddler crab Austruca mjoebergi, for example, is bright yellow and contrasts vividly against the mudflat substrate. It is used in waving displays to attract females and in male territory defense and combat. Claw color varies among males in the degree of “yellowness,” ranging very pale yellow to orange. In this study we examined female responses to claw color variation in two-choice tests using robotic crabs. We found that although females strongly discriminate against colors that fall outside the natural range of intensity, hue and chroma, they show no consistent preferences for different claw colors within the natural range, and no single component of claw color (hue, chroma or intensity) independently affected female choices. Using three-choice tests, we also showed that female preferences induce stabilizing selection on male claw color. We conclude that, although claw color is sufficient to facilitate species recognition, it is unlikely to be used in intraspecific mate choice to provide information about male quality

A Middle Palaeolithic wooden digging stick from Aranbaltza III, Spain

Aranbaltza is an archaeological complex formed by at least three open-air sites. Between 2014 and 2015 a test excavation carried out in Aranbaltza III revealed the presence of a sand and clay sedimentary sequence formed in floodplain environments, within which six sedimentary units have been identified. This sequence was formed between 137±50 ka, and includes several archaeological horizons, attesting to the long-term presence of Neanderthal communities in this area. One of these horizons, corresponding with Unit 4, yielded two wooden tools. One of these tools is a beveled pointed tool that was shaped through a complex operational sequence involving branch shaping, bark peeling, twig removal, shaping, polishing, thermal exposition and chopping. A use-wear analysis of the tool shows it to have traces related with digging soil so it has been interpreted as representing a digging stick. This is the first time such a tool has been identified in a European Late Middle Palaeolithic context; it also represents one of the first well-preserved Middle Palaeolithic wooden tool found in southern Europe. This artefact represents one of the few examples available of wooden tool preservation for the European Palaeolithic, allowing us to further explore the role wooden technologies played in Neanderthal communities

The functions of multiple visual signals in a fiddler crab

In many species, it is common for animals to have multiple signals within one channel of communication. Multiple signals may, however, be inefficient if they are redundant in nature. Identifying the functional significance of these multiple signals is therefore important if we are to understand the evolution of such elaborated behaviours. We proposed to identify the roles of movement‐based multiple signals in a model animal system. Male fiddler crabs wave their sexually dimorphic enlarged claw during social interactions. Some species present multiple signals, where the level of complexity of the movement changes. Males of Austruca mjoebergi can perform a double wave consisting of a high‐ followed by a low‐elevation lifting of the claw, or a single wave consisting of the high‐elevation movement alone. We first investigated structural differences between the double and single wave types, and found that single waves were lower in elevation than double waves. We then explored the adaptive meaning of the wave types by manipulating the social context in which males wave. We found that double waves were given in all contexts and in higher proportions at long distances, suggesting a function of broadcasting male location. Single waves, on the other hand, were mainly given at close range and in the presence of conspecifics, suggesting intraspecific communication. Female presence elicited the highest number and proportion of single waves, a likely result of a female preference for higher wave rates. Finally, we point out that there is an element of interaction between wave types that deserves future attention. This paper is an important contribution to expand our understanding of the adaptive meaning of multiple visual signals and help reach a unified theory of their evolution.This study was funded by an ARC Discovery Grant (S4106048) to P.R.Y.B

Thermal constraints on microhabitat selection and mating opportunities

Abstract not availablePablo Munguia, Patricia R.Y. Backwell, M. Zachary Darnel