Functional morphology of tegmina-based stridulation in the relict species Cyphoderris monstrosa (Orthoptera: Ensifera: Prophalangopsidae)

Male grigs, bush-crickets and field crickets produce mating calls by tegminal stridulation: the scraping together of modified forewings functioning as sound generators. Bush- (Tettigoniidae) and field-crickets (Gryllinae) diverged some 240 million years ago, with each lineage developing unique characteristics in wing morphology and the associated mechanics of stridulation. The grigs (Prophalangopsidae), a relict lineage more closely related to bush crickets than to field-crickets, are believed to retain plesiomorphic features of wing morphology. The wing cells widely involved in sound production, such as the harp and mirror, are comparatively small, poorly delimited and/or partially filled with cross-veins. Such morphology is similarly observed in the earliest stridulating ensiferans, for which stridulatory mechanics remains poorly understood. The grigs, therefore, are of major importance to investigate the early evolutionary stages of tegminal stridulation, a critical innovation in the evolution of the Orthoptera. The aim of this study is to appreciate the degree of specialisation on grig forewings, through identification of sound radiating area areas and their properties. For well-grounded comparisons, homologies in wing venation (and associated areas) of grigs and bush-crickets are re-evaluated. Then, using direct evidence, this study confirms the mirror cell, in association with two other areas (termed ‘neck’ and ‘pre-mirror’), as the acoustic resonator in the grig Cyphoderris monstrosa. Despite the use of largely symmetrical resonators, as found in field-crickets, analogous features of stridulatory mechanics are observed between C. monstrosa and bush-crickets. Both morphology and function in grigs represents transitional stages between unspecialised forewings and derived conditions observed in modern species

Nodules from Fynbos legume Virgilia divaricata have high functional plasticity under variable P supply levels

Legumes have the unique ability to fix atmospheric nitrogen (N2) via symbiotic bacteria in their nodules but depend heavily on phosphorus (P), which affects nodulation, and the carbon costs and energy costs of N2 fixation. Consequently, legumes growing in nutrient-poor ecosystems (e.g., sandstone-derived soils) have to enhance P recycling and/or acquisition in order to maintain N2 fixation. In this study, we investigated the flexibility of P recycling and distribution within the nodules and their effect on N nutrition in Virgilia divaricata Adamson, Fabaceae, an indigenous legume in the Cape Floristic Region of South Africa. Specifically, we assessed tissue elemental localization using micro-particle-induced X-ray emission (PIXE), measured N fixation using nutrient concentrations derived from inductively coupled mass-spectrometry (ICP-MS), calculated nutrient costs, and determined P recycling from enzyme activity assays. Morphological and physiological features characteristic of adaptation to P deprivation were observed for V. divaricata. Decreased plant growth and nodule production with parallel increased root:shoot ratios are some of the plastic features exhibited in response to P deficiency. Plants resupplied with P resembled those supplied with optimal P levels in terms of growth and nutrient acquisition. Under low P conditions, plants maintained an increase in N2-fixing efficiency despite lower levels of orthophosphate (Pi) in the nodules. This can be attributed to two factors: (i) an increase in Fe concentration under low P, and (ii) greater APase activity in both the roots and nodules under low P. These findings suggest that V. divaricata is well adapted to acquire N under P deficiency, owing to the plasticity of its nodule physiologyDST-NRF Centre of Excellence in Tree Health Biotechnology(CTHB).http://www.elsevier.com/locate/jplpham201

Unexploited females and unreliable signals of male quality in a Malawi cichlid bower polymorphism

Complex signals present 2 outstanding questions: why do they exist and how are they interpreted? Multiple signals can be beneficial for the increased diversity or redundancy of information they convey; however, it is not clear how receivers use this additional information. I investigated a lekking Malawi cichlid fish that builds polymorphic bowers; some males build their sand spawning craters on rock platforms, rather than the sand floor, resulting in increased overall height and reduced construction, maintenance, and competition costs. This suggests that rock bowers are an unreliable signal of male investment. Using field observations and in situ bower manipulations I tested fitness costs, female preferences for bower type, bower height, and male displays, and mechanisms for the maintenance of bower polymorphism. In contrast to predictions, observational and experimental data confirmed that females were more likely to visit rock bowers but did not ultimately lay more eggs there. This indicates that females responded to potentially deceptive rock bower males by advancing to the next stage of courtship but were not ultimately fooled by these deceptive signals. Assessing additional signals during the next courtship stage may allow females to counteract initial sensory exploitation or females may be intentionally increasing their investment in mate assessment in response to deceptive signals. Male bower polymorphism may be maintained by the limited availability of rock platforms; there was no evidence for significant variation in individual female preferences or male bower-building strategies. Copyright 2010, Oxford University Press.

Towards Autonomous Artificial Agents? Proposal for a Naturalistic Activity-Based Model of (Artificial) Life

While the contemporary achievements of AI and robotics are indisputable, the issue of autonomy for artificial agents still looms ahead despite technological progress and rich conceptual debates. Drawing on recent theoretical propositions from the enactive approach to autonomy, we first highlight several limitations of what we call an identity-based model. Through the study of four real-life cases, we then not only argue that autonomy cannot be conflated with behavioral self-maintenance or organizational closure, but that it can sometimes violate these conditions. Finally, we propose a naturalistic activity-based model of autonomous agents that emphasizes the importance of norm-establishing processes distributed across an intricacy of milieus.info:eu-repo/semantics/publishe