The occurrence of the extinct shark genus Sphenodus in the Jurassic of Sicily

During the systematic revision of some historical collections containing Mesozoic ammonites, housed at the "G.G. Gemmellaro" Geological Museum of the Palermo University, a fossil shark’s tooth has been discovered. This specimen, indicated as Lamna in the original catalogue, can be attributed to the genus Sphenodus, an extinct cosmopolitan shark ranging from Lower Jurassic rocks to the Paleocene. The specimen is part of the Mariano Gemmellaro Collection which mainly consists of Middle-Upper Jurassic ammonites coming from Tardàra Mountain, between Menfi and Sambuca di Sicilia (Agrigento Province, Southwestern Sicily). Some of the ammonite specimens were listed, but not illustrated, by M. Gemmellaro in a note of 1919. The succession described in this area consists (from bottom to the top) of Lower Jurassic shallow-water carbonates followed by condensed ammonitic limestones of “Rosso ammonitico-type” (Middle-Late Jurassic in age), Calpionellid limestones (Upper Jurassic-Lower Cretaceous) and cherty calcilutites of Scaglia-type (Upper Cretaceous-Eocene). Since the exact stratigraphic level from which the shark tooth comes is not recorded, a thin section was made of the rock matrix surrounding the tooth. The sedimentological and paleontological analysis of the thin section has highlighted the presence of a microfacies characteristic of the Upper Jurassic condensed deposits of Rosso ammonitico-type, data that fits very well with the geology of the Tardàra area. The study of the Tardàra shark’s tooth has provided both the stimulus and opportunity to undertake a taxonomic review of the Jurassic specimens of Sphenodus collected from a range of Sicilian localities (Gemmellaro G.G., 1871; Seguenza G., 1887; Di Stefano & Cortese, 1891; Seguenza L., 1900; De Gregorio A., 1922) that, to date, have not been re-examined in the light of more recent scholarship. In particular, the specimens described and illustrated by G.G. Gemmellaro (1871), and stored in his eponymous museum, have been revised with the aim of providing a contribution to our knowledge of the genus Sphenodus in the Sicilian Mesozoic successions

Humans trade off whole-body energy cost to avoid overburdening muscles while walking

Metabolic cost minimization is thought to underscore the neural control of locomotion. Yet, avoiding high muscle activation, a cause of fatigue, often outperforms energy minimization in computational predictions of human gait. Discerning the relative importance of these criteria in human walking has proved elusive, in part, because they have not been empirically decoupled. Here, we explicitly decouple whole-body metabolic cost and 'fatigue-like' muscle activation costs (estimated from electromyography) by pitting them against one another using two distinct gait tasks. When experiencing these competing costs, participants (n = 10) chose the task that avoided overburdening muscles (fatigue avoidance) at the expense of higher metabolic power (p < 0.05). Muscle volume-normalized activation more closely models energy use and was also minimized by the participants' decision (p < 0.05), demonstrating that muscle activation was, at best, an inaccurate signal for metabolic energy. Energy minimization was only observed when there was no adverse effect on muscle activation costs. By decoupling whole-body metabolic and muscle activation costs, we provide among the first empirical evidence of humans embracing non-energetic optimality in favour of a clearly defined neuromuscular objective. This finding indicates that local muscle fatigue and effort may well be key factors dictating human walking behaviour and its evolution

Hyperparasitoids exploit herbivore-induced plant volatiles during host location to assess host quality and non-host identity

Although consumers often rely on chemical information to optimize their foraging strategies, it is poorly understood how top carnivores above the third trophic level find resources in heterogeneous environments. Hyperparasitoids are a common group of organisms in the fourth trophic level that lay their eggs in or on the body of other parasitoid hosts. Such top carnivores use herbivore-induced plant volatiles (HIPVs) to find caterpillars containing parasitoid host larvae. Hyperparasitoids forage in complex environments where hosts of different quality may be present alongside non-host parasitoid species, each of which can develop in multiple herbivore species. Because both the identity of the herbivore species and its parasitization status can affect the composition of HIPV emission, hyperparasitoids encounter considerable variation in HIPVs during host location. Here, we combined laboratory and field experiments to investigate the role of HIPVs in host selection of hyperparasitoids that search for hosts in a multi-parasitoid multi-herbivore context. In a wild Brassica oleracea-based food web, the hyperparasitoid Lysibia nana preferred HIPVs emitted in response to caterpillars parasitized by the gregarious host Cotesia glomerata over the non-host Hyposoter ebeninus. However, no plant-mediated discrimination occurred between the solitary host C. rubecula and the non-host H. ebeninus. Under both laboratory and field conditions, hyperparasitoid responses were not affected by the herbivore species (Pieris brassicae or P. rapae) in which the three primary parasitoid species developed. Our study shows that HIPVs are an important source of information within multitrophic interaction networks allowing hyperparasitoids to find their preferred hosts in heterogeneous environments

Lygus rugulipennis on chrysanthemum: Supplemental prey effects and an evaluation of trap plants

The European tarnished plant bug, Lygus rugulipennis Poppius, is considered a major pest in chrysanthemum nurseries in The Netherlands. Adults puncture plant's apical meristem, after which the growing point splits and growth is inhibited. Flower buds and flowers can also be severely damaged. Both types of damage result in economic losses for growers. Despite the importance of this pest for chrysanthemum nurseries, there is only very limited information about L. rugulipennis development on chrysanthemum plants, Chrysanthemum × morifolium Ramat., and whether L. rugulipennis can be controlled using trap plants is not known. We investigated whether: (1) L. rugulipennis could develop from egg to adult on the vegetative and flowering stages of chrysanthemum; (2) their performance was enhanced when a supplemental prey source (Ephestia kuehniella Zeller eggs) or another common pest (the green peach aphid, Myzus persicae Sulzer) was present; and (3) there were alternative plant species more attractive than chrysanthemum for use as trap plants for local pest control or monitoring of L. rugulipennis. L. rugulipennis developed on both vegetative and flowering chrysanthemum stages without any additional food source. Nonetheless, when chrysanthemum was supplemented with E. kuehniella eggs, L. rugulipennis achieved the best performance in terms of the number of adults developed and faster developmental time. Interestingly, L. rugulipennis developed faster on chrysanthemum infested with the aphid M. persicae compared to non-infested plants, however, there was no difference in the number of adults developed. In a trap plant experiment with 16 plant species in the vegetative stage, we found that white mustard, Sinapis alba L., was significantly more attractive than chrysanthemum to both adult and nymph L. rugulipennis. Further research is needed to evaluate the potential of S. alba as a trap plant for monitoring L. rugulipennis and how the presence of prey in the crop influences L. rugulipennis

Services and the Business Models of Product Firms: An Empirical Analysis of the Software Industry

Some product firms increasingly rely on service revenues as part of their business models. One possible explanation is that they turn to services to generate additional profits when their product industries mature and product revenues and profits decline. We explore this assumption by examining the role of services in the financial performance of firms in the prepackaged software products industry (Standard Industrial Classification code 7372) from 1990 to 2006. We find a convex, nonlinear relationship between a product firm's fraction of total sales coming from services and its overall operating margins. As expected, firms with a very high level of product sales are most profitable, and rising services are associated with declining profitability. We find, however, that additional services start to have a positive marginal effect on the firm's overall profits when services reach a majority of a product firm's sales. We show that traditional industry maturity arguments cannot fully explain our data. It is likely that changes in both strategy and the business environment lead product firms to place more emphasis on services