In front of a mirror: visual displays may not be aggressive signals in nocturnal tree frogs

Some evidence indicates that in anuran amphibians, visual signalling can be important during social interactions such as territorial disputes among males, especially in diurnal species. The correct identification of a signal is not a trivial matter. A visual signal provides a visual cue during a social interaction, and to be effective it must elicit an immediate response in the receiver. We tested the hypothesis that visual displays in an agonistic context constitute aggressive signals, in three nocturnal species of Hylidae. We predicted that the production of visual displays would increase in the presence of a conspecific intruder male. Males of Hypsiboas raniceps, Dendropsophus nanus and Lysapsus limellum were submitted to two treatments: (1) Self Image, a reflection in a mirror, simulating the presence of an intruder; and (2) Control, a black rectangle covering the mirror. We observed three visual displays: vocal-sac display (inflate the vocal sac and maintain it inflated for some time), limb lifting (rapid up-and-down movements of one or more limbs), and toe/finger trembling (rapid up-and-down movements of one or more toes and/or fingers). This last display was observed only in H. raniceps males. Contrary to our hypothesis, the emission rates of all visual displays of the focal animals did not differ between treatments; and the behavioural response did not differ among species. Therefore, we suggest that these behaviours could not be used directly for communication in agonistic contexts, and may represent displacement activities (involuntary responses). Alternatively, an aggressive bimodal stimulus may be necessary to trigger a behavioural response by using visual signals during territory defence in these three species.     

Travelling waves in the occurrence of dengue haemorrhagic fever in Thailand

Dengue fever is a mosquito-borne virus that infects 50-100 million people each year. Of these infections, 200,000-500,000 occur as the severe, life-threatening form of the disease, dengue haemorrhagic fever (DHF). Large, unanticipated epidemics of DHF often overwhelm health systems. An understanding of the spatial-temporal pattern of DHF incidence would aid the allocation of resources to combat these epidemics. Here we examine the spatial-temporal dynamics of DHF incidence in a data set describing 850,000 infections occurring in 72 provinces of Thailand during the period 1983 to 1997. We use the method of empirical mode decomposition to show the existence of a spatial-temporal travelling wave in the incidence of DHF. We observe this wave in a three-year periodic component of variance, which is thought to reflect host-pathogen population dynamics. The wave emanates from Bangkok, the largest city in Thailand, moving radially at a speed of 148 km per month. This finding provides an important starting point for detecting and characterizing the key processes that contribute to the spatial-temporal dynamics of DHF in Thailand.     

Pseudonemesia tabiskey,a new species of Pseudonemesia Caporiacco 1955 and new ultramorphological data for the Microstigmatinae (Araneae: Microstigmatidae)

Pseudonemesia tabiskey sp. nov. is described from an Andean Forest in Trujillo, Venezuela. The new species is the third for the genus and differs from the other two species by the presence of one short and apically rounded modified seta on the retrolateral distal portion of the male tibia I and clavate setae on the dorsal and lateral sides of abdomen in both sexes. A new diagnosis is given to Pseudonemesia and new morphological data based on scanning electron microscopy for the Microstigmatinae are presented. The presence of posterior median spinnerets in Pseudonemesia is discussed.     

Inorganic polyphosphate induces accelerated tube formation of HUVEC endothelial cells

In this study, the effect of inorganic polyphosphate (polyP) on the initial phase of angiogenesis and vascularization was investigated, applying the HUVEC cell tube formation assay. PolyP is a physiological and high energy phosphate polymer which has been proposed to act as a metabolic fuel in the extracellular space with only a comparably low ATP content. The experiments revealed that polyP accelerates tube formation of human umbilical vein endothelial cells (HUVEC), seeded onto a solidified basement membrane extract matrix which contains polyP-metabolizing alkaline phosphatase (ALP) activity. This effect is abolished by co-addition of apyrase, which degrades ATP to AMP and inorganic phosphate. The assumption that ATP, derived from polyP, activates HUVEC cells leading to tube formation was corroborated by experiments showing that addition of polyP to the cells causes a strong rise of ATP level in the culture medium. Finally, we show that at a later stage of cultivation of HUVEC cells, after 3 d, polyP causes a strong enhancement of the expression of the genes encoding for the two major matrix metalloproteinases (MMPs) released by endothelial cells during tube formation, MMP-9 and MMP-2. This stimulatory effect is again abrogated by addition of apyrase together with polyP. From these results, we propose that polyP is involved either directly or indirectly in energy supply, via ALP-mediated transfer of energy-rich phosphate under ATP formation. This ATP is utilized for the activation and oriented migration of endothelial cells and for the matrix organization during the initial phases of tube formation.