TRACE FOSSILS OF CICADAS IN THE CENOZOIC OF CENTRAL PATAGONIA, ARGENTINA

Abstract:  Hemispherical pan or dish-shaped trace fossils from the Cenozoic of the Central Patagonia are attributed to the burrowing action of cicadas. A new ichnotaxon, Feoichnus challa igen. et isp. nov. is characterized by its hemispherical shape, mostly subvertical orientation, smoothed internal lining showing knobbly surface texture, and rough and irregular external surface devoid of ornamentation. The wall is composed of a lining plus a layer of soil material consolidated passively by cicada excretions. In other specimens the wall shows a repetition of linings and soil layers reflecting changes in the position of the chambers. Grooves, which represent traces of roots originally related to the feeding activities of cicada nymphs, are located in the wall of many specimens of F. challa . These grooves are subvertical to subhorizontal and show smooth surfaces with longitudinal striations. The cicadan origin of these traces is supported by comparison of the fossils to modern cicada nymph chambers and by laboratory experiments. The most significant characters that emerged from the comparison are the differential preservation of the basal part of the chambers, the interior lining with similar surface texture, and the presence of root traces in the wall and in the interior of the chamber. Additional records of F. challa from the Cretaceous–Pliocene of the USA, the Oligocene of Ethiopia, and the Miocene of the United Arab Emirates and Kenya complete the current information yielded by the known body fossil record to help understand the evolutionary history of cicadas.     

Regulation and function of root exudates

Root-secreted chemicals mediate multi-partite interactions in the rhizosphere, where plant roots continually respond to and alter their immediate environment. Increasing evidence suggests that root exudates initiate and modulate dialogue between roots and soil microbes. For example, root exudates serve as signals that initiate symbiosis with rhizobia and mycorrhizal fungi. In addition, root exudates maintain and support a highly specific diversity of microbes in the rhizosphere of a given particular plant species, thus suggesting a close evolutionary link. In this review, we focus mainly on compiling the information available on the regulation and mechanisms of root exudation processes, and provide some ideas related to the evolutionary role of root exudates in shaping soil microbial communities.     

CLEPTOPARASITISM AND DETRITIVORY IN DUNG BEETLE FOSSIL BROOD BALLS FROM PATAGONIA, ARGENTINA

Abstract:  Traces within traces is a new ichnological field that is meant to shed light on significative palaeoecological aspects. Dung beetle fossil brood balls ( Coprinisphaera ispp.), from the Middle Eocene – Lower Miocene Sarmiento Formation of Patagonia, Argentina, show two different trace fossils excavated in its infillings and/or wall that reveal the presence and relationships among different components of past dung communities. Tombownichnus pepei n. isp. is represented by elongated pits, circular to elliptical in cross-section, occurring in the centre or beside ovoid mounds in the internal surface of the Coprinisphaera wall. These traces record the activity of cleptoparasites, such as other dung beetles or flies, whose larvae were probably carried passively with the dung for provisions. Tombownichnus pepei would represent the pupation chambers excavated by full grown larvae in the Coprinisphaera wall after completing their development inside provisioned dung. The other trace fossil, Lazaichnus fistulosus is represented by circular to subcircular borings occurring in Coprinisphaera walls, in connection with an internal gallery in their infillings. Its connection also with meniscate burrows and chambers in the surrounding palaeosol attributable to aestivation chambers of earthworms revealed that these organisms would have been active cleptoparasites or detritivores in dung beetle fossil brood balls.     

Large-scale redistribution of maximum fisheries catch potential in the global ocean under climate change

Previous projection of climate change impacts on global food supply focuses solely on production from terrestrial biomes, ignoring the large contribution of animal protein from marine capture fisheries. Here, we project changes in global catch potential for 1066 species of exploited marine fish and invertebrates from 2005 to 2055 under climate change scenarios. We show that climate change may lead to large-scale redistribution of global catch potential, with an average of 30–70% increase in high-latitude regions and a drop of up to 40% in the tropics. Moreover, maximum catch potential declines considerably in the southward margins of semienclosed seas while it increases in poleward tips of continental shelf margins. Such changes are most apparent in the Pacific Ocean. Among the 20 most important fishing Exclusive Economic Zone (EEZ) regions in terms of their total landings, EEZ regions with the highest increase in catch potential by 2055 include Norway, Greenland, the United States (Alaska) and Russia (Asia). On the contrary, EEZ regions with the biggest loss in maximum catch potential include Indonesia, the United States (excluding Alaska and Hawaii), Chile and China. Many highly impacted regions, particularly those in the tropics, are socioeconomically vulnerable to these changes. Thus, our results indicate the need to develop adaptation policy that could minimize climate change impacts through fisheries. The study also provides information that may be useful to evaluate fisheries management options under climate change.     

Host‐plant dependent wing phenotypic variation in the neotropical butterfly Heliconius erato

Most phytophagous insects feed on a single plant during development, and this may influence not only performance‐linked traits, but also more subtle morphological differences. Insect–plant interactions are thus valuable for studying environmental influences on phenotypes. By using geometric morphometrics, we investigated the variation in forewing size and shape in the butterfly Heliconius erato phyllis reared on six species of passion vines (Passiflora spp.). We detected wing shape sexual dimorphism, for which the adaptive significance deserves further investigation. There was size as well as wing shape variation among individuals fed on different hosts. These subtle differences in shape were interpreted as environmental effects on development, which should be under weak natural selection for these traits, and therefore not strongly canalized. This result reinforces the role of plasticity on host‐plant use, as well as the corresponding consequences on developmental variability among phytophagous insects. We propose that this variation can be an important factor in resource specialization and partner recognition, possibly triggering reproductive isolation and sympatric speciation in phytophagous insects. This interaction also shows itself as a good model for studying the role of environmental and interaction diversity in evolution. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 765–774.     

Characterization of the orchid bee Euglossa viridissima (Apidae: Euglossini) and a novel cryptic sibling species,by morphological,chemical, and genetic characters

In orchid bees, males signal their availability as mates by fanning ‘perfumes’, i.e. blends of volatiles that are collected from environmental sources and stored in hind leg pouches. The chemical composition of such perfumes in males with either two or three mandibular teeth has previously led to the discovery of two sympatric, cryptic lineages within Euglossa viridissima Friese on the Yucatan peninsula, Mexico. Here, we combine chemical, morphological, and genetic data for an integrated characterization of the two lineages. The lectotype of E. viridissima Friese in the Museum of Natural History in Vienna has two mandibular teeth, and the species name viridissima must thus be assigned to the predominantly bidentate lineage, whereas the completely tridentate lineage is described as a novel species, Euglossa dilemma sp. nov. Bembé & Eltz. Chemical profiling and microsatellite genotyping revealed that E. viridissima males can occasionally (～10% of individuals) express a third mandibular tooth, but this tooth is not positioned centrally on the mandible as in E. dilemma, but is displaced towards the tip. Thus, males of the two lineages can be unambiguously diagnosed by mandibular characters alone. Based on 889 bp of CO1 sequence data, we confirm that E. viridissima and E. dilemma constitute a monophyletic group within the genus Euglossa. However, CO1 alone failed to separate these two lineages due to the lack of parsimony‐informative sites. Both species occur in broad sympatry across Central America, but the orchid bees recently introduced to Florida have three mandibular teeth in males, i.e. belong to E. dilemma. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163 , 1064–1076.     

Differential proteomics of dehydration and rehydration in bryophytes: evidence towards a common desiccation tolerance mechanism

All bryophytes evolved desiccation tolerance (DT) mechanisms during the invasion of terrestrial habitats by early land plants. Are these DT mechanisms still present in bryophytes that colonize aquatic habitats? The aquatic bryophyte Fontinalis antipyretica Hedw. was subjected to two drying regimes and alterations in protein profiles and sucrose accumulation during dehydration and rehydration were investigated. Results show that during fast dehydration, there is very little variation in protein profiles, and upon rehydration proteins are leaked. On the other hand, slow dehydration induces changes in both dehydration and rehydration protein profiles, being similar to the protein profiles displayed by the terrestrial bryophytes Physcomitrella patens (Hedw.) Bruch and Schimp. and, to what is comparable with Syntrichia ruralis (Hedw.) F. Weber and D. Mohr. During dehydration there was a reduction in proteins associated with photosynthesis and the cytoskeleton, and an associated accumulation of proteins involved in sugar metabolism and plant defence mechanisms. Upon rehydration, protein accumulation patterns return to control values for both photosynthesis and cytoskeleton whereas proteins associated with sugar metabolism and defence proteins remain high. The current results suggest that bryophytes from different ecological adaptations may share common DT mechanisms.     

Plant traits mediate effects of predators across pepper (Capsicum annuum) varieties

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Germination of Nosema algerae (Microspora) Spores: Conditional Inhibition by D2O, Ethanol and Hg2+ Suggests Dependence of Water Influx upon Membrane Hydration and Specific Transmembrane Pathways

ABSTRACT. The germination of microsporidian spores under conditions expected to affect water flow across the plasma membrane-wall complex was studied by assessing their responses to in vitro stimulation with Na⁺ or K⁺. Partial or full substitution of common water with D₂O, which more effectively coats ions and electrostatically-charged cell surfaces with relatively stable hydration layers, delayed and inhibited spore germination in a concentration-dependent manner; yet, preincubation in 100% D₂O did not change the normal response to standard stimulation. Water structure-breaking conditions, such as an increase in temperature (within the 15° C to 40° C range) or in ionic strength (2- to 10-fold normal), opposed the inhibition by D₂O and allowed significant stimulation by Li⁺, the monovalent cation with the largest hydration diameter and a usually weak stimulant action on the spores. Ethanol, known to reduce water permeation across cell membranes and phospholipid bilayers, also caused a powerful and dose-dependent (1% to 4% v/v) inhibition of spore germination, but pretreatment with ethanol did not affect the normal response. HgCl₂, an inhibitor of specific water channels, blocked spore germination at just 250 μM in the normal stimulation solution irrespective of the temperature, and permitted only a delayed response in high salt stimulation solutions. However, the inhibition by Hg²⁺ was abolished by the simultaneous presence of 2-mercaptoethanol in the medium. These results suggest (1) that spore germination is keenly dependent upon the hydration states of both the plasma membrane-wall complex and the stimulant ions, and (2) that osmotic water flows into the spores through specific transmembrane pathways with critical sulfhydryl groups, i.e. analogous to the water channels that facilitate water movements across the plasma membranes of highly permeable cells.     

Gram-Chromotrope: a New Technique that Enhances Detection of Microsporidial Spores in Clinical Samples

We have developed a new staining procedure that combines the traditional Gram staining for bacteria and the Weber's chromotrope staining method, the standard technique for the detection of microsporidia spores in clinical Specimens. This “Gram-chromotrope” staining technique enhances the staining characteristics of microsporidia spores and facilitates the easy detection and differentiation of spores from other microorganisms that are found in clinical specimens, especially stool samples. This new technique is fast, reliable, and simple to perform, and can be easily adapted for use in clinical laboratories.