Genomes of the Orestias pupfish from the Andean Altiplano shed light on their evolutionary history and phylogenetic relationships within Cyprinodontiformes.

BACKGROUND: To unravel the evolutionary history of a complex group, a comprehensive reconstruction of its phylogenetic relationships is crucial. This requires meticulous taxon sampling and careful consideration of multiple characters to ensure a complete and accurate reconstruction. The phylogenetic position of the Orestias genus has been estimated partly on unavailable or incomplete information. As a consequence, it was assigned to the family Cyprindontidae, relating this Andean fish to other geographically distant genera distributed in the Mediterranean, Middle East and North and Central America. In this study, using complete genome sequencing, we aim to clarify the phylogenetic position of Orestias within the Cyprinodontiformes order. RESULTS: We sequenced the genome of three Orestias species from the Andean Altiplano. Our analysis revealed that the small genome size in this genus (~ 0.7 Gb) was caused by a contraction in transposable element (TE) content, particularly in DNA elements and short interspersed nuclear elements (SINEs). Using predicted gene sequences, we generated a phylogenetic tree of Cyprinodontiformes using 902 orthologs extracted from all 32 available genomes as well as three outgroup species. We complemented this analysis with a phylogenetic reconstruction and time calibration considering 12 molecular markers (eight nuclear and four mitochondrial genes) and a stratified taxon sampling to consider 198 species of nearly all families and genera of this order. Overall, our results show that phylogenetic closeness is directly related to geographical distance. Importantly, we found that Orestias is not part of the Cyprinodontidae family, and that it is more closely related to the South American fish fauna, being the Fluviphylacidae the closest sister group. CONCLUSIONS: The evolutionary history of the Orestias genus is linked to the South American ichthyofauna and it should no longer be considered a member of the Cyprinodontidae family. Instead, we submit that Orestias belongs to the Orestiidae family, as suggested by Freyhof et al. (2017), and that it is the sister group of the Fluviphylacidae family, distributed in the Amazonian and Orinoco basins. These two groups likely diverged during the Late Eocene concomitant with hydrogeological changes in the South American landscape.

Genome sequencing and transcriptomic analysis of the Andean killifish Orestias ascotanensis reveals adaptation to high-altitude aquatic life.

Orestias ascotanensis (Cyprinodontidae) is a teleost pupfish endemic to springs feeding into the Ascotan saltpan in the Chilean Altiplano (3,700 m.a.s.l.) and represents an opportunity to study adaptations to high-altitude aquatic environments. We have de novo assembled the genome of O. ascotanensis at high coverage. Comparative analysis of the O. ascotanensis genome showed an overall process of contraction, including loss of genes related to G-protein signaling, chemotaxis and signal transduction, while there was expansion of gene families associated with microtubule-based movement and protein ubiquitination. We identified 818 genes under positive selection, many of which are involved in DNA repair. Additionally, we identified novel and conserved microRNAs expressed in O. ascotanensis and its closely-related species, Orestias gloriae. Our analysis suggests that positive selection and expansion of genes that preserve genome stability are a potential adaptive mechanism to cope with the increased solar UV radiation to which high-altitude animals are exposed to.

Phylogeny of Telmatobius marmoratus complex (Anura, Telmatobiidae) reveals high cryptic diversity in the Andean Altiplano.

Telmatobius is the most diverse group of anurans in the Andean Altiplano (highlands) Morphologically, these amphibians have a generally conserved morphology but in turn present large intraspecific variation, which has led to a complex taxonomy and systematics. T. marmoratus has the widest distribution of the genus and forms a complex composed of at least two Telmatobius species. Partial systematic studies based on molecular evidence reveal the existence of three lineages with a complex spatial distribution. However, these studies did not include the entire distribution of T. marmoratus. Our study aims to reassess the current systematic scenario including the complete distribution of the complex. For this, we used a multilocus approach based on mitochondrial (16S, Cytb) and nuclear (RAG1-1, BFIB) DNA sequences to build a phylogenetic hypothesis based on Bayesian inference, maximum likelihood and maximum parsimony. Subsequently, we performed single-locus (ABGD and PTP) and multilocus (STACEY) species delimitation analyses to verify the diversity of nominal species within the complex. The analyses suggest seven non-sibling lineages and 6-10 candidate species within the marmoratus complex. Only one of the two lineages restricted to the central northern plateau correspond to T. marmoratus sensu stricto. South-central marbled water frogs belong to completely new lineages closer to T. gigas and T. culeus, evidencing the polyphyletic condition of the marmoratus complex. The findings of several sympatric lineages in some localities reveal a complex history of ancient water connections in south-central Altiplano.

Different phosphorylation patterns regulate α1D-adrenoceptor signaling and desensitization.

Human α1D-adrenoceptors (α1D-ARs) are a group of the seven transmembrane-spanning proteins that mediate many of the physiological and pathophysiological actions of adrenaline and noradrenaline. Although it is known that α1D-ARs are phosphoproteins, their specific phosphorylation sites and the kinases involved in their phosphorylation remain largely unknown. Using a combination of in silico analysis, mass spectrometry and site directed mutagenesis, we identified distinct α1D-AR phosphorylation patterns during noradrenaline- or phorbol ester-mediated desensitizations. We found that the G protein coupled receptor kinase, GRK2, and conventional protein kinases C isoforms α/ß, phosphorylate α1D-AR during these processes. Furthermore, we showed that the phosphorylated residues are located in the receptor's third intracellular loop (S300, S323, T328, S331, S332, S334) and carboxyl region (S441, T442, T477, S486, S492, T507, S515, S516, S518, S543) and are conserved among orthologues but are not conserved among the other human α1-adrenoceptor subtypes. Additionally, we found that phosphorylation in either the third intracellular loop or carboxyl tail was sufficient to regulate calcium signaling desensitization. By contrast, mutations in either of these two domains significantly altered mitogen activated protein kinase (ERK) pathway and receptor internalization, suggesting that they have differential regulatory mechanisms. Our data provide new insights into the functional repercussions of these posttranslational modifications in signaling outcomes and desensitization.

Assesment and interpretation of negative forelimb allometry in the evolution of non-avian Theropoda.

BACKGROUND: The origin of birds is marked by a significant decrease in body size along with an increase in relative forelimb size. However, before the evolution of flight, both traits may have already been related: It has been proposed that an evolutionary trend of negative forelimb allometry existed in non-avian Theropoda, such that larger species often have relatively shorter forelimbs. Nevertheless, several exceptions exist, calling for rigorous phylogenetic statistical testing. RESULTS: Here, we re-assessed allometric patterns in the evolution of non-avian theropods, for the first time taking into account the non-independence among related species due to shared evolutionary history.We confirmed a main evolutionary trend of negative forelimb allometry for non-avian Theropoda, but also found support that some specific subclades (Coelophysoidea, Ornithomimosauria, and Oviraptorosauria) exhibit allometric trends that are closer to isometry, losing the ancestral negative forelimb allometry present in Theropoda as a whole. CONCLUSIONS: Explanations for negative forelimb allometry in the evolution of non-avian theropods have not been discussed, yet evolutionary allometric trends often reflect ontogenetic allometries, which suggests negative allometry of the forelimb in the ontogeny of most non-avian theropods. In modern birds, allometric growth of the limbs is related to locomotor and behavioral changes along ontogeny. After reviewing the evidence for such changes during the ontogeny of non-avian dinosaurs, we propose that proportionally longer arms of juveniles became adult traits in the small-sized and paedomorphic Aves.

Noradrenaline, oxymetazoline and phorbol myristate acetate induce distinct functional actions and phosphorylation patterns of α1A-adrenergic receptors.

In LNCaP cells that stably express α1A-adrenergic receptors, oxymetazoline increased intracellular calcium and receptor phosphorylation, however, this agonist was a weak partial agonist, as compared to noradrenaline, for calcium signaling. Interestingly, oxymetazoline-induced receptor internalization and desensitization displayed greater effects than those induced by noradrenaline. Phorbol myristate acetate induced modest receptor internalization and minimal desensitization. α1A-Adrenergic receptor interaction with ß-arrestins (colocalization/coimmunoprecipitation) was induced by noradrenaline and oxymetazoline and, to a lesser extent, by phorbol myristate acetate. Oxymetazoline was more potent and effective than noradrenaline in inducing ERK 1/2 phosphorylation. Mass spectrometric analysis of immunopurified α1A-adrenergic receptors from cells treated with adrenergic agonists and the phorbol ester clearly showed that phosphorylated residues were present both at the third intracellular loop and at the carboxyl tail. Distinct phosphorylation patterns were observed under the different conditions. The phosphorylated residues were: a) Baseline and all treatments: T233; b) noradrenaline: S220, S227, S229, S246, S250, S389; c) oxymetazoline: S227, S246, S381, T384, S389; and d) phorbol myristate acetate: S246, S250, S258, S351, S352, S401, S402, S407, T411, S413, T451. Our novel data, describing the α1A-AR phosphorylation sites, suggest that the observed different phosphorylation patterns may participate in defining adrenoceptor localization and action, under the different conditions examined.

Hidden and cryptic species reflect parallel and correlated evolution in the phylogeny of the genus Callyntra (Coleoptera: Tenebrionidae) of Central Chile.

The origin of cryptic species has traditionally been associated with events of recent speciation, genetic constraints, selection of an adaptive character, sexual selection and/or convergent evolution. Species of the genus Callyntra inhabit coastal terraces, mountain slopes, and peaks; their elytral designs are associated with each of these habitats. However, cryptic species have been described within each of these habitats; the taxonomy of this group has been problematic, thus establishing the phylogenetic relationships in this group is fundamental to clarify the systematics and evolutionary patterns of Callyntra. We reconstructed the phylogeny of this group using two mitochondrial genes (COI, 16S) and one nuclear gene (Mp20). We also performed species delimitation using PTP based methods (PTP, mlPTP, bPTP) and GMYC, and evaluated the evolution of the elytral design related to habitat preference. The results showed a tree with five clades, that together with the different methods of species delimitation recovered the described species and suggested at least five new species. The elytral design and habitat preference showed phylogenetic signals. We propose a new classification based on monophyletic groups recovered by phylogenetic analyses. We also suggest that parallel evolution in different habitats and later stasis in the elytral design would be the cause of the origin of cryptic species in this group from central Chile.

Development and characterization of 22 polymorphic microsatellites of the Andean frog Telmatobius chusmisensis (Anura, Telmatobius) and cross amplification in seven Chilean species of the genus.

The genus Telmatobius Wiegmann, 1834 is composed of a wide variety of species and is one of the most diverse native components of the high-altitude Andean environments. The species of the genus present in Chile are considered as endangered, critically endangered or data deficient. We isolated and evaluated 44 microsatellites in 80 individuals of 8 species of Telmatobius present in Chile, obtaining 22 polymorphic microsatellite loci for Telmatobius chusmisensis. The cross-amplification test was successful in all other species tested. For the first time, microsatellite markers are described for Telmatobius. The description of these primers will be useful for further genetic studies for T. chusmisensis and other species of the same genus; allowing further analyses of population structuring, dispersal patterns, recent demographic history and population effective size. This information is also significant to undertake conservation actions for the species of the genus Telmatobius, since most species have conservation issues.

Protein Kinase C Activation Promotes α1B-Adrenoceptor Internalization and Late Endosome Trafficking through Rab9 Interaction. Role in Heterologous Desensitization.

Upon agonist stimulation, α1B-adrenergic receptors couple to Gq proteins, calcium signaling and protein kinase C activation; subsequently, the receptors are phosphorylated, desensitized, and internalized. Internalization seems to involve scaffolding proteins, such as ß-arrestin and clathrin. However, the fine mechanisms that participate remain unsolved. The roles of protein kinase C and the small GTPase, Rab9, in α1B-AR vesicular traffic were investigated by studying α1B-adrenergic receptor-Rab protein interactions, using Förster resonance energy transfer (FRET), confocal microscopy, and intracellular calcium quantitation. In human embryonic kidney 293 cells overexpressing Discosoma spp. red fluorescent protein (DsRed)-tagged α1B-ARs and enhanced green fluorescent protein--tagged Rab proteins, pharmacological protein kinase C activation mimicked α1B-AR traffic elicited by nonrelated agents, such as sphingosine 1-phosphate (i.e., transient α1B-AR-Rab5 FRET signal followed by a sustained α1B-AR-Rab9 interaction), suggesting brief receptor localization in early endosomes and transfer to late endosomes. This latter interaction was abrogated by blocking protein kinase C activity, resulting in receptor retention at the plasma membrane. Similar effects were observed when a dominant-negative Rab9 mutant (Rab9-GDP) was employed. When α1B-adrenergic receptors that had been mutated at protein kinase C phosphorylation sites (S396A, S402A) were used, phorbol ester-induced desensitization of the calcium response was markedly decreased; however, interaction with Rab9 was only partially decreased and internalization was observed in response to phorbol esters and sphingosine 1-phosphate. Finally, Rab9-GDP expression did not affect adrenergic-mediated calcium response but abolished receptor traffic and altered desensitization. Data suggest that protein kinase C modulates α1B-adrenergic receptor transfer to late endosomes and that Rab9 regulates this process and participates in G protein-mediated signaling turn-off.

Novel Structural Approaches to Study GPCR Regulation.

BACKGROUND: Upon natural agonist or pharmacological stimulation, G protein-coupled receptors (GPCRs) are subjected to posttranslational modifications, such as phosphorylation and ubiquitination. These posttranslational modifications allow protein-protein interactions that turn off and/or switch receptor signaling as well as trigger receptor internalization, recycling or degradation, among other responses. Characterization of these processes is essential to unravel the function and regulation of GPCR. METHODS: In silico analysis and methods such as mass spectrometry have emerged as novel powerful tools. Both approaches have allowed proteomic studies to detect not only GPCR posttranslational modifications and receptor association with other signaling macromolecules but also to assess receptor conformational dynamics after ligand (agonist/antagonist) association. RESULTS: this review aims to provide insights into some of these methodologies and to highlight how their use is enhancing our comprehension of GPCR function. We present an overview using data from different laboratories (including our own), particularly focusing on free fatty acid receptor 4 (FFA4) (previously known as GPR120) and α1A- and α1D-adrenergic receptors. From our perspective, these studies contribute to the understanding of GPCR regulation and will help to design better therapeutic agents.

Evolution and Conservation on Top of the World: Phylogeography of the Marbled Water Frog (Telmatobius marmoratus Species Complex; Anura, Telmatobiidae) in Protected Areas of Chile.

The Andean Altiplano has served as a complex setting throughout its history, driving dynamic processes of diversification in several taxa. We investigated phylogeographic processes in the Telmatobius marmoratus species complex occurring in this region by studying the geographic patterns of genetic variability, genealogies, and historical migration, using the cytochrome b (cyt-b) gene as a marker. DNA sequences from Telmatobius gigas and Telmatobius culeus, Bolivian species with an uncertain taxonomic status, were also included. Additionally, we evaluated the phylogenetic diversity (PD) represented within Chilean protected areas and the complementary contribution from unprotected populations. Phylogenetic reconstructions from 148 cyt-b sequences revealed 4 main clades, one of which corresponded to T. culeus. T. gigas was part of T. marmoratus clade indicating paraphyletic relationships. Haplotypes from Chilean and Bolivian sites were not reciprocally monophyletic. Geographic distribution of lineages, spatial Bayesian analysis, and migration patterns indicated that T. marmoratus displays a weaker geographic structure than expected based on habitat distribution and physiological requirements. Demographic and statistical phylogeography analyses pointed out to a scenario of recent population expansion and high connectivity events of a more recent age than the post Last Glacial Maximum, probably associated to more humid events in Altiplano. PD of T. marmoratus populations within protected areas represents 55.6% of the total estimated PD. The unprotected populations that would contribute the most to PD are Caquena and Quebe (21%). Recent evolutionary processes and paleoclimatic changes, potentially driving shifts in habitat connectivity levels and population sizes, could explain the phylogeographic patterns recovered herein.

Population structure and microscale morphological differentiation in a freshwater snail from the Chilean Altiplano.

BACKGROUND: The diversity and population genetic structure of many species have been shaped by historical and contemporary climatic changes. For the species of the South American Altiplano, the historical climatic changes are mainly related to the wet events of great magnitude and regional influence that occurred during the Pleistocene climatic oscillations (PCOs). In contrast, contemporary climate changes are associated with events of lesser magnitude and local influence related to intensifications of the South American Summer Monsoon (SASM). Although multiple studies have analyzed the effect of PCOs on the genetic patterns of highland aquatic species, little is known about the impact of contemporary climate changes in recent evolutionary history. Therefore, in this study, we investigated the change in population structure and connectivity using nuclear and mitochondrial markers throughout the distribution range of Heleobia ascotanensis, a freshwater Cochliopidae endemic to the Ascotán Saltpan. In addition, using geometric morphometric analyses, we evaluated the concomitance of genetic divergence and morphological differentiation. RESULTS: The mitochondrial sequence analysis results revealed the presence of highly divergent co-distributed and geographically nested haplotypes. This pattern reflects an extension in the distribution of groups that previously would have differentiated allopatrically. These changes in distribution would have covered the entire saltpan and would be associated with the large-scale wet events of the PCOs. On the other hand, the microsatellite results defined five spatially isolated populations, separated primarily by geographic barriers. Contemporary gene flow analyses suggest that post-PCO, climatic events that would have connected all populations did not occur. The morphometric analyses results indicate that there is significant morphological differentiation in the populations that are more isolated and that present the greatest genetic divergence. CONCLUSIONS: The contemporary population structure and morphological variation of H. ascotanensis mainly reflect the post-PCO climatic influence. Although both markers exhibit high genetic structuring, the microsatellite and morphology results show the preponderant influence of fragmentation in recent evolutionary history. The contemporary genetic pattern shows that in species that have limited dispersal capabilities, genetic discontinuities can appear rapidly, erasing signs of historical connectivity.

Crosstalk of growth factor receptors at plasma membrane clathrin-coated sites.

Cellular communication is regulated at the plasma membrane by the interactions of receptor, adhesion, signaling, exocytic, and endocytic proteins. Yet, the composition and control of these nanoscale complexes in response to external cues remain unclear. Here, we use high-resolution and high-throughput fluorescence imaging to map the localization of growth factor receptors and related proteins at single clathrin-coated structures across the plasma membrane of human squamous HSC3 cells. We find distinct protein signatures between control cells and cells stimulated with ligands. Clathrin sites at the plasma membrane are preloaded with some receptors but not others. Stimulation with epidermal growth factor induces a capture and concentration of epidermal growth factor-, fibroblast growth factor-, and low-density lipoprotein-receptors (EGFR, FGFR, and LDLR). Regulatory proteins including ubiquitin ligase Cbl, the scaffold Grb2, and the mechanoenzyme dynamin2 are also recruited. Disrupting FGFR or EGFR individually with drugs prevents the recruitment of both EGFR and FGFR. Our data reveals novel crosstalk between multiple unrelated receptors and regulatory factors at clathrin-coated sites in response to stimulation by a single growth factor, EGF. This behavior integrates growth factor signaling and allows for complex responses to extracellular cues and drugs at the plasma membrane of human cells.

Glutamate-dependent translational control in cultured Bergmann glia cells: eIF2α phosphorylation.

Glutamate (Glu), the major excitatory amino acid, activates a wide variety of signal transduction cascades. Synaptic plasticity relies on activity-dependent differential protein expression. Glu receptors have been critically involved in long-term synaptic changes, although recent findings suggest that Na(+)-dependent Glu transporters participate in Glu-induced signalling. Within the cerebellum, Bergmann glia cells are in close proximity to glutamatergic synapses and through their receptors and transporters, sense and respond to neuronal glutamatergic activity. Translational control represents the fine-tuning stage of protein expression regulation and Glu modulates this event in glial cells. In this context, we decided to explore the involvement of Glu receptors and transporters in the regulation of the initiation phase of protein synthesis. To this end, Bergmann glia cells were exposed to glutamatergic ligands and the serine 51-phosphorylation pattern of the main regulator of the initiation phase of translation, namely the α subunit of eukaryotic initiation factor 2 (eIF2α), determined. A time and dose-dependent increase in eIF2α phosphorylation was detected. The signalling cascade included Ca(2+) influx, activation of the Ca(2+)/calmodulin-dependent protein kinase II and protein kinase C. These results provide an insight into the molecular targets of the Glu effects at the translational level and strengthen the notion of the critical involvement of glia cells in glutamatergic synaptic function.

Drainage Network Morphology Influences Population Structure and Gene Flow of the Andean Water Frog Telmatobius pefauri (Anura: Telmatobiidae) of the Atacama Desert, Northern Chile.

Desert aquatic species tend to show isolated and disconnected populations due to the fragmented nature of their environment; however, the morphology of the hydrographic basins, added to humid climatic conditions, can allow dispersion between populations in a desert environment. The aim of this study was to examine the influence of drainage morphology on the phylogeographic structure and gene flow (using a fragment of the mitochondrial control region and seven microsatellite markers) of an endemic taxon of the Andean Precordillera in the Atacama Desert, the aquatic frog species Telmatobius pefauri. We detected three genetic clusters, one cluster present in the Lluta basin and two clusters in the Azapa basin. The results suggest that the genetic structure of T. pefauri is influenced by the morphology of the drainage network formed by the Lluta and Azapa basins: localities present in the same drainage, Tignamar River, were less differentiated and showed higher gene flow levels among them than to their conspecifics belonging to the other drainage in the same basin, Seco River, and those belonging to the other basin, Lluta basin. Gene flow patterns and genetic structure to populations Atacama Andean aquatic taxa would be influenced by basin morphology, with dispersion being stimulated in dendritic hydrological systems, and eventually by humid climatic (regional) events.

Dual clathrin and integrin signaling systems regulate growth factor receptor activation.

The crosstalk between growth factor and adhesion receptors is key for cell growth and migration. In pathological settings, these receptors are drivers of cancer. Yet, how growth and adhesion signals are spatially organized and integrated is poorly understood. Here we use quantitative fluorescence and electron microscopy to reveal a mechanism where flat clathrin lattices partition and activate growth factor signals via a coordinated response that involves crosstalk between epidermal growth factor receptor (EGFR) and the adhesion receptor ß5-integrin. We show that ligand-activated EGFR, Grb2, Src, and ß5-integrin are captured by clathrin coated-structures at the plasma membrane. Clathrin structures dramatically grow in response to EGF into large flat plaques and provide a signaling platform that link EGFR and ß5-integrin through Src-mediated phosphorylation. Disrupting this EGFR/Src/ß5-integrin axis prevents both clathrin plaque growth and dampens receptor signaling. Our study reveals a reciprocal regulation between clathrin lattices and two different receptor systems to coordinate and enhance signaling. These findings have broad implications for the regulation of growth factor signaling, adhesion, and endocytosis.

Micronutrient deficiencies in patients with typical and atypical celiac disease.

OBJECTIVE: The extent of the digestive/absorptive involvement in atypical presentation of celiac disease (CD) is not always clear. The aim of the study was to assess nutritional status of iron (Fe), copper (Cu), and zinc (Zn) in patients with typical CD (TCD) and atypical CD (ACD). PATIENTS AND METHODS: A cross-sectional study was done in patients with TCD, ACD, and healthy controls (HC). Hemoglobin, serum ferritin, free erythrocyte protoporphyrin, Fe, Cu, ceruloplasmin, Zn, anti-endomysial antibodies, and anti-tissue transglutaminase antibodies were measured. Data were analyzed by Kruskal-Wallis, principal component analysis, and linear discriminant analysis. RESULTS: : One hundred nine individuals were studied (54 TCD, 19 ACD, 36 HC); mean age  ±  standard deviation was 23 ± 15.8 (range 1.6-75.4) years. Median and range of hemoglobin were 12.8 g/dL (8.1-17.6) in TCD, 12.4 g/dL (10.5-14.5) in ACD, and 13.6 g/dL (11.1-16.7) in HC (P < 0.0001); serum ferritin was 17.7 µg/L (2.9-157), 10.8 µg/L (2.7-39.8), and 28.7 µg/L (4.5-127.2), respectively (P < 0.01). Cu was 105 µg/dL (60-185), 97.5 µg/dL (40-130), and 125 µg/dL (80-205), respectively (P < 0.05). Ceruloplasmin was 21.6  mg/dL (14.2-73.2), 22.6  mg/dL (0.9-34.3), and 32.1 mg/dL (5.8-72.6), respectively (P < 0.01). There were no differences in Fe, free erythrocyte protoporphyrin, and Zn. Principal component analysis showed that 58% of observed variability was explained by Fe and Cu indicators. Linear discriminant analysis revealed differences between CD and HC (P < 0.0001), with high values of correct classification for TCD (73%) and HC (72%), but not ACD (16%), which were mostly classified as TCD (79%). CONCLUSIONS: Deficiency of micronutrients was found both in typical as well as in atypical cases.

The Atacama toad (Rhinella atacamensis) exhibits an unusual clinal pattern of decreasing body size towards more arid environments.

BACKGROUND: The causes of geographic variation of body size in ectotherms have generally been attributed to environmental variables. Research in amphibians has favored mechanisms that involve water availability as an explanation for the geographic variation of body size. However, there are few studies at intraspecific level on amphibians that inhabit desert or semi-desert environments, where hydric restrictions are stronger. Here, we describe and inquire as to the causes of the geographic variation of body size in the semi-desert toad Rhinella atacamensis, a terrestrial anuran that is distributed over 750 km along a latitudinal aridity gradient from the southern extreme of the Atacama Desert to the Mediterranean region of central Chile. We measured the snout-vent length of 315 adults from 11 representative localities of the entire distribution of the species. Then, using an information-theoretic approach, we evaluate whether the data support eight ecogeographic hypotheses proposed in literature. RESULTS: Rhinella atacamensis exhibits a gradual pattern of decrease in adult body size towards the north of its distribution, where the climate is more arid, which conforms to a Bergmann's cline. The best model showed that the data support the mean annual precipitation as predictor of body size, favoring the converse water availability hypothesis. CONCLUSIONS: Most studies in amphibians show that adult size increases in arid environments, but we found a converse pattern to expected according to the hydric constraints imposed by this type of environment. The evidence in R. atacamensis favors the converse water availability hypothesis, whose mechanism proposes that the foraging activity determined by the precipitation gradient has produced the clinal pattern of body size variation. The variation of this trait could also be affected by the decreasing productivity that exists towards the north of the species distribution. In addition, we found evidence that both pattern and mechanism are independent of sex. Lastly, we suggest that behavioral traits, such as nocturnal habits, might also play an important role determining this differential response to aridity. Therefore, the support for the converse water availability hypothesis found in this study shows that amphibians can respond in different ways to water restrictions imposed by arid environments.

Unraveling the Morphological Variation of Triatoma infestans in the Peridomestic Habitats of Chuquisaca Bolivia: A Geometric Morphometric Approach.

Morphometrics has been used on Triatomines, a well-known phenotypically variable insect, to understand the process of morphological plasticity and infer the changes of this phenomenon. The following research was carried out in two regions of the inter-Andean valleys and two Chaco regions of Chuquisaca-Bolivia. Triatoma infestans adults were collected from the peridomestic (pens and chicken coops) along a geographic gradient in order to evaluate the morphological differentiation between groups and their pattern of sexual shape dimorphism. Geometric morphometric methods were applied on the wings and heads of T. infestans. The main findings include that we proved sexual dimorphism in heads and wings, determined the impact of environmental factors on size and shape and validated the impact of nutrition on head shape variation. These results show that geometric morphometric procedures can be used to provide key insight into the biological adaptation of T. infestans on different biotic (nutrition) and abiotic (environment) conditions, which could serve in understanding and evaluating infestation processes and further vector control programs.

The structure and spontaneous curvature of clathrin lattices at the plasma membrane.

Clathrin-mediated endocytosis is the primary pathway for receptor and cargo internalization in eukaryotic cells. It is characterized by a polyhedral clathrin lattice that coats budding membranes. The mechanism and control of lattice assembly, curvature, and vesicle formation at the plasma membrane has been a matter of long-standing debate. Here, we use platinum replica and cryoelectron microscopy and tomography to present a structural framework of the pathway. We determine the shape and size parameters common to clathrin-mediated endocytosis. We show that clathrin sites maintain a constant surface area during curvature across multiple cell lines. Flat clathrin is present in all cells and spontaneously curves into coated pits without additional energy sources or recruited factors. Finally, we attribute curvature generation to loosely connected and pentagon-containing flat lattices that can rapidly curve when a flattening force is released. Together, these data present a universal mechanistic model of clathrin-mediated endocytosis.