Geographic variation in thermal physiological performance of the intertidal crab Petrolisthes violaceus along a latitudinal gradient

© 2014. Published by The Company of Biologists Ltd. Environmental temperature has profound effects on the biological performance and biogeographical distribution of ectothermic species. Variation of this abiotic factor across geographic gradients is expected to produce physiological differentiation and local adaptation of natural populations depending on their thermal tolerances and physiological sensitivities. Here, we studied geographic variation in whole-organism thermal physiology of seven populations of the porcelain crab Petrolisthes violaceus across a latitudinal gradient of 3000 km, characterized by a cline of thermal conditions. Our study found that populations of P. violaceus show no differences in the limits of their thermal performance curves and demonstrate a negative correlation of their optimal temperatures with latitude. Additionally, our findings show that high-latitude populations of P. violaceus exhibit broader thermal tolerances, which is consistent with the climatic variability hypothesis. Interestingly, under a future scenario of warming oceans, the thermal safety margins of P. violaceus indicate that lower latitude populations can physiologically tolerate the ocean-warming scenarios projected by the IPCC for the end of the twenty-first century.Link_to_subscribed_fulltex

Heterogeneous environmental seascape across a biogeographic break influences the thermal physiology and tolerances to ocean acidification in an ecosystem engineer

Aim: Understanding how spatio-temporal environmental variability influences stress tolerance, local adaptation and phenotypic variation among populations is a key challenge for evolutionary ecology and climate change biology. Coastal biogeographic breaks are natural laboratories to explore this fundamental research question due to the contrasting environmental conditions experienced by natural populations across these regions. Location: In the South East Pacific (SEP) coast, a major break (30º-32ºS) is characterized by extreme natural variability in sea surface temperature (SST) and carbonate chemistry parameters related to temporal and spatial dynamics in upwelling events. Calcifying organisms inhibiting this zone are exposed to marked fluctuations and clines in SST that together with naturally acidified waters can impact their metabolism, calcification and fitness, making them particularly prone to the effects of climate change (e.g. ocean acidification, OA). We investigated to what extent the spatial and temporal environmental variability (in SST and seawater carbonate conditions) that characterizes the biogeographic break in the SEP influences intra-specific differences in the thermal ecology and the tolerances to OA of the limpet Scurria araucana. Methods: During two years, we conducted field surveys of limpet populations at sites across the SEP break (27ºS, 30ºS and 32ºS). We collected individuals from each population to test for geographic differences in morphometric (e.g. total buoyancy weight, shell length) and physiological (e.g. oxygen consumption rate, cardiac activity and thermal performance curves; TPC) responses to local environmental conditions (Tº and pH/pCO2) and to simulated OA scenarios. Results: Populations of S. Araucana exhibit high tolerance to OA with no signal of geographic influence on this attribute. However, inter-population differences in thermal physiology (metabolic rates and performances) were found across the biogeographic break in the SEP coast. Limpets from the central part of the break (30ºS) exhibit higher thermal performance compared to limpets from populations at both sides of the break. Main conclusions: Variation in SST has a greater effect shaping inter-population differences in thermal physiology of the limpet S. araucana. These physiological differences are aligned the thermal heterogenous seascape along the biogeographic break in the SEP. Contrarily, temporal and spatial variation in seawater carbonate conditions does not influence inter-population differences in phenotypic response populations, but an overall high tolerance to OA.We would like to thank Carolina Fernández for field and laboratory assistance and Bernardo Broitman for providing map figure. This work was funded by FONDECYT Grant No. 1190444 and 1190710 to MAL. Also, this work was partially funded by ANID–Millennium Science Initiative Program–Code ICN2019_015". MAL also thank the support from Programa Investigación Asociativa (ANID ACT 172037) and the ARR was supported by the Spanish grant “Juan de la Cierva Formación 2015” (grant no. JCI-2015-26873) and “Juan de la Cierva Incorporación 2019” (grant no. IJC2018-037545-I). JDGE was supported by the Research Grants Council (ECS 27124318) of Hong Kong

Exploring physiological plasticity and local thermal adaptation in an intertidal crab along a latitudinal cline

© 2017 Elsevier Ltd Intertidal organisms have evolved physiological mechanisms that enable them to maintain performance and survive during periods of severe environmental stress with temperatures close to their tolerance limits. The level of these adaptive responses in thermal physiology can vary among populations of broadly distributed species depending on their particular environmental context and genetic backgrounds. Here we examined thermal performances and reaction norms for metabolic rate (MR) and heart rate (HR) of seven populations of the porcelanid crab Petrolisthes violaceus from markedly different thermal environments across the latitudinal gradient of ~3000 km. Physiological responses of this intertidal crab under common-garden conditions suggest the absence of local thermal adaptation along the geographic gradient (i.e., lack of latitudinal compensation). Moreover, thermal physiological sensitivities and performances in response to increased temperatures evidenced the existence of some level of: i) metabolic rate control or depression during warm temperature exposures; and ii) homeostasis/canalization (i.e., absence or low levels of plasticity) in physiological traits that may reflect some sort of buffering mechanism in most of the populations. Nevertheless, our results indicate that elevated temperatures can reduce cardiac function but not metabolic rate in high latitude crabs. The lack of congruence between HR and MR supports the idea that energy metabolism in marine invertebrates cannot be inferred from HR and different conclusions regarding geographic differentiation in energy metabolism can be obtained from both physiological traits. Integrating thermal physiology and species range extent can contribute to a better understanding of the likely effects of climate change on natural populations of marine ectotherms.Link_to_subscribed_fulltex

Pilocytic Astrocytomas Have Telomere-Associated Promyelocytic Leukemia Bodies without Alternatively Lengthened Telomeres

Telomere maintenance by either telomerase activity or the recombination-mediated alternative lengthening of telomeres (ALT) mechanism is a hallmark of cancer. Tumors that use ALT as their telomere maintenance mechanism are characterized by long telomeres of great heterogeneity in length and by specific nuclear structures of co-localized promyelocytic leukemia protein and telomere DNA, called ALT-associated promyelocytic leukemia bodies (APBs). Recent advances have revealed a direct role for APBs in telomere recombination in ALT-positive cells. In this study, we investigated the possibility that APBs could occur before the long ‘alternatively’ lengthened telomeres arise, particularly in low-grade tumors. We measured APBs, telomere length, and telomerase activity in 64 astrocytomas inclusive of grade 1−4 tumors. Almost all grade 1−3 tumors (93%) were APB-positive using published criteria. Grade 2−3 APB-positive tumors also had long telomeres and were confirmed as ALT positive. However, grade 1 tumors lacked long telomeres and were therefore classified as ALT negative, but positive for telomere-associated promyelocytic leukemia bodies (TPB). This is the first report of a TPB-positive but ALT-negative tumor, and suggests that low-grade tumors have the foundation for recombinational telomere repair, as in ALT. Further work is warranted to characterize the TPB-positive phenotype in other early malignancies, as well as to determine whether TPBs predispose to telomere maintenance by ALT