Host selection,host-use pattern and competition in Dissodactylus crinitichelis and Clypeasterophilus stebbingi (Brachyura: Pinnotheridae)

The genera Dissodactylus and Clypeasterophilus are commensal or parasitic crabs that live in association with irregular sea urchins. Only a single pinnotherid species is expected to occur on a sand dollar; however, during field observations, D. crinitichelis and Clypeasterophilus stebbingi were found co-occurring on a single host (Clypeaster subdepressus). Laboratory experiments and in situ observations were conducted to explore mechanisms of host selection and use by C. stebbingi, as well as the possibility of competition with D. crinitichelis. Analysis of 213 specimens of Encope emarginata and 33 C. subdepressus revealed a high frequency of infestation (90 %) by brachyurans. The number of D. crinitichelis was positively correlated with the size of E. emarginata. During field observations and experiments, D. crinitichelis was able to colonize both echinoids, while C. stebbingi was found mainly on C. subdepressus. No exclusion was reported between individuals of the same sex for both crab species. However, D. crinitichelis may be territorial, since a single male occurred when adult females were added to the host. D. crinitichelis and C. stebbingi co-occurred on the same individual of C. subdepressus on rare occasions during field observations. C. stebbingi may exclude D. crinitichelis from the echinoid to avoid competition, as observed during the experiments. We suggest a species-specific association between C. stebbingi and C. subdepressus, while D. crinitichelis associated mainly with E. emarginata, but also with C. subdepressus. Both crabs may harm the echinoids by consuming their spines, but additional research is necessary to determine whether this is a parasitic association.     

Structural integrity affects nitrogen removal activity of granules in semi-continuous reactors

Granules were observed after more than two years of operation in two semi-continuously fed intermittently aerated reactors treating swine wastewater with aerobic:anoxic cycles of 1:1 h and 1:4 h. Subsequently, the granules and flocs were compared with respect to physical characteristics, activity, and microbial community structure. Granules exhibited higher specific nitrification and denitrification rates than flocs. However, once granule structural integrity was disrupted, the rates decreased to levels similar to those of flocs. Membrane hybridizations using 16S rRNA-targeted probes showed that ammonia oxidizing bacteria populations in flocs and granules were dominated by Nitrosomonas and Nitrosococcus mobilis. Granules provided better conditions for Nitrospira compared to flocs. The diversities of the dominant bacterial populations in granules and flocs were not significantly different. Our findings highlight the importance of structural integrity of granules to their nitrogen removing activity.     

Skeletal Muscle Abnormalities in Pulmonary Arterial Hypertension

Background

Pulmonary arterial hypertension is a progressive disease that is characterized by dyspnea and exercise intolerance. Impairment in skeletal muscle has recently been described in PAH, although the degree to which this impairment is solely determined by the hemodynamic profile remains uncertain. The aim of this study was to verify the association of structural and functional skeletal muscle characteristics with maximum exercise in PAH.

Methods

The exercise capacity, body composition, CT area of limb muscle, quality of life, quadriceps biopsy and hemodynamics of 16 PAH patients were compared with those of 10 controls.

Results

PAH patients had a significantly poorer quality of life, reduced percentage of lean body mass, reduced respiratory muscle strength, reduced resistance and strength of quadriceps and increased functional limitation at 6MWT and CPET. VO₂ max was correlated with muscular variables and cardiac output. Bivariate linear regression models showed that the association between muscular structural and functional variables remained significant even after correcting for cardiac output.

Conclusion

Our study showed the coexistence of ventilatory and quadriceps weakness in face of exercise intolerance in the same group of PAH patients. More interestingly, it is the first time that the independent association between muscular pattern and maximum exercise capacity is evidenced in PAH, independently of cardiac index highlighting the importance of considering rehabilitation in the treatment strategy for PAH.     

Population Dynamics of the Andean Lizard Anolis heterodermus: Fast‐slow Demographic Strategies in Fragmented Scrubland Landscapes

Habitat fragmentation and loss affect population stability and demographic processes, increasing the extinction risk of species. We studied Anolis heterodermus populations inhabiting large and small Andean scrubland patches in three fragmented landscapes in the Sabana de Bogotá (Colombia) to determine the effect of habitat fragmentation and loss on population dynamics. We used the capture‐mark‐recapture method and multistate models to estimate vital rates for each population. We estimated growth population rate and the most important processes that affect λ by elasticity analysis of vital rates. We tested the effects of habitat fragmentation and loss on vital rates of lizard populations. All six isolated populations showed a positive or an equilibrium growth rate (λ = 1), and the most important demographic process affecting λ was the growth to first reproduction. Populations from landscapes with less scrubland natural cover showed higher stasis of young adults. Populations in highly fragmented landscapes showed highest juvenile survival and growth population rates. Independent of the landscape's habitat configuration and connectivity, populations from larger scrubland patches showed low adult survivorship, but high transition rates. Populations varied from a slow strategy with low growth and delayed maturation in smaller patches to a fast strategy with high growth and early maturation in large patches. This variation was congruent with the fast‐slow continuum hypothesis and has serious implications for Andean lizard conservation and management strategies. We suggest that more stable lizard populations will be maintained if different management strategies are adopted according to patch area and habitat structure.     

New karyotype for Mesomys stimulax (Rodentia,Echimyidae) from the Brazilian Amazon: A case for species complex?

Mesomys Wagner, 1845 (Rodentia, Echimyidae, Eumysopinae) currently has four recognized species, three of which occur in Brazil: Mesomys hispidus (probably a species complex), M. occultus, and M. stimulax. Mesomys leniceps is found in montane forests of northern Peru. Mesomys stimulax, the focus of the present study, has a distribution that is restricted to the central and eastern Amazonia south of the Amazon River, extending from the left bank of the Tapajós River to the right bank of the Tocantins River, and south to the southeast portion of Pará State. The genus presents karyotypes with diploid number 2n = 60 and Fundamental Number (FN) = 116 for M. hispidus and M. stimulax, and 2n = 42, FN = 54 for M. occultus. We studied the karyotype of a female specimen of M. stimulax collected from the Tapirapé‐Aquiri National Forest, Marabá, Pará, Brazil, in the Xingu/Tocantins interfluvium. The obtained karyotype (2n = 60 and FN = 110) differs from that described in the literature for both M. stimulax and M. hispidus by exhibiting more biarmed chromosomes, probably due to pericentric inversions and/or centromeric repositioning, and exhibiting differences in the amount and distribution of constitutive heterochromatin (CH). These results suggest that, similar to what has already been proposed for M. hispidus, M. stimulax may represent a species complex and/or cryptic species. The mechanisms of chromosomal diversification in Mesomys and the biogeographic implications are discussed reinforcing the need for broad systematic review for Mesomys.     

On-farm assessment of eucalypt yield gaps — a case study for the producing areas of the state of Minas Gerais,Brazil

International Journal of Biometeorology - The concept of yield gaps provides a basis for identifying the main sources of production losses, caused by water or management deficiencies, which may...     

Keeping zombies alive: The ER-mitochondria Ca2+ transfer in cellular senescence

Cellular senescence generates a permanent cell cycle arrest, characterized by apoptosis resistance and a pro-inflammatory senescence-associated secretory phenotype (SASP). Physiologically, senescent cells promote tissue remodeling during development and after injury. However, when accumulated over a certain threshold as happens during aging or after cellular stress, senescent cells contribute to the functional decline of tissues, participating in the generation of several diseases. Cellular senescence is accompanied by increased mitochondrial metabolism. How mitochondrial function is regulated and what role it plays in senescent cell homeostasis is poorly understood. Mitochondria are functionally and physically coupled to the endoplasmic reticulum (ER), the major calcium (Ca²⁺) storage organelle in mammalian cells, through special domains known as mitochondria-ER contacts (MERCs). In this domain, the release of Ca²⁺ from the ER is mainly regulated by inositol 1,4,5-trisphosphate receptors (IP3Rs), a family of three Ca²⁺ release channels activated by a ligand (IP3). IP3R-mediated Ca²⁺ release is transferred to mitochondria through the mitochondrial Ca²⁺ uniporter (MCU), where it modulates the activity of several enzymes and transporters impacting its bioenergetic and biosynthetic function. Here, we review the possible connection between ER to mitochondria Ca²⁺ transfer and senescence.Understanding the pathways that contribute to senescence is essential to reveal new therapeutic targets that allow either delaying senescent cell accumulation or reduce senescent cell burden to alleviate multiple diseases.     

The phylogeny of Dendropsophini (Anura: Hylidae: Hylinae)

The relationships of the hyline tribe Dendropsophini remain poorly studied, with most published analyses dealing with few of the species groups of Dendropsophus. In order to test the monophyly of Dendropsophini, its genera, and the species groups currently recognized in Dendropsophus, we performed a total evidence phylogenetic analysis. The molecular dataset included sequences of three mitochondrial and five nuclear genes from 210 terminals, including 12 outgroup species, the two species of Xenohyla, and 93 of the 108 recognized species of Dendropsophus. The phenomic dataset includes 46 terminals, one per species (34 Dendropsophus, one Xenohyla, and 11 outgroup species). Our results corroborate the monophyly of Dendropsophini and the reciprocal monophyly of Dendropsophus and Xenohyla. Some species groups of Dendropsophus are paraphyletic (the D. microcephalus, D. minimus, and D. parviceps groups, and the D. rubicundulus clade). On the basis of our results, we recognize nine species groups; for three of them (D. leucophyllatus, D. microcephalus, and D. parviceps groups) we recognize some nominal clades to highlight specific morphology or relationships and facilitate species taxonomy. We further discuss the evolution of oviposition site selection, where our results show multiple instances of independent evolution of terrestrial egg clutches during the evolutionary history of Dendropsophus.