The Elongated, the Squat and the Spherical: Selective Pressures for Phytoplankton Shape

One of the unifying traits of life on this planet is reproduction, or life's ability to make copies of itself. The mode of reproduction has evolved over time, having almost certainly begun with simple asexual reproduction when the ancestral single celled organism divided into two. Since these beginnings' life has tried out numerous strategies, and perhaps one of the most important and successful has been sexual reproduction. This form of reproduction relies on the union of gametes, otherwise known as sperm and egg. Evolutionarily, sexual reproduction allows for greater adaptive potential because the genes of two unique individuals have a chance to recombine and mix in order to produce a new individual. Unlike asexual reproduction which produces genetically-identical clones of the parent individual, sex produces offspring with novel genes and combinations of genes. Therefore, in the face of new selective pressures there is a higher chance that one of these novel genetic profiles will produce an adaptation that is advantageous in the new circumstances. Dr Akihiko Watanabe is a reproductive biologist based in the Department of Biology, Faculty of Science Yamagata University in Japan, he is currently working on three research projects; a comparative study on the signalling pathways for inducing sperm motility and acrosome reaction in amphibians, the mechanism behind the adaptive modification of sperm morphology and motility, and the origin of sperm motility initiating substance (SMIS).

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Shifts in morphology, gene expression, and selection underlie web loss in Hawaiian Tetragnatha spiders

BMC Ecology and Evolution ◽

10.1186/s12862-021-01779-9 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Cory A. Berger ◽

Michael S. Brewer ◽

Nobuaki Kono ◽

Hiroyuki Nakamura ◽

Kazuharu Arakawa ◽

...

Keyword(s):

Genetic Basis ◽

Adaptive Traits ◽

Deep Time ◽

Selective Pressures ◽

Silk Production ◽

Silk Glands ◽

Genetic Mechanisms ◽

Orb Web ◽

Short Time ◽

Web Building

Abstract Background A striking aspect of evolution is that it often converges on similar trajectories. Evolutionary convergence can occur in deep time or over short time scales, and is associated with the imposition of similar selective pressures. Repeated convergent events provide a framework to infer the genetic basis of adaptive traits. The current study examines the genetic basis of secondary web loss within web-building spiders (Araneoidea). Specifically, we use a lineage of spiders in the genus Tetragnatha (Tetragnathidae) that has diverged into two clades associated with the relatively recent (5 mya) colonization of, and subsequent adaptive radiation within, the Hawaiian Islands. One clade has adopted a cursorial lifestyle, and the other has retained the ancestral behavior of capturing prey with sticky orb webs. We explore how these behavioral phenotypes are reflected in the morphology of the spinning apparatus and internal silk glands, and the expression of silk genes. Several sister families to the Tetragnathidae have undergone similar web loss, so we also ask whether convergent patterns of selection can be detected in these lineages. Results The cursorial clade has lost spigots associated with the sticky spiral of the orb web. This appears to have been accompanied by loss of silk glands themselves. We generated phylogenies of silk proteins (spidroins), which showed that the transcriptomes of cursorial Tetragnatha contain all major spidroins except for flagelliform. We also found an uncharacterized spidroin that has higher expression in cursorial species. We found evidence for convergent selection acting on this spidroin, as well as genes involved in protein metabolism, in the cursorial Tetragnatha and divergent cursorial lineages in the families Malkaridae and Mimetidae. Conclusions Our results provide strong evidence that independent web loss events and the associated adoption of a cursorial lifestyle are based on similar genetic mechanisms. Many genes we identified as having evolved convergently are associated with protein synthesis, degradation, and processing, which are processes that play important roles in silk production. This study demonstrates, in the case of independent evolution of web loss, that similar selective pressures act on many of the same genes to produce the same phenotypes and behaviors.

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Multifunctional Role of Astrocyte Elevated Gene-1 (AEG-1) in Cancer: Focus on Drug Resistance

Cancers ◽

10.3390/cancers13081792 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1792

Author(s):

Debashri Manna ◽

Devanand Sarkar

Keyword(s):

Drug Resistance ◽

Cancer Cells ◽

Cancer Development ◽

Epigenetic Alterations ◽

Hallmarks Of Cancer ◽

Comprehensive Description ◽

Molecular Abnormalities ◽

Selective Pressures ◽

Resistance To Chemotherapy

Cancer development results from the acquisition of numerous genetic and epigenetic alterations in cancer cells themselves, as well as continuous changes in their microenvironment. The plasticity of cancer cells allows them to continuously adapt to selective pressures brought forth by exogenous environmental stresses, the internal milieu of the tumor and cancer treatment itself. Resistance to treatment, either inherent or acquired after the commencement of treatment, is a major obstacle an oncologist confronts in an endeavor to efficiently manage the disease. Resistance to chemotherapy, chemoresistance, is an important hallmark of aggressive cancers, and driver oncogene-induced signaling pathways and molecular abnormalities create the platform for chemoresistance. The oncogene Astrocyte elevated gene-1/Metadherin (AEG-1/MTDH) is overexpressed in a diverse array of cancers, and its overexpression promotes all the hallmarks of cancer, such as proliferation, invasion, metastasis, angiogenesis and chemoresistance. The present review provides a comprehensive description of the molecular mechanism by which AEG-1 promotes tumorigenesis, with a special emphasis on its ability to regulate chemoresistance.

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Brain morphology predicts social intelligence in wild cleaner fish

Nature Communications ◽

10.1038/s41467-020-20130-2 ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

Zegni Triki ◽

Yasmin Emery ◽

Magda C. Teles ◽

Rui F. Oliveira ◽

Redouan Bshary

Keyword(s):

Social Intelligence ◽

Brain Plasticity ◽

Decision Rules ◽

Brain Morphology ◽

Brain Anatomy ◽

Environmental Complexity ◽

Learning Abilities ◽

Cleaner Fish ◽

High Performing ◽

Selective Pressures

AbstractIt is generally agreed that variation in social and/or environmental complexity yields variation in selective pressures on brain anatomy, where more complex brains should yield increased intelligence. While these insights are based on many evolutionary studies, it remains unclear how ecology impacts brain plasticity and subsequently cognitive performance within a species. Here, we show that in wild cleaner fish (Labroides dimidiatus), forebrain size of high-performing individuals tested in an ephemeral reward task covaried positively with cleaner density, while cerebellum size covaried negatively with cleaner density. This unexpected relationship may be explained if we consider that performance in this task reflects the decision rules that individuals use in nature rather than learning abilities: cleaners with relatively larger forebrains used decision-rules that appeared to be locally optimal. Thus, social competence seems to be a suitable proxy of intelligence to understand individual differences under natural conditions.

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Floral Scent and Pollinators of Cypripedium calceolus L. at Different Latitudes

Diversity ◽

10.3390/d13010005 ◽

2020 ◽

Vol 13 (1) ◽

pp. 5

Author(s):

Herbert Braunschmid ◽

Robin Guilhot ◽

Stefan Dötterl

Keyword(s):

Floral Scent ◽

Latitudinal Gradients ◽

Isolated Populations ◽

Floral Scents ◽

Selective Pressures ◽

Octyl Acetate ◽

Important Trait ◽

Cypripedium Calceolus ◽

Negative Frequency Dependent Selection ◽

Plant Pollinator

Floral scent is an important trait in plant–pollinator interactions. It not only varies among plant species but also among populations within species. Such variability might be caused by various non–selective factors, or, as has been shown in some instances, might be the result of divergent selective pressures exerted by variable pollinator climates. Cypripedium calceolus is a Eurasian deceptive orchid pollinated mainly by bees, which spans wide altitudinal and latitudinal gradients in mainly quite isolated populations. In the present study, we investigated whether pollinators and floral scents vary among different latitudes. Floral scents of three C. calceolus populations in the Southern Alps were collected by dynamic headspace and analyzed by gas chromatography coupled to mass spectrometry (GC/MS). These data were completed by previously published scent data of the Northern Alps and Scandinavia. The scent characteristics were compared with information on pollinators recorded for present study or available in the literature. More than 80 scent compounds were overall recorded from plants of the three regions, mainly aliphatics, terpenoids, and aromatics. Seven compounds were found in all samples, and most samples were dominated by linalool and octyl acetate. Although scents differed among regions and populations, the main compounds were similar among regions. Andrena and Lasioglossum species were the main pollinators in all three regions, with Andrena being relatively more abundant than Lasioglossum in Scandinavia. We discuss natural selection mediated by pollinators and negative frequency–dependent selection as possible reasons for the identified variation of floral scent within and among populations and regions.

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Assessing evidence for adaptive evolution in two hearing-related genes important for high-frequency hearing in echolocating mammals

G3 Genes|Genome|Genetics ◽

10.1093/g3journal/jkab069 ◽

2021 ◽

Author(s):

Hui Wang ◽

Hanbo Zhao ◽

Yujia Chu ◽

Jiang Feng ◽

Keping Sun

Keyword(s):

Adaptive Evolution ◽

Hair Cells ◽

High Frequency ◽

Phylogenetic Trees ◽

Outer Hair Cells ◽

Functional Domain ◽

Coding Region ◽

Selective Pressures ◽

Wide Range ◽

Different Parts

Abstract High-frequency hearing is particularly important for echolocating bats and toothed whales. Previously, studies of the hearing-related genes Prestin, KCNQ4, and TMC1 documented that adaptive evolution of high-frequency hearing has taken place in echolocating bats and toothed whales. In this study, we present two additional candidate hearing-related genes, Shh and SK2, that may also have contributed to the evolution of echolocation in mammals. Shh is a member of the vertebrate Hedgehog gene family and is required in the specification of the mammalian cochlea. SK2 is expressed in both inner and outer hair cells, and it plays an important role in the auditory system. The coding region sequences of Shh and SK2 were obtained from a wide range of mammals with and without echolocating ability. The topologies of phylogenetic trees constructed using Shh and SK2 were different; however, multiple molecular evolutionary analyses showed that those two genes experienced different selective pressures in echolocating bats and toothed whales compared to non-echolocating mammals. In addition, several nominally significant positively selected sites were detected in the non-functional domain of the SK2 gene, indicating that different selective pressures were acting on different parts of the SK2 gene. This study has expanded our knowledge of the adaptive evolution of high-frequency hearing in echolocating mammals.

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The Challenge of Illusory Perception of Animals: The Impact of Methodological Variability in Cross-species Investigation

Animals ◽

10.3390/ani11061618 ◽

2021 ◽

Vol 11 (6) ◽

pp. 1618

Author(s):

Maria Santacà ◽

Christian Agrillo ◽

Maria Elena Miletto Petrazzini

Keyword(s):

Research Field ◽

Choice Test ◽

Training Procedure ◽

Biologically Relevant ◽

Selective Pressures ◽

Extensive Training ◽

Behavioural Research ◽

Illusory Perception ◽

Methodological Approaches ◽

The Impact

Although we live on the same planet, there are countless different ways of seeing the surroundings that reflect the different individual experiences and selective pressures. In recent decades, visual illusions have been used in behavioural research to compare the perception between different vertebrate species. The studies conducted so far have provided contradictory results, suggesting that the underlying perceptual mechanisms may differ across species. Besides the differentiation of the perceptual mechanisms, another explanation could be taken into account. Indeed, the different studies often used different methodologies that could have potentially introduced confounding factors. In fact, the possibility exists that the illusory perception is influenced by the different methodologies and the test design. Almost every study of this research field has been conducted in laboratories adopting two different methodological approaches: a spontaneous choice test or a training procedure. In the spontaneous choice test, a subject is presented with biologically relevant stimuli in an illusory context, whereas, in the training procedure, a subject has to undergo an extensive training during which neutral stimuli are associated with a biologically relevant reward. Here, we review the literature on this topic, highlighting both the relevance and the potential weaknesses of the different methodological approaches.

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Telomere Length and Arsenic: Improving Animal Models of Toxicity by Choosing Mice With Shorter Telomeres

International Journal of Toxicology ◽

10.1177/10915818211009844 ◽

2021 ◽

Vol 40 (3) ◽

pp. 211-217

Author(s):

Brayden Whitlock

Keyword(s):

Animal Models ◽

Telomere Length ◽

Mouse Models ◽

Arsenic Exposure ◽

Tumor Formation ◽

The Body ◽

Cancer Resistance ◽

Selective Pressures ◽

Toxicity Monitoring ◽

In Captivity

Arsenic is both a chemotherapeutic drug and an environmental toxicant that affects hundreds of millions of people each year. Arsenic exposure in drinking water has been called the worst poisoning in human history. How arsenic is handled in the body is frequently studied using rodent models to investigate how arsenic both causes and treats disease. These models, used in a variety of arsenic-related testing, from tumor formation to drug toxicity monitoring, have virtually always been developed from animals with telomeres that are unnaturally long, likely because of accidental artificial selective pressures. Mice that have been bred in captivity in laboratory conditions, often for over 100 years, are the standard in creating animal models for this research. Using these mice introduces challenges to any work that can be affected by the length of telomeres and the related capacities for tissue repair and cancer resistance. However, arsenic research is particularly susceptible to the misuse of such animal models due to the multiple and various interactions between arsenic and telomeres. Researchers in the field commonly find mouse models and humans behaving very differently upon exposure to acute and chronic arsenic, including drug therapies which seem safe in mice but are toxic in humans. Here, some complexities and apparent contradictions of the arsenic carcinogenicity and toxicity research are reconciled by an explanatory model that involves telomere length explained by the evolutionary pressures in laboratory mice. A low-risk hypothesis is proposed which has the power to determine whether researchers can easily develop more powerful and accurate mouse models by simply avoiding mouse lineages that are very old and have strangely long telomeres. Swapping in newer mouse lineages for the older, long-telomere mice may vastly improve our ability to research arsenic toxicity with virtually no increase in cost or difficulty of research.

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