Eco-Devo-Toxo

     While searching for articles to support my statement in class on the industrial pollutant cadmium, specifically in birds, I came across this review. This post is connected to Lecture 4 in regard to gonadal development, and additionally ties in the effects of heavy metals (specifically cadmium) on germinal, Sertoli, and Leydig endocrine cells, mentioned in detail in Lecture 4.      The review provided insight and data relating to mammals and avian species, but as for this post, I will be referencing the avian related findings. Here is the article should anyone wish to investigate the effects of cadmium further. Relating cadmium (Cd) to our Lecture 4 topic of sex determination and gonadal development      In this review by Marettová, the aim is to provide current knowledge on cadmium's toxic effects in germinal and supporting Sertoli cells of seminiferous tubules and Leydig endocrine cells. When exposed to this heavy metal, effects in...

My personal motto has pretty much always been to do the thing I’m most afraid of, within reason of course. Following this guideline has opened me up to a world of opportunities and personal growth. So, I decided for this blog post I’d take the same approach and dive into an area that I’m not very comfortable with. For me this area of discomfort is the intersection between large diverse communities and evolution.  Trophic interactions define our understanding of ecosystem resource cycling and diversity. Understanding the spatial and evolutionary scales at which trophic ecology influences biodiversity of central import to understanding long term macro-evolutionary dynamics.  A 2019 paper, “Reef fish functional traits evolve fastest at trophic extremes”, dives into the impact trophic position exerts on trait evolution in coral reef environments. Coral reefs sit on the upper limit of ecosystems teeming with  biodiversity. That said, they are an excellent setting for trophic s...

I have a deep personal interest in animal behavior and cognition, so when I came across a research article relating behavioral traits to life-history factors including fecundity and growth, I had to share it.  Animal personality traits (PTs) vary across individuals, and can be categorized in the same way human behavior is- shyness, boldness, sociability, aggressiveness, activity level, and tendency for exploration. While it is known that individuals vary in their behavior, it's still a bit of a mystery as to why some individuals act consistently different than their local conspecifics. A current hypothesis states that behavioral differences between individuals may be a result of life-history tradeoff differences.  Given that personality traits (and especially behavior) are somewhat plastic, scientists are also puzzled as to why individual behavior is consistent throughout time. This does not mean that an individual always acts in the same way, but rather that they will always ...

 The Joro spider (Tichonephila clavata) is native to Eastern Asia and Japan but in 2013 was found in Georgia and has since rapidly established large populations in much of Georgia. These large, flashy spiders are part of the golden-orb weaver genus and are easily visible in a wide range of habitats from front yards to riparian forests. Over the past 2 years I have been fascinated with this species and regularly observe and collect individuals. Even to the causal observer it will quickly become obvious that the adult females of this species can display a huge range of sizes from smaller than a quarter to having a leg span that is as large as your hand. I regularly asked myself why this is? As it turns out, a good deal of work on this species has been done in their native range. In 1991, Tadashi Miyashita from Tokyo University did a number of experiments on how food availability affects the size of female Joro spiders. She found that it is highly plastic and that there is a strong co...

      Recently in class, we've been examining sex determination and reproductive development. One topic in particular that stuck out to me was the idea of sex change at the adult stage of an organism's life. Such an incredible display of plasticity is very fascinating to me, and I've been thinking about the literature we've taken a look at in class (Matsumoto et al. 2014 & Capel et al. 2017). On one hand, we've seen how exposure to PCB's at the embryonic stage in turtles can redirect gonadal directory (Matsumoto et al. 2014), and on the other hand we learned how adult fish can change sex based on visual and social cues (Capel et al. 2017). Something significant that I feel like we haven't covered but I'm familiar with from past courses is the effect of pollution (PCB's and estrogen in particular) on the endocrine system in fish species.       Wastewater treatment runoff into streams wreaks havoc on aquatic species. Chemicals acting as endocrin...

       We’ve all been somewhat scarred by our parents at some point in our lives, whether by seeing pictures of them in their 80’s workout clothes or catching them smooching in the kitchen. But what if even before we were born, even before we were thought of, the actions of our parents changed our destiny?  We all understand that our DNA gets passed down from generation to generation and results in us having blue eyes or brown hair or large foreheads, but often it’s a little more complicated than that. Our DNA makeup is consistent in every cell of our body, however each cell type requires the expression of only a certain number and kind of genes. This can be mediated through epigenetic mechanisms that suppress or turn on certain genes without changing the actual DNA structure. DNA methylation is a prime mechanism in epigenetics where a methyl group (three hydrogen atoms bound to a carbon atom) prevents a transcription factor from binding to DNA resulting in the ...

    Phenotypic plasticity arises through three primary mechanisms: genetic, environmental and the interaction between the two (Martin et al 2021). Although the Martin et al paper focused on applying the reaction norm framework to exploring immunology, I believe the premise can be extrapolated to other fields of ecological importance. For example, a November 2020 study from Amiri et al examined factors influencing variation in the size of eggs produced by honeybee ( Apis mellifera ) queens.      Amiri et al found that certain genetic lineages produced larger eggs on average. However, there was significant variability of egg size produced by queens within the same lineage. This suggests that external factors, outside of genetics, influence egg size plasticity. Amiri et al looked into two environmental conditions that could influence egg size:  colony size and nutritional status. Colony size is a factor of the social environment within the hive. Queens wi...

      Pollutants are known for their effects on development and growth of living organisms. I became curious as to what effects they have on different marine arthropods and how they affected development, and that was how I stumbled upon a chapter by Mark L. Botton and Tomio Itow. The book covers horseshoe crab biology and conservation, but the chapter that I read focused on how pollutants affected the development of horseshoe crab embryos and larvae.      The chapter addresses how horseshoe crab populations across the world are declining, and one of the reasons could be pollution. The chapter looks at multiple different studies that were done on different horseshoe crab species and how their development was affected by certain pollutants, and the results were shocking to me. Horseshoe crab are pretty resilient to pollutants all around. Most pollutants had little effect on horseshoe crabs which didn't make much sense to me....

Recently, in class we have been discussing plasticity in a variety of different environments and functions. Phenotypic plasticity plays a very important role in organisms ability to respond to new environments and situations. I read a review the other day from Frontiers in Genetics, discussing the impact of genomics on developmental plasticity, and the effects that this plasticity can have upon adaptation in later life.  One of the most interesting things about the review for me was the discussion about the potential mitigating effects of plasticity on the detrimental impacts of future climate change. As climate change progresses, it is likely that temperatures will fluctuate, and many biomes will change drastically in a relatively short period of time. As these changes occur, organisms will have to adapt, die out, or migrate. When organisms are forced to adapt it can be an enormous benefit to be more "plastic" in terms of traits. Greater plasticity allows an organism to surv...

Reptiles and amphibians are cold-blooded! This phrase has gone out of style in recent years because it's not true. There's nothing cold about their blood at all. Reptiles and amphibians are ectothermic! What's the difference? Because honestly in my head that's just a fancy word for cold-blooded. It turns out that few amphibians and reptiles are at the mercy of the Weather Channel app on your phone. In fact we can remove this picture of a snake that operates at an internal temperature of 27F if it's 27F outside, or 100F internally if it's 100F outside. Instead it's better to think of ectotherms as creatures that must adjust their activity, behavior, and physiology according to the demands of the thermal environment to keep their body temperature within a range of functionality. Limiting exposure to suboptimal temperatures through thermoregulation is known as the Bogert effect. Marine iguanas, the only lizards that hunt in the ocean, display the Bogert effect ...

  Recently, we have been discussing vertebrate sex determination and the diverse mechanisms that have evolved to control and regulate these important developmental decisions. Traditionally, many vertebrate species have been governed by genetic sex determination (GSD) or environmental sex determination (ESD). However, several studies have found that in many species both GSD and ESD mechanisms operate simultaneously in response to a broad range of heritable and environmental factors. This is thought to be the case for many amphibian species. One aspect of this that I find particularly interesting is the role of environmental contaminations and how they may modify the traditional amphibian sex ratios and the mechanisms of sex determination.     A paper published in 2016 by Max Lambert and colleagues entitled “Interactive effects of road salt and leaf litter on wood frog sex ratios and sexual size dimorphism” had me thinking about the role of not only or...

    So far in this class, we have studied the concept of phenotypic plasticity in the terms of animal models such as rodents and amphibians. This makes perfect sense, as these animal models can be made the subject of experimentation with the goal of understanding the genetic and environmental factors and mechanisms that drive phenotypic plasticity. However, I'd like to look at this concept from a different scope; while humans are not used for experimentation of this kind for obvious reasons, they can still make for useful models by applying geographical and physiological data into a framework.     One paper by Zaccone et al. (2006) reviews the genetic and environmental evidence for the increased rates of autoimmune disorders in highly developed countries. Using the Hygiene Hypothesis, which suggests that parasites have been instrumental in the development and fine-tuning of the human immune system,  Zaccone et al. cites the use of sanitation techniques and antib...

    The driving forces behind the evolution of plasticity have been studied, but the ways in which plasticity evolves and is maintained are still unclear. A relatively recent paper in 2020 by Warren Burggren entitled  Phenotypic Switching Resulting From Developmental Plasticity: Fixed or Reversible? had me wondering about the reversibility of phenotypes resulting form plasticity during development. The paper follows a similar approach of a previous review by Beaman et al. (2016). Both papers, along with others, argue for a change in viewpoint about plasticity and the trade-offs associated with it, something that has peaked my interest.      Burggren (2020) starts out by introducing a new framework for understand plasticity, mainly a push to move away from the classical G x E model for plasticity to include more terms that contribute to plastic traits. The new model, G x (E + Epi) x (D x S) incorporates epigenetics (Epi; a mediator between genes an...

       In class we most recently discussed how phenotypes may be lost or gained over time, the potential role of genetic accommodation in shaping genotypes, and how plasticity may be another driver in natural selection through adaptation. I looked into this a little further and found two different theories of adaptive evolution pertaining to phenotypic plasticity. These were described as "gene leading" and "gene following" approaches by Ghalambor and colleagues. Gene leading is the typical thought of evolution as the process of change in allele frequencies over time, which would shape traits that are plastic and environmentally induced variation is not heritable and actually slows the rate of adaptive evolution. Gene following is the idea that environmentally induced and weak genetic control of phenotypic variation becomes established in a population and results in genetic assimilation of a trait so that the need for environmental cues are not required.    ...

       Over the past couple of weeks, we have spent a lot of time focusing on plasticity responses in amphibians to different environmental scenarios, covering everything from pond drying to predatory cues. I recently came across a great literature review that not only covers both of these studies, but also dives into the proximate hormonal mechanisms driving such cases of plasticity in amphibians (the author of the paper, Robert Denver, is actually the same person who did the studies on pond drying and spadefoot toads). The literature review goes through the main hormones of the neuroendocrine stress axis before discussing how these various hormones specifically affect development in amphibian larvae.      One particular aspect that I found fascinating was the role of corticosterone in predatory response. We have already discussed some of the morphological effects caused by exposure to chemical cues given off by predators in class, but something tha...