How does heavy metal cadmium get into your chocolate?
Cocoa is a chocolate powder made from ground cacao seeds.
Cacao seeds naturally contain cadmium originating from the soil because of volcanic activities, eroded rocks, and forest fires.
Cadmium is a soft, silvery-white metal and is similar in many respects to zinc.
Cadmium can cause damage to the kidney especially to the proximal tubular cells.
Cadmium can also cause bone demineralization through direct bone damage or as a result of renal dysfunction.
Abnormal high concentration of cadmium in cacao and other cocoa-based products such as chocolate may cause serious human health issues.
Current regulations established a threshold for cadmium content of cocoa-based products.
However, the biophysical factors such as climate and soil conditions that determine the concentration of soil-derived cadmium in the cacao seed are not well understood.
Researchers used scientific literature to compile a database from across the Cacao Belt to determine the primary drivers of cacao seed cadmium.
Cacao Belt refers to the regions approximately 20 degrees latitude on either side of the equator.
Researchers discovered that total soil cadmium and soil pH can significantly affect the concentration of cadmium in cacao seeds.
Both available soil cadmium and soil organic carbon content do not influence cacao seed cadmium concentration.
Soil pH and soil organic carbon decreased the degree of bioconcentration of total soil cadmium in the cacao seed cadmium concentration.
The results suggest that cadmium reduction strategies utilizing plant physiology-based approach are better compared to soil-based approaches.
If using soil-based approaches, researchers suggest to use strategies that can increase soil pH greater than 6.0.
Wade J, Ac-Pangan M, Favoretto VR, Taylor AJ, Engeseth N, Margenot AJ (2022) Drivers of cadmium accumulation in Theobroma cacao L. beans: A quantitative synthesis of soil-plant relationships across the Cacao Belt. PLoS ONE 17(2): e0261989. https://doi.org/10.1371/journal.pone.0261989
Sound communication among fishes is more common that we thought
Fishes produce sound and has been recognized for many years; however, this behavior is usually regarded as comparatively rare.
Researchers map the most comprehensive dataset of sound produced by fishes.
The sound production dataset was constructed onto a family-level phylogeny of ray-finned fishes.
Ray-finned fishes or Actinopterygii were named because their fins are webs of skin supported by bony or horny spines.
This clade of fishes contains more than 34,000 living species.
Eighty two percent of the analysis of sound production were based on illustrations of acoustic recordings and morphological specialization.
Eighteen percent were based along with qualitative descriptions.
Data reveal that fishes are more likely to communicate using sound than previously thought.
Sixty families are able to produce sound using muscles coupled to swim bladder vibration.
Swim bladder is an internal gas-filled organ which allows many fishes to control their buoyancy.
Thirty nine families are able to produce sound using movement of skeletal parts such stridulation.
Stridulation is the act of rubbing together certain body parts to produce sound such as in crickets or grasshoppers.
Eighteen of these families which include 13 catfishes exhibit both the sound-producing mechanisms.
Additionally, researchers discovered that about 67 percent of the families with sound-producing species are ray-finned fishes including a clade originating about 155 million years ago, and that sound production has evolved about 33 times within the ray-finned fish clade.
Researchers proposed that these patterns of shared ancestry are robust based on sensitivity analyses.
Sensitivity analysis refers to the study of how variables of interest is affected by changes in external conditions.
Overall, these findings highlight a novel perspective on the origin, background, and convergent evolution of sound production among ray-finned fishes.
The study strongly support the hypothesis that sound production among ray-finned fishes is ancient and that sound communication among fishes is more common than previously thought.
Aaron N. Rice, Stacy C. Farina, Andrea J. Makowski, Ingrid M. Kaatz, Phillip S. Lobel, William E. Bemis, Andrew H. Bass “Evolutionary Patterns in Sound Production across Fishes,” Ichthyology & Herpetology, 110(1), 1-12, (20 January 2022). https://doi.org/10.1643/i2020172
Limb regeneration is one of the most sought regeneration among vertebrates.
It is important to identify the triggers of natural morphological responses to induce the development of healthy-patterned tissue.
The discovery should help millions of patients suffering from diabetes and traumatic injuries.
Human limb loss in the United States is expected to increase significantly affecting more than 3 million individuals per year by 2050.
Adult African clawed frog has a limited regenerative capacities similar to humans.
This frog can serve as a model to test interventions for regeneration.
Researchers revealed tissue regrowth and functional restoration of an amputated African clawed frog hind limb.
The regeneration process took about 18 months.
The frog’s hind limb was exposed to a multi-drug pro-regenerative treatment delivered by a wearable bioreactor.
The bioreactor contains silk protein and five small-molecule compounds namely 1,4-dihydrophenonthrolin-4-one-3carboxylic acid, brain-derived neurotrophic factor, growth hormone, resolvin D5, and retinoic acid.
The treatment regenerated the skin, bone, and nerves up to a point that exceed the complexity of untreated control group.
RNA analysis of the new tissues showed that some of the developmental pathways were activated.
The study highlights the way of triggering the internal regenerative processes in vertebrates.
Murugan, N. J., Vigran, H. J., Miller, K. A., Golding, A., Pham, Q. L., Sperry, M. M., Rasmussen-Ivey, C., Kane, A. W., Kaplan, D. L., & Levin, M. (2022). Acute multidrug delivery via a wearable bioreactor facilitates long-term limb regeneration and functional recovery in adult Xenopus laevis. Science advances, 8(4), eabj2164. https://doi.org/10.1126/sciadv.abj2164
Some plants stop growing and die after producing fruits, here’s why
Monocarpic plants are plants that die after producing fruits.
When these plants reach certain number of fruits, flower production stops and cells responsible for growth cease dividing.
This process of cessation is called proliferative arrest which ensures that nutrient is available for the formation of seeds.
Proliferative arrest is an agricultural interest because it influences the flowering time scale and fruit production.
The mechanism behind the initiation of the flowering period is well studied.
However, the regulatory pathways and cellular processes that take part in the flowering cessation and triggering proliferative arrest is not well understood.
Researchers identified the molecular and cellular changes associated with cell division and tissue growth in the shoot apical meristem throughout the flowering time period and proliferative arrest.
Shoot apical meristem is the region of a plant that contains multipotent stem cells responsible for the development of plant organs above the ground.
Researchers discovered that before proliferative arrest occurs, cytokinin signaling was suppressed.
Cytokinin is a plant hormone that induces cytokinesis or plant growth.
Additionally, researchers observed that repression of type B cyclins and WUSCHEL is correlated with proliferative arrest.
B cyclins are proteins involved in the process of cell cycle.
WUSCHEL is a master regulator involved in plant growth signaling.
These molecular changes were observed to go along with changes in cell number and size.
A separate analysis revealed that a mutation in FUL does not trigger proliferative arrest.
FUL is the gene associated with controlling flowering time, meristem identity and leaf formation.
The study determined two phases that lead to proliferative arrest: early reduction and late blocking of cytokinin-related events.
Paz Merelo et al. (2021). A cellular analysis of meristem activity at the end of flowering points to cytokinin as a major regulator of proliferative arrest in Arabidopsis, Current Biology. DOI: 10.1016/j.cub.2021.11.069
Study reveals what’s behind the king baboon spider’s painful bite
King Baboon spider is a large African tarantula scientifically named Pelinobius muticus.
The spider usually has dark brown to orange coloration and lives in grasslands and shrublands of east Africa.
It has been reported that the spider’s bite can cause severe pain, swelling, itchiness, and muscle cramping.
Hyperalgesia, an abnormal increase sensitivity to pain, is the most well-known symptom after a bite from king baboon spider.
However, the molecular basis by which the venom induces the severe pain is not well understood.
Analysis of the venom revealed that a cysteine-rich peptide called δ/κ-theraphotoxin-Pm1a (δ/κ-TRTX-Pm1a) induced nocifensive behavior when injected into mice.
Nocifensive behavior is the response of an animal to very unpleasant or painful stimuli.
When a synthetic version of the peptide was introduced into the small dorsal root ganglion neurons, hyperexcitability was observed.
During the excessive excitation, tetrodotoxin-resistant sodium currents were enhanced, repolarization was impaired, and the threshold of action potential firing was lowered, all consistent with the severe pain associated with venomous bite.
The molecular mechanism of nociceptor sensitization by the cysteine-rich peptide involves several modes of actions over several ion channel targets.
The unselective targeting approach of the peptide may be an evolutionary adaptation in pain-causing defensive venom.
Rocio K. Finol-Urdaneta, Rebekah Ziegman, Zoltan Dekan, Jeffrey R. McArthur, Stewart Heitmann, Karen Luna-Ramirez, Han-Shen Tae, Alexander Mueller, Hana Starobova, Yanni K.-Y. Chin, Joshua S. Wingerd, Eivind A. B. Undheim, Ben Cristofori-Armstrong, Adam P. Hill, Volker Herzig, Glenn F. King, Irina Vetter, Lachlan D. Rash, David J. Adams, Paul F. Alewood Proceedings of the National Academy of Sciences Feb 2022, 119 (5) e2110932119; DOI: 10.1073/pnas.2110932119. https://www.pnas.org/content/119/5/e2110932119
Where we plant coffee, cashew, and avocado right now may not be suitable in the future
Coffee, cashew, and avocado are among the most important cash crops and possess importance in the economy.
Coffee beans are used in many beverages and drink products.
Cashew seeds are commonly consumed as snack nuts.
Avocados are used as ingredient to many food items.
Coffee, cashew, and avocado are plantation crops with a long lifespan of several decades and their cultivation requires long-term planning.
The Intergovernmental Panel on Climate Change predicted that the global temperature will be 1.2 to 3.0°C higher by year 2050.
Scientists highlight the importance of evaluating the impact of climate change on the plants biophysical suitability in order to develop adaptation measures and selecting appropriate varieties of crops.
Researchers created model of the current and future suitability of these plants on a global scale based on climate and soil requirement.
They model the year 2050 climate change impact on the crops both globally and in the countries mainly producing the crops.
Researchers discovered that climate factors including long dry season, mean temperatures, low minimum temperatures, and yearly precipitation reduce the suitability of growing these crops more than land and soil factors which include soil pH, texture, and slope steepness.
They predicted that there will be shifts in suitable growing regions due to global warming.
Coffee will be the most susceptible with negative climate impacts highly expected in all main producing regions which include Brazil, Vietnam, Indonesia and Colombia.
Areas suitable for cultivating cashew and avocado are expected to expand globally; however, most main producing countries will experience decrease in suitability.
The main cashew-producing countries include Vietnam, India, Côte d’Ivoire and Benin, while the main avocado-producing countries include Mexico, the Dominican Republic, Peru and Indonesia.
The study highlights the importance of climate change adaptation in most major producing regions of all the three crops.
Areas with lower temperature such as in high latitudes and altitudes may profit from increasing minimum temperatures.
The study shows the first global evaluation of the impacts of climate change on cashew and avocado suitability.
Evidence Shows Sixth Mass Extinction Is In Progress
The history of Earth’s biodiversity already went five Mass Extinctions.
All previous mass extinction events were all caused by natural phenomena.
Scientists claim that the Sixth Mass Extinction may be in progress, but this time caused by humans.
There are numerous signals suggesting the presence of biodiversity crisis which includes increasing extinction and decreasing abundances.
However, some speculated that these signals could not be the Sixth Mass Extinction.
Scientists usually use the IUCN Red List to support their stance on extinction.
Opponents of the theory of Sixth Mass Extinction argued that the rate of species loss is the same as the background extinction rate or the normal extinction rate.
Proponents suggest that the IUCN Red List is significantly biased and that the IUCN Red List mostly contains birds and mammals, and only a small portion of invertebrates have been evaluated against conservation criteria.
Proponents said that if we include estimates of the true number of invertebrate extinctions, species loss rate will exceed the background rate suggesting that the Sixth Mass Extinction is underway.
Researchers reviewed extinction rate according to realms.
Marine organisms face significant threats; however, marine biota crisis has not reached the same level as the non-marine biota crisis.
Island species have suffered more compared to continental species.
Although there are clues that plants may have suffered lower extinction rate, plants face similar conservation biases as with invertebrates.
Other extinction crisis believers thought that these evidences could be a new trajectory of evolution because humans are part of the natural world.
Humans are the only species capable of manipulating the Earth on a grand scale, and they let the current crisis to happen.
Numerous conservation efforts have been implemented at different levels; however, most are not species oriented and specific measures to protect every extant species individually are simply inconvenient.
Researchers encourage the nurturing of the innate human appreciation of biodiversity, but assert strongly that biodiversity is disappearing at an unprecedented rate.
With the mounting crisis, scientists should embrace the practices of preventive archaeology and document as many species before they go extinct.
Without crisis intervention, we could pave the way for the Earth to carry on its unfortunate trajectory towards a Sixth Mass Extinction.
Cowie, R. H., Bouchet, P., & Fontaine, B. (2022). The Sixth Mass Extinction: fact, fiction or speculation?. Biological reviews of the Cambridge Philosophical Society, 10.1111/brv.12816. Advance online publication. https://doi.org/10.1111/brv.12816