Saturday 13 April 2024

A hitchhiking Pseudoscorpion from Chiapas Amber.

Phoresis is an interaction in which an Animal hitches a ride on another Animal purely for the purpose of transport. This is found in a variety of Animal groups, but is particularly common in Mites and Pseudoscorpions. Unusually for an Animal behaviour, phoresis has a fairly long fossil record, with the oldest known example being a Mite found attached to an early Orthopteran Insect from from the Carboniferous Tupo Formation of China, and the oldest known example involving a Pseudoscorpion coming from Cretaceous Burmese Amber.

In a paper published in the journal Historical Biology on 7 April 2024, Víctor Córdova-Tabares of the Universidad Autónoma del Estado de Morelos and the Departamento de Zoología at the Escuela Nacional de Ciencias Biológicas, Francisco Riquelme, also of the Universidad Autónoma del Estado de Morelos, and Gabriel Villegas-Guzmán, Javier Víctor, and Emilio Estrada Ruiz, also of the Departamento de Zoología at the Escuela Nacional de Ciencias Biológicas, describe an example of phoresis from Mexican Chiapas Amber, in which a Pseudoscorpion is attached to a Crane Fly.

Chiapas Amber comes from the Simojovel, Totolapa, and Estrella de Belén localities in the Chiapas Highlands of southern Mexico, with the Simojovel site being the main centre of commercial amber extraction. The amber comes from a series of limestone, sandstone, siltstone, shale, and lignite beds of Late Oligocene to Early Miocene age, referred to as either the Simojovel Formation or the La Quinta Formation. The amber here is thought to have derived from a type of Leguminous tree of the genus Hymenaea; resin-producing trees belonging to this genus are also thought to have been responsible for Dominican Amber, which is of approximately the same age as Chiapas Amber, and are still found today across the Neotropics. 

The Amber-Lagerstätte from Chiapas in southern Mexico: Simojovel, Totolapa, and Estrella de Belén, Late Oligocene to Early Miocene. Schematic map showing the location of the Montecristo mines in Simojovel. Córdova-Tabares et al. (2024).

The specimen described is a piece of amber from the Montecristo Mine at Simojoval in the Colección de Artrópodos Fósiles of the Escuela Nacional de Ciencias Biológicas. The Pseudoscorpion involved is assessed to belong to the genus Hysterochelifer, which has four extant species, but differs from these in the structure of its chelicerae. It is therefore assigned to a new species, Hysterochelifer manpauch, becoming the designated holotype of that species. The specific name 'manpauch' derives from the Tzotzil ‘man pauch’, meaning a person who works with amber.

Hysterochelifer manpauch. (A) Holotype CAF-1 (phoront) and CAF-2 (carrier), general view. (B) CAF-1 in dorsal view; (C) CAF-1 in a closer view. Legs in Roman numerals, abbreviations ab, abdomen; c, carapace; che, chelicera; gt, genitalia pa, patella. Córdova-Tabares et al. (2024).

The Pseudoscorpion is attached to the trochanter (second segment) of the foreleg of a Cranefly assigned to the species Trentepohlia immemorata, one of two species of this genus previously described from Chiapas Amber.

The Pseudoscorpion genus Hysterochelifer belongs to the family Cheliferidae, which is distinguished by having  a well-developed venom apparatus in both chelal fingers. The family dates back to the Middle Cretaceous, with the oldest specimen coming from Cenomanian Archingeay Amber, which comes from the Charente Maritime district of south-western France. A protonymph (hatchling) assigned to the Cheliferidae has previously been described from Chiapas Amber, but this is the first adult specimen. 

Pseudoscorpions attached as phoronts to other Insects have previously been described from both  Baltic and Dominican amber, most commonly targetting Dipterans (True Flies) or Wasps. Living Pseudoscorpions will attach to a variety of organisms, including Vertebrates such as Birds and Mammals, but generally prefer Insects or larger Arachnids, and in particular Beetles. Beetles tend to have fairly specific environmental requirements, as do Pseudoscorpions, so a Pseudoscorpion attaching to a Beetle has a good chance of being carried to a suitable new environment. Flies are more tolerant in their environmental needs, typically settling on a wide range of surfaces, making them less ideal carriers. 

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Thursday 11 April 2024

Hoard of medieval silver coins found on Visingsö Island, Sweden.

Archaeologists from the Jönköping County Museum carrying out surveying work ahead of the installation of geothermal heating system in a church on Visingsö, an island on Lake Vättern in south-central Sweden, have uncovered a pair of medieval graves, one of which contained a hoard of silver coins. The coins were found close to the foot of the skeleton of a man thought to have been between 20 and 25 when he died. Similar finds are common in earlier, pre-Chistian burials in Scandinavia, but their inclusion in what is thought to have been a Christian burial is very unusual.

A hoard of silver coins discovered on Visingsö Island, Sweden. Jönköping County Museum.

The hoard comprises 170 coins of a type known as silver bracteates, which had a stamped motif on one side only, which were common in Germany and Scandinavia after between the twelfth and fifteenth centuries. These coins retained their value for only a limited time, then had to be taken back to the issuing authority and restamped, which was intended as a way of ensuring that money continued to circulate and couldn't be hoarded. The coins in the Visingsö hoard are thought to date to between 1150 and 1180, and contain many stamps not previously seen by modern archaeologists.

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Wednesday 10 April 2024

Assessing the habitability of the clouds of Venus.

The surface of Venus has long been considered to be unsuitable for life. The temperature here averages about 427°C, which is not only far to hot for liquid water to exist, but which would also cause the near instantaneous inactivation of any enzymes, the denaturing of any proteins, and the thermal decomposition of almost all biological organic molecules. This has not, however, prevented all speculation about the possibility of life existing on Venus, with some scientists suggesting that it might be possible for life to exist within the planet's cloud layer. One proposed theoretical dweller in the clouds of Venus is the spherical hydrogen gasbag isopyenic organism, which would keep its position within the cloud layer by means of a bag-like body containing the lighter-than-air gas hydrogen, although calculations suggest that such an organism would require a minimum diameter of 4 cm to stay aloft on Venus, which seems improbable.

The detection of phosphene gas in the clouds of Venus, which on Earth would  be considered a clear indicator of microbial activity, has led to renewed consideration of the possibility of life in the Venusian clouds, possibly in the form of microbes within fluid droplets, a habitat which would protect them from dehydration, otherwise a problem for small organisms floating in an atmosphere. However, living within floating droplets would present micro-organisms with another problem, due to the limited lifespan of droplets large enough to sustain such organisms, which would tend to settle out of the cloud layer and evaporate. 

In a paper published on the arXiv database at Cornell University on 8 April 2024, Jennifer Abreu of the Department of Physics and Astronomy at Lehman College at City University of New York, Alyxander Anchordoqui of the John F. Kennedy School in Somerville, Massachusetts, Nyamekye Fosu, Michael Kwakye, Danijela Kyriakakis, and Krystal Reynoso, also of the Department of Physics and Astronomy at Lehman College at City University of New York, and Luis Anchordoqui, again of the Department of Physics and Astronomy at Lehman College, and of the Department of Physics at the Graduate Center at City University of New York, and of the Department of Astrophysics at the American Museum of Natural History, present a potential scenario for the survival of microbes within the Venusian cloud layer. 

The cloud layer completely encircles Venus, giving it a planetary albedo of about 0.8 (i.e. causing it to reflect about 80% of the light it receives back into space). The base of the cloud layer is about 47 km above the surface, at which altitude the atmosphere has a temperature of about 100°C. The top of the cloud layer reaches about 74 km above the surface at the equator, decreasing to about 65 km at the poles. This cloud layer can further be divided into three zones, an upper layer, above 56.5 km, a middle layer between 50.5 km and 56. 5 km, and a lower layer less than 50.5 km above the ground. Droplets within the cloud layers can be divided into three types, based upon their size. Type 1 droplets have a diameter of about 0.2 µm, type 2 droplets have a diameter of 1-2 mm, and type 3 droplets have a diameter of about 4 mm. Types 1 and 2 are found in all three cloud layers, whereas type 3 droplets are only found in the middle and lower layers.

Within the cloud layer, the availability of carbon dioxide, sulphuric acid compounds, and ultraviolet light would provide any microbes with sources of food and energy. Optimum conditions for survival would probably be found about 50 km above the surface, where the temperature fluctuates between about 60°C and about 100°C, and the pressure is about one atmosphere.

On Earth, long lived aerosols, acidic clouds, and atmospheric temperatures consistently above the boiling point of water are not present. However, life, in the form of Bacteria, Pollen, and Algae, has been found in the atmosphere as far as 15 km above sealevel, and Bacteria have been found growing in droplets of moisture gathered from super-cooled clouds above the Alps. It has been proposed that microbes have been able to reach such heights via evaporation, storms, eruptions, or meteor impacts, all processes likely to have been found on an early Venus, where the surface is likely to have been more conducive to life. Unlike their Earthly counterparts, the clouds of Venus are not transient, but are a constant, global phenomenon, where individual aerosol particles can be sustained for a long period of time, rather than for a maximum of a few days, potentially providing a stable home for Venusian life.

Abreu et al. suggest that life may be present in the lower haze layers of the Venusian atmosphere as desiccated spores, ready to become activated when updrafts carry them into the habitable layer within the clouds. After reaching the habitable middle and lower cloud layers, the spores would act as condensation nuclei around which water droplets would form, allowing them to germinate and become metabolically active. Metabolically active microbes could grow by division (as with Prokaryotes on Earth) within the droplets, which would themselves grow further by coagulation. Eventually the droplets would grow so large that they would gravitationally settle out of the cloud layer into the hotter layers beneath, causing their liquid content to evaporate, and the micro-organisms to desiccate and re-enter the spore state. The desiccated spores would then be small and light enough to resist further downwards movement, remaining in the haze layer until a new updraft carries them back into the clouds and the process begins again.

Hypothetical life cycle of the Venusian microorganisms. Top panel: Cloud cover on Venus is permanent and continuous, with the middle and lower cloud layers at temperatures that are suitable for life. Bottom panel: Proposed life cycle for Venusian aerial microbial life. Abreu et al. (2024).

All living organisms have to be able to replicate, and in Bacteria, used as the model for Abreu et al.'s proposed Venusian microorganisms, this is achieved by binary fission; i.e. the division of one Bacterium into two. Thus, a population of Bacteria can double in size in a single generation, and the time which it takes for a population of Bacteria to double can be taken as a generation time. For many common Bacteria the generation time is less than an hour, for example in Escherichia coli it is typically about 20 minutes under ideal conditions (which assume an aerobic, nutrient-rich environment at an optimum temperature), which the marine Bacterium Vibrio natriegens can have a generation time as low as 7-10 minutes. 

If a Bacterium has a generation time of 20 minutes, then it would go through three generations in an hour (so that one Bacterium will become sixteen) and 36 in 12 hours (so that one Bacterium will become about 70 000 000 000, assuming a suitable source of nutrients).

Abreu et al. further calculate that a droplet with a diameter of about 0.1 µm would be effectively neutrally buoyant in Venus's cloud layer, and that a droplet would need to reach about 100 µm in diameter before it began to fall consistently at a velocity of 1 m per second, within a cloud layer that can be up to 27 km thick, enabling plenty of time for reproductive fission.

Unlike Earth, Venus lacks an intrinsic magnetic field which prevents cosmic radiation from reaching the atmosphere. This means that molecules in the upper atmosphere are ionized by ultraviolet radiation, forming an ionosphere, with interactions between this ionosphere and the solar winds producing a magnetic field within the outer atmosphere, capable of slowing down particles with energies of up to a few hundred kiloelectron volts and diverted them around the planet. More energetic particles are able to penetrate this weak magnetic field. Particles with energies of greater than one giga electron volt will provoke cascade reactions in the atmosphere, with nuclei scattered by interaction with the initial particle interacting to cause secondary, tertiary, and subsequent generations of particles, losing energy with each reaction. 

The terrestrial biosphere on Earth benefits from about 1033 g/cm² of protection against the harmful effects of cosmic rays, compared to about 200 g/cm² of shielding available to any Venusian organisms at the top of the cloud layer. However, this protection will have risen to about 1000 g/cm² in the middle cloud layer, comparable to conditions on Earth. Furthermore, cosmic rays are generally considered to be less harmful to Prokaryotic organisms than to multicellular organisms (an interaction with a charged particle may well kill an individual Bacterial cell - but this has no effect on any other cell, and the high rates of reproduction mean that lost Bacteria are replaced quickly, whereas a multicellular organism with many cells needs most of them to survive until the whole organism can reproduce).

Based upon these calculations, Abreu et al. calculate that micro-organisms with similar properties to those found on Earth could potentially exist within the clouds of Venus, reproducing exponentially within droplets in the clouds during the lifetime of those droplets.

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Tuesday 9 April 2024

March 2024 was the hottest March since records began.

March 2024 was the hottest March since records began, according to the European Copernicus Climate Change Service,  making it the tenth consecutive month to be the hottest recorded instance of that month; i.e. every month since June 2023 has been the hottest example of that calendar month. In addition, July 2023 was the hottest calandar month ever recorded, while 2023 was the hottest year since records began.

The average global surface air temperature for March 2024 was 14.14°C, which is 0.10°C higher than the previous hottest March recorded (in 2016) and 0.73°C above the March monthly average for the period 1990-2020, as well as 1.68°C warmer than the March average for the period 1850-1900.  The global average surface air temperature for the period April 2023-March 2024 was also the highest ever recorded for that period, 0.70°C above the average for 1990-2020 and 1.58°C above the average for the period 1850-1900.

Surface air temperature anomoly for March 2024. European Copernicus Climate Change Service.

The average sea surface temperature between 60° north and 60° south for March 2024 was 21.07°C, the hottest for any calendar month ever recorded, exceeding the previous record holder, February 2024, by 0.01°C, and only 0.02°C below the highest daily sea surface temperature ever recorded, on 26 February 2024. 

Sea surface temperature percentiles for March 2024. European Copernicus Climate Change Service.

The high temperatures experienced in the past year have been linked to a combination of anthropogenic global warming, driven by emmissions of carbon dioxide and methane, with an El Niño - Southern Oscillation climate system over the Pacific Ocean, a natural phenomenon which also tends to drive temperatures upwards. However, the El Niño system appears to have been weakening over the past months, with sea surface temperatures over the eastern equatorial Pacific actually being lower than the average for 1990-2020, while global temperatures have continued to rise, suggesting that the El Niño system may be playing as large a role in driving this year's high temperatures as previously assumed.

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Fireball meteor over Albuquerque, New Mexico.

Witnesses across parts of New Mexico and southwest Texas have reported observing a bright fireball meteor slightly after 2.30 am local time (slightly after 8.30 am GMT) on Tuesday 2 April 2024. The fireball is described as having moved from southwest to northeast, slightly to the east of Albuquerque. A fireball is defined as a meteor (shooting star) brighter than the planet Venus. These are typically caused by pieces of rock burning up in the atmosphere, but can be the result of man-made space-junk burning up on re-entry.

The 2 April 2024 fireball meteor seen from Albuquerque. American Meteor Society.

Objects of this size probably enter the Earth's atmosphere several times a year, though unless they do so over populated areas they are unlikely to be noticed. They are officially described as fireballs if they produce a light brighter than the planet Venus. The brightness of a meteor is caused by friction with the Earth's atmosphere, which is typically far greater than that caused by simple falling, due to the initial trajectory of the object. Such objects typically eventually explode in an airburst called by the friction, causing them to vanish as a luminous object. However, this is not the end of the story as such explosions result in the production of a number of smaller objects, which fall to the ground under the influence of gravity (which does not cause the luminescence associated with friction-induced heating).

Heat map showing areas where sightings of the meteor were reported (warmer colours indicate more sightings), and the apparent path of the object (blue arrow). American Meteor Society.

These 'dark objects' do not continue along the path of the original bolide, but neither do they fall directly to the ground, but rather follow a course determined by the atmospheric currents (winds) through which the objects pass. Scientists are able to calculate potential trajectories for hypothetical dark objects derived from meteors using data from weather monitoring services.

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Monday 8 April 2024

Nannotanyderus granieri: A new species of Primitive Crane Fly from Early Cretaceous Lebanese Amber.

Primitive Crane Flies, Tanyderidae, are a widely distributed group of mostly aquatic True Flies, Diptera, generally thought to be a relict group. There are 39 living species in ten genera found around the globe, with 34 fossil species dating as far back as the Early Jurassic, which show a greater morphological diversity than is found in the group today. Larval Primitive Crane Flies are typically found in aquatic or semi-aquatic environments, such as wet sandy soil and the outer layers of submerged rotting logs in streams. Adults vary between about 5 mm and about 35 mm in length, and typically have a mottled pattern on their wings, conspicuous mouthparts, and elongated cervical (neck) sclerites.

In a paper published in the journal Carnets Geol. on 1 April 2024, Dany Azar and Sibelle Maksoud of the State Key Laboratory of Palaeobiology and Oil Stratigraphy at the Nanjing Institute of Geology and Palaeontology, and the Natural Sciences Department at the Lebanese University, Di-Ying Huang, also of the State Key Laboratory of Palaeobiology and Oil Stratigraphy at the Nanjing Institute of Geology and Palaeontology, Mounir Maalouf, also of the Natural Sciences Department at the Lebanese University, and Chen-Yang Cai, again of the State Key Laboratory of Palaeobiology and Oil Stratigraphy at the Nanjing Institute of Geology and Palaeontology, describe a new species of Primitive Crane Fly from Early Cretaceous Lebanese Amber.

The new species is placed in the genus Nannotanyderus, which contains six previously described species from the Early Jurassic to Early Cretaceous of Germany, England, Kazakhstan, Mongolia, and Lebanon, and given the specific name granieri, in honour of Bruno Granier, whose research has significantly advanced the dating of amber outcrops in Lebanon. The species is described from a single female specimen, preserved in a piece of amber from the Bqaatouta outcrop in Caza District, which also includes a Spider and a male Chironomid Dipteran.

Nannotanyderus granieri, holotype, female, specimen number BKT-11A.  (A) Habitus, right lateral side. (B) Habitus, left lateral side. (C) Head photomicrograph with confocal microscope. (D) Wing photomicrograph with confocal microscope. (E) Female terminalia, photomicrograph with confocal microscope. (F) Female terminalia, photomicrograph with compound microscope. Scale bars are 500 µm (A), (B), & (D), 100 µm (C), and 50 µm (E) & (F). Azar et al. (2024).

Nannotanyderus granieri is tiny compared to modern Primitive Crane Flies, measuring only 1571 µm in length. making it the smallest known member of the Tanyderidae (the next smallest, measuring only 1890 µm, is Nannotanyderus ansorgei, also from Lebanese Amber). It lacks an elongated neck, but does have well-developed mouthparts, with sclerotized maxillae longer than the head.

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