Testing the strength of the Coconut Crab.

Coconut Crabs, Birgus latro, are the largest terrestrial Crustacean species, and indeed largest terrestrial Arthropod of any description. It is found across much of the Indian and Pacific Oceans, living on most landmasses where Coconuts are found (though in some areas they have been exterminated to protect commercial Coconut crops). They are descended from Hermit Crabs, and younger Coconut Crabs still use borrowed Snail shells for protection, but the adult Crabs have developed tough calcareous exoskeletons. Like other Decapod Crustaceans, Coconut Crabs have large chelae (claws) which are their main method of food manipulation and defence. Studies of other Decapods have been shown to be capable of exerting a considerably greater pinching force with their claws than the bite of similarly sized Vertebrates, making the pinching force of the Coconut Crab potentially very formidable.

In a paper published in the journal PLoS One on 23 November 2016, Shin-ichiro Oka, Taketeru Tomita and Kei Miyamoto of the Okinawa Churashima Foundation, describe the results of an experiment designed to test the strength of the claws of the Coconut Crab.

Oka et al. collected 29 Coconut Crabs from Ocean Expo Park on Northern Okinawa Island, ranging in size from 16.2 mm in length and 33 g in weight to 64.5 mm in length and 2120 g in weight and measured their pinching force with a device used to measure crushing force when an animal bites down on a stainless steel stick-shaped sensor, and in addition took measurements of their claws.

Measurement of the pinching force and claw morphology in the Coconut Crabs. (a) The force was measured with the SK-MBF-01F device (SkyScience Co. Tokyo, Japan) and related sensors and (b) demonstration of the method by which pinching force was measured. (c) Claw measurements of the Coconut Crab used in this study. The placement of the sensor used for pressure measurement is highlighted in green. The measurements used for claw length (CL), claw height (CH), and claw width (CW) are also indicated. L1: in-lever length from the fulcrum to the apodemes insertion; LBAE: out-lever length from the fulcrum to the tubercle (the contact point with the device sensor). Oka et al. (2016).

Oka et al. found that the pinching force of the claws related directly to the size of the Crabs, with the smallest Crab exerting a pinch of 29.4 Newtons, and the largest 1765.2 Newtons. However even the largest Crabs used in the study were considerably smaller than the maximum size for the species, about 4 kg. Assuming that the strength of larger Crabs continues to scale up in the same way, Oka et al. calculate that they could exert a pinch-force of 3300 Newtons, greater than the pinch-force measured from any other Crustacean, and higher than the bite-force recorded from any terrestrial predator except Alligators.

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Understanding the origins of the Giant Tortoises of the southwest Indian Ocean.

Giant Tortoises were once numerous on both continental and island landmasses, though most of the continental species became extinct in the Late Pleistocene and most of the island species in the Holocene, all of which extinctions have been linked to a single cause, the spread of Modern Humans around the globe. Today only two species of Giant Turtle remain, Chelonoidis nigra in the Galapagos and Aldabrachelys gigantean on Aldabra Island, a small coral atoll in the Indian Ocean, about 400 km north of Madagascar and about 600 km west of the east coast of Africa. The southwest Indian Ocean was formerly somewhat of a hotspot for Giant Tortoise diversity, with at least two species on Madagascar, plus two species on Mauritius, two species on Rodrigues and one on La Réunion.

An Aldabra Giant Tortoise, Aldabrachelys gigantean. Wikipedia.

How the Tortoises got to these islands is somewhat of a mystery; the ancestors of the Giant Tortoises of Madagascar presumably reached there while Madagascar was still attached to the Gondwanan supercontinent in the Cretaceous, or floating there from Africa in the Eocene or earlier, when prevalent currents in the southwest Indian Ocean ran from Africa towards Madagascar (Giant Tortoises seldom voluntarily swim, but float well and can survive long periods at sea, so Tortoises swept out to sea by, for example, flood events, have a reasonable chance of surviving till they reach a new landmass). However from the end of the Eocene onwards, prevalent currents in the southern Indian Ocean have all flowed east-to-west, making it highly unlikely that a Tortoise could drift from island to island in this direction without swimming hundreds of kilometres against the current. This makes the presence of Tortoises on smaller Indian Ocean islands hard to understand, as all of these islands have appeared since the end of the Eocene; Mauritius having first appeared about 8.9 million years ago, La Réunion about 2.2 million years ago and Rodrigues about 1.5 million years ago, while Aldabra, with a highest point only eight meters above sea level, has emerged from and been covered by the sea several times during the past million years, and is thought to have been continuously exposed only for the last 80 000 years.

In a paper published in the Journal of Biogeography on 11 March 2016, Lucienne Wilmé of the School of Agronomy at the University of Antananarivo, and the Missouri Botanical Garden's Madagascar Research & Conservation Program, Patrick Waeber of Forest Management and Development at the Swiss Federal Institute of Technology Zurich, and Joerg Ganzhorn of Animal Ecology and Conservation at Hamburg University, discuss the possibility that Giant Tortoises may have reached the islands of the southwest Indian Ocean not by drifting on ocean currents, but by active movement by Humans.

The earliest Humans arrived on Madagascar about 4000 years ago. These were fairly advanced, already having metal tools, and are thought to have come from Southeast Asia, with subsequent waves of arrivals from Arabia, Africa and eventually Europe. People from Southeast Asia began making ocean-crossing journeys about 45 000 years ago, hopping from island-to-island to reach remote parts of the Indian and Pacific Oceans, as well as the continent of Australia, and possibly South America.

During this process they introduced many animals and plants to the islands they visited, such as Pacific Rat, Rattus exulans, Chicken, Gallus gallus, Sweet Potato, Ipomea batatas, Taro, Colocasia sp., and Banana, Musa sp.. Giant Tortoises have been considered to be excellent eating by most cultures that have encountered them (most species being wiped out by encounters with hungry European sailors in the eighteenth and nineteenth centuries). It is not, therefore, an outlandish idea that early navigators might, having encountered Giant Tortoises on Madagascar, have moved small populations to other islands in the Indian Ocean as a potential food source, either for colonists living permanently on the islands or for other sailors visiting the islands (European sailors introduced Sheep and Goats to many small islands for similar reasons).

Giant land tortoises, geology, oceanography, archaeology of the south-western Indian Ocean, and distance between islands and ocean surface currents prevailing since the closure of the Tethys Ocean. (SdM = Saya de Malha; N = Nazareth; StB = St Brandon; LGM = Last Glacial Maximum). Wilmé et al. (2016).

Wilmé et al. note that no ancient archaeological sites have been found on the Mascarine Islands (Mauritius, Rodrigues and La Réunion), which would seem to present a problem to this theory. However they note that sealevels have varied considerably over the past few thousand years, which has a particularly strong effect on small islands, so that it is quite possible ancient coastal settlements around these islands may have been covered by rising seas.

More problematically, the Tortoises of the southwest Indian Ocean are considered to have belonged to eight different species, which seems unlikely if they were all transplanted from Madagascar (where only two species are known). Wilmé et al. do not dispute the current accepted taxonomy of these species, however they do observe that species isolated on small islands are known to evolve rapidly, and that Tortoises, which produce particularly large clutches of young, are potentially more prone to this effect than slower breeding groups such as Birds or Mammals.

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The Alpha Centaurid Meteors.

The Alpha Centaurid Meteors are visible in the Southern Hemisphere (but not the Northern Hemisphere) between 28 January and 21 February each year, peaking on 7-8 February, with best viewing at about 5.00 am local time wherever you are, with about 1 meteor per hour appearing to radiate from a point close to the star Alpha Centuari (the radiant point). The Alpha Centaurids can be difficult to spot, not just because of their low density, but because they are among the fastest meteors, crossing the sky and disappearing very quickly; in 2017 this will not be helped by the waxing Moon, which will be half full on 4 February and full on 11 February, making meteor viewing difficult over this time.

The approximate location of the radiant point of the Alpha Centaurid Meteors. Universe Guide.

Metoer showers are thought to be largely composed of material from the tails of comets. Comets are composed largely of ice (mostly water and carbon dioxide), and when they fall into the inner Solar System the outer layers of this boil away, forming a visible tail (which always points away from the Sun, not in the direction the comet is coming from, as our Earth-bound experience would lead us to expect). Particles of rock and dust from within the comet are freed by this melting (strictly sublimation) of the comet into the tail and continue to orbit in the same path as the comet, falling behind over time. The parent body of the Alpha Centaurids is not known, though the path which the meteors follow is; this follows an elliptical path tilted at 105° to the plane of the Solar System, with its perihelion (closest point to the Sun) at about 1 AU (i.e. the same distance from the Sun as the Earth) and an average distance from the Sun of 2.5 AU (about 2.5 times as far from the Sun as the Earth.

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Magnitude 5.6 Earthquake to the northeast of Martinique.

The United States Geological Survey recorded a Magnitude 5.6 Earthquake at a depth of 35.1 km roughly 62 km northeast of the town of Sainte-Marie on the French island of Martinique in the Lesser Antilles, slightly before 3.55 pm local time (slightly before 7.55 pm GMT) on Friday 3 February 2017. This was a large quake, but at some depth as well as some way offshore, and there are no reports of any casualties or serious damage, though the quake was felt over a large area, with people reporting feeling it across Guadeloupe, Dominica, Martinique, Saint Lucya, and Saint Vincent and the Grenadines.

The approximate location of the 3 February 2017 Martinique Earthquake. USGS.

The Lesser Antilles are located at the eastern fringe of the Caribbean Tectonic Plate. The Atlantic Plate (strictly speaking, an extension of the South American Plate which runs to the northeast of the Caribbean) is being subducted beneath this, and as it sinks into the Earth, is melted by the heat of the planets interior. Some of the melted material then rises up through the overlying Caribbean Plate as magma, fuelling the volcanoes of the Lesser Antilles Volcanic Arc. The subduction of the Atlantic Plate beneath the Caribbean Plate is not a smooth process, with the two plates constantly sticking together then breaking apart as the tectonic pressure builds up, causing Earthquakes in the process, though since the boundary between the two plates is some way to the east of the islands, Earthquakes in the Lesser Antilles tend to be both deep and offshore, which lessens their destructive potential.

 The subduction of the Atlantic Plate beneath the Caribbean Plate fuels the volcanoes of the Lesser Antilles Volcanic Arc. George Pararas-Carayannis.

Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organisation Earthquake Report is interested in hearing from people who may have felt this event; if you felt this quake then you can report it to Earthquake Report here.

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Muricea subtilis: A new species of Octocoral from Costa Rica.

Octocorals of the genus Muricea are found in shallow coastal waters along the tropical and subtropical coasts of North, Central and South America, from California to Peru and possibly Chile in the East Pacific, and from North Carolina across the Caribbean to Brazil on the Western Atlantic. Most species are found in shallow waters from the intertidal zone to depths of about 30 m, though a few species are known from deeper waters, such as Muricea midas, which was found on the North Coast of South America at a depth of 201 m, Muricea fruticosa, which has been found at depths of 102 m off the coast of California and Muricea galapagensis, which was recorded at a depth of 94 m in the Galapagos.

In a paper published in the journal ZooKeys on 7 November 2016, Odalisca Breedy of the Centro de Investigación en Estructuras Microscópicas and Centro de Investigación en Ciencias del Mar y Limnología at the Universidad de Costa Rica and the Smithsonian Tropical Research Institute and Hector Guzman, also of the Smithsonian Tropical Research, describe a new species of Muricea from the Pacific coast of Costa Rica.

The new species is named Muricea subtilis, meaning ‘slender’ or ‘thin’, in reference to the thin, spiny branches of the species. Colonies are white or pale yellow, roughly fan shaped with irregular, usually dichotomous branching (branching by repeatedly splitting in two). The species was found on muddy sand at depths of between 30 and 54 m.

Colony of Muricea subtilis. Breedy & Guzman (2016).

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Odontoma found in a Late Permian Gorgonopsian Synapsid from Tanzania.

Odontoma is a condition known in a variety of Mammal species in which small tumours appear in the jaw, made up of differentiated tooth material with differentiated enamel and dentine. This can lead to the re-absorption of the roots of the functional teeth, resulting in tooth loss. This condition has been detected in the recent fossil record, in species such as Mammoths up to a few million years old, and can be expected to have existed in the common ancestor of all the animals in which it has been recorded (Humans, Horses, Mammoths and Deer), probably in the Late Cretaceous, its presence earlier in the fossil record is unknown.

In a paper published in the journal JAMA Oncology on 8 December 2016, Megan Whitney, Larry Mose and Christian Sidor of the Department of Biology at the University of Washington, describe a case of odontoma in a 255-million-year-old Gorgonopsian Synapsid from the collection of the National Museum of Tanzania.

Synapsids split from the ancestors of modern Reptiles and Birds about 320 million years ago. Today the only surviving Synapsid group are the Mammals, but in the Permian a diverse range of Synapsids dominated most terrestrial ecosystems. The Gorgonopsians diverged from the ancestors of Mammals before the development of traits such as large brain size, diphyodonty, distinct thoracic and lumbar vertebrae, and 3 middle ear ossicles, though they did have Mammalian traits such as differentiated teeth and an upright gait.

Whitney et al. worked upon a right dentary (jawbone) of an unnamed Gorgonopsian. The specimen was embedded in polyester resin, then cut it into a series of thin sections, which were ground down to a thickness of approximately 100 μm using a variable-speed grinder and polisher. This revealed a series of eight ectopic toothlike lessons, close to the labial edge of the functional canine root. These range in size from 0.3 to 3.9 mm, some of which incur into the root of the tooth, causing loss of the cementum and dentine.

(A) Computed tomogram of a Gorgonopsian anterior dentary (red) with dentition (blue) highlighted (National Museum of Tanzania specimen RB382), indicating approximate positions of thin sections where the pathologic features are visible (National Museum of Tanzania specimen RB404). Successive slides representing the cervical (B) and midroot (C) portions of the functional root with odontomes. (D) Clustering of odontomes at the apical end of the tooth root. All histologic images were taken under cross-polarized light. Ca indicates root of canine; d, dentine; e, enamel; i, root of incisor; od, odontome; and pc, root of postcanine. Whitney et al. (2016). 

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The Ya Ha Tinda Fossil Assemblage: An Early Jurassic Lagerstätten from North America.

Fossil Lagerstätten are sites of exceptional preservation, where organisms are preserved better and in greater numbers than in other parts of the fossil record. These sites provide unique insights into the history of life on Earth, preserving organisms that cannot be found in other places, or in more common organisms, tissues that are not otherwise seen. The Early Jurassic was a time of major ecological and environmental change, with a number of distinct events that influenced the change in the marine fauna that occurred during this time, most notably the Toarcian Oceanic Anoxic Event (about 183 million years ago). Sadly only three fossil Lagerstätten are known from the Early Jurassic, all of them from European deposits, so that we have almost no knowledge of many important groups outside of Europe during this period.

In a paper published in the journal Geology on 9 January 2017, Rowan Martindale of the Department of Geological Sciences at The University of Texas at Austin and the Department of Organismic and Evolutionary Biology at Harvard University, Theodore Them of the Department of Geosciences at the Virginia Polytechnic Institute and State University and the Department of Earth, Ocean and Atmospheric Science & National High Magnetic Field Laboratory at Florida State University, Benjamin Gill, also of the Department of Geosciences at the Virginia Polytechnic Institute and State University, Selva Marroquín also of the Department of Geological Sciences at The University of Texas at Austin and of the Department of Geosciences at the Virginia Polytechnic Institute and State University, and Andrew Knoll, also of the Department of Organismic and Evolutionary Biology at Harvard University, describe a new fossil Lagerstätten from the Early Jurassic of southwest Alberta, Canada.

The Ya Ha Tinda Fossil Assemblage comprises several outcrops of the Fernie Formation outcropping on the Ya Ha Tinda Ranch. These deposits have been dated using Ammonites and Coccoliths (groups with very high species turnover often used to date Mesozoic strata), carbon isotope chemostratigraphy (the ratios of different carbon isotopes incorporated into sedimentary rocks varies in direct relation to global atmospheric temperature; this means that the proportion of these elements rises and falls at the same rate in rocks all over the world, creating a fingerprint that can be used to date rocks) and uranium-lead zircon dates from intercalated ash beds (zircon is a mineral formed by the crystallization of cooling lavas.; when it forms it often contains trace amounts of uranium, which decays into lead at a known rate - since lead, which has a much lower melting point, will not have been present in the original lava, it is possible to calculate the age of a zircon crystal from the ratio between these elements.), giving a very high confidence to the dates assigned to these beds; which are calculated to span the boundary between the Pliensbachian and Toarcian stages, including the Toarcian Oceanic Anoxic Event.

This site is the first Early Jurassic Lagerstätten known from outside Europe, and the third Lagerstätten to include the Toarcian Oceanic Anoxic Event. It has yielded Vampyropod Cephalopods (Vampire Squid), Lobsters, Shrimps, Leptolepiform and Saurichthyiform Fish, Ichthyosaurs, Ammonites, isolated Dinosaur bones, Brachiopods, Gastropods, Bivalves, wood, and Coccolithophores.

Exceptionally preserved fossils of Ya Ha Tinda Lagerstätte (Alberta, Canada). RDM—Red Deer Member; PCS—Poker Chip Shale Member. (A) Articulated Ichthyosaur vertebrae and ribs (RDM, late Pliensbachian). (B) Skull of small Teleost Fish (PCS, within Toarcian Oceanic Anoxic Event [T-OAE] carbon isotope excursion [CIE]); note preservation of gills (arrow). (C) Seirocrinus subangularis (Crinoid) calyx collected by Russell Hall (RDM, late Pliensbachian). (D) Vampyropod gladius with mantle muscle (white arrow) and ink sac (black arrow) (RDM, early Toarcian). (E) Loligosepiid Vampyropod gladius with ink sac (arrow) (RDM, early Toarcian). (F) Shrimp body fossil (PCS, within T-OAE CIE). (G) Complete body fossil of Uncina pacifica, Lobster, proximodistally flattened (RDM, late Pliensbachian). (H) Complete body fossil of Eryonid Lobster, dorsoventrally flattened, ventral view (RDM, late Pliensbachian). Martindale et al. (2017).

These specimens are preserved in finely laminated clays (shales) laid down on a gently sloping shelf and basin. The articulation of the skeletons preserved and high organic carbon content of the shales suggests that the specimens were preserved under anoxic (or at least very low oxygen) conditions, though the presence of large benthic (bottom dwelling) invertebrates and patches of bioturbation suggests normal oxygen levels were present for at least some of the time. Pyritization (the conversion of organic material to iron pyrites, which can occur under anoxic conditions) is rare, with most specimens preserved as carbonaceous impressions or calcareous shells with occasional replacement by apatite or clay minerals. Only hard, mineralize tissues such as shells and bones are preserved in three dimensions, suggesting that mineralization occurred after tissue collapse. 

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