Friday 31 July 2020

Notopterus synurus: A cryptic species of Bronze Featherback from South Asia.

The complex geological history of the Oriental region caused a high degree of geographical genetic structure within freshwater organisms and species, once considered widely distributed in this region, are often formed by distinct genetic lineages. The Bronze Featherback Fish Notopterus notopterus, currently the only valid species of the genus Notopterus, is one of such widely-distributed species, occurring from the Indus basin (Pakistan and India) in the west, to the Mekong region – slightly extending east to the Annamite Range – (Cambodia, Laos, Thailand and Vietnam) in the east and to Java (Indonesia) in the south. Intriguingly, Notopterus notopterus has not yet been recorded in Borneo where it is most likely absent. Specimens of Notopterus notopterus are identifiable from all other Oriental Freshwater Fish based on (amongst other features) their distinct tapered tail and the corners of their mouth below eye (not behind as in the other Oriental Notopterid genus Chitala. It is reported that this species reaches up to 60 cm in standard length. A wealth of data is available for this species, documenting its reproductive behaviour and embryonic development, cytogenetics, and phylogeography. However, none of these studies simultaneously examined specimens sampled across the whole distributional range of Notopterus notopterus.

In 2009 a group of scientists led by Jun Inoue of the Ocean Research Institute at University of Tokyo published a paper in the journal Molecular Phylogenetics and Evolution, which reconstructed the molecular phylogeny of the family Notopteridae to discuss its evolution and biogeography. These authors sequenced the complete mitogenomes of two specimens of Notopterus notopterus, one from India and the other from Thailand. The comparison of these two mitogenomic sequences revealed that these two specimens diverged from each other about 25 million years ago. This result was unexpected because no consistent morphological variation was previously reported within this species. 

In a paper published in the journal Zoosystematics and Evolution on 1 July 2020, Sébastien Lavoué of the School of Biological Sciences at the Universiti Sains Malaysia, Siti Zafirah Ghazali, also of the School of Biological Sciences at the Universiti Sains Malaysia, and of the Institute of Marine Biotechnology at the Universiti Malaysia Terengganu, Jamsari Amirul Firdaus Jamaluddin, again of the School of Biological Sciences at the Universiti Sains Malaysia, Siti Azizah Mohd Nor, again of the Institute of Marine Biotechnology at the Universiti Malaysia Terengganu, and Khaironizam Zain, once again of the School of Biological Sciences at the Universiti Sains Malaysia, present the results of a study which investigated the genetic diversity within the genus Notopterus across its full range, for which, they analysed a dataset comprising 72 publicly available sequences of the standard barcoding fragment (655 base pairs) of the cytochrome oxidase I gene that were determined from specimens of Notopterus with precise information on their geographical collection plus two cytochrome oxidase I sequences extracted from two complete mitogenomes from two specimens of Notopterus without precise localities and four sequences Lavoué et al. newly determined from specimens collected in Peninsular Malaysia.

Haplotypes of Notopterus segregate into two main groups having distinct distributions. The first group includes all haplotypes from India and Bangladesh (South Asia group). The second group includes all haplotypes from Peninsular Malaysia, Thailand (Mekong River), Indonesia (Sumatra and Java) and Myanmar (Lake Inle, Salween basin) (Southeast Asia group). These two main groups diverge by 7.5% p-genetic distance that represents, on average, 45 differences between any combination of two specimens sampled from different groups. In contrast, each of these two groups is genetically uniform with intra-group differentiation that does not exceed 1% (within the South Asia group, mean p-distance equals 0.4%; and within the Southeast Asia group, mean p-distance equals 1%). This represents six nucleotide differences on average within the Southeast Asian group and only two nucleotide differences on average within the South Asian group. Furthermore, the two specimens examined by Inoue et al. (2009) fell in their corresponding geographic origin groups.

The minimal genetic distance separating the genus Notopterus into two main groups is well above 3% (using cytochrome oxidase I marker) which is considered as a conservative threshold between population and species levels in Vertebrates. Furthermore, the existence of a so-called barcode gap between these two groups, along with the fixation of more than 40 diagnostic nucleotide changes in cytochrome oxidase I, strongly indicate that Notopterus is formed by two species. One species is distributed in South Asia (from the Indus basin to Ganga-Brahmaputra basin) and the other in Southeast Asia (from the Salween basin to Mekong basin plus Malay Peninsula, Sumatra and Java).

(A) Map covering the Oriental biogeographic region and showing the distribution of localities (black and red circles) of specimens of Notopterus examined. Black star indicates the estimated type locality of Notopterus notopterus in Java (i.e. Jakarta region) and red stars indicate the likely origin localities of the two syntypes of Notopterus synurus (i.e. coast of Malabar and Coromandel coast at Tharangambadi, formerly Tranquebar). Main Oriental river basins from West to East: (1) Indus basin; (2) Ganga-Brahmaputra river system; (3) Irrawaddy basin; (4) Salween basin, (5) Mekong basin. Insert shows the left lateral view of a specimen of Notopterus notopterus (Penang State, west Peninsular Malaysia; 20 cm in standard length, voucher specimen number USMFC (3) 00002, NO_1). (B) Unrooted network constructed with the software PopArt and a median-joining algorithm showing the cytochrome oxidase I haplotype relationships within the genus Notopterus. Branch lengths are not proportional to the number of changes. Red circles indicated haplotypes of Notopterus synurus (South Asia) and black circles indicated haplotypes of Notopterus notopterus (Southeast Asia). Lavoué et al. (2020).

A 1992 study by Tyson Roberts of the California Academy of Sciences examined the variation of several meristic characters of Notopterus notopterus throughout its entire range. He did not report any significant intraspecific variability that could be additional evidence for the recognition of more than one species in the genus Notopterus. The low amount of morphological variability within the genus Notopterus, however, is not surprising given that the family Notopteridae is known for its morphological stasis. Several valid species of Notopteridae are morphologically similar. For example, species of the genus Chitala are only distinguishable based on their colour pattern and more than one species is suspected to occur within Chitala lopis.

Lavoué et al.'s cytochrome oxidase I-based results strongly support the presence of two allopatric species of Notopterus which need names. There are several nominal species of Notopterus which have been described from Southeast Asia and South Asia and several of these names are available. To determine which name should be applied to each of our two species, Lavoué et al. examined synonym lists and checked the date of description and type locality of these synonyms.

Notopterus notopterus was described and illustrated by Peter Pallas in 1769 as Gymnotus notopterus from a specimen said to have been collected nearby Ambon (Ambon Island), in the Indian Ocean, a region where this species has never been recorded since. More recent studies have suggested that the type locality given in the description of Pallas is an error because this species does not occur on the Island of Ambon which lies east of the Wallace Line, in a different biogeographical region. Furthermore, the local vernacular name of this species 'Ikan Pangaio', reported by Pallas, is in the Malay language which was not used in Ambon at that time. For these reasons, ichthyologist Maurice Kottelat has suggested that the specimen used by Pallas  for the description of Notopterus notopterus should have been collected in Java where the Dutch established their main colony in Indonesia. Consequently, the name Notopterus notopterus should be retained for the species occurring in Southeast Asia with Java as its type locality. There is no type specimen known.

Marcus Bloch and Johann Schnieder described Clupea synura in 1801 from two syntypes, a name which was soon considered as a junior synonym of Notopterus notopterus. Bloch and Schneider first indicated that these specimens are from the coast of Malabar, India. However, in a following remark signed only by Johann Schneider, China and Tranquebar (now known as Tharangambadi, India) were listed as the localities of the syntypes. Notopterus, however, does not seem to occur in China, and zoologist Hans-Joachim Paepke found convincing explanations why Schneider could have mistaken China with the coast of Malabar, India. According to Paepke, the localities of the dry right skins of the two syntypes of Clupea synura that are housed in the Berlin Museum under catalogue numbers ZMB 8806 and ZMB 32057 are coast of Malabar and Tranquebar, respectively. Lavoué et al. suggest the revalidation of Clupea synura for the species of Notopterus occurring in South Asia which should be recognised as Notopterus synurus

Whereas the genetic evidence presented in Lavoué et al.'s work supports the recognition of two valid living species of Notopterus, a detailed morphological comparison of the two species is lacking. Such morphological study is needed to identify possible diagnostic characters (in addition to the molecular diagnostic characters presented by Lavoué et al.) and to document the early diversification of the genus Notopterus in the Orient. In this respect, a fossil of Notopterus, morphological similar to living species, indicates that this genus was already present in Sumatra at least 33 million years ago (the Eocene-Oligocene boundary). In addition, because of the cryptic diversity occurring in the genus Notopterus and the difficulty to identify the type localities of species of this genus, it will be important to designate a neotype for Notopterus notopterus and a lectotype for Notopterus synurus. Finally, the geographic coverage needs to be expanded with the study of specimens collected from the Mekong basin, Indus basin and, especially, from the region comprising the Irrawaddy basin situated between the Ganga-Brahmaputra river system and the Salween basin to determine the location of the exact distributional limit between these two species.

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Magnitude 5.7 Earthquake off the coast of Surigao del Sur, Philippines.

The Philippine Institute of Volcanology and Seismology recorded a Magnitude 5.7 Earthquake at a depth of 14 km slightly off the coast of Hinatuan in Surigao del Sur Province on Mindanao Island, Philippines, slightly before 2.10 pm local time (slightly before 6.10 am GMT) on Friday 31 July 2020. There are no reports of any damage or casualties associated with this event, but it was widely felt across eastern Mindanao.

The location of the 31 July 2020 Surigao del Sur Earthquake. USGS.

The geology of the central Philippines is Complex. The west of Mindanao Island is located on the Banda (or Sunda) Microplate, and the east on the Philippine Plate, which is being subducted beneath the Sunda (or Banda) Microplate along the central part of the island. Immediately to the east of the Island the Pacific Plate is being subducted along the Philippine Trench, and passes beneath eastern Mindanao as it sinks into the Earth. This is not a smooth process, an the plates constantly stick together then break apart again as the pressure builds up, resulting in Earthquakes.

Subduction beneath the Philippines. Yves Descatoire/Singapore Earth Observatory.

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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Western Australian surfer recovering after Shark attack.

A surfer is recovering in hospital after a Shark attack off the coast of Bunker Bay, near Dunsborough, in southern Western Australia on Friday 31 July 2020. The incident happened at about 2.15 pm local time, when he was attacked from below by the animal, believed to have been a Great White, Carcharodon carcharias, which bit him on the legs before disengaging and swimming off, a pattern typical of Great White attacks. The victim was able to reach shore with the aid of other surfers, where he received first aid at a nearby home before being airlifted to hospital for further treatment.

A Shark near the beach in Bunker Bay in 2011. Westpac Lifesaver Rescue Helicopter.

Despite their fearsome reputation, attacks by Sharks are relatively rare, and most  attacks on Humans by Great White Sharks are thought to be mistakes. The species feeds principally on Marine Mammals, which we superficially resemble when we enter the water, gaining the majority of their nutrition from the thick adipose (fat) layers of these animals, which we lack. Due to this, when Great Whites do attack Humans these attacks are often broken off without the victim being consumed. Such attacks frequently result in severe injuries, but are seldom immediately fatal, with victims likely to survive if they receive immediate medical attention.
The distribution of Great White Sharks around Australia. Fishes of Australia.
Despite this general rarity, Australia appears to be suffering a sharp rise in Shark attacks, with five fatal attacks so far this year, three of them in the past five weeks, as well as several non-fatal attacks, the most recent of which occurred near Fitzroy Island off the coast of Cairns in North Queensland on Tuesday 14 July. Marine biologist Julian Pepperell has suggested that this increase might be linked to a rise in the number of Humpback Whales, Megaptera novaeangliae, passing through Australian waters each year. Humpback Whales are a significant food source for many Sharks; adult Whales are beyond their hunting capacity, but do die of other causes and are enthusiastically scavenged, while larger Sharks such as Great Wights will attack Whale calves. Around 35 000 Humpback Whales currently migrate through Australian Waters each year, according to  zoologist Vanessa Pirotta of Macquarie University, a number which is growing by about 11% each year.
A Humpback Whale, Megaptera novaeangliae, off the East Coast of Australia in July 2017. ABC.

Humpback Whales were nearly exterminated by commercial Whaling in the first part of the twentieth century. The species has been protected since 1946, and in recent years their population has appeared to be recovering in many areas, now being seen as being of Least Concern  under the terms of the International Union for the Conservation of Nature's Red List of Threatened Species. The Whales are recovering in many parts of the globe, and are starting to appear in areas where they have not previously been recorded.
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Thursday 30 July 2020

Landslide destroys house and two shops in Uttarakhand.

A home and two shops have been destroyed in a landslide at Mussoorie in Dehradun District, Uttarakhand, on Thursday 30 July 2020. No casualties were reported in the incident, which happened following days of rain in the area, associated with the annual Monsoon. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall.

The aftermath of a landslide at Mussoorie in Dehradun District, Uttarakhand, on Thursday 30 July 2020. Hindustan Times.

 Monsoons are tropical sea breezes triggered by heating of the land during the warmer part of the year (summer). Both the land and sea are warmed by the Sun, but the land has a lower ability to absorb heat, radiating it back so that the air above landmasses becomes significantly warmer than that over the sea, causing the air above the land to rise and drawing in water from over the sea; since this has also been warmed it carries a high evaporated water content, and brings with it heavy rainfall. In the tropical dry season the situation is reversed, as the air over the land cools more rapidly with the seasons, leading to warmer air over the sea, and thus breezes moving from the shore to the sea (where air is rising more rapidly) and a drying of the climate. This situation is particularly intense in South Asia, due to the presence of the Himalayas. High mountain ranges tend to force winds hitting them upwards, which amplifies the South Asian Summer Monsoon, with higher winds leading to more upward air movement, thus drawing in further air from the sea.

Diagrammatic representation of wind and rainfall patterns in a tropical monsoon climate. Geosciences/University of Arizona.

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Asteroid 2006 TU7 passes the Earth.

Asteroid 2006 TU7 passed by the Earth at a distance of about 16 052 000 km (41.8 times the average distance between the Earth and the Moon, or 10.7% of the distance between the Earth and the Sun), slightly after 4.45 pm GMT on Thursday 23 July 2020. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2006 TU7 has an estimated equivalent diameter of 78-250 m (i.e. it is estimated that a spherical object with the same volume would be 78-250 m in diameter), and an object at the upper end of this range would be predicted to be capable of passing through the Earth's atmosphere relatively intact, impacting the ground directly with an explosion that would be 350 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater roughly 15 km in diameter and devastation on a global scale, as well as climatic effects that would last decades or even centuries.

The orbit of 2006 TU6, and its current position. JPL Small Body Database.

2006 TU7 was discovered on 12 October 2012 at Siding Spring Observatory in Australia. The designation 2006 TU7 implies that it was the 164th asteroid (asteroid U6 - in numbering asteroids the letters A-Y, excluding I, are assigned numbers from 1 to 24, with a number added to the end each time the alphabet is ended, so that A = 1, A1 = 25, A2 = 49, etc., which means that U6 = 20 + (24 X 6) = 164) discovered in the first half of October 2006 (period 2006 T).

2006 TU7 has a 287 day (0.78) orbital period, with an elliptical orbit tilted at an angle of 2.92° to the plain of the Solar System which takes in to 0.45 AU from the Sun (45% of the distance at which the Earth orbits the Sun, and slightly outside the distance at which Mercury orbits the Sun) and out to 1.25 AU (25% further away from the Sun than the Earth). This means that close encounters between the asteroid and Earth are fairly common, with the last thought to have happened in October 2017 and the next predicted in October 2021. Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, 2006 TU7 spends most of its time closer to the Sun than we are, and is therefore classified as an Aten Group Asteroid. As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, 2006 TU7 is also classified as a Potentially Hazardous Asteroid.

2006 TU7 also has occasional close encounters with the planets Mercury, which it last came close to in January 2918 and is next predicted to pass in February 2021, and Venus, which it last came close to on 8 Jubethis years (2020) and is expected to pass again in February 2028. Asteroids which make close passes to multiple planets are considered to be in unstable orbits, and are often eventually knocked out of these orbits by these encounters, either being knocked onto a new, more stable orbit, dropped into the Sun, knocked out of the Solar System or occasionally colliding with a planet.

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