Sturgeon is the common name for the 27 species of fish belonging to the family Acipenseridae. Their evolution dates back to the Triassic some 245 to 208 million years ago. The family is grouped into four genera: Acipenser, Hugo, Scaphirhynchus and Pseudoscaphirhynchus. Four species may now be extinct. Two closely related species, Polyodon spathula (American paddlefish) and Psephurus gladius (Chinese paddlefish, possibly extinct) are of the same order, Acipenseriformes, but are in the family Polyodontidae and are not considered to be “true” sturgeons. Both sturgeons and paddlefish have been referred to as “primitive fishes” because their morphological characteristics have remained relatively unchanged since the earliest fossil record. Sturgeons are native to subtropical, temperate and sub-Arctic rivers, lakes and coastlines of Eurasia and North America. They are long-lived, late-maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to that of sharks, and an elongated spindle-like body that is smooth-skinned, scale-less and armoured with 5 lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging 7–12 feet (2-3½ m) in length. The largest sturgeon on record was a Beluga female captured in the Volga estuary in 1827, weighing 1,571 kg (3,463 lb) and 7.2 m (24 ft) long. Most sturgeons are anadromous bottom-feeders which migrate upstream to spawn but spend most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively while others primarily inhabit marine environments near coastal areas, and are known to venture into the open ocean. Several species of sturgeon are harvested for their roe which is processed into caviar—a luxury food and the reason why caviar-producing sturgeons are among the most valuable of all wildlife resources. They are particularly vulnerable to overexploitation and other threats, including pollution and habitat fragmentation. Most species of sturgeon are considered to be at risk of extinction, making them more critically endangered than any other group of species. Credit: Wikipedia.
- Psalm 16:8 Tuesday, 20 August, 2019“I keep my eyes always on the LORD. With him at my right hand, I will not be shaken.”
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QUOTE OF THE WEEK: No man can become rich without himself enriching others. Andrew Carnegie (1835 – 1919).
- Alert - Ebola in Democratic Republic of the Congo Thursday, 8 August, 2019There is an outbreak of Ebola in the North Kivu (Kivu Nord) and Ituri provinces in the Democratic Republic of the Congo (DRC).
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- India Tuesday, 20 August, 2019Summary - removal of information about the Independence Day national holiday on 15 AugustGOV.UK
- Italy Tuesday, 20 August, 2019Terrorism section and summary - updated information and advice on the threat from terrorism in Italy, reflecting a reduced threat; Summary - removal of information about heatwave in June 2019 and volcanic eruption on the island of Stromboli in July 2019GOV.UK
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