منتديات سودانيزاونلاين    مكتبة الفساد    ابحث    اخبار و بيانات    مواضيع توثيقية    منبر الشعبية    اراء حرة و مقالات   
News and Press Releases    اتصل بنا    Articles and Views    English Forum    ناس الزقازيق   
Welcome Guest [Login]
Your last visit: 12-19-2018, 06:42 AM Home


Printable Version   Forward   Threaded View « Previous Topic | Next Topic »
Jump to newest reply in thread »


02-12-2014, 04:50 AM
Thomas T. George



    Prof. Thomas T. George
    Global Aquaculture Consultants (GAC)
    [email protected]
    C. +416-75-7365

    Fish have shown a remarkable persistence and adaptation to underwater life by colonizing the waters of the world over four hundred million years ago. There are about 20,000 species of which 8,000 or 40% live in freshwater and some survive at depths of 7,000 meters in the oceans. Over the years, some became extinct and are only known from fossils. In 1839, Louis Agassiz, an English naturalist, named the first fish fossil, coelacanth (see-la-kanth), a word meaning hollow spine in Greek, for a lob-finned fish species believed to have gone extinct at the time of the dinosaurs 65 million years ago. Fossils of ancient coelacanths (more than 120 known species) have been found on every continent except Antarctica. They reveal that coelacanths date back 410 million years, pre-dating the dinosaurs by millions of years!

    Accidentally, the first “Living Fossil” or “Deep-Sea Dinosaur” known to modern science was rediscovered in 1938 when Marjorie Courtenay-Latimer, Curator of East London Museum in South Africa, examined a 54 kg strange fish in the catch of the trawler called Nerine whose Captain, Hendrick Goosen, fished the east coast of South Africa in the Indian Ocean, off the mouth of the nearby Chalumna River. With the assistance of Prof. James Leonard Brierley Smith at Rhodes University, Grahams-town, South Africa, the fish was recognized as a coelacanth and named Latimeria chalumnae in honor of Marjorie Courtenay-Latimer. This became known as the first “living fossil” and “the most important zoological find of the 20th century”. After a local newspaper reporter took a photograph of the mounted coelacanth, the picture soon appeared around the world and Smith, Latimer and the coelacanth became overnight celebrities!!

    In 1952, Smith got a second 45 kg coelacanth caught by a local fisherman, Ahamadi Abdallah, who used a hand-line at the Comoro Island between the tip of Madagascar and East Africa; locally called ‘gombessa’ or ‘mame’. Later on, about a hundred more specimens had been caught in the Comoros area on line by native fishermen at depths of 150-400 meters. Since then, specimens have been confirmed living off South Africa in 2000, Kenya, 2001, Tanzania and Zanzibar, 2003, and possibly even the South Pacific, 2007. The white scale flecks of these specimens set against a cobalt blue body color offer excellent camouflage against the cave surfaces covered with white sponges and oyster shells. In 1987, coelacanths were first filmed from a submersible at the Comoros. In 1988 Hans Fricke, National Geographic photographer, was the first to photograph the species in its natural habitat, 180 m off Grand Comoro’s west coast. In 2004, Canadian researcher William Sommers captured the largest recorded specimen of coelacanth off the coast of Madagascar!

    On September 18, 1997, Arnaz and Mark Erdmann traveling on their honeymoon in Indonesia saw a coelacanth in the local market and asked local fishermen to bring to them future catches. On July 30, 1998, a second Indonesian specimen, 1.2 m in length and weighing 50 kg was captured alive; it lived for 6 hours. This Indonesian coelacanth, locally called ‘raja laut’ (King of the Sea), was the same found in the Comoros except that the background coloration of the skin is brownish-grey rather than bluish. It was given the scientific name, Latimeria menadoensis in 1999. On May 19, 2007, Justinus Lahcama, a local Indonesian fisherman, caught a 1.3 m long, 50 kg coelacanth off the coast near Manado, on northern Sulawesi Island near Bunaken National Marine Park. After spending 30 minutes out of water, the fish, still alive, was placed in a netted pool at the edge of the sea and it survived for 17 hours. The fish was filmed by local authorities.

    Unlike any other living animal, coelacanths have a hinged joint in the skull, which allows the front part of the head to be lifted and widen its mouth while feeding. They have a well developed pressure sensitive lateral line along the body sides to sense the proximity of the surrounding structures. They are mucilaginous; not only the modified ‘cosmoid’ scales exude mucus, but their bodies continually ooze a large quantity of oil. Their backbone is composed of a fluid-filled cartilaginous tube called notochord, which provides a firm yet flexible support for muscles. Their chambered heart is similar to humans. They have limb-like, lobed pectoral and pelvic fins, hollow fin spines and a unique tri-lobed tail (diphycercal caudal fin), the middle one of which protrudes as a continuation of the notochord. The eyes are well developed, with reflecting cells called ‘tapita’ to enhance night vision as they are most active at night, spending the day hovering in submarine caves. A further unique feature is the special electro-receptive device called a ‘rostral organ’ in the front of the head, which probably helps in prey detection. They are opportunistic drift-feeders, predating mainly on fish with a suction action of the jaw and hinged cranium. They can swim head down, backwards or belly up to locate their prey.

    Coelacanth adult females are slightly larger than males. Their reproductive behaviors are not well known, and they are not sexually mature until 20 years old; gestation time is 13-15 months. They are ovoviparous, giving birth to as many as 26 live ‘pups’ which develop from eggs in the oviduct, feeding off a large yolk sac until birth. By studying their ear bones (otoliths), scientists believe that individual coelacanths may live as long as 80 to 100 years. They prefer a temperature range of 14 to 22 Celsius and rest in caves as deep as 700 m below sea level during daylight, but are more commonly found at depths as shallow as 55 to 200 m when hunting at night. They can slow down their metabolisms at will, sink into the less inhabited depths and minimize their nutritional requirements in a sort of hibernation mode; that is why they have been so successful to survive.

    The scientific controversy has been whether coelacanth or lungfish represent the closest living relatives to the first creature to walk on land. While coelacanths have not been observed to “walk” on the bottom, their pectoral and pelvic fins can be seen as “pre-adaptations” to land locomotion.
    However, many scientists believe that the unique characteristics of the coelacanth represent an early step in the evolution of fish to terrestrial four-legged animals like amphibians, a possible “missing link” as the ancestors of the tetrapods (land-living, four-legged animals, including humans). But now, it is believed that lungfishes are the closest living relatives to tetrapods. However, because the living coelacanths changed little from the fossil ancestors with respect to size and habitat, creationists have used this fact as evidence against Darwin’s Theory of Evolution. Today’s coelacanths can reach almost 2 m in length (80 kg weight) while ancient ancestors seldom exceed 55 cm; also, modern coelacanths inhabit caves and overhang in near vertical marine reefs of newly formed volcanic islands at about 200 m depth and not in deep-water oceanic habitats as ancient coelacanths behaved.

    African conservationists need to know more about this creature in order to protect it as this unique fish has gained a high value on the black market, fetching up to $2,000 an ounce. In Africa, coelacanths have now an iconic status on par with the Panda Bear in China! In 1989 the coelacanth was added to Appendix 1 (threatened with extinction) in accordance with the conservation on International Trade of Endangered Species Treaty which forbids international trade for commercial purposes and regulates all trade, including sending specimens to museums, through a system of permits. This is because in 1998, the total population of the West Indian Ocean coelacanth was estimated to have been 500 or fewer, a number that would threaten the survival of species.

    Moreover, it is also interesting to know that the “living fossil” earned its place in music, video games, literature and television. “Coelacanth” is the little of songs and albums by bands including John Fahey, Shriekback, Mr. Children and Polysics. In video games such as Animal crossing, Mega Man X2, SEGA Marine Fishing, E.V.O. Search for Eden, We Love Katamari, Me and My Katamari, Endless Oceans and Aquanaut’s, Holiday: Hidden Memories. In novels: Margaret Atwood’s Novel, Oryx and Crake, Anne Landman’s novel. In films and TV series such as Atlatics: The lost Empire, Monister on the Campus and Faturama. As early as 1956, J.L.B. Smith wrote his book “Old Fourlegs” about the coelacanth story. His other book “Sea Fishes of the Indian Ocean, illustrated and co-authored by his wife Margaret, remains the standard icthiological reference of the region!!

    Now, the coelacanths which captured the attention of the scientific world, are represented by only two known living species, Latimeria chalumnae and Latimeria menadoensis. Once they were very successful with many genera and species that left an abundant fossil record after suffering a nearly complete extinction. The scientific community worldwide commends with great respect and gratitude those who found and identified the first “living fossil”: Professor Smith who died in 1968 after a long illness, Captain Goosen who passed away in 1988 after the fiftieth anniversary of the coelacanth, and Latimer, the museum curator who died in South Africa on May 17, 2004 at age 97. Beyond doubt, they were the heroes of the greatest fish story of the “living fossil” or “deep-sea dinosaur” in the 20th century!!

Arabic Forum

[Post A Reply] Page 1 of 1:   <<  1  >>

Comments of SudaneseOnline.com readers on that topic:

at FaceBook
Report any abusive and or inappropriate material

فيديوهات سودانيزاونلاين Sudanese Online Videos
Latest Posts in English Forum
Articles and Views
اراء حرة و مقالات
News and Press Releases
اخبار و بيانات
اخر المواضيع فى المنبر العام
صور سودانيزاونلاين SudaneseOnline Images
ويكيبيديا سودانيز اون لاين
Sudanese Online Wikipedia

فيس بوك جوجل بلس تويتر انستقرام يوتيوب بنتيريست Google News
الرسائل والمقالات و الآراء المنشورة في المنتدى بأسماء أصحابها أو بأسماء مستعارة لا تمثل بالضرورة الرأي الرسمي لصاحب الموقع أو سودانيز اون لاين بل تمثل وجهة نظر كاتبها
لا يمكنك نقل أو اقتباس اى مواد أعلامية من هذا الموقع الا بعد الحصول على اذن من الادارة
About Us
Contact Us
About Sudanese Online
اخبار و بيانات
اراء حرة و مقالات
صور سودانيزاونلاين
فيديوهات سودانيزاونلاين
ويكيبيديا سودانيز اون لاين
منتديات سودانيزاونلاين
News and Press Releases
Articles and Views
SudaneseOnline Images
Sudanese Online Videos
Sudanese Online Wikipedia
Sudanese Online Forums
If you're looking to submit News,Video,a Press Release or or Article please feel free to send it to [email protected]

© 2014 SudaneseOnline.com

Software Version 1.3.0 © 2N-com.de