古代水手:棱皮龟 Leatherback Turtles
发布: 2009-4-18 16:47 | 作者: cnnas | 来源: 大风车中英文门户网站社区
棱皮龟:古代水手
Ancient Mariner 古代水手
棱皮龟是所有龟类当中个头最大，潜得最深，分布最广的一种，棱皮龟已经在地球上生活了1亿年之久。
The biggest, deepest diving, widest ranging of all turtles, the leatherback has endured for 100 million years.
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棱皮龟是世界上龟鳖类中体形最大的一种，堪称“巨龟”，体长在200—230厘米之间，体重一般为100—200千克。据说最大的体长为250厘米，体重达300千克，也有达800千克的说法。它的头部、四肢和躯体都覆以平滑的革质皮肤，没有角质盾片，背甲的骨质壳由数百个大小不整齐的多边形小骨板镶嵌而呈，其中最大的骨板形成7条规则的纵行棱起，因此得名，也有人叫它革龟。这些纵棱在身体后端延伸为一个尖形的臀部，体侧的两条纵棱形成不整齐的甲缘。腹甲的骨质壳没有镶嵌的小骨板，由许多牢固地嵌在致密组织中的小骨构成5条纵行，其中中央一行在脐带通过处裂开。它的嘴呈钩状，头特别大，不能缩进甲壳之内。四肢呈桨状，没有爪，前肢的指骨特别长。成龟身体的背面为暗棕色或黑色，缀以黄色或白色的白斑，腹面为灰白色。
棱皮龟头顶鳞片排列复杂而不规则。背甲的骨质壳由大小不等的多边形小骨板镶嵌而成，有7条规则的纵棱。腹面有5条纵棱。整个骨壳覆以平滑的革质皮肤。上颌有两个大的三角形齿突起。四肢呈桨状，前肢特别发达，后肢短。尾十分短小。背面黑褐色，有浅黄色斑，腹面颜色较浅。
维基百科：
棱皮龟（学名：Dermochelys coriacea），又称革龟，是龟鳖目中个体最大者，最大体长可达3米，龟壳长2米余；体重可述800-900公斤。棱皮龟主要分布在热带太平洋、大西洋和印度洋，偶尔也见于温带海洋。
据美国杜克大学研究小组发表的海龟调查报告表明，棱皮龟的产卵数量，在过去的20年间减少了95％以上，有可能在今后10－20年内灭绝。
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来自古代的水手 Ancient Mariner
在1961年夏末某日，生物学家薛尔曼‧布里克尼接到了一通电话，得知渔民刚刚在加拿大新斯科细亚省哈利法克斯的一座码头卸下了一只奇怪的海洋生物。住在附近的布里克尼深深为现场的景况着迷：一只巨大的黑色海龟仰卧在好奇的围观群众间，重达400公斤，有着橡胶般的柔软背甲、翼状前鳍肢，还有长得像炮弹的圆锥形大头。布里克尼认出这是一只革龟——最大型的海龟。他记得革龟应该是热带生物，牠出现在冰冷灰白的加拿大海域里，就和鹦鹉出现在哈利法克斯的公园里一样奇怪。
One late summer day in 1961 a biologist named Sherman Bleakney got a telephone call about a strange sea creature that fishermen had just unloaded on a wharf in Halifax, Nova Scotia. Bleakney, who lived nearby, was captivated by what he found there. Sprawled on its back amid a curious crowd was an immense black sea turtle tipping the scales at 900 pounds, with a soft, rubbery carapace, winglike front flippers, and a massive, conical head like an artillery shell. Bleakney recognized it as a leatherback, the biggest of all sea turtles. Leatherbacks, he recalled, were supposed to be creatures of the tropics, as out of place in chilly, gray Canadian waters as parrots in a Halifax park.
不过，布里克尼开始四处打听后发现，渔民经常看到革龟在加拿大沿岸的外海游动，频繁到他们还因此称夏末为「海龟季」。这只有一种结论，1965年他写道：
「源自热带的海龟显然每年都会游进凉快的加拿大大西洋沿岸水域。」从他检视过的几只死海龟身上，即可明显看出牠们是来自南方。有一只革龟眼睛插了一根热带红树林的细枝，有的革龟身上附着温暖水域的藤壶。即使在这种会冷死其它海龟的温度下，革龟依然存活了下来，甚至还很健壮。更怪的是他从牠们体内找到的东西：牠们巨大的胃里有大量嚼碎的水母，包括带刺的触手；而牠们的食道内排列着长七公分的刺，这些刺向内倾斜，好钩住滑溜溜的食物。
When Bleakney began asking around, though, he learned that fishermen saw leatherbacks swimming in the waters off Maritime Canada regularly enough to call late summer "turtle season." The conclusion was inescapable, he wrote in 1965. "Evidently there is an annual invasion of our cool Atlantic coastal waters by turtles of tropical origin." Their southern roots were obvious from the few dead turtles he examined. One had a twig from a tropical mangrove tree stuck in its eye; others carried warm-water barnacles. Yet the leatherbacks were surviving, even flourishing, at temperatures that would kill other sea turtles. Stranger still was what he found inside them: Their huge stomachs contained masses of chewed-up jellyfish, stinging tentacles and all, and their gullets were lined with three-inch spines, angled inward to hold in all that slippery prey.
布里克尼后来改研究其它生物——他特别钟爱海蛞蝓——但在新斯科细亚省那些渔人码头上看到的巨大动物，一直令他很惊奇。「真令人难以置信，」最近他接受加拿大保育人士专访时回忆道。「那么大的爬行动物，可以活在冰冷的水中、靠猎食水母兴旺繁衍。」近50年后，革龟的非凡体力依旧令科学家惊讶，不过今天的惊讶中又多了几分现时的感伤：担忧在完全了解革龟和牠长远的身世背景之前，我们自己的所作所为就已经造成牠们灭绝了。
Bleakney eventually moved on to other studies—sea slugs were a special passion of his—but he never stopped marveling at the great beasts he had encountered on the fishing piers of Nova Scotia. "It was mind-boggling," he recalled in a recent interview with Canadian conservationists. "A reptile of that size, that lives in ice water, that can thrive on jellyfish." Almost 50 years later, scientists are still astonished at the leatherback's physical prowess, though today wonder is alloyed with a more modern sentiment: fear that even before we fully understand the leatherback and its epic life story, our own activities may be driving it to extinction.
过去25年来，研究人员持续计算爬上热带与亚热带海滩营巢的革龟数量；而随着数字骤减，他们已发出警讯：以往墨西哥与中美洲的太平洋沿岸海滩上有上万只、甚至数十万只的革龟，如今只剩几百只；在马来西亚也从几千只锐减为零星的几只。国际自然保育联盟把革龟列为严重濒绝的动物，而将牠们丧命的多种方式列举出来，更是令人丧气：被渔具缠结而溺毙、被漂浮的塑料袋噎死、被船只撞死、遭到捕食、龟卵尚未孵化就被人挖出巢穴，当成食物或春药贩卖。革龟家族可远溯及1亿年前——「当时暴龙是主要天敌，革龟还出现在海滩上。」美国杜克大学加勒比海地区海龟保育网的史考特‧艾克特表示。如今，革龟在牠的一些分布区域内已经快要消失了。
Over the past 25 years, researchers counting the leatherbacks that crawl out to nest on tropical and subtropical beaches have sounded the alarm as the numbers plummeted: from tens or even hundreds of thousands of turtles on the Pacific beaches of Mexico and Central America to a few hundred today; from thousands in Malaysia to a handful. The International Union for the Conservation of Nature lists leatherbacks as critically endangered, and to list the many ways they die is to despair: tangled and drowned in fishing gear, choked on drifting plastic bags, struck by ships, slaughtered for meat, doomed even before they can hatch when nests are dug up and the eggs sold as food or aphrodisiacs. The leatherback lineage goes back a hundred million years—"it was on the beaches when T. rex was the primary predator," says Scott Eckert of the Wider Caribbean Sea Turtle Conservation Network at Duke University. Now, in some parts of its range, it is at the end of the line.