DINOSAURS OF THE SEA

　　Sea turtles are fascinatingmarine animals! Found intropical and subtropical seasthroughout the world, theylive in diverse habitats.

　　It is estimated that they live approximatelyeighty years in the wild and take twentyto fi fty years to reach sexual maturity.

　　It isthought that only one out of one thousandhatchlings will make it to adulthood. Sincethey are reptiles, they need to breathe airand can hold their breath up to fi ve hours,although they usually breathe everyfi ve minutes or so while feeding. Whileadult sea turtles are mostly herbivorous,juveniles are carnivorous and prefer tofeast on jellyfi sh, crustaceans, fi sh eggs,molluscs, and sponges. The largestspecies of sea turtle, the leatherback, canweigh up to nine hundred kilograms andcan dive up to one thousand metres!

　　Migrating thousands of miles to mate andlay their eggs, sea turtles often return tothe exact beaches where they were bornto reproduce. Females will mate withseveral males and store their sperm for afew months, which helps to maintain thegenetic diversity of the population sincea clutch of eggs will have several fathers.

　　Most sea turtles nest twice in a breedingseason and can lay anywhere from fi ftyto three hundred eggs. Unlike mammals, the females do not exhibit any parental care of the eggs or thehatchlings once they are born.

　　Generally speaking, sea turtles are calm and photogenic animals.They often accommodate encounters with scuba divers, especiallyin areas that divers frequent visit. It is important to alwaysapproach them slowly to not scare them away and to never touchthem. Dive sites with known ‘cleaning stations’ are also terrificplaces to interact with sea turtles as they tend to stay put in onesmall area while getting ‘cleaned’ by other fish. This symbioticrelationship between the turtles and the fish benefit both parties,where the fish get food by removing algae and parasites from theturtles’ shells.

　　海龟是非常迷人的海洋动物！它们活跃在全球的热带和亚热带海域，栖息地丰富多样。据说野生海龟的寿命约为 80岁，经过 20 至 50 年才能达到性成熟。此外，幼龟成年的概率只有千分之一。它们属于爬行动物，需要呼吸空气，而且最长屏息时间可达 5 小时，但在进食期间一般每五分钟呼吸一次。成年海龟大多以植物为食，幼龟却食肉，爱吃水母、甲壳纲动物、鱼卵、软体动物及海绵。体型最大的海龟是革龟，重量可达 900 公斤，而潜水深度可达1,000 米！

　　到繁衍季，海龟们通常洄游数千英里，返回出生的海滩进行交配、产卵。雌海龟会与多只雄海龟交配，而后精子在她们体内保存数月，这有助于保持龟群的基因多样性，因为同一批卵拥有不同的父系基因。大多数海龟在繁衍季会筑巢两次，产下 50 至 300 枚卵。但与哺乳动物不同的是，雌海龟对卵或破壳的幼龟没有任何母性关怀。

　　一般说来，海龟性格平和且上照。它们大都不怕水肺潜水员，尤其在潜水员经常光顾的地方。不过靠近它们的时候一定要慢，不要惊吓它们，也绝对不要触摸它们。有“清洁站”的潜点也是与海龟互动的理想地点，因为它们会停在一小片区域，让其他鱼类“清扫”身体。鱼类在清扫龟壳的过程中可以获得藻类和寄生虫等食物，所以海龟和鱼类的这种共生关系是双赢的。

　　海龟也有助于平衡全球生态系统。例如，它们喜欢吃海草，但只吃草尖不噬草根，因而不仅能促进海草生长，还有利于维护栖息环境。如果没有海龟，海草就会变老并开始分解，滋生出藻类、一只年轻的绿蠵龟在夏威夷科纳一个清洁站中接受清洁服务微生物，甚至黏菌！玳瑁龟还可以吃掉某些损害珊瑚的海绵，帮助拯救珊瑚礁。同时，革龟以水母为食，可通过控制水母数量来平衡海洋生态系统。如果没有它们，水母数量会大幅上升，消耗过多仔鱼，最终使鱼类数量锐减。

　　气候变化对海龟产生了重大影响。令人惊奇的是，海龟不像哺乳动物那样拥有性染色体，它们的性别是由窝巢附近沙子的温度决定的。如果温度升高，沙子就会更热，这就意味着雌性数量将远多于雄性。一般情况下，沙子温度达到 29 度及以上就会生成雌龟。澳大利亚的英格拉姆岛栖息着太平洋中最大的绿海龟群，研究发现这里 99% 的海龟都是雌龟！由于海龟要经过许多年才能达到性成熟，而只有极少数后代能够成年，它们目前的状态其实非常脆弱。

　　Sea turtles help to balance healthyecosystems around the world. Forexample, they love to feed on seagrassesby trimming only the tops of the leavesand leaving the roots, which not onlyimproves the growth of the seagrassbut also helps to normalize the habitat.

　　Without turtles around, the seagrassbecomes old and starts to decompose,encouraging the growth of algae,microorganisms, and even slime mold!The hawksbill turtle also helps to savecoral reefs by eating certain spongesthat can destroy the corals. Likewise,leatherback sea turtles dine on jellyfish,which balances the marine ecosystemby controlling the jellyfish population.

　　Without these turtles, the jellyfish wouldincrease in numbers and would overconsume the larval fish they eat, makingthe fish population crash.

　　Climate change is causing some majortroubles for sea turtles. Surprisingly, seaturtles don’t have sex chromosomes likemammals do, and their sex is determinedby the sand temperature around thenest. With warmer temperatures, thesand becomes hotter, and hotter sandmeans significantly more females thanmales. Generally, twenty-nine degreesCelsius and above will produce females.At Ingram Island in Australia where thereis the largest population of green seaturtles in the Pacific Ocean, a study foundthat 99% of the sea turtle rookery werefemales! Since it takes so many years forsea turtles to reach sexual maturity andbecause only a very small percentageof their offspring reach adulthood, theyare a very fragile species in terms of theirreproduction.

　　Affecting sea turtle populationsworldwide, Fibropapillomatosis is themost significant infectious disease theycan contract and is most common ingreen sea turtles, or Chelonia mydas.

　　Fibropapillomatosis is believed tobe caused by a herpes virus andtransmitted by leeches. It causes the growth of tumors on the outsideof the turtle’s body and inside around their organs as well. Over time,these tumors can be lethal. In Hawaii, where green sea turtles havestrong legal protections, there are still many turtles that suffer fromFibropapillomatosis.

　　Humans pose the greatest danger to sea turtles. Turtles and their eggsare still hunted for food in certain countries and their shells are soldto make jewelry and crafts. Pollution, fishing nets, trawlers, habitatloss, plastic ingestion, and the illegal trade market all contribute toputting sea turtles at risk throughout the world. For example, the IUCNRed List classifies the hawksbill turtle, or Eretmochelys imbricate, as‘Critically Endangered’ and the green sea turtle, or Chelonia mydas, as‘Endangered.’ Under the Endangered Species Act, sea turtles are givenlegal protections in the United States. Likewise, some regulations areglobal such as the ‘Convention on International Trade in EndangeredSpecies’ or CITES, which controls international trade in endangered andthreatened animals. Sea turtles receive protection by all nations thathave signed the treaty. Many different countries must come together andshare the responsibility to give and enforce stronger legal protectionsthroughout the world or we will lose these ancient dinosaurs from ourplanet forever.

　　纤维乳突瘤症（Fibropapillomatosis）是海龟中最常见的传染病，影响着全世界的海龟，而在绿海龟（Chelonia mydas）中尤为普遍。一般认为，纤维乳突瘤症是由疱疹病毒引起并由水蛭传播的，它会导致海龟体外以及体内器官周围滋生肿瘤。久而久之，这些肿瘤就会变成致命的杀手。夏威夷的绿海龟虽然受到强而有力的法律保护，但仍然有许多海龟患有纤维乳突瘤症。

　　人类对海龟的威胁最大。某些国家仍然在捕食海龟及龟卵，贩卖龟壳来制造珠宝和手工艺品。污染、渔网、拖网渔船、栖息地丧失、塑料摄入和非法贸易市场等因素威胁着全世界的海龟。国际自然保护联盟濒危物种红色名录（IUCN Red List）已将玳瑁龟（Eretmochelysimbricate）归类为“极度濒危动物”，同时绿海龟归为“濒危动物”。根据《濒危物种法》（EndangeredSpecies Act），海龟在美国受到法律保护。而且某些法规是全球性的，例如管控濒危和临危动物国际贸易的《濒危野生动植物国际贸易公约》（CITES）。海龟可以受到所有签约国的保护。不同的国家必须通力合作，在保护物种方面共同提高全世界的立法和执法力度，否则我们将永远失去地球上这些古老的“恐龙”。