Австралийн Их хаалт хадны бүсэд хийсэн удаан хугацааны судалгаагаар энэхүү далайн амьтан нь урьд өмнө төсөөлж байснаас илүү урт насладаг болох нь батлагдлаа.
Австралийн далайн шинжлэх ухааны хүрээлэнгийн (AIMS) судлаач Свен Утикэ болон түүний баг 2000 онд Их хаалт хадны бүсээс 76 ширхэг хар тэнгисийн өргөст хэмх (Holothuria whitmaei) цуглуулж, ДНХ-ийн дээжийг нь авчээ. Судлаачид 2024 оны есдүгээр сард тухайн газраа эргэн очиж, амьд үлдсэн амьтдын ДНХ-г анхны дээжтэй харьцуулан шинжилсэн байна. Шинжилгээнд хамрагдсан 52 амьтны 31 нь 24 жилийн өмнөх дээжтэй таарч байгаа нь энэ төрөл зүйл 100-аас дээш жил амьдрах боломжтойг харуулж байна.
Судалгааны үр дүнд эдгээр амьтан нь насанд хүрсэн үедээ маш удаан өсөлттэй төдийгүй, байгалийн жамаар хорогдох түвшин нь жилд 4 хувиас бага болохыг тогтоожээ. Сонирхолтой нь, 24 жилийн дараа дахин баригдсан амьтад анхны хэмжээнээсээ дунджаар 21 хувиар хөнгөрч, 14 хувиар агшсан байв. Эрдэмтэд үүнийг хүрээлэн буй орчны өөрчлөлт болон далайн өргөст хэмх биеийн жингээ алдаж, дахин нөхөн сэргээх чадвартай холбоотой байж болзошгүй гэж таамаглаж байна.
Тус судалгаа нь хар тэнгисийн өргөст хэмхний популяци нь загас агнуурын нөлөөлөлд өртсөний дараа сэргэхдээ маш удаан болохыг анхааруулж байна. Судалгааны явцад ямар ч залуу бодгаль олдоогүй нь тус зүйлийн үржил удаан явагддаг болохыг илтгэж байгаа юм. Иймд эрдэмтэд энэхүү амьтдыг хамгаалах болон агнуурын менежментийг дахин үнэлэх шаардлагатай гэж үзэж байна.
“iScience” сэтгүүлд нийтлэгдсэн уг бүтээл нь хар тэнгисийн өргөст хэмхийг 100-аас дээш жил амьдардаг болох нь батлагдсан анхны төрөл зүйл гэдгийг онцолсон юм. Гэсэн хэдий ч судалгааны явцад зарим бодгаль нүүдэллэсэн эсвэл олдоогүй байж болзошгүй тул бодит нас нь тооцоолсноос ч өндөр байх магадлалтайг судлаачид тэмдэглэжээ.
Дэлгэрэнгүйг эх сурвалжаас харах
↓Эх сурвалжийг нээх ↓
In 2000, biologists on Australia’s Great Barrier Reef took tiny tissue samples from 76 sea cucumbers, put them back on the seafloor, and froze the DNA. In September 2024, they returned to the same reef and sampled the animals living there again.
Thirty-one of the sea cucumbers they found were genetic matches to animals sampled 24 years earlier. Most of them had also shrunk.
The species is the black teatfish, Holothuria whitmaei, a sand-dusted, lumpy black animal that somewhat resembles poop. According to the team’s calculations, published in the journal iScience, a small share of adults can live for more than 100 years. “This species is the first sea cucumber species known to surpass a longevity of a century,” the authors write.
A Delicacy That Cannot Be Tagged
The black teatfish lives on reefs across the Pacific and Indian Oceans. Its common name comes from the small bumps along its sides. Dried, it becomes bêche-de-mer, a prized delicacy fished in Australia, the Pacific Islands and Southeast Asia.
That demand has taken a toll. The species is classified as endangered on the IUCN Red List and listed on CITES Appendix II. In 1999, falling numbers around the Great Barrier Reef forced the black teatfish fishery to close.
That is when the problem of tracking began. Biologists usually estimate an animal’s lifespan by tagging individuals and checking which ones are still alive years later. Sea cucumbers do not cooperate: physical tags tend to fall off within weeks or months.
So Sven Uthicke of the Australian Institute of Marine Science (AIMS) and his colleagues turned each animal’s DNA into its tag. They sampled black teatfish at several reef sites, returned after six months and again after a year, and recognized individuals by their genetic profiles. The short study pointed to a long life, but the window was too narrow to say how long.
Most Survivors Had Shrunk
The frozen DNA extracts stayed in storage for more than two decades. In September 2024, the team went back to one of the original sites, Bird Islet at Lizard Island, and found 53 black teatfish. They weighed and measured each one and took a fresh sample.
Of the 52 animals analyzed successfully, 31 matched samples from 2000. That means about 60 percent of the population was at least 24 years old.
The matched animals were already large adults in 2000, measuring 26 to 42 centimeters (10 to 17 inches), close to the maximum size for the species. Since then, they had lost weight: on average, they were 21 percent lighter and 14 percent shorter. Sea cucumbers can lose and regain body mass over time, and the researchers suggest changing environmental conditions may have played a role.
“We had a hunch that they could get older than the ten years that was commonly thought,” Uthicke said in an AIMS statement.
An Annual Death Rate Under 4 Percent
Of the 76 animals profiled in 2000, at least 31 were still alive in 2024, a survival rate of at least 41 percent. From that figure, the team calculated an annual adult mortality rate of just 0.037.
Assuming that rate stays constant through adulthood, about 1 percent of a group of adults would still be alive at 123 years. The study gives a conservative average lifespan of about 24 to 27 years, with maximum longevity above 100 years.
The real figure could be higher. Some survivors from 2000 may have moved away from the sampling area or simply been missed, which would make them indistinguishable from dead animals and inflate the apparent death rate.
“It shows adult black teatfish have extreme longevity and very low natural death rates,” Uthicke said.
No Juveniles in either Survey
The team found no juveniles at Lizard Island, neither in 2000 nor in 2024. Every animal sampled was a large adult. Other populations of the species and its close relatives show the same scarcity, suggesting that new generations join the population only slowly.
For Uthicke, that changes the math for fisheries. “These findings suggest black teatfish populations recover much more slowly from fishing pressure than previously assumed,” he said. “Harvesting long-lived reef animals like black teatfish is unlikely to be sustainable under current fishing pressures and environmental stress.”
The researchers argue that conservation and management of many sea cucumber species should be reassessed, especially for the three teatfish species. Sea cucumbers sift reef sediment and recycle nutrients, and the authors note that removing them adds stress to coral reefs already under pressure from climate change.
The black teatfish’s sand coating remains unexplained. In another sand-coated sea cucumber, researchers have found specialized skin cells that likely secrete an adhesive.
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