10 avanços recentes na biologia marinha

Os oceanos do mundo estão repletos de algo como 700.000 a 1 milhão de espécies, até dois terços das quais os biólogos nunca nomearam ou caracterizaram [fonte: Appeltans et al. ]. Mas mesmo as espécies que conhecemos melhor – as amêijoas e as trutas que comemos, as águas- vivas que tememos e os baiacus que tememos e comemos – mantêm o poder de surpreender.

Todas essas criaturas desconhecidas ressaltam os desafios que os biólogos marinhos enfrentam, sendo o mais óbvio o acesso. Talvez uma espécie mergulhe fundo demais ou vagueie no oceano desconhecido por décadas a fio. Possivelmente, faz sons muito fracos para captar ou apenas revela suas cores verdadeiras dentro de estranhos comprimentos de onda visuais. E, claro, a complexa interação entre a pesca humana, a caça e a tecnologia, e a fauna dos mares e oceanos do mundo, fornece seus próprios problemas únicos. (Pense na redistribuição de espécies invasoras por meio de veículos de comércio internacional ou no impacto dos sons dos motores dos barcos em alguma vida marinha.)

Mas o fluxo constante de novos fatos sobre espécies familiares e estranhas atesta a marcha – ou natação – do progresso no campo. Para ajudá-lo a molhar os pés, selecionamos uma amostra de descobertas recentes do Almirante, e não vai custar tanto quanto uma carona com um capitão de submarino maluco. Aproveitar.

1. Pequenas tartarugas marinhas fazem mais do que pegar a deriva
2. A expansão das zonas proibidas para a pesca ajuda a truta coral na Grande Barreira de Corais
3. Os peixes larvais são francamente tagarelas
4. RNA de cefalópodes é editado com mais frequência do que uma mixtape reutilizada
5. Baiacu realmente não prende a respiração
6. Luz UV sugere as cores verdadeiras das conchas antigas
7. TB pré-colombiana nadou para as Américas em nadadeiras de foca
8. Focas do porto jogam pontos e caixas com parques eólicos para encontrar comida
9. Um câncer de molusco contagioso
10. Catadores das águas-vivas mortas cavam fundo depois de tudo

Os pais estremecem ao pensar em seus filhos como vagabundos sem rumo, mas até recentemente isso era o que os biólogos marinhos pensavam ser literalmente verdade para alguns filhotes de tartarugas marinhas. Mas quando pesquisadores do Serviço Nacional de Pesca Marinha em Miami usaram minúsculos rastreadores de satélite para seguir os movimentos de pequenas tartarugas verdes ( Chelonia mydas ) e tartarugas-de-Kemp ( Lepidochelys kempii ) capturadas na natureza, eles tiveram uma surpresa. Em comparação com um grupo de controle de objetos inanimados flutuantes, as tartarugas jovens moviam-se mais rápido e ao longo de caminhos diferentes [fontes: Putman e Mansfield ; Zielinski ].

Esta descoberta, juntamente com um estudo anterior de filhotes de cabeçuda ( Caretta caretta ), está mudando a forma como vemos os ciclos de vida de tartarugas marinhas jovens. Após a eclosão, muitas tartarugas marinhas, incluindo as espécies estudadas, passam vários anos sem serem observadas em mar aberto, um intervalo misterioso que os biólogos marinhos chamam de "anos perdidos" [fontes: Mansfield et al. ; Putman e Mansfield ; Skwarecki ]. Com base em certas evidências, como pequenas tartarugas ocasionalmente aparecendo onde as correntes oceânicasnaturalmente, os cientistas acreditavam que as tartarugas marinhas juvenis se engajavam em "migração passiva" ao sabor do mar. Esses dois estudos mostram que pelo menos três espécies influenciam seus destinos nadando.

A Grande Barreira de Corais evoluiu ao longo de milhões de anos para sustentar uma das mais diversas coleções de animais em qualquer lugar. Mas hoje suas 7.700 milhas quadradas (20.000 quilômetros quadrados) de comunidades de corais estão ameaçadas por sedimentos, poluição, estrelas-do-mar-coroa-de-espinhos e mudanças na temperatura e na química [fontes: ABC ; Unesco ].

Agora há boas notícias, pelo menos no que diz respeito à truta coral ( Plectropomusgênero) estão em causa. De acordo com um relatório de progresso de 10 anos, os peixes comerciais se beneficiaram significativamente de uma expansão de seis vezes das zonas proibidas, iniciada em julho de 2004. A mudança, que aumentou as áreas protegidas de 5% para quase um terço da área de estudo, foi controverso porque alguns temiam que aumentaria a intensidade da pesca em áreas não protegidas. Em vez disso, as trutas em zonas proibidas cresceram além dos tamanhos mínimos de captura e, como as trutas maiores tendem a fazer mais filhotes do que as trutas menores, produziram descendentes suficientes para manter as zonas vizinhas em níveis de equilíbrio. Algumas evidências também sugerem que a pesca reduzida em torno das zonas proibidas ajudou a recuperar os corais porque reduziu os danos causados ​​pelas linhas de pesca, que podem causar cicatrizes nos corais e abri-los à infecção [fontes: ABC ; Milius ].

Infelizmente, esses programas podem funcionar apenas em áreas individuais de pesca comercial. Em partes do mundo onde a sobrevivência é uma perspectiva de captura como captura, a caça furtiva, brechas e outros desafios regulatórios persistem. Enquanto isso, o aquecimento global continua sendo a maior ameaça aos recifes em todo o mundo [fontes: ABC ; Milius ].

Like sea turtles during their aforementioned "dark years," many young fish have long been regarded as passive creatures, floating where time and tide might carry them. And as with the turtles, researchers have begun to question that received wisdom. For example, when scientists involved in the Great Barrier Reef study we just mentioned tracked the movements of larval coral trout, they found that the baby fish could swim against the current and navigate by sun and smell back to their coral home [source: ABC]. Other fish larvae can control their vertical position in the water and find beneficial places to flap their fins [source: Milius].

Moreover, a study in the October 2014 issue of Biology Letters has revealed for the first time that one-month-old gray snappers (Lutjanus griseus) can make growls and knocking vocalizations that might aid them in schooling in the dark. A similar mechanism has been proposed for aiding adult fish in schooling [source: Milius]. Unfortunately, the discovery also demonstrates yet another aspect of life in the big briny that might be perturbed or even damaged by human activities, such as the sounds produced by boat motors.

An animal's adaptability is tied to its genetic makeup, but for a long time we've had a limited window into how this process works. It goes something like this: DNA is copied into RNA, which codes for particular proteins and lays out the proper amino acid sequence for building them. You can change how those proteins are expressed, says the model, but if you want different ones, then for the most part, you need different DNA. Editing RNA is possible, but rare and usually not important.

Well, don't tell that to squids and octopuses, both of which majorly edit their RNA, according to recent research. This tweaking enables the cephalopods to build proteins for which their DNA lacks a blueprint. In fact, it allows them to make several different proteins from identical strands of RNA [sources: Alon et al.; Baggaley].

Researchers suspect that such abilities might exist elsewhere in the animal world and could provide a more rapid response to environmental requirements than waiting for DNA mutations. At least one octopus study, published in the February 2012 issue of Science, bears this out. It reveals that Antarctic and Arctic species of octopuses use RNA editing to correct neural imbalances brought on by colder waters [sources: Courage; Garrett and Rosenthal].

Plumping up isn't the only protective option for a puffer fish. It also can defend itself via its onboard tetrodotoxin -- one of the most toxic poisons known. But unless we're actually eating fugu, as Japanese gourmands call it, it's the puffing that typically comes to mind. It's right there in the name.

Until recently, scientists thought that puffer fish accomplished their ballooning by "holding their breath" -- that is, by shutting down their gills and pulling in oxygen from the surrounding water using capillaries in their skin [sources: Diep; Zielinski]. It's an image in keeping with the fish's appearance -- the pursed lips, the wide eyes, the engorged Dizzy Gillespie "cheeks" -- but it also turns out to be a lot of hot air.

According to a study published in the December 2014 edition of Biology Letters, the puffery has more to do with gulping than gasping. It turns out that a puffer fish actually bloats itself by trapping large gulps of seawater in its stomach, then clamping the organ off at either end. Far from holding its breath, it continues to respire through its gills all the while, which is just as well, because the process costs the fish dearly in terms of oxygen consumption and is therefore quite tiring [sources: Diep; McGee and Clark; Zielinski].

To anyone who's ever compared a beached-and-bleached seashell to that of a living snail in the ocean, the ravages of age and weathering are clear. These blanching effects can frustrate fossil hunters, who must sometimes rely on color patterns to distinguish one shell from another.

But according to research by San Jose State University geologist Jonathan Hendricks, just because we can't see the patterns doesn't mean they aren't still there. Take the shells of ancient cone snails, for example. Under normal light, their bone-white forms are indistinguishable, but place them in ultraviolet light and they erupt in sublime swirls and polka-dot patterns not seen in their modern descendants. Hendricks used the technique to identify 28 species among a group of 4.8-million- to 6.6-million-year-old Dominican Republic shells, 13 of which constituted new discoveries [sources: Fessenden; Hendricks; Thompson].

Ultraviolet -- the same wavelength used in black lights -- has revealed other aspects of the biological world previously hidden to human eyes. Many scorpions fluoresce in it. Some butterflies use UV-visible patterns to lure mates, while the carnivorous pitcher plant species Nepenthes khasiana uses it as a beacon to lure ants to their deaths [source: Stromberg]. For paleontologists, UV light can hint at plumage patterns on feathered dinosaurs [source: Switek].

As for the shells, more work remains before scientists can determine why they fluoresce in UV wavelengths, a process that appears to relate to oxygen exposure [sources: Thompson].

Cows. They've been blamed for the Great Chicago Fire , for blowing up barns with their flatulence and for plunging towns into darkness by rubbing electrical poles [sources: AP; BBC]. But thanks to a genetic analysis of tuberculosis DNA taken from a trio of 700- to 1,000-year-old Peruvian skeletons, they might at long last be in the clear for a more serious crime: originating the bacterium that later jumped species to cause tuberculosis in humans. According to research published in the Aug. 20, 2014, issue of Nature, that dubious distinction now belongs to seals [sources: Bos et al.; Saey].

Actually, the pinnipeds didn't so much originate the disease as transport it to the New World. The new research suggests that TB originated in Africa about 4,000 to 4,400 years ago and produced seven strains, some of which jumped to animals and then later back to humans. The seal explanation is supported by the fact that ancient Peruvians used tools made from seal remains and depicted seals and seal hunting on their pottery [source: Doucleff]. The theory helps to explain how they could have become infected with TB when no land route to the New World existed at the time [sources: Bos et al.; Saey].

The thing about sinking structures offshore is that certain kinds of sea life love nothing better than a foundation, an anchor amid the sea's shifting tides where they can build, find food or just hang out. We've encouraged reefs to form by taking advantage of this fact, and opportunistic mussels and crabs have gravitated toward the shelter offered by offshore windmills' sunken bases for similar reasons [source: Zielinski].

Of course, where there's forage, there's bound to be foragers, as Deborah J.F. Russell of the University of St. Andrews in Scotland found when she and her colleagues used GPS devices to track the movements of harbor and gray seals (Phoca vitulina and Halichoerus grypus) near offshore wind farms in Europe. As described in the July 21, 2014, issue of Current Biology, they observed that 11 out of 200 seals made a series of beelines to each turbine, tracing out a clear grid pattern that matched the turbines' configuration and lingering at each "node" to look for food [source: Rosen]. Since the wind farms were somewhat recent additions, chances are good that the elite 11 were particularly pioneering pinnipeds [sources: Russell et al.; Zielinski].

The vast majority of cancers remain in our innards, turning our own bodies against us. We don't think of them spreading to other hosts like a blight or a disease. Yet, biologists have discovered at least two cancers that do exactly that: One threatens Tasmanian devils and spreads through biting, and another is transmitted sexually among dogs. Now, according to an article in the journal Cell, they've found a third, a leukemia-like agent that has been attacking soft-shell clams (Mya arenaria, aka steamers and little necks) from Maine to the Chesapeake for the past 40 years [sources: Dallas; Gorman; Metzger et al.].

Researchers have long known about the clam cancer, but have focused their search for a cause on environmental elements and, more recently, a possible virus . But when they examined the DNA of cancerous cells from clams across the region, they found something quite surprising. Instead of resembling the genes of their host clams as expected, the cancer cells were clones of a single genetic source, presumably some cancerous "clam zero" from which the cancer had initially escaped and spread [sources: Dallas; Gorman; Metzger et al.]. Such a mechanism is risky for the cancer, not only because its cells cannot long survive outside their host, but also because they must face a victim's immune defenses every time they spread [source: Gorman].

The researchers plan to look into similar illnesses that strike cockles, mussels and oysters to see if a similar marine metastasis affects them as well [source: Gorman].

Jellyfish have long been a source of concern for swimmers, fish farmers and any machine with an oceanic intake. But they've more recently become a headache for oceanographers, who must puzzle out why jellyfish blooms are on the rise, and how that rise threatens to upset the balance of life in Earth's oceans -- and that's just among the living [sources: Flannery; Gorman]. Because dead jellyfish apparently pose a problem as well: When large die-offs occur, it appears that their bodies just jelly up the ocean floor, where scavengers seemingly turn up their collective noses at them [sources: Gorman]. Or so we thought.

Thanks to experiments conducted by Andrew Sweetman of the International Research Institute of Stavanger and his colleagues, published in the December 2014 issue of Proceedings of the Royal Society B, we now know that scavengers such as crabs and hagfish actually chow down on jellies with at least as much relish as they do mackerel. This is important, because it means that jellyfish are an integral part of the

]carbon cycle, and not some kind of carrion cul-de-sac [sources: Gorman; Sweetman et al.].

Então, por que a mistura? É possível que as observações anteriores apenas tenham capturado mortes em massa e/ou que as observações tenham ocorrido em áreas que não tinham necrófagos comedores de geleia. Em outras áreas, a rapidez com que as águas-vivas são comidas (cerca de duas horas, no experimento) pode ter removido quaisquer casos contrastantes antes de serem observados [fontes: Gorman ; Sweetman et ai. ].

Nota do autor: 10 avanços recentes na biologia marinha

Este artigo foi extremamente divertido. Eu só gostaria de ter mais espaço para descrever os métodos usados ​​em alguns desses estudos engenhosos. Espero que você tenha a chance de ver alguns deles.

Por mais que eu goste de ler sobre espécies recém-descobertas, acho que fico ainda mais emocionado ao descobrir algum fato novo sobre uma criatura familiar ou, melhor ainda, descobrir que uma ideia há muito aceita não se sustenta. Ao pesquisar este artigo, encontrei exemplos de todos os três.

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