This ray-finned fish was my dinner last night. Photo by Andrew David Thaler
When Carl Sagan described our planet as a “pale blue dot” he was invoking the fact that, despite being called Earth, our world is mostly Ocean. The surface of the Earth is a little more than 70% water and the ocean accounts for 98-99% of our total biosphere–the volume of the planet that can support life. Most contemporary theories point to ocean ecosystems–like deep-sea hydrothermal vents–as the launching point for the emergence and evolution of life. Ocean processes dominate biological interactions, even among unwitting terrestrial actors. A new paper, published in the Proceedings of the Royal Society: Biological Sciences, revisits an old debate about the ocean biodiversity and challenges the notion the ray-finned fishes have a marine origin.
In Why are there so few fish in the sea? the authors begin with the seemingly innocuous question–why are there so many more species in terrestrial environments than in marine environments? From there, they look at species counts, phylogenetic relationships, and diversification rates to determine the ancestral state of the most recent common ancestor of one fish class, Actinopterygii, the ray-finned fish. What they found was that, despite the vastly smaller habitat available for freshwater fish, the number of actinopterygian species found those ecosystems was roughly equivalent to the number of species found in marine systems. In both systems, the dominant groups are relative newcomers on the evolutionary stage, with superorder-level radiations happening between 111 – 150 million years ago. Most surprising, the authors discovered that the most recent common ancestor of actinopterygians may have been a freshwater, not marine, fish. Ray-finned fishes may have invaded the ocean from lakes and rivers.
In The Mass Extinction of Scientists Who Study Species, Dr. Craig McClain argues that we are loosing a fundamental unit of biological science – the Taxonomist. He’s right, of course. Taxonomy is a shrinking field. Entire phyla sit, unstudied, as the expertise necessary to understand them retires and expires. With few to train the next generation of taxonomists, the field could slowly vanish. Molecular tools are supplanting traditional taxonomy (once described to me as “the ability to identify hundreds of species of centimeter-long worms by counting ass-hairs under a microscope”) as the de rigueur method for identifying organisms.
I do not disagree with Craig. Losing skilled taxonomists is tragic for the biological sciences. Unlike many leading the charge in support of taxonomy, I did not benefit from a rigorous taxonomic study in my early career. I fall into the same camp as Dr. Holly Bik, relying primarily on molecules, not morphology, to draw the distinctions between my samples. I never identified species by counting the ass-hairs on a worm, and my education is poorer for it.
Earth is facing a biodiversity crisis so severe that many conservation scientists refer to it as a mass extinction event. The International Union for the Conservation of Nature (IUCN), a professional network of 11,000 volunteer scientists belonging to more than 1,000 government and NGO agencies in 160 countries, evaluates species worldwide and determines their risk of extinction. This Red List, which ranks species in increasing risk of extinction – Least Concern, Near Threatened, Conservation Dependent, Vulnerable, Endangered, Critically Endangered, Extinct in the Wild, and Extinct – is described as “the world’s most comprehensive information source on the global conservation status of plant and animal species”.
Statistics from the Red List are terrifying. One fifth of all evaluated vertebrate species are threatened with extinction, including 12% of birds, 21% of mammals, 30% of amphibians, and 26% of fish. On average, fifty species of amphibians, birds, and mammals move measurably closer to extinction each year. One fifth of the world’s plant species are in danger of extinction. Critical habitat-builders, including 33% of reef building coral species and 14% of seagrass species are in very big trouble.
While a large percentage of the world’s shark fins pass through Hong Kong fish markets, most come from far-away countries and little attention has been paid to shark populations in adjacent waters. An important new paper, appropriately titled “The sharks of South East Asia – unknown, unmonitored and unmanaged” provides new insight into this problem.
I write a lot about shark conservation issues, but I rarely focus on their fellow elasmobranchs. Rays and skates have similar life history strategies as sharks, and many species are similarly overfished. A friend just sent me a cool paper about the conservation of skates, which provides an excellent opportunity to remedy this oversight.
A major issue standing between well-managed elasmobranch fisheries and the mess we find ourselves in today is species identification. Many species look very similar (in some cases, DNA tests are required to tell them apart), which makes recording catch statistics extremely difficult. In fact, United States fishery management policy sometimes focuses on species complexes (i.e. “Large Coastal Sharks”) of sharks rather than individual species. Species identification is a major issue for skates as well.
A few weeks ago, my co-bloggers were doubtful that it is possible to watch 36 hours of television in a week. The main factor that makes television viewing on this scale possible for me is the DVR, which allows
me to tape two shows simultaneously. It also allows me to easily fast-forward through commercials, and because of the DVR, the only commercials I see anymore are when I’m watching live sports. While the ability to easily record a show and watch it later (and fast forward through commercials as you watch it later) has improved the quality of life for my roommates and me, I’ve often wondered how it affects advertisers. After all, it’s their money that pays for my favorite shows.