13 amazing things scientists discovered about sharks in 2013

Other than a certain week in August whose name we shall not speak here, 2013 was a great year for both shark science and the communication of that shark science. There were many important and fascinating discoveries, and many of the world’s top media outlets covered them. Presented here is a list of 13 amazing scientific discoveries made in 2013, in no particular ranking order. To make the list, research must have been published in a peer-reviewed scientific journal in 2013, and someone else other than me must have also thought it was awesome (i.e. it received mainstream media or blog coverage). In the interest of objectivity, I did not include any papers that I or my lab were directly involved with. Whenever possible, I’ve linked to an accessible version of the paper.

 

1) A two-headed bull shark!

From Wagner et al. 2013

From Wagner et al. 2013

 

Citation: Wagner, CM, Rice, PH, and Pease, AP 2013. First record of dicephalia in a bull shark Carcharhinus leucas foetus from the Gulf of Mexico. Journal of Fish Biology 82: 1419-1422.

Brief description: Researchers presented the first case of a bull shark embryo with 2 heads (the mother was caught by a Florida fishermen). In response to the most common question I received about this study, no, this animal would not have survived to adulthood.  While this is a cool discovery, the broader significance is somewhat minimal. As I told science writer Douglas Main in an interview about a similar study, “There have been a number of reports of deformed shark and ray embryos in recent years— two heads, one eye, etc. There’s no evidence to suggest these defects represent a new phenomenon or that they are harmful to shark populations as a whole.”

Media coverage highlights: A figure from this study was named one of the coolest science photos of the year by the International Science Times. It was also covered by National Geographic, the Guardian, and TIME magazine. Continue reading

What does the new species of hammerhead mean for shark science and conservation?

In the year 2000, Dr. William Driggers, now of the National Marine Fisheries Service’s Southeast Fisheries Science Center in Mississippi, was sampling for sharks in South Carolina. Dr Driggers recalls that “at the time I was collecting samples from various species of sharks for life history studies and also collecting tissues for Dr. [Joseph] Quattro’s genetics work.” Dr. Quattro, a professor at the Marine Science Program and Department of Biological Sciences at the University of South Carolina, had been working on a project to characterize the population genetics of fish in South Carolina by “working my way down river systems to the coast,” he told me. “Even sturgeons were showing population differentiation, so I thought the next animal would be marine, but estuarine dependent – sharks.” Analysis of the samples Dr. Driggers collected led to a surprising result.

“I was asked “what are the chances that I would misidentify a ‘scalloped hammerhead’ and answered that there was no chance as they are very morphologically distinctive (looks like I was wrong),” Dr. Driggers told me. “I was then informed that genetic sequences indicated that some of the specimens I had labeled as ‘scalloped hammerhead’ were distinctly different from known S. lewini sequences. At Dr. Quattro’s request, I began bringing back whole specimens so they could be archived and morphometric analyses conducted. The first whole specimen that was vouchered and shown to be the new species was collected in Bulls Bay in July of 2001.”

 

In 2006,  Dr. Quattro and his team published a paper entitled “Genetic evidence of cryptic speciation within hammerhead sharks,” showing that there may be a previously-unknown species hiding within scalloped hammerheads. When genetic samples of scalloped hammerheads, great hammerheads, and bonnethead sharks were phylogenetically mapped, the team found an unexpected result. Dr. Quattro, told me that “while doing the population genetics of this animals, we found two divergent genetic lineages within what were morphologically scalloped hammerheads.  We gathered sequences and specimens from other known species and didn’t find a match – that’s what got us on the whole cryptic species [defined by Bickford et al. 2007 as “two or more distinct species erroneously classified and hidden under one species name”] thing.”

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