New Species of Hybrid Sharks Found Near Australia by CAITLIN E

NEWS & FEATURES BRIEF Journal of Young Investigators

New Species of Hybrid Sharks Found Near Australia by CAITLIN E. DEVOR

16 January 2011 – Researchers have detecting hybrids and their offspring is revealed that some of those individuals discovered a new species of hybrid shark extraordinary,” said Jennifer Ovenden, a were first generation hybrids while others off the east coast of Australia which genetics specialist with Queensland were a second generation of hybrid, appears to be a cross between two other Primary Industries and Fisheries and meaning the offspring from C. tilstoni and shark species common in the area. The member of the scientific team that C. limbatus matings are not sterile, unlike discovery challenges several standing discovered the hybrids. animals such as mules, which are the scientific shark behavior theories and may The hybrid sharks are a result of offspring of horses and donkeys. indicate that species are changing in interbreeding between the Australian Researchers do not yet know which response to climate change. black tip shark, Carcharhinus tilstoni, and species the hybrids are mating Hybrids and their offspring were the common black tip shark, C. with. “Most likely the hybrids are back- found in five different locations along limbatus. C. limbatus is found in sub- crossing to the parent species of black tip, 1,243 miles (2,000 kilometers) of tropical waters around the globe, while C. but we don’t have the [necessary DNA] coastline—an unprecedented range— tilstoni is found only around markers to tell for certain yet,” said indicating the new species may be better Australia. The two species have Morgan. able to tolerate a variety of temperatures overlapping migration ranges along the Since sharks must physically contact than their non-hybrid peers—a valuable northern and eastern coasts of Australia, each other to mate, hybrid species of trait in a changing global climate. with C. limbatus favoring the temperate sharks are less common than hybrids of “Wild hybrids are hard to find, so waters in the southeast, and C. tilstoni other marine animals that mate via more common in the north. spawning, including many fish, where egg Jess Morgan of the and sperm cells are released en-mass into University of Queensland and open water. However, discovery of primary author of the report said hybrid species of black tip sharks both species of shark are a indicates other closely related species of common catch for Australian sharks and rays may be hybridizing as fisheries, which will often sell well. the meat to the Australian market Current research projects include and export the fins to Asia. studying the fitness of the hybrid sharks The hybrids were first and the full extent of the area inhabited by recognized through an these hybrids. Details regarding the inconsistency in species prevalence and fitness of hybrid animals identification made by two will be relevant to making accurate separate groups of researchers recommendations to fisheries for working alongside each other responsible population management of with specimens obtained from marine food resources. the fisheries. According to The hybrid sharks were identified by Morgan, the study’s original researchers at the University of objective had been to monitor the Queensland and James Cook University’s shark population to ensure Fishing and Fisheries Research accurate management of the Centre. The article “Detection of fisheries. Identification based on interspecies hybridization in DNA sequences isolated from Chondrichthyes: hybrids and hybrid mitochondria, the energy- offspring between Australian Mix and mingle. Scientists have identified a new species of producing organelle inside all (Carcharhinus tilstoni) and common (C. shark which they believe to be a hybrid of two common species cells, was incongruent with limbatus) blacktip shark found in an near Australia. identifications made from Australian fishery” can be read online in morphological measurements of Conservation Genetics. ■ Image: “Color line contact in Australia” by color line available the animals. under Creative Commons license at A total of 57 hybrid sharks Caitlin Devor is a student at Allegheny http://www.flickr.com/photos/sunrise/4064971/. were identified. Genetic analysis College.