Funky new ghostshark species found

11/12/2009

The Eastern Pacific black ghostshark, a chimaera, is new to science/ Photo Courtesy Monterey Bay Aquarium Research Institute (MBARI)

Science has a new cartilaginous fish species, “a big weird looking freaky thing,” says Ichthyologist Douglas Long, Research Associate from the California Academy of Sciences and the Curator of the Oakland Museum of California, who helped describe the species. “They have some shark characteristics and they have some that are very non-shark.” For starters, this guy has a sex organ on its head.

Kelsey James, a student with Moss Landing Marine Laboratories (MLML) named and described this funky fish in a recent issue of the scientific journal Zootaxa, along with MLML research faculty David Ebert, Millersville University biology professor Dominique Didier Dagit, and Long. The Eastern Pacific black ghostshark (Hydrolagus melanophasma) lives off the coast of southern California and Baja, Mexico in deep ocean water within the Gulf of California, preferring soft-bottom ocean floor, with an occasional cobble patches; other Hydrolagus species seem to prefer rocky areas with a lot of vertical relief.

Scientists had captured several specimens of this purplish-black ghostshark over the years, as far back as the 1960s, but it took time to figure out whether it represented a unique species. Not only did biologists collect specimens, they also observed and videotaped the ghostshark alive in the Sea of Cortez using a deep water submersible.

The cartilaginous fish (Class Chondrichthyes) lineage includes the sharks and rays, but the chimaera lineage diverged evolutionary from them nearly 400 million years ago. Ghostsharks get called many names, including chimaera, rabbitfish, and ratfish. Like sharks, they have skeletons made of flexible cartilage and use “claspers” for internal fertilization as opposed to laying eggs like most bony fish. Like sharks, they have sandpaper-like skin that has interlocking “placoid” scales, unique from the scales of bony fish. Unlike sharks, chimaeras lay eggs encased in leathery shells that some call a “mermaid’s purse.” And they stand alone from sharks in having a retractable club-shaped appendage emerging the males' foreheads, called a tentaculum, used during sex. According to Dagit, it's not used to transfer gametes but to grasp the female. You can watch a short video of the new ghostshark here, taken on a remote operated vehicle (ROV) by scientists at MBARI.

Paleontologists have documented many, diverse species of chimaera throughout the fossil record, but in the modern world we live in, they’ve been somewhat elusive. Scientists have recently found new species in remote little-explored locales as more and more expeditions explore the deep sea. The co-authors of this study, Didier, Ebert, and Long had named two new ghostsharks frin the deep water off of the Galapagos Islands in 2006.