Featured Research

from universities, journals, and other organizations

Virgin Birth: Shark Expert Comments On Parthenogenesis

Date:
June 23, 2007
Source:
Saint Joseph's University
Summary:
A shark evolution expert discusses recent parthenogenesis findings in female sharks in captivity. The biologist said this mode of reproduction could have significant impact on small, isolated populations.

Shark evolution expert Eileen Grogan, Ph.D., discusses recent parthenogenesis findings in female sharks in captivity. The Saint Joseph’s University biologist said this mode of reproduction could have significant impact on small, isolated populations.

Birds do it, bees do it, and now there is evidence that female sharks are able to do it on their own -- without the contribution of male DNA. A recent report from a team of American and Irish researchers has concluded that the mysterious appearance in 2001 of an infant female bonnethead shark at Omaha’s Henry Doorly Zoo in a tank that held only two adult female sharks was the result of parthenogenesis (Gr. virgin birth.) Parthenogenic reproduction takes place without fertilization by a male through the process of cell division, when the mother’s egg fuses with a degenerative cell called a polar body, producing a new individual.

What does this mean for lonely-heart sharks on a Saturday night, or for that matter, the evolution of the species? “Parthenogenesis appears to be a rare phenomenon in sharks, and it is unlikely to have an impact on the evolution of a particular lineage,” said Saint Joseph’s University Professor of Biology Eileen Grogan, Ph.D., a noted expert in shark evolution and research associate at both the Academy of Natural Sciences and the Carnegie Museum of Natural History. “However, one might conceive that this mode of reproduction could have a significant impact on small populations because there is less genetic diversity in small, isolated populations.”

While parthenogenesis can ensure the short-term survival of the species, for the long term it is advantageous to keep male DNA in the mix. “The newborn shark derived from this phenomenon would have only half the genetic diversity of the sexually reproduced form because it is based entirely on the mother’s genome,” said Dr. Grogan. “In terms of evolution, it is preferable to have a greater diversity of genes, because that offspring is more likely to have ‘what it takes’ to survive.”

The collective sigh of relief you just heard came from male sharks relieved to learn that they are still necessary to the survival of the species. Male and female sharks that migrate along shorelines this summer will follow their biologic imperative by reproducing the old fashioned way, and may even choose to come into shallower waters to mate or give birth. “Most people don’t realize just how close -- normally and regularly -- sharks come to the beaches as they migrate and follow whatever they are feeding on. Patterns of water flow, temperature of the water, and where typical prey are found can help predict where sharks might be found in local waters,” added Dr. Grogan.

Sharks are fascinating, magnificent animals that draw crowds at aquariums and zoos. “Some sharks are quite reserved, and the smallest shark, the pygmy, might fit in your hand. The largest sharks, the whale and basking sharks, are filter feeders; others prefer grazing on shelled animals rather than acting as an apex predator,” noted Dr. Grogan.

So this summer as we head to the shore for fun in the surf, Dr. Grogan advises us to remember that we are invading their world, and that sharks vary in their aggressiveness. To die-hard surfers and others in search of the perfect wave: “Logic informs us to stay out of waters in which sharks have been recently sighted. Research has shown that shark attacks are more likely at certain times of the day, based on the feeding regime of the animal. In particular, dusk and dawn have been associated with a higher incidence of attacks, so it is recommended that people stay out of the water at these times. If one is in the ocean with sharks nearby, do not thrash around, as this sort of activity can attract the animals much as a struggling fish could attract its predator.

“If someone encounters a shark in its natural environment, it needs to be respected,” she added. “Hopefully it can be appreciated from a distance, but if it is seen in a bathing area, report the sighting to the beach patrol or other local authorities. Even if the animal turns out to be relatively harmless, it is important to confirm the type of shark visiting the area and to take appropriate precautions. If a shark aggressively approaches someone, its snout is a very sensitive sensory area; one should try to hit the snout to fend off an attack.

“Of course, the buddy system is critical for recreational enthusiasts going into or on the water. If something unfortunate happens, it is crucial to have someone to help you and to seek emergency support,” she continued. “Of boaters, surfers, divers, and snorkelers in general, the surfer may be at highest risk since they are more likely to be mistaken for prey.”


Story Source:

The above story is based on materials provided by Saint Joseph's University. Note: Materials may be edited for content and length.


Cite This Page:

Saint Joseph's University. "Virgin Birth: Shark Expert Comments On Parthenogenesis." ScienceDaily. ScienceDaily, 23 June 2007. <www.sciencedaily.com/releases/2007/06/070622213311.htm>.
Saint Joseph's University. (2007, June 23). Virgin Birth: Shark Expert Comments On Parthenogenesis. ScienceDaily. Retrieved October 23, 2014 from www.sciencedaily.com/releases/2007/06/070622213311.htm
Saint Joseph's University. "Virgin Birth: Shark Expert Comments On Parthenogenesis." ScienceDaily. www.sciencedaily.com/releases/2007/06/070622213311.htm (accessed October 23, 2014).

Share This



More Plants & Animals News

Thursday, October 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Working Mother DIY: Pumpkin Pom-Pom

Working Mother DIY: Pumpkin Pom-Pom

Working Mother (Oct. 22, 2014) How to make a pumpkin pom-pom. Video provided by Working Mother
Powered by NewsLook.com
San Diego Zoo's White Rhinos Provide Hope for the Critically Endangered Species

San Diego Zoo's White Rhinos Provide Hope for the Critically Endangered Species

Reuters - Light News Video Online (Oct. 22, 2014) The pair of rare white northern rhinos bring hope for their species as only six remain in the world. Elly Park reports. Video provided by Reuters
Powered by NewsLook.com
Raw: Bear Cub Strolls Through Oregon Drug Store

Raw: Bear Cub Strolls Through Oregon Drug Store

AP (Oct. 22, 2014) Shoppers at an Oregon drug store were surprised by a bear cub scurrying down the aisles this past weekend. (Oct. 22) Video provided by AP
Powered by NewsLook.com
Family Pleads for Pet Pig to Stay at Home

Family Pleads for Pet Pig to Stay at Home

AP (Oct. 22, 2014) The Johnson family lost their battle with the Chesterfield County, Virginia Planning Commission to allow Tucker, their pet pig, to stay in their home, but refuse to let the board keep Tucker away. (Oct. 22) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins