A Masterpiece of Evolution - The Shark


Welcome to Ben S. Roesch's shark page. Although this site mainly deals with sharks, there's also material on the other elasmobranchs, the skates and rays.

This site is always under construction. Don't hold your breath though, as I am extremely busy with other commitments. Thanks for visiting, and enjoy your stay!

Shameless promotion: Check out the new shark bookstore (link is at the bottom of the page), where you can buy shark books and videos! (Presented in association with Amazon.com, the Internet's foremost book seller).


General Shark Biology

Before continuing, it would be wise to examine some of the basic details of the shark's existence.

Shark Classification Where do sharks fit into the "Tree of Life" and how many species are there?

Do Sharks Have Tongues? A frequently asked question!

More to Come!


White shark (Carcharodon carcharias)

Those Predatory Sharks...

Predatory animals inspire a sense of awe, respect and fear among humans. On land, big cats, wolves, and bears are some of the quintessential predators. Dip beneath the waves, however, and sharks take the stage, alongside orcas, sperm whales, and large squids and fishes. Although there are many marine predators, it is the sharks that have been most stereotyped as the "killers from the deep".

There's no denying the fact that sharks are carnivorous and predatory. Generally, however, sharks have a more diverse diet than usually credited by the general public. The giant filter-feeding basking shark (Cetorhinus maximus) is inclined to consume copepods of the genus Calanus. The whale shark (Rhincodon typus), another very large filter-feeder (see link on this species below), also feeds on zooplankton, although it is not averse to taking small- to medium-sized fishes swept up in its enormous maw. Some sharks concentrate mainly on certain types of prey, such as cephalopods (squids and octopuses); crustaceans (lobsters, shrimps, etc.); shellfish, or small fishes, whereas others will take prey from any of these groups. Many sharks are oppurtunistic, meaning they will feed on most edible items they encounter.

Whatever their dietary preference, sharks are well-adapted to deal with their prey type. Many bottom-dwelling sharks, such as the orectolobiformes (including the nurse sharks) and heterodontiformes (such as the Port Jackson shark [Heterodontus portjacksoni]) have flattened molar-like teeth and strong jaw muscles, all the better to crush the shells of their common prey, molluscs and crustaceans. Another, better known, example of dietary adaptation is the infamous white shark...

The white shark is an apex predator, with a varied diet including fishes and pinnipeds. It is also notorious for having attacked (and in some cases killed) more than a couple of humans. This reputation, and its unforgettable visage, have made it the world's most famous shark. Beyond the sensational attacks, however, is a spectacular creature which deserves a reputation not as a mindless man-eater but as a true predatory masterpiece.

Here is a rare first-hand account of a white shark attack on a diver. Thanks to Marco Flagg for the report.

One of the more potentially dangerous sharks is the oceanic whitetip. Read more about this fascinating open-sea predator. (An Italian version is available through www.squali.com.)

About 15 million years ago, a huge shark known as Carcharodon (or Carcharocles) megalodon appeared in the warm Miocene seas. This 15 m super predator, related to the extant white shark, probably fed on large fishes, small whales, and everything in between. Luckily for us, it appears to have died out at the beginning of the Pleistocene era, around 1.5 million years ago. Some researchers (mainly cryptozoologists), however, believe there is evidence that suggests that megalodon is still alive. Like most shark specialists and paleontologists, I do not subscribe to this theory, which is based on scant, poor evidence and requires an ignoration of accepted ecological and paleontological facts. I wrote a paper, published in The Cryptozoology Review, criticizing the theory of megalodon survival: "A Critical Evaluation of the Supposed Contemporary Existence of Carcharodon megalodon".

In a recent issue of Wild About Animals (vol. 12, no 2), a British magazine about pets, Karl Shuker (a prominent cryptozoologist) reiterated his claims that Megalodon may still be around, dismissing my research linked above. I wrote a response to the article, but Wild About Animals felt it would be inappropriate for publication as it was too long and not of great import to them (this is unfortunate, but understandable as they are a popular magazine about pets, not a journal). So, I have instead posted it here.

For an interesting article on megalodon, with photographs, visit John Bruner's Home Page and choose one of the links at the bottom of the page.

The white shark was recently protected under a new law in Malta, along with the basking shark and manta ray. Alex Buttigieg and the Marine Life Care Group spearheaded the effort, and details can be found on Alex's shark news site.

Biology of the Mako (Isurus oxyrinchus) by Rick Martin. Find out more about this high-speed shark.

ReefQuest South Africa Great White Shark Expedition Have you ever wanted to assist in research on great white sharks and see these magnificent animals in their element? This expedition, led by marine biologist Rick Martin, is just such an oppurtunity! (You can also check out the results of the 2000 expedition, of which I was lucky enough to be a member).


Weird and Wonderful Sharks

Sharks are not particularly speciose animals, but they are still diverse in form and function. There are over 400 species and 8 distinct orders (not including the skates and rays, which are basically flattened sharks). The origin of elasmobranchs has been traced back to about 400 million years ago, and since then they have evolved many different morphotypes, experimenting with many of the concievable forms and shapes of an aquatic animal. Here are some highlights of some of the weird and wonderful elasmobranchs.

* Investigate the several species of planktivorous elasmobranchs in an article by marine biologist and author Rick Martin entitled "The Big Shift."

* The goblin shark fully deserves its name, as Rick Martin explains. With colour photos.

* Travel back in time and take a look at some veryweird fossil sharks (electrical, spiny and otherwise).

* Do giant cookiecutter sharks exist? Click here to find out.

* One thing's for sure, very large nurse sharks do exist!

* Several specimens of megamouth shark have been caught or stranded since the species was discovered in 1976. Here is a list of these specimens courtesy of the Florida Museum of Natural History. Also check out the FLMNH's megamouth page.

*New specimens of megamouth have been caught in recent years in the Phillipines. Check out Elson Elizaga's reports on a megamouth from 1998 and a megamouth from 2005.

* A rare incident occurred in 1998 when a megamouth was observed being attack by several sperm whales off Sulawesi, Indonesia. Go here to find out more.

Coming in this section!: Weird predatory behaviour, more Megamouth, and more!


Blue shark (Prionace glauca)
Photo copyright Jim Knowlton/JimKnowlton.com



White shark (Carcharodon carcharias) with diver.
Photo Copyright Howard Hall

Sharks and Humans

The relationship between sharks and humans, whether involving shark attacks, shark fisheries or recreational shark diving, is a wide and controversial subject. More info will be added in time, but for now, a few pointers on diving with sharks.

* Diving in the Company of Sharks by Rick Martin.

* Contrary to some claims, sharks do get cancer (though admittedly at very low levels of incidence), and shark cartilage supplements have not been shown to have cancer-curing properties. Read this news report on a recent study about the use of shark cartilage as a cure for cancer.


Shark Links and Resources

* Virtual Sharks: The On-Line Shark Book Store In association with Amazon.com, I am happy to announce that I am now selling shark books and videos through my website. You'll find listings for a variety of shark books and videos, with short reviews by myself to give you an idea of what the book is about, what's good or bad about it, and why I like or don't like it.

* Immerse yourself in the on-line world of sharks through my Ultimate Shark Links, and navigate my many links to other resources and home pages on sharks.

* There are many shark books out there, and a great Elasmobranch Reference List is available, thanks to Rob Annis.

* The white shark's famous extinct relative - Carcharodon megalodon, or Megatooth shark - has been the topic of many bad novels published recently. The most recent is Steve Alten's "MEG." Before you believe what the jacket blurb says, read this excellent review by Richard Ellis.


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