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Dissection

On August 5th 2004, a female great white shark was found drowned in snapper longlines in the Spencer Gulf off the coastal town of Port Pirie, South Australia. The carcass was transported to the South Australia Research and Development Institute research centre in Adelaide where a dissection was performed.

Initial measurements were first taken. Her total length was measured at 479cm with an estimated weight of 1300kg.

 

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4.79m female
The shark had a number of healed bite marks around the gills and dorsal surface in front of the dorsal fin. These were likely made by other white sharks, either during mating rituals or as a result of competition. Males of other species are known to bite the females in order to subdue them during mating, and since this female showed evidence of having been pregnant in the past, it is possible that the old bite marks were a result of past breeding episodes.
Dissection
Bite Marks
The first incision from the pelvic fins to the pectoral fins revealed the large liver, a pale orange-pink colour, which occupies the largest portion of the body cavity (up to 90%). A shark's liver is made of two large lobes that concentrate and store oils and hydrocarbons. The liver acts as an energy store and the shark’s buoyancy control device (since sharks lack a swim bladder), and constitutes 8-12% of the total body weight. The white sharks relatively small liver in relation to other shark species is consistent with its active lifestyle.
Dissection
Dissection

The stomach was then revealed and opened to examine the contents. Stomach contents included two stingray barbs and various partly digested snapper carcasses. A stingray barb was found lodged in the shark’s throat. The stomach of the white shark is J-shaped and located posterior to the gills along the midline of the body. The maximum capacity of the stomach is around 10% of the total weight of the shark.

The white shark, along with six other mackerel shark species, is able to elevate parts of its body above that of the ambient water temperature, a process named regional endothermy. Through a counter-current heat exchange system, the temperature in the brain, eye and swimming muscles can be up to 13 °C higher than its surroundings with its stomach remaining at about 25°C. Increased temperatures in the viscera will result in an increase in the digestion and absorption of large amounts of blubber thereby preventing the defecation of undigested material

The stomach terminates at the pylorus, which leads to the duodenum and to the ring valve intestine. The ring valve intestine resembles a series of tightly packed plates (lamellae), which increases the surface area for maximum absorption of nutrients. The intestine leads to the rectum, and ultimately to the cloaca. This is the common opening for the urinary, digestive and reproductive systems.

On inspection of the reproductive organs, it was ascertained that the shark had previously produced young but was not gravid at the time of her death.

DNA samples of the muscle and liver, as well as vertebrae and other tissue samples were collected by SARDI scientists and were sent to CSIRO in Tasmania. The jaws were removed and frozen, to go to the South Australian Museum.

Fox Shark Research Foundation scientist Rachel Robbins also recorded skin thickness measurements from various positions on the sharks skin for future comparisons. Whilst not pregnant at the time of dissection, she did bear a number of mating scars around the upper anterior gill area. Measurements around the gill area on the dorsal surface  (adjacent to top of 5th gill slit, vertically above mid pectoral fin), where mating scars were observed and thicker skin was expected, revealed a skin thickness of 19mm. However, the skin thickness of the area surrounding the uterus (280cm from anal fin margin), was measured to be 17mm. Without data from males and indeed other females to compare this data to, no conclusion can be drawn, but the figures tentatively imply that the thickened skin of the ‘shoulder’ area is continued around the animal’s torso.

In the blue shark (Prionace glauca), the skin of adult females is three times thicker than that of males throughout the body (Pratt & Castro 1990).  This adaptation has evolved due to the aggressive nature of mating in elasmobranchs – in order to subdue a female, the male holds the female in his jaws, often inflicting damage. Having thicker skin acts to minimise the injury inflicted during mating and, in the case of the blue shark, the skin of the female is measured as being thicker than the length of the males’ teeth (Pratt & Castro 1990). This phenomenon has never before been examined in the white shark and so no corroborating data is available.

Stomach
Stomach