Thursday, September 25, 2014

Marine Science @ Otago - Spectacled Porpoise

Scientists dissect a rare find

On Wednesday 17th September 2014 a Spectacled Porpoise was stranded on Pipikaretu Beach on the Otago Peninsula.  Very little is known about this marine mammal. There have been infrequent sightings round the southern oceans, and most specimens are from strandings in Tierra del Fuego.  As far as we know, there have been no sightings around New Zealand and only ten of these porpoises have ever been found washed up on our shores.

The round mark around the eye is how they got the "spectacled" name.  A key feature is the extraordinarily large dorsal fin, which is much larger in males than females.  These porpoises grow up to about 2.25 metres in length.  This male measured 2.15 metres.

A team of marine mammal scientists from the University, the Otago Museum and Department of Conservation dissected the porpoise at Invermay.  Here, Professor Ewan Fordyce works on dissecting the ribs, freeing them from the overlying tissue.

In the final picture below, the ribcage as been removed, and the massive muscles along the back that flex the tail flukes, to exposed the internal organs.

In addition to getting a rare look at the anatomy of the species, the team discovered this porpoise had  a fractured lower jaw, and broken hyoid bones. The hyoids support the larynx.  It appears the animal  had suffered a blunt trauma of some sort.  The stomach was effectively empty and there was water in the lungs, suggesting the animal probably drowned.

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