Fish: my gory introduction

I had an interesting lab practical at university today, and was given the chance to dissect either a mackerel, trout or herring for the first time. I settled on the mackerel (not that I have a preference), and their internal anatomy is rather interesting, as long as the smell doesn't overpower you.




To the right is an untouched Mackerel fish. These fish when alive inhabit tropical and temperate waters, and are characterised by the vertical stripes on their backs, as well as their deeply forked tails.

 These stripes surprisingly enough, are not used as camouflage, but rather as visual cues when these fish form schools with other members of the species. As their eyes are sensitive to moving stripes, these patterns allow the fish to follow each other and thus move efficiently in a group, as an anti-predatory adaptation.


The first incision to the fish is seen here, being administered by my lab partner along the bottom of the body; originating at the anus. He goes on the run the scissors along the full length of the fish, before cutting a few centimetres higher along the top length of the fish. This allows the skin to be neatly peeled back, revealing the inside.

However before doing so, we first peeled back some of the skin covering the head and pharynx, and had a look at the gills that lie underneath (the red structures pictured). As fish take in water through the mouth, the liquid rushes across these filament-like structures which are covered in capillaries (tiny vein-like structures full of blood). These capillaries absorb the oxygen in this water and transfer it to the bloodstream, which gets pumped through the rest of the body.

Carbon dioxide, which the fish must remove, is also passed through these capillaries. But rather than being pumped through the body, is transferred from the body to this same water entering the mouth. As the water gets expelled out of the gills and into the surrounding water, it takes this excess carbon dioxide with it.  (Microscopic view of gill below)

And the skin is off!!!

The strange white/yellow/red structure that makes up most of the internal view is mainly fish adipose (fatty) tissue. The lightish yellow structure above the tip of the scissors is known as the "pyloric Ceaca" and contains enzymes that help with the digestion of food. Although not very visible, the intestine is can be seen (light beige structure directly above pyloric ceaca)


After further dissection, we found the fish heart (triangular red structure pictured), a muscular organ used of course to pump blood throughout the body. To its far left is whats left of the mackerel eye.








Zoology: sticky, slimy, and gross at times. But no one can ever say it isn't interesting (me in middle, along with high-spirited fellow students)

-Thomas Glen

Facebook.com/goodnaturepage

Good Natured book review: Sea Change-A message of the oceans. By Dr Sylvia Earle

I have always considered myself as someone who does a good job of keeping up with the latest news and ideas of the natural world, evident from the  growing piles of books, magazines and documentary DVD'S in my bedroom. However for some unknown reason, i have gone years without ever coming across the name of the wonderful oceanographer, conservationist and scientific writer, Dr Sylvia Earle. After discovering a brilliant documentary  about her life, research, and the plights the worlds oceans face at the hands of us savage humans, called "Mission Blue", on Netflix, I decided to buy one of her books to improve my knowledge on ocean life, and hear about her other thoughts on how to protect these large blue oases of life. And I am very glad I did.

From the get go, I realised the book did not just contain information on marine life and conservation, but also contained detailed anecdotes from Sylvia Earle about her own scientific exploits through the years. Such as her adventures to great depths in submersible vehicles, and her attempts to improve the efficiency and development of other such vehicles and thus improve the abilities of scientists like herself to  gain more knowledge on the underwater world; mostly hidden from and grossly unappreciated by us land dwellers. Sylvia also tells of the great difficulties she has had juggling family life, relationships, as well as her scientific career, which was a real eye opener for me; a work in progress zoologist with little awareness of the time and energy required for such a career. Sylvia also discussed the ways women in science were viewed in the 60's and 70's, especially the patronisation of the media at the thoughts of a female oceanographer, which made me shake my head vigorously at the idea of such sexism; something that I hope exists to a much lesser extent today.

Of course, you cannot have a book discussing the wonders of the ocean, without the topic of humans and our undeniable effects on the natural world. From overfishing, to pollution runoff, and a frankly horrifyingly detailed account of the Persian gulf oil spill that consumed the lives of many organisms, to call this section of the book harrowing reading would be an understatement. But for our oceans, as well as the other natural environments planet earth has to offer, to be in with a chance of brimming with life for years to come, such issues must be taught to the public, and Dr Sylvia Earle achieves this wonderfully. She not only tells the reader about the incredibly effective and barbaric fishing methods used to catch gigantic populations of fish, and the selfishness of many corporation big wigs with pound signs in their eyes and hearts depleted of natural wonder, but she also tells of the many ways that the natural world can be protected to benefit not just marine life, but human life also.

All in all, I must say that I found the book informative, charming and incredibly eye opening, and I truly believe I am much more intelligent at finishing the last page, than when I first cracked it open a couple months ago. I highly recommend this book to everyone with an interest in nature and conservation, and if you do not, read it anyway. You will have afterwards.

-Thomas Glen

To see zoology-based news stories, articles and photography, visit my Facebook page: Facebook.com/goodnaturepage