Blacktip shark

I recently started to work on a very exiting project: a complete blacktip reef shark (Carcharhinus melanopterus), an aquaria casualty which was donated to the lab a few years ago and which has been sitting in the freezer since then. It's a small male (under 1 m long) and the head was cut off a few years ago as well, probably due to storage issues. Fortunately (and contrary to what is suggested by the picture below), the branchial apparatus was not-or only very little damaged in the process. However the scapulocoracoid is cut in half.

Head of the specimen as it was stored.

I took care of the head first. Cleaning was pretty straightforward using the method I already outlined on this blog (more detailed protocol to come later). I saved the scleral capsules, optic pedicels, and the complete branchial apparatus, including the extra branchials.

Cleaned and wet neurocranium. Note the optic pedicel (arrows) which articulates with the scleral capsules and help to move and stabilize it. Scale bar: 1cm.

The optic pedicels had to be removed since they tend to dry poorly. I treated them separately and will reattach them later.

Scleral capsule. Scale bar: 0,5cm. The hole is the optic foramen.

The scleral capsules are often completely overlooked on chondrichthyan skeletal preparations, which is a shame since they are very cool and interesting little pieces of cartilage.

Finished neurocranium. a: dorsal view, b: palatine view, c: lateral view. Scale bar: 1cm. The optic pedicels have been removed to be dried separately, due to their tendency to shrink and warp badly.

So far this specimen is a delight to work with since it is showed very little warping and shrinking (the main issues when dealing with cartilage skeletons) compared to other chondrichthyan species I've worked on (more on that later) during the drying process.

Neurocranium and jaws being coated with Paraloid B-72.

I usually don't coat my finished specimens, be they bone or cartilage, with anything since I am very careful with them, and most are stored either in specimen boxes or in display cases. However since this shark is going to be part of the lab teaching collection (we don't have a museum over here) I felt it needed to be properly protected. To do this I soaked or coated every piece of cartilage with Paraloid B-72, an acrylic resin soluble in acetone, which can be used either as an adhesive or as a consolidant on a wide variety of specimens, from skulls to ceramic objects.

 The rest of the body, still frozen.

About half of the gill apparatus is now clean and dry as well, so I just need to clean the rest and rearticulate everything. Next will be the rest of the body, which should be pretty straightforward, since it's basically only fins and vertebrae. More pictures later, so check back for updates on this specimen.