Half digested baby barracuda skull

Well, maybe not quite exactly, but close. It's certainly partially digested, and I'm quite sure it's a sphyraenid, though it might be difficult to get a more precise ID based on its morphology. This guy was found in the stomach of a nicely sized small-spotted catshark (Scyliorhinus canicula) during last week comparative anatomy practicum. It's always interesting to see students' reactions when offered to investigate stomach contents, some are totally grossed out, but quite a few get really excited about it. We found all sort of things this week, mainly crustaceans, worms and small fish. I remember when I performed this same dissection as an undergrad a few years ago and found a large squid in the stomach of my specimen, a large female. I still have the beak I extracted from the half digested meal and the eggs I removed from the uterus laying around in a jar somewhere.

Partially digested sphyraenid head. Yum.

Catshark breeding

For once this post will not feature too much dead stuff, but there will still be plenty of fish. We've had our own small catshark (Scyliorhinus canicula) breeding facility for a few months now. We currently have 15 mature individuals kept in a large tank at a nearby marine station, where they're happily reproducing and laying plenty of eggs.

The adults. They usually rest on the bottom of the tank but grow quite animated during feeding time.

Curious catsharks.

Plenty of eggs. Embryos are visible through many of them.

We bring the eggs to the lab every week or so, where we keep them in a large aquarium until the reach the desired developmental stage. The nice part is that although the eggcase color will vary from female to female, you can always see through it and check on the developing embryo inside.

Developing embryo.

We keep our weekly harvest in individual baskets in a large aquarium. The sausage shaped things on the bottom are tunicates (Ciona intestinalis). In the lower right corner you can see a newly hatched catshark resting on the bottom of the aquarium.

Catshark embryos at various developmental stages. From left to right: 1.5, 4 and 5 months old.

Scale bars: 0.4/0.6/0.8 cm

Blue-tongued skink skeleton

Some time ago I was asked by a french veterinarian to clean and articulate a complete blue-tongued skink skeleton (Tiliqua scincoides). The specimen had been autopsied, and the ribcage was damaged in the process. It was not in very good condition when I got it, especially the tail which was badly decomposed. For some reason the last caudal vertebrae had turned soft and spongy, and I could not save them, not sure what caused this. Here are a few pictures of the articulation process.

Sorting out the ribs

Almost done.

Finished skeleton

I usually reconstruct the sternal ribs using wire, but in this case I decided against it since most of the sternal region was missing in the first place (interclavicle, sternum, xiphisternum and sternal ribs were mostly destroyed during the autopsy). I did however reconstruct the missing suprascapulae and am rather pleased with how they turned out.

Here are a couple of pictures of the finished skeleton:

Dorsal view

The yellow spot on the hands and feet are remaining ligaments that didn't whiten very well.

Overall a very cool skeleton to work on, looking a bit like a reptilian version of the daschund.

Blue shark skull

This post is a bit overdue since this specimen has been completed for almost a year now, but I still wanted to write a few lines about it. It was my first large shark skull (and one of my first shark skulls for that matter, since I only started experimenting on numerous catshark specimens a few months later), and I made several mistakes in the process which I'll discuss a bit here.

I found this specimen quite unexpectedly while out to buy some food during the summer of 2013. I always check the fish department as well in case they might have anything of interest, and got really excited when I noticed the large shape on the stall. Although it's meat is sold on a regular basis around here (I'm located on the Mediterranean coast) it was the first time I saw the head in a shop, and the guys there were nice enough to give me the head for free.

Blue shark (Prionace glauca) head.

Close up on the snout showing the ampullae of Lorenzini. The medial rostral cartilage is also visible through the skin.

Dissection of the head, with palatoquadrate and right optic capsule exposed.

The first mistake I made with this specimen was to attempt a complete dissection of the head. While it can be done, it often leads to broken structures in the skull, since in some areas the skin is a lot tougher than the cartilage underneath, especially around the rostrum and orbital processes. Doing so, I damaged one of the preorbital processes, which are fairly developed in this species.

The second mistake was to apply too much heat to the jaw which separated at the joints. Fortunately, the teeth didn't fall out, which is also a common occurrence when too much heat is applied. This is why you can't clean shark jaws by boiling them as Quinn is doing in Jaws.

Re-articulation of the jaw joints.

The jaws can be glued back in place, and on large skulls I use wire as well for additional strength. Even then, the jaws will be much more fragile and delicate than if the ligaments are preserved. The palatoquadrate and meckel's cartilage are carefully drilled and wired with brass wire and glued back together. The same process can be used for the hyomandibulars and to glue the jaw to the chondrocranium. On large specimens, I prefer to remove the jaw from the chondrocranium for proper cleaning. This way I can also apply heat to the chondrocranium without damaging the jaws.

Gluing the hyomandibulars back in place on a blacktip reef shark (Carcharhinus melanopterus).

 Another issue with the blue shark is the tendency of the chondrocranium to warp a lot as it dries. Freeze drying might reduce this issue, but every specimens I've been able to see so far displayed a high degree of distortion.

Dorsal view of a blue shark skull, showing important distortion.

Anyway, it was still a very interesting specimen to work on. I hope to get my hands on a second one later one so I can clean it properly without repeating the same mistakes.

The finished specimen. I also kept the ceratohyals and basihyal and might glue them back later.