Friday mystery object #287 answer

Last week I gave you this specimen from the Grant Museum of Zoology Micrarium to try your hand at identifying:

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I enjoyed the variety of entertaining answers, ranging from a preschool drawing of a grandma with a beehive hairdo to a larval Alien, but I was also impressed by the range of cryptic clues about the identity of the specimen.

A favourite was a reference to “dealing with a pea covering” or variations on that theme, which gives us “Cope” and “pod”, which is what this is – a Copepod (which means “oar-foot” in Greek). For those of you unfamiliar with copepods are small crustaceans, many of which live as zooplankton and that as a group may make up the majority of the Earth’s animal biomass. They’re tiny, but there are countless billions of them.

This one isn’t as tiny as many of its relatives, because it has a rather different lifestyle to planktonic forms. This is a sea louse and it’s a parasite of fish. They feed on the mucus, skin and blood of fish and if they reach high levels of infestation they can be a real problem, potentially killing fish. This particular specimen has two trailing egg cases, which I think threw some of you. It was removed from a Brill and as Daniel Calleri recognised from a visit to the Grant Micrarium, it’s Lepeophtheirus hippoglossi (Krøyer, 1837).

If you’ve been to the Grant Museum and have photos from the Micrarium, or if you have any photos of tiny animals, you might fancy entering a Twitter and Instagram competition by sharing them with the hashtag #MicroMultitudes, Have fun with your photos!

Friday mystery object #286 answer

Last week I gave you this mystery object to identify, found on a beach in Ireland:

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It led to a lot of great cryptic comments relating to marine birds and sternum keels, but Lena was the first to comment and was spot on with the species (or at least as far as I can tell!)

Bird sterna are quite distinctive, with overall shape giving an indicator of mode of life. Long narrow but well-developed keels like this tend to be seen in marine birds that use their wings to fly underwater. The shape of the bottom and sides of the sternum tend to be quite specific to particular genera and species, making sterna pretty good for identification.

Of course that depends on having good comparative material and I was delighted to find John Rochester’s very helpful Flickr page, that has a comparison of British Auks (in this case we’re talking about the geographical British Isles rather than the sociopolitical concept of Britain).

If you take a look at those images you’ll notice that one fits the shape very well indeed – the Guillemot or Common Murre Uria aalge (Pontoppidan, 1763).

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Guillemot with its meat and feathers on. Image by Dick Daniels, 2011

So that’s the identification I gave to Emer, Ronan, Rory and Paddy who found it on their hols!

 

Friday mystery object #285 answer

Last week I gave you this unassuming bit of bone, that I found with no identification in the Grant Museum of Zoology stores:

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Daniel Jones and Daniel Calleri identified the element as a radius, but beyond that there was a general feeling that identification of species was a bit on the tricky side. Palfreyman1414 pointed out that it’s something approximately human sized, with Lena ruling out an ungulate, suggesting that it could be from a carnivore or possibly a marsupial.

I must admit that my mind immediately went to carnivores and I initially thought it could be from a Black Bear, since it’s fairly robust and about the right length. However, after checking the ever helpful Adams & Crabtree book I realised that bears are even more chunky than this.

It didn’t look right for a dog since they are straighter, have a flatter profile and a narrower distal end. However, it did look right for a big cat and I’m fairly certain that it’s from a Leopard Panther pardus (Linnaeus, 1758). If you want to compare a Leopard with a Dog radius you can see them compared in this paper, along with a good description of the bones of the Leopard forearm.

A bit of a tricky challenge – so next time I may try to do something a bit more distinctive!

Friday mystery object #284 answer

Last week I gave you this part of a skull to have a go at identifying:

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It’s quite a distinctive structure and very particular to one particular group of mammals. It is of course an external auditory meatus (or ear hole as it’s more commonly known), but instead of opening directly into the auditory bulla (the inflated bony bulb that holds the ear bones) it has a long and robust tube.

Lee Post, Daniel Calleri & Dan Jones and Allen Hazen recognised this characteristic feature as belonging to a Beaver and Richard Lawrence went one better and narrowed it down to Castor canadensis Kuhl, 1820 – an identification that I agree with having seen the whole skull:

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I’m not sure if there’s any real functional reason for the ear tube, but it looks to me like it might be a “spandrel” a feature that’s an artefact of another adaptive feature – in this case the articulation of the mandible.

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Gnawing through a tree trunk is no easy task, so it’s not surprising that the Beaver has some serious adaptations to deal with the work involved. Unlike carnivores, which have a fixed lateral mandibular articulation powered mainly by the temporalis muscles, rodents have a dorso-ventral articulation usually powered by the masseter muscles, which allows the jaw to move backward and forward. In the Beaver the sagittal crest suggests that the temporal muscles are more involved than usual which, with the orientation of the articulation, may necessitate the ear tubes as lateral braces against which the mandible can secondarily articulate. That’s my guess…

Great work on identifying this specimen using very limited information!