Field of Science

Name the Bug # 31

Last week, I put up an ID challenge that I thought would be relatively simple but which was apparently more difficult. Does that mean that today's challenge, which I think is damn near impossible, is really quite simple?

As a clue, the animal shown lives in fresh water. The scale bar represents 1 mm for all figures except fig. 73, for which it represents 0.5 mm. Attribution to follow.

The last few ID challenges have been getting good responses, so I think it may be time to up the stakes a little. Like Alex Wild does for his challenges, I'm going to award points for correct answers. But unlike Alex, I'm not going to have any set rules about how those points are divvied up. Basically, three points will be awarded to the person who gets the closest to the correct identification. Bonus points (one or two points) may be awarded to up to two less precise answers that contribute to the correct identification (say, if someone identifies the family but not the species, or draws attention to a significant diagnostic feature).

But that's not all there is to it, because I'm also going to take a certain degree of inspiration in awarding points from QI. If you want to win points, but find that someone else has already correctly identified the species, don't despair: if you can provide a better answer than the one they gave, you may be able to steal their three-point spot off them! Examples of better answers would be if you provide a better explanation of the diagnostic features, or if you tell me something really interesting about the organism in question. If you do bump the previous leader from the top spot, they'll be knocked down to the two-point position. Even if you don't successfully knock down the leader, you may be able to get the two-point or one-point position yourself. Unless, of course, someone else pushes you out in turn. Also, I should note that all three point-spots are awarded entirely at my discretion: if there are not suitable answers, I may not award one or more of the point slots.

The first person to get a total of ten or more points from successive Name the Bug posts will win the first round. I'm still deciding what exactly you'll win; my current inclination is to give you a choice between requesting a post on the topic of your choice, or of being given a guest post on Catalogue of Organisms.

As this is the first round, I'll be generous in my judgement of which comments are worthy of the points (so please have a go—after all, I'd look a right twit if I didn't get to award any points in the first challenge!) Let battle commence!


  1. Well, it's a gastropod -- spiral shell, not a nautilus.

    '68' looks like an operculum, so that probably rules out Pulmonata.

    Hmm... family Valvatidae?

    '67' looks pretty much *exactly* like one picture I found of Valvata macrostoma.

    So with steadily decreasing confidence:
    Gastropoda (not Pulmonata)
    Valvata macrostoma

  2. That's pretty good; and even though the species isn't quite right (you're at least in the right superfamily), I would definitely be calling that a 3-point answer if no-one brings a better one.

  3. This makes me want to go back to school so I can have access to a good library. :)

    I hope it's ok not to -really- know, but I get

    Figure 67 has the shell almost but not quite planiform, smooth, circular apature with no distinctive notches, etc. No closeup of the protoconch provided.

    68-71 Operculum, paucispiral, few whorls, central nucleus. Showing increasing thickness with age(???) So probably a Prosobranch snail since the pulmanates tend to not have operculums.

    78 Bursa copulatris extends through albumin gland into capsule gland. Seminal receptacle small relative to BC, and connected to capsule gland by sperm tube running along the side of CG.

    76- OS is a small osphradium?

    I don't know what 73-75 depict at all!

    So family Hydrobiidae? Those are small (1-10mm), generally freshwater, have wildly varying shell morphologies (but the terrestrial genus Clenchiella within the family has a very similar non-planiform shell), have generally flat operculums, but with some variation including some genii which have central pegs, and to the extent I'm able to read the internal anatomy, the female reproductive system and reduced osphradium is consistent with the family diagnosis in Kabat and Hershler 1993. (Total misread is my fault, not theirs. :)

    Kabat, AR & R. Hershler. 1993. "The prosobranch snail family Hydrobiidae (Gastropoda: Rissooidea) : review of classification and supraspecific taxa", Smithsonian contributions to zoology, no. 547

  4. Oops... I'm in the wrong superfamily then. intercostal and Dr. Taylor's comments weren't there when I hit post. :)

  5. No, my mistake. I misremembered and thought that Valvatidae were rissooids. They're not, but this animal is.

  6. Ampullariidae? It definitely has an operculum, which means it can't be a Hydrobiidae.


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  8. Oh Points to be won! So sad I haven't the first idea about molluscs. As far as I'm concerned, if it ain't got tentacles and a beak, then it's in the supercategory Vermes...

  9. Thanks to everybody! I'm closing the challenge now so I can write the follow-up post (in which I'll announce the winner).

    Figures 73-75 show the penis, with variation between different individuals of the species.


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