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Sunday Spinelessness – Mostly True Facts about land snails David Winter Feb 17

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The ailing laptop on which I write these posts has developed a new symptom – a non-deterministic keyboard. So, I hope you’ll excuse me if I just paste a link and get on with something less annoying than trying to write a post via a cellphone.

It’s a pretty good link too. Ze Frank‘s “True Facts” series of zoological oddities has finally got to the best creatures on earth, land snails:

 

Pretty much everything Frank says about snail mating is true so, laptop permitting, I’ll use next week’s post to expand on how anatomy and behaviour have co-evolved  to give us produce these mating habits, and how they effect evolutionary processes in land snail populations.

Sunday Spinelessness – Cannibalism in the garden David Winter Feb 03

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The most common jumping spider in our garden, Trite auricoma, with the remains of it most recent meal… a smaller T. auricoma:


Cannibalism,  animals eating members of their own species, is a pretty common and widespread behavior. Species in almost every phylum have been shown to occasionally (or frequently) eat members of their own species. Even herbivores like monarch butterfly caterpillars will eat any monarch eggs they encounter.

In spiders, the most well-studied form of cannibalism relates to mating. In a very few species male spiders will offer themselves as a meal to their mate. In so doing, males make sure their offspring get the best start in life, by providing their mother with a nutrition meal. They are often also posthumously rewarded by female, who reject other suitors and ensure the sacrificial male’s legacy. The best example of this behaviour comes from the Australian red back spider (Latrodectus hasseltii). In this species males actually pirouette their way into their mate’s fangs, and females take up the offer about 65% of the time. New Zealand’s endemic red back relative, the katipo, does not exhibit this behavior (nor does the North American black widow, despite the name).

Such sexual cannibalism isn’t known from jumping spiders (although females will certainly eat unwary males), and a wider (and earlier) shot lets you see that this was a case of a mature spider taking a younger one (males and females are about equally sized in Tauricoma).



Sunday Spinelessness – Native bees again David Winter Jan 27

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Last year, at about this time, I wrote a little about our native bees. Though I’m glad to have done my little bit to promote the existence of these all too anonymous members of our natural heritage  I’ve always felt a little embarrassed by the photos in that post. As I admitted at the time the photos are staged. Photographing our twitchy little bees is hard – apart from being small, they zip about from flower to flower much more quickly than I can line up, let alone focus, shots.

So, to illustrate the original post I used half-drowned bees, scooped out from a swimming pool. The time it took the bees to dry out gave me a chance to take the photos, but I set them up on exactly the type of flower they’d never visit in the wild. So, not only did I cheat, but the photos I took actively misled about the true nature of bees!

So, here are some much worse photographs of native bees that do a much better job of representing their lifestyles. First off, a bee perched on a favourite flower, a hebe,  and deciding on its next move:

 

and another collecting pollen from the same plant:
These hebes, and a few parsley plants left to go to flower, make my parent’s house in the Wairarapa a mecca for native bees. They certainly make their mark around the garden, if you don’t notice them drowned in the pool or visiting flowers you can see their nests in the soil:

Sunday Spinelessness – 5 down…. quite a few to go David Winter Jan 20

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I got some good news this week – a paper I’m an author on was accepted for publication pending some minor revisions. That’s great because career advacement in academia rests largely on what we publish, and this is a good paper that I’ll be happy to add to my CV. It’s also quite happy about his particular paper being (almost) accepted because it’s about serpulids, segmented worms of the phylum Annelida (relatives of earthworms). A new phylum for me.

Biology is about diversity. I know I always go on about this, and end up affecting the overly-enthusiastic style of the guide in Douglas Adams’s Hitchiker’s Guide to the Universe:

Biological is diverse. You just won’t believe how vastly, hugely, mind- bogglingly diverse it is. I mean, you might think there are lot of creatures in your average David Attenborough documentary, but that’s just peanuts to the true diversity of biological systems, listen…

Well, I don’t know to put in words, so let’s try a picture. All that biological diversity got here because life evolves. When populations break up they are free to evolve apart from each other and develop entirely new functions or features and so become different. In this way, life is a tree, forming new branches as populations split. When we come to deal with the diversity of life, biologists try to reconstruct that tree, giving names to those tips and twigs which belong to a particular branch. In that  system of classification the phylum (plura phyla) is the one of the deepest divisions.

 Creatures in separate phyla have usually been evolving apart from each other for 600 million years or more, and represent entirely different ways to deal with the trials of life. The annelid paper will mean I’ve published on 5 different phyla. That’s exciting for me – it’s nice to think I’ve added a little to our knowledge of decent sampling of the tree of life. But the truth is, biology is just so diverse that I’ve not even made a dent the tree of life. Here’s a picture of all the Eukaryotic phyla (that is, creatures with cells like ours, but not bacteria and archaea) with only those I’ve published at least one paper on labeled:




Tree was drawn and shaded with iTOL‘s nifty interfact to the NCBI taxonomy. There’s a couple of things to note here. Because this is the NCBI taxonomy it’s a curated tree rather than the result of any particular analysis. Although we aim to create biological groups “natural”, in the sense they are a single branch in the tree of life, the rank giving to a particular branch is somewhat arbitrary and will differ between different groups (so green plants, which traditionally had “divisions”  rather than phyla are certainly underrepresented here). Protists (single-celled eukaryotes) are certainly diverse, but Psi Wavefunction tells me protistologists have almost given up on rank-based taxonomy so this might not be a fair representation of them.
In any case, it’s certainly a spur to me to get back to work and fill in a few blanks on the figure!

Sunday Spineless – On the Wing David Winter Jan 13

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Just a photo today, but a pretty awesome one I reckon. An inbound bumble bee from my parents’ garden in the Wairarapa:

(~50 out of focus shots from same session not shown!)

Sunday Spinelessness – A Clearwing moth David Winter Dec 09

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At last, Dunedin has managed to arrange a proper summer day for a weekend.

The extra heat and sun saw plenty of bugs out and about, and I spotted plenty of familiar critters (native bees,  cicadas, drone flies and magpie moths) for this first time this year.  The real find of the weekend though, was something entirely new to me:
 

You might be a little surprised to learn that you are looking at a moth.

I’m helping design an undergraduate lab on systematics and taxonomy at the moment.  Since the new lab is about insects I’ve suddenly become very aware of the traits that distinguish various insect groups.  Moths, along with butterflies, make up the order Lepidoptera. You can see a few lepitoperan characters in the above photo: a mouth designed for siphoning nectar from flowers and a body covered in fine scales.

“Lepitoptera” actually mans “scaley wing”, and, indeed most butterflies and moths have scales on their wings. This species, though, has got rid of most of it’s wing scales (there are plenty of scales on the trialing edge though):

Synanthedon tipuliformis * is member of the “clear wing” moth family Sesiidae. Although I think this one is pretty neat, the family contains some striking species, the most interesting of which are wasp-mimics
Bembecia ichneumoniformis photographed by Lamois and licensed CC3.0



Yes, that’s a moth! Sesis apiformis from Flickr user Oldbilluk. Licensed CC2.0




*The species name means, I guess, “looks like a crane fly“… don’t see it myself

Sunday Spinelessness – Bark Lice David Winter Dec 02

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I should have known that the little challenge I put up last week wouldn’t so much as wrinkle the brow of the bug-blogo-sphere’s best. The Atavism‘s two homes means there were two winners. Ted MacRae of Beetles in the Bush chimed in at he blogspot version, correctly identifying the insect as a “bark louse” or psocopteran, and recognizing those stubby white protrusion as yet-to-be expanded wings . Morgan Jackson of Biodiversity in Focus did the same at SciBlogs.

Thanks too to Deborah from Bee of a Certain Age, who hazarded a guess that those white protrusions might be eggs. Certainly a more reasonable guess that my own first thoughts at seeing these bugs crawling over the the Big Tree* in our garden. The plump abdomens and long antennae made me think of the large (but certainly not GIANTspringtails. Ripping up a couple of pieces of bark revealed a whole colony of these odd-looking bugs, and evidence for just how wrong I was. 

The adults have wings, which they hold tent-like over their bodies. Insects are the only invertebrates with wings, so, since spring tails aren’t insects, my first guess was horribly inaccurate (glossing over about 400 million years of evolutionary divergence).

As Ted and Morgan worked out, these are “bark lice”, members of the order Psocoptera. Although they are related to the “true lice” (Order Phthiraptera), psocopterans are not parasites. Rather, they wander around their trees eating algae, fungi and whatever detritus might be clinging to the bark. The only species that could be considered pests are the “book lice” – small flightless psocopterans that sometimes turn up in old books where they eat the paste that binds pages together. (I have it on good authority that book lice can also destroy botanical collections, so certainly a pest)

A couple of weeks ago I gave Veronika Meduna a tour of our garden and its bugs, and I gather you can hear the result on Radio New Zealand’s Our Changing World next week. While I was catching my breath between talking about the mating habits of spiders, and how our native slugs are much more sluggish then their introduced counterparts she asked the obvious question – “why?”. Why do I care so much about odd little creatures like bark lice and slugs and spiders? I’m not sure I managed a coherent answer at the time, but I can tell you now, spineless creatures need evangelists because most people have a very skewed view about the way biology works. If your vision of biodiversity is limited to pandas and dolphins and lions and tigers then you are missing out on millions of other ways to be alive.

Take bark lice as an example. I’ll admit that I’d never given these creatures a moments thought  before running into them last week. But, in researching this post I found out there are more than four thousand psocopteran species. That is to say, there are almost as many bark lice species as there are mammals – all the lions, tigers, bears, dolphins, whales, marsupials, rodents and bats in the world add up to about 5 400. That matters because species are the fundamental units of biological diversity. Each species represents a distinct evolutionary lineage – free to take up different ecological niches, develop new morphological features or occupy a different geographic range.

To try an illustrate how diverse these unassuming little critters really are, I’ve put together a “treemap“. In the plot below, each of the stained-glass window panels represents the number of species in one psocopteran genus, nested within a family (the heavier lines, with labels ending in -DAE) which in turn is nested within a suborder (the very heaviest lines, labeled -MORPHA). These higher taxonomic ranks are not fundamental units in the way species are. Even so, species placed within a taxonomic group share evolutionary history, and are united by particular morphological characters which they share.  It turns out there are quite a few ways to be a bark louse:

And that’s just bark lice!

For me, this chart is the best answer to “why?”. How can you know you share the world with all this extraordinary diversity and not want to want to spend your time working out how it got here?



*This is not a botany blog… I really have no idea what the tree is

Sunday Spinelessness – An ID challenge David Winter Nov 25

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OK, here’s a chance for the bug nerds to show off. A photo of a strange-looking beast I recently ran into:

 

The challenge to readers is to answer the two questions that went through my head when I first uncovered the creature (1) What the hell is that? (2) What’s going with those opaque white projections?
Unlike others, I can’t often you anything cool as a prize for being right, but surely an electronic record to your entomological know-how will be enough?

Sunday Spinelessness – Shocked from sloth by a beautiful spider David Winter Nov 18

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Regular readers will know that I’ve been pretty slack in posting here in recent weeks. Just the same old boring reason – lots of “real” work to get done and, as much as I enjoy it, blogging necessarily floats to the bottom of TODO lists.

But I was shocked from my sloth this afternoon when I passed that accursed agapanthus and saw a spider I really had to share with the world:

It’s an orb-weaving (araneid) spider, a relative of the familiar garden spiders like the very common Eriophora pustulosa that spin orb-shaped webs and catch unlucky flying insects. I can’t be sure on the identification of this one, but I reckon (with some support from twitter’s resided spider experts, [1], [2]) its a species a species of Novaranea. According to Ray and Lyn Foster’s  Big Spider Book New Zealand Novaranea species are most commonly encountered in in grasslands and tussocks, so perhaps this one blew in from the tall grass that covers some the abandoned gardens in our block.

However it made it our garden, I’m very happy to have encountered a such a neat looking spider, and even done a half-decent job capturing some of its beauty:

Sunday Spinelessness – How snails conquered the land (again and again) David Winter Aug 05

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Christie Willcox wrote a nice article this week on how one small group of organisms called “vertebrates” first evolved to live on land. Since you are a vertebrate who lives on land, you should probably go and read Christie’s piece. I wouldn’t want you, however, to go around thinking those first fish to leave the ocean behind were pioneers making a uniquely difficult transition. By my figuring, onycophorans (velvet worms like peripatus), tardigrades, annelids, nematodes, nemerteans (ribbon worms) and quite a few arthropod lineages have also taken up a terrestrial lifestyle. Many of those lineages were already breathing air before Tiktaalik, Ichthyostega and your other long-lost relatives came along to join them on land. But if you want to talk about transitions from marine to terrestrial lifestyles then you really want to talk about snails. You can find snails living in  almost every habitat between the deep ocean and the desert, and snails have adapted to life on land many different times. In fact, a litre of leaf litter taken from a New Zealand forest can contain snails representing three separate transitions from water to land.

Almost all the land snails I’ve talked about here at The Atavism are descendants from just one invasion of the land. We call these species the stylommatophorans and you can tell them from other landlubber-snails because they have eyes on stalks (as modeled here by  Thalassohelix igniflua):

These snails are part of a larger group of air-breathing slugs and snails (including species living in fresh water,  estuaries and even the ocean) called pulmonates or “lung snails”. As both the common and the scientific names suggest, pulmonates breathe with lungs. Specifically, the mantle cavity, which contains gills in sea snails, is perfused with fine veins that allow oxygen to permeate the snails’s blood. In relatively thin-shelled species you can often see this “vasculated” tissue in living animals:

Blacklight photo of Cepaea nemoralis showing ‘vascularised’ lung. Photo is CC BY-SA via Wikipedian Every1Blowz
The pulmonates can also regulate the amount of air entering their lungs with the help of an organ called the pneumatostome or breathing pore –  an opening to the mantle cavity that the snail can open or close at will:

A leaf-veined slug from my garden – the small opening near the “centre line” of the slug is the pneumatostome. Interestingly, leaf-veined slugs don’t have lungs, the pneumatostome opens to a series of blind tubes not unlike an insect’s respiratory system

So that, along with a whole load of adaptations that prevent a fundamentally wet animal from drying out, is your basic land snail. But those little leaf-litter snails I’ve been talking about for the last couple of weeks provide a good reminder that other snail lineages have left the life aquatic. Here’s a species you find almost everywhere there is native forest in Otago, Cytora tuarua:

Holotype of Cytora tuarua B. Marshall and Barker, 2007. Photo is from Te Papa Collectons onlne, and provided under a CC BY-NC-ND license
Cytora is from the superfamily Cyclophoroidea, a group of snaisl that have indepedantly adapted to life on (relatively) dry land. (The weirdly un-twisted Opisthostoma is in this post is another cyclophoroid).  Cyclophoroids share some stylommatophoran adaptations to life on land, they’ve lost their gills and replaced them with a heavily vesculalised mantle cavity. Slightly oddly, cyclophoroids also breathe with their kidneys. Or, at least, the nephridium, an organ which does the same job as a vertebrate kidney, includes “vascular spaces” that the snail can use to collect oxygen from the air. Cyclophoroids don’t have an organ equivalent to the breathing pore to control the flow of air into the mantle cavity. Instead the mantle cavity is open and air enters by diffusion, or in larger species, as the result of movements of the animals head. 
For the most part, the respiratory and excretory systems in cyclophoroids are not as well adapted to life on land as those in their stylommatophoran cousins. For this reason, most cyclophoroids are only active in very humid conditions. In my limited experience, Cytora species are usually found deep in moist leaf litter and soil samples, and I’ve never seen one crawling about. Nevertheless, some species can survive in drier situations, and these are certainly terrestrial snails.
Local leaf litter samples reveal a third move from the water to land. I don’t have nice photo of Georissa purchasi, and I can’t find anything else on the web either, so you’re stuck with a crumby drawing from my notebook:




I did warn you that it was a crumby drawing. In life G. purchasi have an orange-red sort of a hue, and you can often see patches of pigment from the animal through the shell.  Georissa species are from the family Hydrocenidae and are quite closely related to a group of predominantly freshwater snails called nerites. Just like the other lineages discussed, the Hydrocenidae have given up their gills and breathe through a vasculated mantle cavity. Very little is known about the biology of these snails. G. purchasi is sometimes said to be limited to very wet conditions, but I’ve collected (inactive) specimens form the back of fern fronds well above ground so it can’t be completely allergic to dry . 
So, in a handful of leaf litter collected from a Dunedin park you might have cyclophoroids, hydrocenids and  stylommatophorans – descendants from three different moves from sea to land. If we look a little more broadly,  there are are many more examples of this transition.  I’ve written about the the helicinids before, then there are terrestrial littorines (perwinkle relatives) some of which have both gills and lungs. Plenty of other pulmonate lineages that have also taken up an entirely terrestrial lifestyle. Because some of these groups have adapted to life on land multiple times, there have probably been more than 10 invasions of the land by snails.

Most of the description of Cyclophoroids here is taken from:

Barker, GM (2001) Gastropods on land: phylogeny, diversity and adaptive morphology In Barker (Ed.),  The biology of terrestrial molluscs (pp 1146) CABI Publishing.

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