The Atavism

Sunday, February 3, 2013

Sunday Spinelessness - Cannibalism in the garden

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).




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Posted by David Winter 7:51 PM | comments(1)| Permalink |

Sunday, January 27, 2013

Sunday Spinelessness - Native bees again

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:

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Posted by David Winter 9:36 PM | comments(0)| Permalink |

Sunday, January 13, 2013

Sunday Spineless - On the Wing

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!)




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Posted by David Winter 1:01 PM | comments(0)| Permalink |

Sunday, November 25, 2012

Sunday Spinelessness - An ID challenge

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?


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Posted by David Winter 8:09 PM | comments(2)| Permalink |

Sunday, November 18, 2012

Sunday Spinelessness - Shocked from sloth by a beautiful spider

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:

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Posted by David Winter 3:45 PM | comments(0)| Permalink |

Sunday, August 5, 2012

Sunday Spinelessness - How snails conquered the land (again and again)

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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Posted by David Winter 2:12 PM | comments(0)| Permalink |

Sunday, July 22, 2012

Sunday Spinelessness - New Zealand microsnails

When I tell people I study snails for a living I get one of two replies. There's either some version of the "joke" that goes "that must be slow-going" or "sounds action packed", or there's "oh, you mean those giant killer ones we saw when we went tramping?". I guess the joke is funny enough, but I want to make it clear that those giant killer snails from the family Rhytidae, cool as they might be, are not the most interesting land snails in New Zealand.

The local land snail fauna displays a pattern that is quite common for New Zealand animals - we have a very large number of species but those species are drawn from relatively few taxonomic families. Since taxonomic groups reflect the evolutionary history of the species they contain, that pattern most likely arises because New Zealand is (a) quite hard to get to, so few would-be colonists make it here and (b) full of ecological niches and geographic pockets that can drive the formation of new species. In total, there are are probably about 1200 native land snail species in New Zealand - about ten times the number found in Great Britain, which is approximately the same size. That diversity extends to the finest scales - individual sites in native forest might have as many as 60 species sharing the habitat. New Zealand forests probably have the most diverse land snails assemblages in the world (although tropical ecologists, who generally hold that diversity in terrestrial habitats almost invariably increases as you approach the equator, have argued against this conclusion).


You may now be asking why, if this land snail fauna is so diverse, have you never seen a native snail. Well, you've probably walked past thousands of them without noticing. Most of our native land snail species are from the families Punctidae and Charopidae, groups that are sometimes given the common name "dot snails". Meembers of these families are usually smaller than 5 mm across the shell, and are restricted to native forest and in particular to leaf litter. But in native forests, where there's leaf litter there's snails. Grab a handful of leaves, or pull up a log and you're likely to find a few tiny flat-spired snails going about their business. Hell, down here in Dunedin you can even find charopids living under tree-fuschia in a suburban garden.


Like so many native invertebrates, we know very little about our land snails. Lots of people have dedicated substantial parts of their lives to documenting and describing the diversity of these creatures, but even so we don't have a clear understanding of how the native species relate to each other or to their relatives in the rest of the world, or even where one species starts and another ends. Without such a basic understanding, its very hard to ask evolutionary and ecological questions about these species, so for now we remain largely ignorant of the forces that have created the New Zealand land snail fauna.


For the time being I can tell you that a lot of them are really quite beautiful. Since most people don't have handy access to a microscope to see these critters, I thought I would share a few photos from this largely neglected group over the next few weeks. The 2D photographs, with the relatively fine depth of field, don't quite record the beauty of these 3D shells, but I hope it's at least a window into the diversity of these snails.


 Let's start with a snail that is very common in Dunedin parks and forests. This is a species from the genus Cavellia (the strong, sine-shaped ribs being the giveaway) but I won't be able to place it to species until a new review of that genus is published. 




This particular shell is from an immature specimen, and is about 2mm across. When flipped, you can see an open umbilicus that lets you see straight through to the apex of the shell.





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Posted by David Winter 5:30 PM | comments(1)| Permalink |

Sunday, June 3, 2012

Sunday Spinelessness - Nothing to see here

I'm off to the Transit of Venus Forum next week. I'm looking forward to meeting all sorts of clever and interesting people (and escaping the coming snow), but travelling and conferring won't leave much time for a few projects I really need to work on. So, today's blog post is going to have to be squeezed down to its smallest possible form (a queen ant that dropped in to read an early draft of my thesis last spring):



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Posted by David Winter 7:32 PM | comments(0)| Permalink |

Sunday, May 27, 2012

Sunday Spinelessness - Even their eggs are spikey

I really like the leaf vein slugs (Athoracophoridae) that live in our garden and  have featured here in the past. Here's the latest one to pass under my camera:


As much as I like them, I have to admit these guys are actually one of the more boring leaf vein slug species in New Zealand. Some of their relatives are much larger or more colourful and quite a few of them sport large wort-like growths (technically called papillae) that pattern their bodies in various ways. Te Ara and Soil Bugs both have galleries that let you get an idea of their diversity.

A couple of weeks ago I made a little discovery. Some of these slugs also have eggs that are covered in papillae


Not the greatest photo I'll admit. But it's hard work taking photographs in the dense New Zealand bush at the best of times, and I found these eggs in the low-growing cloud forest that covers the Leith Saddle on Mt Cargill. These are certainly slug eggs, so  I did a bit of snooping among Astelia and ferns and other likely looking roosts for these nocturnal animals. I couldn't find any parents-in-waiting, but the ferns were utterly covered in what people that follow mammals might call "sign", so clearly there's a big population in the area. 

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Posted by David Winter 8:05 PM | comments(1)| Permalink |

Sunday, May 20, 2012

Sunday Spinelessness - Lazy Link Blogging Edition

I though I'd do something a little bit different today. Instead of coming up with anything new to say or show you I'm going to steal from give a shout-out to a few New Zealand organisations that highlight  some of the amazing ways that spineless creatures get on with business of living.

Let's start with Landcare Research (Manaaki Whenua), the Crown Research Institute that focuses on bioiversity and environmental issues. As you'd expect, Landcare do lots of work on invertebrates an that's refelected in their public face. Their "What is this bug?" site is a great starting point for anyone trying to put a name to some weird critter that's crawled out from the garden, and topic pages on some of our most interesting creatures (Onychophora, stick insects and our amazingly diverse moth fauna) make for a nice introduction to these groups.

The Landcare site I really want to pull out for special focus is their recently developed guide to freshwater invertebrates. Freshwater invertebrates are often use as "indicator species". Because certain groups of stream invertebrates are very susceptible to pollution or changes to a stream's natural flow, the presence or absence of these groups in particular stretch of water can give us an idea of the health of that water. In order to help community groups or landowner monitor their streams, Landcare has produced some beautiful photographs of stream invertebrates (along with information on how to sample them, and how well each species acts as an indicator). You really should check out the whole site, because some of them are quite beautiful, I'll just give you a taster here:


Left: Kempynus lacewing sporting some impressive 'tusks'. Right: Head shot of the larvae of an Onychohydrus diving beetle. Both images © Landcare Research

The other Crown Research Institute with a special interest in biodiversity is NIWA (the National Institute of Water and Atmosphere, if really wanted to know), who have a particular focus in the strange and wonderful creatures that live in the deep seas. NIWA scientists were part of the team that pulled up those mega-amphipods and I'm really pleased to say they have a great Facebook page dedicated entirely to their invertebrate collection. The NIWA Invertebrate Collection page has recently featured Phronima (one of favourites), Nematodes (perhaps the most under-studied group of animals on earth) an cold-water corals. Again, I encourage you to check out (an follow!) the page, but here are a couple of recent photos to entice you:


Phronima having recently evacuate its salp (© Owen Anderson). Tiny octopus! (photo from Ocean Survey 20/20)


Finally, let's leave the Crown Research Institutes behind and go to Massey University and "Soil Bugs: A guide to New Zealand's soil invertebrates". Soil bugs is run by Dr Maria Minor and contains information and photographs of some of the thousands of species that live in the soil, leaf litter and rotting logs that cover the floors of our forests. Soil invertebrates a hugely important animals, being as they help to release the nutrients locked up in dead wood, but I've gone on about that plenty of times. So let's look a couple of my favourites GIANT Springtails and native land snails:

Left: Holacanthella spinosa Right: Flamulinna zebra. Note, these images are © Massey University, and premission sought be sought to use them elsewhere.


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Posted by David Winter 1:25 PM | comments(0)| Permalink |

Sunday, April 29, 2012

Sunday spinelessness - live-bearing land snails

People seemed to like the idea of a marsupial land snail, so today I thought I'd go one step further, and introduce you to land snails that give birth to live young. 

I was lucky enough to spend a little time in Vanuatu a while ago, and, although I was really there to relax and see in a new year, I couldn't travel that far and not spend a little of my time looking for snails. As it turns out the island on which we stayed  is heavily modified, and there is not much natural habitat left for native land snail species. In fact, the only really interesting snails I found were living on the side of our host's house. I collected a few of those snails, transported them to the fridge in our lab and forgot about them for the best part of year.

More recently it dawned on me that these snails would be useful for a project I am working on, so I grabbed them from the fridge, set them up under the microscope ready to dissect away a tissue sample for genetic work and saw this:

 

Embryos developing inside the shell of their mother. 

We sometimes think of live-bearing as being a trait that sets the mammalian branch of the tree of life apart from other animals, but that's wrong. Most of the major groups of animals have some species that give birth to live young - there are live-bearing frogs, snakes, lizards, insects, fish, crustaceans and star fish. In fact, the only large group without live-bearing species that I can think of is birds (and, it seems, dinosaurs, a group that contains birds). Most land snails lay a clutch of many eggs, each containing a single-celled zygote which is left to develop on its own. A few species, like theses ones, have evolved a different reproductive strategy: producing fewer eggs than their relatives, but retaining those eggs within their shell before giving birth to much more developed young.

This behaviour seems to be particular common in snails that live in rocky outcrops, and those that live in the tropics, especially the Pacific. I'm not sure about what species the snail depicted above fall into - but they are from the sub-family Microcystinae, which is one of the dominant groups of land snails in the Pacific and is made up entirely of live-bearing species. The large evolutionary radiations that used to live in Hawai'i and the Society Islands were also all live-bearers.

So why give birth to live young? It is easy to see why live-bearing is an advantage to snails living in rocky habitats with few places to deposit eggs. It's less clear why the Pacific is full of live-bearers. It has been suggested that tropical weather can lead to unpredictable patterns of boom and bust - with snails that can hold on to and grow their offspring in the bad times and release them "ready to go" when conditions are better having an advantage over egg-layers. As far as I know no one has ever come up with a way of testing that idea, so the reasons for the prevalence of live-bearers in the Pacific remains an open question.

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Posted by David Winter 7:14 PM | comments(1)| Permalink |

Sunday, April 8, 2012

Sunday Spinelessness - Molluscan mausoleum

Going way back today, to a photo I took about 6 years ago:

 

This is from the high tide mark at Aramoana, and the shells that dominate the little assemblage are Zethalia zelandica - the New Zealand wheel shell.  I don't have anything particularly important or meaningful to say about these shells. I was just struck by the diversity of the patterns and colours that they bear, and the concentration of shells into a relatively small stretch of a relatively large beach. Zethalia live in sandy conditions and somewhat deep water, so the shells presumably washed in from the harbour and had collected over time at a point at which the waves and currents coalesce.

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Posted by David Winter 4:35 PM | comments(0)| Permalink |

Sunday, April 1, 2012

Sunday Spinelessness - A marsupial snail

I never thought I'd become a fan of land snails. As I've said before, I started my PhD with the quaint idea that you could study a  group of organisms for years and still regard them as little bags of genes with no particular importance beyond their ability to help you answer questions. Perhaps that's true for some people and some animals, but not me and snails. I'm now a card-carrying member of the land snail fan club, and take every opportunity to remind people of the amazing lives these creatures lead.

Snail shells are beautiful. You don't need to know anything special about biology or maths to see that:

Nature Pattern


But, as is so often the case, the more you learn about snail shells the more beautiful they become. I'm not much of a mathematician. To be honest I find a lot of maths to be a horribly complex, and seemingly arbitrary, and I could never really follow it past basic algebra. Still, every now and again I'm struck by the beauty of a system that can explain parts of reality with such ease (and by envy for those who can see so much deeper than me). The mathematical description of snail shells is one of those cases in which the maths is easy enough for me to understand, and so I can appreciate the elegance.

The simplest way to model a snail's growth would be to say it adds its shell at a constant rate. In that case, we could know the size of a shell at any given time (x) using the exponential function ex (e being the base of the natural logarithm, which you can think of as the base unit for any pattern of continuous growth). You can  probably remember the exponential function from high school maths, it's the one that gets big quickly:

 

The exponential function can tell us how big a shell gets, but of course, shells don't simply grow, they also spiral at the same time. If we want to model both the growth and the spiral pattern of a snail's shell we need to leave our familiar "x,y" system of placing points (called the Cartesian coordinate system) and think in "polar coordinates".

Just as any point in a two-dimensional space can be identified by its distance from another point along horizontal and vertical axes (x and y), it can also be identified by its angle and distance from another point. Think about a point at x=3 and y=2, you can just as easily, and just as uniquely, identify that point with polar-coordinates:


Using polar coordinates it's very easy to write an equation that describes the growth of a snail shell:

r = e k.θ 

Here "θ" (theta) is an angle relative to the starting point, "r" is the amount of growth the spiral has made by the time is swings around to that angle and k determines the "tightness" of the spiral the shell forms. I was playing around with Wolfram Alpha in preparation for this post, drawing spirals with different values of k, when I came across this spiral at k = -0.2:


I know that shape, that's a Wainuia shell!

 


 With a little bit of tweaking you can make a paua (= -0.6) or something close to a tightly-turning charopid (k = -0.1).




Just changing one parameter in a pretty simple equation is enough to produce spirals that fit most snails' shells. In fact, spirals like these ones, which are called logarithmic spirals, pop up in nature all the time - from the arms of galaxies to the nerves in your eyes. Logarithmic spirals have some pretty cool properties, the most interesting of which is that not matter how large they grow they ever change shape. A snail that grows according to these equation will be the same shape from the day it's born to the day that it dies.

If you know a bit more maths you can extend these models into a third dimension and, with one more parameter, create flat disc-like shells or tall conical ones. I think it's truly amazing that you can get a good approximation of snail shells using so few parameters - but it's worth remembering mathmatical constructs are just models we use to examine reality. David M. Raup got a bit carried away with the mathematical description of shells in the 1960s, and created what he called the "museum of all shells" by exploring the three dimensional shapes you could make by tweaking just three parameters in a model of shell-growth. But Raup's virtual musuem doesn't include all the shells that snails can grow. Biology is weird, and any "law" that a biologist might claim to have discovered will have an exception. None of the shells above quite fit the spiral I've super-imposed on them, and some snails grow shells that radically deviate from logarithmic growth . My favourite example of such a radical departure are the "worm snails", marine snails that cement the apex of their shell to a rock then grow an almost un-coiled tube of a shell.

Worm snails grow in way that is radically different from most of their close relatives, but more subtle deviations from logarthmic spiralling are just as interesting. Remember these guys?


 Libera fartercula are one of a great deal of snails that change shape as they age. Very young shells have a very broad opening (an umbilicus) on the underside:


As the shell get's bigger, the opening to the umbilicus gets smaller...

...and smaller.


Of course, the original "wide" umbilicus is still part of the older shells. In effect, this pattern of growth creates a cavity within the shell which has lots of space at the top, but a very narrow opening. Amazingly, L. fratercula is a marsupial snail. Over the course of its growth this species creates a pouch within its shell, which it then lays its eggs in, protecting them from would-be predators who can't get inside the narrow opening.

Land snails usually don't do much for their young. A few snails lay extra large clutches, so that the first of their offspring to emerge will have eggs to eat before they set off on their lives. Others hang on to their eggs, either within their shells or withing their body. Libera fratercula takes parental investment to a much greater level. Here's an older shell:


Most of the larger shells from this species show this sort of damage. When you zoom in on the damage you can see a slighltly irregular pattern.


These holes are creatued by immature snails emmerging within the brood pouch and eating their way out of their parent's shell. Such damage doesn't seem to kill the snails - they effectively wall-off the first few whorls of the shell once they are large enough, so there is no animal within the part of the shell that is broken.

I can tell you  a lot more about these snails. Allen Solem described the "brood pouch" and a little of their ecology in 1968, but he worked from old shells and no one has studied their behaviour in situ to be able to measure the impact of this strange adjustment to snail-life has on parents.



The shell photographs onto which I've super-imposed the sprials are all Creative Commons Licensed courtesy of Te Papa 1,2,3.

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Posted by David Winter 4:21 PM | comments(2)| Permalink |

Sunday, February 12, 2012

Sunday Spinelessness - A fly in the bee garden

Just a couple of photos today.

We planted a bee garden this year - Borage, Phacelia foxglove and a couple of other plants that are known to attract honey bees and and their bumbling cousins into the garden:


The "bee garden" has worked - there is hardly a moment during the day when there isn't at least one bee making it's way around the little patch of garden. I'll show you some photos of them soon, but today I wanted to share a much smaller creature. A tiny fly perched on the leaf of a chickweed (Stellaria):


I'm terrible with fly taxonomy (or flylogeny if you'd rather) - I like to think I can at least get most of the spiders and insects I encounter down to the family level (roughly equivalent to successfully identifying myself as a great ape). With the exception of a few groups - crane flies, robber flies and hover flies,  I get nowhere with flies. And so it is with this one, all I can tell you is that it's small (~3mm) probably from group called Schizophora. And that I quite like this photo.

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Posted by David Winter 8:17 PM | comments(0)| Permalink |

Sunday, February 5, 2012

Sunday Spinelessness - King of the castle

A moment of life in the undergrowth captured (leaf beetles playing king of the castle?):


I don't know exactly what was going on here, though I've got my ideas. Whatever I saw, it involved a lot of wild antennae-shaking from the two beetles facing each other and apparently very little interest in proceedings from the base of the "short, blunt beetle-pyramid".


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Posted by David Winter 8:12 PM | comments(0)| Permalink |

Sunday, January 29, 2012

Sunday Spinelessness - We have bees


If I asked you to think of a bee I'm willing to bet you'd come up a with picture of a honey bee: a fuzzy little creature with yellow and black stripes and a rear end that can deal damage. Perhaps you'd think of a big fat bumblebee making its way between garden flowers, or, if you are lucky enough to live near them, some commercially important pollinator like a mason bee. Even if we including those extra forms in the way we think about bees, we are only taking a tiny sampling of the twenty thousand species that make the superfamily Apoidaea.

There are giant sex-crazed killer-bees, and tiny bees that specialise in gathering nectar from the false-flowers of Euphorbia. Bees that form colonies with thousands of adults, and bees that keep to themselves. There are hairy bees, and hairless bees, bees that specialise in stealing honey from other bees and bees that develop "soldiers" who give their lives to fight these would-be thieves off. There are even bees that eat meat. Given the huge number of ways there are to be a bee, you might ask what unites this group. Bees (like ants) are specialised wasps. They all descend from a group of wasps that gave up a typical waspish lifestyle, providing insect or spider flesh for their young while using nectar to fuel their activities as adults, and instead started provisioning their larvae with nectar and pollen. From so simple a switch the seemingly endless forms of bee have arisen.

It might come as a surprise to New Zealanders that we have native bees. Our natives aren't hugely important pollinators of commercial crops, in fact, long-tongued bumblebees were introduced for just this reason. Though our bees pollinate plenty of native plants, they don't play as large role in plant reproduction as their relatives in some eco-systems - birds, beetles, butterflies, lizards true files and bats are all important pollinators in New Zealand natural habitats (and introduced rats have partly replaced declining bats in this role). But the 30 or so native bee species that we know about (there could well be more) are still part of our natural heritage, and what's more, they are a part that goes unnoticed under many of our noses - as a few species can do quite well in suburbia. The locals come in two of the nine recognised bee families , so let's treat each seperately.

Colletidae (plasterer bees)

The colledtids are called "plasterer bees" because they smooth-off the walls of their nests with a secretion that create with their mouths. In New Zealand we have 18 large-ish (up to 12mm) species in Leioproctus and another 9 or so Hylaeus species. The spur for me writting this post was encountering a member of the South Island species Le. fulvescens sitting in our hallway last weekend (duly photographed and moved off to the garden).



Le. fulvescens is the only native bee that fufills the yellow black and fuzzy sterotype for bees. The others are black and relatively hairless. Bees often specialise on collecting pollen and nectar from a particular group of flowers, and most New Zealand colledtids search for flowers from the Myrtle family (e.g. rātā, pōhutukawa, mānuka and kānuka). I've never stopped to watch them, but I gather that native bees can outnumber introduced ones on these flowers at the right time of the year. A few other colledtids, including Le. fulvescens, prefer flowers (native and introduced) from the family Asteraceae (daisies, sunflowers and their kin). I'd like to think the the one photographed above had been brought into our garden by the display the federation daises are putting on - but the hawkbit taking over the less acessable regions of the section is a probably a more likely source.

These bees all produce nests in the soil, and when the conditions are right females can lay an egg and provision a nest with nectar at the rate of one per day. The clay bank that our house sits under is full of little drilled holes, which I'm sure mark the start of Leioproctus nests. They're most abundant towards the start of summer (November-December) but they'll hang around until February when the last generation of females will find somewhere to hide over the winter.


Halictidae (sweat bees)

The halicitids get their scientific and their common name from the fact they are attracted to the salt in human sweat. This family is represented in New Zealand by 4 or 5 species of Lasioglossum, with one, La. sordum common in disturbed habitats. I've only ever seen one of these bees moving about between flowers, but must have scooped hundreds of them out of the my parent's swimming pool in the Wairarapa. I don't know if the chlorine salts that balance the pool's chemistry set them off, if they're thirsty or if the polarised blue light that shines off the water plays tricks with their eyes, but something about the pool leads to a fatal attraction.

Scooping these guys out of the pool let's you learn a little about them, first, the males are substantially smaller and thinner waisted than the females and second, the females are capable of delivering a very small sting. Steven O. Schmidt, an entomologist who has evidently been stung by most of the venomous insects in the world , has created an index to measure the power of an insects sting. The sweat bee scores lowest on the Schmidt Pain Index - a 1.0 with the desctiption "Light, ephemeral, almost fruity. A tiny spark has singed a single hair on your arm". Certainly nothing compared with the pain of the tarantula hawk (relatives of the spider-hunting wasp featured here), which weighs in at 4.0 and is "blinding, fierce, shockingly electric...". Lasioglossum seem's to live up to its famaly's reputation - it took me a little while to convince myself that I had just been stung (by a creature who's life I was trying to save no less!) and it does feel a little bit like a spark fading out on your skin.

The time it takes for a water-logged bee to get back to being airworthy also gave me a chance to take a few photos - you can tell these are staged because this is exactly the sort of flower (requiring a long tongue to get the sweet reward) that a native bee would never visit!



In terms of their habits, our native halicitids are much less fussy than the colledtids - they've been recorded from at least 80 species of plants across many families. This undemanding approach to life might be a result of their longer lifecycle - females start emerging as soon as August, the first males appear around November and both sexes will persist until frosts send them into dormancy (I don't know of any records from Northland, but bumblebees can keep year-round colonies up there, and these bees could conceivable survive the winter their too. Lasioglossum are described as solitary, but, although they don't form huge colonies, there is evidence that female La. sordum will share nest entrances. Such behaviour is probably one part of a continuum that goes from solitary behavior, through to shared provisioning of nests and on to super-colonies like those of honey bees (and some sting-less bees). Both the behaviour (provisioning of nests with honey, a food that can be stored) and the genetics (a form of sex determination that means sisters are effectively more closely related to each other than they are to their mothers) of bees open the door to evolution of "true social" behaviour, and the steps along the way provide scientists with rich ground to test their ideas about this evolutionary phenomenon.

That's it really. Next time you're see some bare soil in a nice flowery habitat, why don't you look and see if you can find some perfectly cyclindrical holes (and piles of soil beside). Or better yet, spend a little time in the garden and see if you can't spot a native bee making its way from flower to flower.

Check out Te Ara's article on native bees here, and the source of most of the information above:

Donovan, B.J. (1980).Interactions between native and introduced bees in New Zealand [pdf]. NZ Journal of Ecology 3:104-116.

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Posted by David Winter 5:25 PM | comments(0)| Permalink |

Sunday, January 22, 2012

Sunday Spinelessness - For Ted

As I said last week, I've just returned from a bit of a summer holiday. I'm not the sort of person who can do absolutely nothing for any length of time, so I tend to find my relaxation in doing things that I wouldn't have a chance to if I was at home.Like riding a mountain bike. As far as I'm concerned, the best place in Dunedin is  the top of Sandymount, an eroded volcanic cone that marks the start of the descent from Highcliff down to Portobello when you ride the Otago peninsular*. I could get all lyrical about the feeling of being away from the rest of the world, or the joy of the moment that you roll from the stiff climb into the fast and flowing descent, but thankfully Brian Tuner has already written a poem about my favourite bike ride:

... I push the gear
down a little and the chain
drops onto a small sprocket
and the wheels start to spin
faster, and the air's
like a quick tongue
in my hair as I descend
swinging in wide curves
around the hill...

      Training on the Peninsular

When I spend time at my parent's house in the Wairarapa I leave my road bike behind and borrow my dad's old mountain bike to explore some slower, bumpier rides. That's how I ended up, in the middle of a mid-summer day, struggling my way up a crushed limestone path in a small reserve in Masterton. Bike riding is one of the past times that had to give way when my thesis ate all my spare time, so this really was a struggle. Even riding in the lowest gear I could, I soon gave up on the nice "upright" form that helps a rider spin their way up a hill and instead grovelled my way up, shoulders slumped and head down. And that was a good thing, because with my eyes pointing down I spotted a small creature, seeming to hover just above the ground as it zoomed out across the path, .The creature stopped, turned a few degrees, sprinted down the path a little and stopped again. So I stopped, not, of course, because I needed a break from the hill, but because I've read Ted MacRae's blog long enough to recognise the behaviour playing out in front of me.

If you like bugs and you don't read Ted's blog (Beetle's in the Bush) then you really ought to fix that oversight. He's a great photographer and an immensely knowledgeable entomologist, but the thing that really  springs from Ted's posts is a love for natural history. Tiger beetles are one of the bits of natural history that Ted loves the most, and its through his photos and posts that I've been introduced to these wonderfully rapacious critters. Tiger beetles live almost everywhere on earth. New Zealand plays hosts to a small radiation (12 species, all arising in the last 10 million years, Pons et al. 2011, doi: 10.1016/j.ympev.2011.02.013s) and, although they aren't particularly rare, I'd never seen one before this day. So I scooted a little closer, and the beetle (raised up from the ground by slender legs, and not actually hovering above it) sprinted a little further. And so it went: scoot. sprint. scoot, sprint, until I got within a metre or so and the beetle added "fly" to its repertoire and disappeared into the long grass.

I was happy just to have at last seen one of our tigers, but I wanted to get a little closer and even see if I could grab a photo of the skittish creature. So that evening I drove out to the reserve and walked along the paths at the top of the hill, hoping to see another beetle zoom into view. A couple of laps of those tracks yielded nothing. If you want to see something interesting the best bet is stop and let the world happen around for you for a little bit, so I stopped. Before long I was watching native (Lasioglossum) bees investigating nesting sites on the ground and then, out of the corner of me eye: Sprint. Stop. Sprint.


 


Neocicindela tuberculata is the most widespread of our tiger beetles, and an ecological generalist that copes with disturbed habitats as well as beaches, riverbanks and forests. Like tiger beetles everywhere, they are predators that use their bursts of speed to hunt down smaller insects. The harsh light, the beetle's shininess and my lack of photographic skills didn't combine all that favourably, but I did get a few headshots that let you get an idea of what happens to a prey item once a tiger beetle has caught it:


I'm not sure, but I think the protuberance you can see in these photos may be an ovipositor - an organ used for laying eggs. These beetles lays their eggs in burrows, and the larvae that develop in them are every bit as fearsome looking as the elders. Since it seemed like this beetle might in the process of keeping this population going, I decided I should let her get on her way while I could be satisfied with a beetle I'd long wanted to see marked off my "life list". The only problem with being a invertebrate fancier is that makes it another one down, approximately 10 million to go!

* At least it is if you don't find yourself stuck behind a camper van trundling down the skinny road at 20 kph!

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Posted by David Winter 9:34 AM | comments(4)| Permalink |