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Lethiferous Latrodectus – part 1

21 May 2009 – 3.10pm
Katipo spider

Katipo with 3 egg sacs, 1967, by Richard Sharell. Te Papa

One of my previous posts discussed a recent study on New Zealand’s only endemic spider regarded as dangerous to people, the katipo. I thought readers might be interested to learn a little more about what’s behind the bad reputation of katipo and its’ close relatives.

As I said then, katipo belongs to the genus Latrodectus, a group of spiders that includes infamous species such as the black widow spider (Latrodectus mactans) and the Australian redback (Latrodectus hasseltii) amongst its ranks. The cliché that ‘the female of the species is deadlier than the male’ applies here as the male is very much smaller and incapable of biting through human skin.

Latrodectus venom contains potent neurotoxins capable of putting an adult in hospital and in some cases may even fatal. While fatalities are rare, a bite from one of these spiders can be EXTREMELY painful and deeply unpleasant. The symptoms are many and varied, but pain, particularly in association with severe abdominal cramping is common.

Not all bites are necessarily the same. The age, health and size of the victim as well as the amount of venom injected are just some factors that can influence the severity of a bite.

In New Zealand, katipo bites are very uncommon. For one thing, katipo prefers to run rather than bite. For another, katipo is nowhere near as widespread as it used to be as humans make more and more changes to the beach-front habitat katipo prefers. While there are parts of the country where katipo exist in good numbers, your chances of meeting one are small and the chance of being bitten by one smaller still.

Even if you defied the odds and were bitten by a katipo, your suffering is likely to be less severe than if you were bitten by another species such as black widow. This is because katipo is the smallest Latrodectus species and thus delivers the least amount of venom when biting. Nonetheless, a good dose of katipo venom is probably going to have you feeling very sorry for yourself. Fortunately, New Zealand hospitals carry suitable anti-venom.

There will be more on the subject of Latrodectus in my next posting, including where I found the word ‘lethiferous”.

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Latrodectus Love Bites

13 February 2009 – 7.30am
Latrodectus valentini (Valentine's widow spider)

St Valentine's widow spider

 

In honour of Valentine’s Day this post will look at the wonderful world of courtship in the spider genus Latrodectus, more commonly known as the widow spiders. Readers of my previous post will recall this genus includes species such as the American black widow (Latrodectus mactans), the Australian redback (L. hasseltii) and the New Zealand katipo (L. katipo), all spiders with a toxic reputation.

Mating: We all know the birds and the bees do it, but what about spiders? Well obviously they have to reproduce but spider courtship presents some problems. Imagine yourself as a male black widow for a moment.  First of all your prospective mate is an aggressive carnivore many times your size.  If that’s not bad enough, you’re venturing into her web where she holds all the advantages. Worst of all, her first reaction is going to be ‘dinner!’ As you can see, mating is a risky business from his point of view!

However, if male spiders were always eaten before they got to mate we’d soon run out of spiders.  In order to approach females in relative safety, male spiders have special courtship signals to let them get up close and personal. Unfortunately, this doesn’t always work and the poor lovelorn male may end up as a snack if he puts a foot wrong. Even if he gets his moves right, he still may not make it out alive. This is how the black widow earned its’ name. It was widely believed that the female black widow would always devour the hapless male after mating. However, it turns out that the black widow’s femme-fatale image is exaggerated because while males may sometimes end up as lunch, it’s not all that common.

So are widow spiders still deserving of the name? Yes!  While the black widow’s reputation might not be completely justified, mating in the Australian redback species can accurately be described as the ultimate dinner date. Not only is the redback male eaten by the female after mating, he voluntarily places himself under her fangs to make it easier.

So what drives this suicidal strategy? Redbacks often live in arid areas where food is short. It’s thought that by feeding his mate she in turn has more nutrients to better provision more eggs and thus develop more of his offspring. But there’s a further twist to this tale. Female redbacks can store sperm from more than one mating for months at a time so one male’s sacrifice may end up being used to provide for another male’s offspring.

Female katipo is a bit gentler on her male counterpart and typically lets him escape to try and mate another day. Katipo and redbacks are close relatives and can still mate, but only one way. This means female katipo can mate with males from either species, but redback females will only mate with their own kind. The male redback will still offer himself up to be bitten when mating with katipo but she’s too polite to nibble!

And before anyone asks, there is no such thing as the St Valentine’s widow spider!

This post is dedicated to the late Dr Lyn Forster, a New Zealand arachnologist who was the first to document sexual cannibalism in the redback spider.

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Skin Deep Differences Don’t Matter In Katipo

10 February 2009 – 11.03am

Skin Deep Differences Don’t Matter in Katipo

Katipo with 3 egg sacs, 1967, by Richard Sharell. Te Papa.

Katipo with 3 egg sacs, 1967, by Richard Sharell. Te Papa.

Having spent my last two postings dealing with butterflies and moths, it’s time to move on to the animals I love the most – spiders!

The subject of this posting is the katipo spider (Latrodectus katipo), New Zealand’s only endemic spider known to be dangerous to humans. Katipo is a Maori word meaning ‘night stinger’. The genus Latrodectus includes a number of species with a nasty reputation such as the black widow of North America and the Australian redback spider.

Katipo like sandy beaches (especially dune systems with native vegetation). The range for katipo covers much of the coast of the North Island and extends down as far as Dunedin on the South Island’s eastern side. On the South Island’s west coast they are known from Greymouth north.

The female katipo looks is pea-sized and satiny black. Her abdomen is marked with a red stripe on top and a red hourglass below. However, a completely black form of katipo can be found in the northern half of the North Island. Going by the unimaginative common name of black katipo, it has been considered a separate species (Latrodectus atritus) in its own right.

However, a recently published study I was involved with found otherwise. I joined forces with Christchurch-based scientists Cor Vink, Adrian Paterson and Jagoba Malumbres-Olarte, fellow Wellingtonian James Griffiths and US-based Pierre Paquin to see just how different the two types of katipo really were.

We looked at DNA, body measurements, cross-breeding and more besides only to find no meaningful differences aside from the absence of a red stripe in black katipo females. In short, they are not different enough to warrant being treated as two separate species.

Why then do we get the black form of katipo in northern New Zealand? We found a strong correlation between higher annual mean temperature and the presence of black katipo. Darker colouration tends to be associated with a need to absorb more heat, something we wouldn’t expect in the warmer, northern parts of the country. What benefits (if any) the black katipo gets from the loss of her red markings is still a mystery to us but temperature may still have something to do with it.

My co-author Adrian Paterson has also blogged about this study and you can read his post here. Amongst other things, Adrian’s post gives more detail on how we evaluated the differences between the two forms. Readers interested in learning more about katipo and other spiders might like to visit the spider section on the Te Papa website.

There’ll be more on katipo and its close relatives next post.

Reference:  Cor J. Vink, Phil J. Sirvid, Jagoba Malumbres-Olarte, James W. Griffiths, Pierre Paquin and Adrian M. Paterson (2008).  Species status and conservation issues of New Zealand’s endemic Latrodectus spider species (Araneae : Theridiidae). Invertebrate Systematics 22(6): 589-604.

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A Tiger with Crimson Wings

2 February 2009 – 8.53am

A Tiger with Crimson Wings

Cinnabar moth from Te Papa’s ‘Blood Earth Fire’ exhibition (©Te Papa).

 This post is inspired by Smiv’s reminiscences about cinnabar moth caterpillars when commenting on my previous blog entry:
http://blog.tepapa.govt.nz/2009/01/26/a-menu-for-monarchs/#comments

Also, as adult cinnabar moths are on the wing this time of year in New Zealand summer and sightings always generate a number of calls to Te Papa’s entomology department, I thought this species deserved a posting of its’ own.

The cinnabar moth (Tyria jacobaeae) is part of the family Arctiidae (also known as tiger moths). With its distinctive red and black wings, the cinnabar moth is often and aptly described as striking. Its bold colours mean it is sometimes mistaken for a butterfly.  Even the older caterpillars are strongly coloured with alternating yellow and black bands. These sharply contrasting colours are a warning to would-be predators that these insects taste bad because of the toxic alkaloids they’ve taken up while feeding on ragwort (Senecio jacobaea).

A taste for ragwort is the very reason this moth was introduced from the UK to New Zealand. While ragwort’s toxins help protect the cinnabar moth’s caterpillars, they are a menace to livestock. Thus, it was hoped the cinnabar moth would help reduce the risk ragwort posed to stock.

These moths were first imported into New Zealand from the UK in the 1920s. By 1932 cinnabar moths had been released over much of the country. Alas, the moth didn’t really prosper outside of central New Zealand and its value as a ragwort biological control agent in its own right is mixed. Thanks to re-establishment efforts in the 1980s the cinnabar moth is more widely established in NZ than it once was. While it may not win the fight against ragwort on its own, it still has a part to play when used with other ragwort control agents such as ragwort flea beetle and ragwort plume moth.

Anyone interested in learning more about biological control of ragwort and other weeds might like to visit the ‘Biological Control of Weeds Book’ site here:
http://www.landcareresearch.co.nz/research/biocons/weeds/book.asp

Visitors to Te Papa can also see specimens of the moth in the ‘Blood Earth Fire’ exhibition on level 3.
More about Blood Earth Fire

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A Menu for Monarchs

26 January 2009 – 11.37am

 

R Sharell, Copyright Te Papa

Monarch butterfly caterpillar Photo credit: Richard Sharell, © Estate of Richard Sharell(used with permission).

In the summer months I get plenty of phone calls and emails from monarch butterfly fanciers, all with a common problem:

“My swan plants are almost stripped bare yet I have so many monarch butterfly caterpillars I really don’t know what to do. Is there anything else I can feed the caterpillars on?”

This problem arises because at times there are too many butterflies laying too many eggs on too few swan plants! It’s as though the butterfly is gambling that at least some of her offspring might somehow get enough food to make it through to the chrysalis stage. If she doesn’t lay eggs on the right food plant they have no chance at all.

So what can you do besides buy more swan plants? Well, there is a partial alternative – pumpkin! I say ‘partial alternative’ because only the older, larger caterpillars can make use of it. While smaller caterpillars can feed on pumpkin flesh, pumpkin doesn’t provide everything they need to properly develop. In contrast, larger caterpillars that have been reared on swan plants are likely to have picked up enough of the chemicals they need to undergo metamorphosis.

It may not work in every case, but it’s worth a try if you don’t want to purchase more swan plants. If you’re still sceptical, check out what the Monarch Butterfly NZ trust has to say on the subject here: http://www.monarch.org.nz/monarch/2005/08/13/pumpkin/

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