Sexing instars

Ralph_moore84

Arachnobaron
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Sep 6, 2009
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What's the earliest instar for sexing scorpions?Other than Centruroides.I seen an add that had the sex listed 2.2,they were second instar.Can you possibly tell at that size?
 

Roy

Arachnosquire
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Apr 8, 2010
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I wonder if second instar is too early for pectine counts.
 

RyoKenzaki

Arachnoknight
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Aug 17, 2008
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For genus parabuthus, its fairly easy to determine the sex if u could have a clear view of its pectines
Female have very big 1st pair of pectines tooth, which make it very obvious
 

Michiel

Arachnoking
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Species of most genera do not express sexual dimorphism at that age. Normally only adults show sexual dimorphism. Species of genera like Parabuthus and Grosphus are an exception, because they have modified lammelae or pectinal teeth in females.

So, no, besides these exceptions (and possibly more exceptions) second instars cannot be sexed.
 

psychofox

Arachnoknight
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Does the number of pectinal teeth change throughout a specimen's development? If they don't, why shouldn't it be possible to sex a specimen by the number of pectinal teeth already from second instar? Naturally provided that it is a species that can be sexed this way, like an Androctonus or Hottentotta species.

Parabuthus, Grosphus and the related genus Uroplectes can all, with some exceptions (P. villosus not being one), be sexed by a modified lamellae as mentioned.
 

Ralph_moore84

Arachnobaron
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I think it might be interesting to look at,and compare the pectines of different species 2i until adult hood.See when if any changes in them happen,and document at what instar it happened.What would be the best way of seeing the pectine teeth of something that small?It just got me curious after seeing that ad.Thanks for all the replies.
 

Michiel

Arachnoking
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I think it might be interesting to look at,and compare the pectines of different species 2i until adult hood.See when if any changes in them happen,and document at what instar it happened.What would be the best way of seeing the pectine teeth of something that small?It just got me curious after seeing that ad.Thanks for all the replies.

Buy a hobby stereomicroscope.
 

Ralph_moore84

Arachnobaron
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Sep 6, 2009
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Considering I have more time to do things now.Since I'm not working 7 days a week 12 hrs a day.I'll definately have to get one of those.
 

skinheaddave

SkorpionSkin
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I think it might be interesting to look at,and compare the pectines of different species 2i until adult hood.See when if any changes in them happen,and document at what instar it happened.What would be the best way of seeing the pectine teeth of something that small?It just got me curious after seeing that ad.Thanks for all the replies.
This has been done at least once. Polis and Farley examined the growth of pectines in S.mesaensis over time (it should be noted that the number of teeth is constant, but the length does change with time). Basically it was shown that the rate of growth is more-or-less constant in both sexes when they are young but takes off dramatically in males towards maturity. A stereomicroscope with a reticule would allow you to take all the requisite measures to conduct a similar study on any species you wanted to. Obviously you would need a large number of specimens to make the results meaningful. It would also be important that the identity of the specimens be certain and that they are not all related.

As it relates to sexing instars, those species with a significantly dimorphic pectine count can be done as soon as they are large enough to be examined with whatever degree of magnification you can bring to bear. For many species, however, there is some ambiguity and they may overlap entirely or overlap significantly in the middle of the range. I would also view the published data with at least a little skepticism and allow for maybe +/- 10-15% in the count before you call things for certain. If the maximum for females is listed at 23 and you get one with 24 you can't really be sure.

Speaking of published data, before anyone buys a scope I would suggest they also invest in some literature. The Biology of Scorpions, Polis (1990) is still pretty much required reading for anyone who is going to take things a bit more seriously. Scorpion Biology and Research, Brownell and Polis (2001) covers fewer topics but in a lot more depth. Stockmann and Ythier (2010) continued with that tradition of a more far-reaching summary and would definitely be a must-have. Obviously if you are getting into taxonomy and have access to journals then the Catalogue, Fet et al (2000) is critical. http://www.ntnu.no/ub/scorpion-files/litterature.php shows even more books that are available. In general, those closer to the bottom are either out of date (Scorpions of medical importance) or somewhat specialized (Scorpions of Southern Africa .. well done book, BTW). The books at the top, access to journals and a microscope could get you pretty far.

Cheers,
Dave
 
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