Experiment to investigate the effect of photoperiod on a S, limbata ooth.

[PhilinYuma]

I guess that I should put on record the fact that I am now wintering two ooths out of doors, in close proximity. One, laid last night on a piece of sponge, will be exposed to the normal photoperiod plus incandescent light, a 60 W flood at a range of two feet from before dusk until midnight, and the other, laid on a twig (how considerate!) on Nov 1, exposed to the natural photoperiod only.

I have tried, so far as know how, to make the two setups identical. In my cages, I keep a shotglass full of sand planted with dry grass and a single verticle twig. The Nov 1st ooth was laid on that, and I have cut off most of the sponge from the second ooth and mounted it on a twig, "tail down" with tacky glue (not the usual cyanocrylate which, though often recommended, is pretty toxic stuff).

Such an amateurish setup is very far from bulletproof. I shall have to ensure that the floodlight does not unduly raise the temperature in the vincinity of the first ooth and that it does not cause an abnormally low humidity.

Since desiccation could prevent hatching, and since the humidity is a not supposed to be a variable in this experiment, I shall keep the sand in each shotglass moist even though that will create a micro climate that differs from the surrounding air. The thrd ooth, laid on October 6th will be raised indoors.

One interesting experimental advantage shared by the two outside ooths is that they were laid by the same female within a couple of days of each other, so if they hatch at substantially different times, that too will be worth consideration.

I shall post on this again, if and when I get a hatch or if some disaster strikes, but if anyone can come up with any "doable" way of improving the experiment, I should like to hear from you ASAP.

If anyone else can duplicate the experiment, we will have more data.

 

[rayg]

I hope you can learn something about photoperiodism in ooth diapause. I can't quite believe it is the influencing factor, but thats what experiments are for. What about keeping an ooth in a situation where it will not receive any light while holding temp and humidity constant with the others?

I have S. carolina and if they deposit a few more ooths I will design some kind of similar experiment. I wouldn't be able to duplicate the experiment because I can't leave anything outdoors up here, but there is alot to be learned. This is fun stuff.

Ray

 

[hibiscusmile]

Hummmm, very interesting... It would be a surprise if both ooths since laid so close together hatch at the same time.

 

[sidewinder]

PhilinYuma,

The quality of your experiment depends on the hypothesis you are testing and the variables that you are including in the test. The ideal test only has one variable. I don't know what hypothesis you are testing, but you have several variables.

If you are testing the hypothesis that photoperiod alone controls (or does not control) diapause, the experiment would be better conducted indoors where you could control light exposure, temperature, and humidity. The only difference in the test should the photoperiod. Temperature and humidity would be the same for both oothecae. One oothecae would be exposed to an appropriately short photoperiod and the other would be exposed to an appropriately long photoperiod. Day length at Summer Solstice in Tuscon is 14:15 while at Winter Solstice it is 10:02. So exposing one ootheca to 15 hours of daylight per day and the other to 10 hours of daylight per day would be logical. A humidity level of about 50% would make sense that is the morning humidity level often seen in Yuma and it would keep both ootheca from drying out. The average high temperature that ootheca are incubated at is right at 80° so that would be a good temperature at which to keep the oothecae.

Both oothecae would need to be freshly laid so they would not be exposed to environmental cues for any length of time already. The tests would not need to start on the same day as long a freshly laid oothecae were used.

That's how I would do it anyway....

Scott

 

[PhilinYuma]

PhilinYuma,

The quality of your experiment depends on the hypothesis you are testing and the variables that you are including in the test. The ideal test only has one variable. I don't know what hypothesis you are testing, but you have several variables.

I should have been more clear.

It appears to be agreed among the members of this board, that the ootheca of the bordered mantis, Stegmomantis limbata undergoes a facultative diapause during the winter after or during which it is laid. This is supported by the experience of members who have raised it and by field experiments conducted on this species in an outdoor insectiary maintained by the Bureau of Entomology between 1931 and 1934 and cited elsewhere on this board. The trigger that terminates this diapause has been traditionally believed to be a drop in temperature, and in at least three areas in which this insect has been observed, in Texas, Arizona and California, experience winter temperatures (December, January) that are at least intermittently around 32F, several degrees below that used by breeders of captive specimens, who place the ootheca in a refrigerator with a temperature of around 35-36F. I am aware that some members may not employ this practice, but it certainly obtains in nature and will not be considered as an independent variable.

In analogy with some other diapausal insects of different families, such as the silk moth and flesh fly, it has been suggested that southwestern U.S. mantises, such as S. limbata may have their diapause terminated by a reduction in photoperiod rather than by, or in conjunction with a drop in temperature. My preliminary experiment tests the converse of that hypothesis, and is designed to demonstrate that oothecae will hatch even when there is no reduction in photoperiod. This is much more persuasively demonstrated than by attempting to show that ootheca not exposed to a reduction in photoperiod do not hatch, since there are a number of uncontrolled factors that might prevent hatching.

Although an experiment using regression analysis with an error term as one of the variables would be more persuasive, my experiment employs only one independent and one dependent variable. This is because n=2 and because in this first year, my concern is with experimental design and not, obviously, with statistical analysis.

In this experiment, the independent variable is the photoperiod during the winter and the dependent variable the hatching of nymphs by May. The number of nymphs hatched under one set of experimental conditions or a delay in hatching may become issues later, but are not now.

In order to create the most natural conditions, and to accomodate (eliminate) temperature as an independent variable, the two ooths, laid within three and one day prior to the beginning of the experiment were placed outside. Both were attached to a twig, one naturally, one glued, and both in their normal orienation of "tail down".

Both will experience the natural drop in temperature -- which would not occur if they were kept indoors -- but one will experience a natural photoperiod, while the other will be exposed to a photoperiod that will begin with sunrise, but be extended to midnight by the use of artificial light. This period, although it will shorten slightly until December 22nd, with a later sunrise, will still exceed the photoperiod that obtains when the eggs are laid.

My concern is much less with the analytical model than with the experiment's design. For example, it has just occured to me that exposed as they are, the ooths are very likely to be eaten by the furkin pigeons if I dont cover them. I shall use inverted egg crates. They are free, furkin pigeon resistant, and will not affect the photoperiod any more than, say, long grass.

I hope that that clarifies the experiment.

Hibiscusmile: You made a very interesting observation, based, I am sure, on your experience, that the two ooths, laid a few days apart, will not hatch around the same time. In that case, I would imagine that that the second one will hatch rather later. Is that correct?

 

[sidewinder]

PhilinYuma,

I have some comments on your hypothesis:

1. The silkworm (Bombyx mori) diapause is a unique facultative/obligate blend and was referenced because the article cited discussed it in detail. Also, I thought the mechanism was intriguing, but not relevant to Stagmomantis limbata.

2. Where was it suggested that the diapause could be terminated by by a reduction in photoperiod? Did I miss that somewhere? It's a possibility, but in most temperate species, diapause, facultative and obligate, is broken by an extended chilling period. What has been suggested (by me) is that diapause is induced by a photoperiod threshold often called the "critical day length". If the photoperiod is shorter than the critical day length at the right time in the prediapause period, the threshold has been crossed and diapause will be entered at the appropriate time in the embryo's development.

3. If you keep the oothecae, both laid in early November, outside subject to normal Fall and Winter temperatures during the incubation period, neither one could hatch until sometime in the spring. The temperatures aren't warm enough long enough to properly incubate the eggs in the ootheca for which you are providing an extended photoperiod. If photoperiod alone is what induces diapause, the embryos won't survive because there will be no arrest in development. Does your lamp emulate sunlight? I ask this because the extraretinal photoreceptors in insects typically respond to blue light. If there is not enough blue light, it may be the same as having no light at all. Standard incandescent bulbs don't put out much blue light.

4. What does this mean?: "This is much more persuasively demonstrated than by attempting to show that ootheca not exposed to a reduction in photoperiod do not hatch, since there are a number of uncontrolled factors that might prevent hatching." That sounds like you are referring to breaking diapause again. Are you?

5. It seems from your text that you are more interested in what breaks diapause than what induces it. Is this the case? Because that isn't what has been discussed throughout the "Ooths outside hatch in fall in So. Cal?" thread.

6. The disadvantage your experiment has over what I suggested previously in this thread is that you have to wait until the end of spring to know the results. My experiment would be over in no more than 8 weeks. It could be repeated two maybe three times before your experiment ended.

Scott

 

[Rick]

I don't think it is going to make any differnce. I have kept ooths in a pitch dark room and they still hatched on time.

 

[PhilinYuma]

I don't think it is going to make any differnce. I have kept ooths in a pitch dark room and they still hatched on time.

Me neither! My indoor specimen is in the dark. But we shall see!

 

[PhilinYuma]

Salomis:

"I have some comments on your hypothesis:"

I had no doubt that you would!

"1. The silkworm (Bombyx mori) diapause is a unique facultative/obligate blend and was referenced because the article cited discussed it in detail. Also, I thought the mechanism was intriguing, but not relevant to Stagmomantis limbata."

My bad. Since this is th Mantid Forum and we were discuusing factors that might affect the hatching and survival of the bordered mantid in S. Cal, I wrongly supposed that you were positing a possible analogy.

2. "... What has been suggested (by me) is that diapause is induced by a photoperiod threshold often called the "critical day length". If the photoperiod is shorter than the critical day length at the right time in the prediapause period, the threshold has been crossed and diapause will be entered at the appropriate time in the embryo's development."

Sounds good.

3. "If you keep the oothecae, both laid in early November, outside subject to normal Fall and Winter temperatures during the incubation period, neither one could hatch until sometime in the spring. The temperatures aren't warm enough long enough to properly incubate the eggs in the ootheca for which you are providing an extended photoperiod. If photoperiod alone is what induces diapause, the embryos won't survive because there will be no arrest in development."

True enough, though failure of the eggs to hatch could be due to many causes, such as an infertile ooth. This is why a hypothesis that is tested by the eggs' hatching is experimentally more persuasive.

"Does your lamp emulate sunlight? I ask this because the extraretinal photoreceptors in insects typically respond to blue light. If there is not enough blue light, it may be the same as having no light at all. Standard incandescent bulbs don't put out much blue light."

You bet! It's one of those daylight thingies. Would I put my babies' extraretinal photoreceptors at risk? I don't think so!

4. "What does this mean?: "This is much more persuasively demonstrated than by attempting to show that ootheca not exposed to a reduction in photoperiod do not hatch, since there are a number of uncontrolled factors that might prevent hatching." That sounds like you are referring to breaking diapause again. Are you?"

No, see above. By eliminating a reduction in photoperiod from laying to hatching, I can say, however tentatively, that if the eggs hatch, reduction of photoperiod is not a factor, either coming in or going out.

5. "It seems from your text that you are more interested in what breaks diapause than what induces it. Is this the case? Because that isn't what has been discussed throughout the "Ooths outside hatch in fall in So. Cal?" thread."

No.

6. "The disadvantage your experiment has over what I suggested previously in this thread is that you have to wait until the end of spring to know the results. My experiment would be over in no more than 8 weeks. It could be repeated two maybe three times before your experiment ended."

Your experiment sounds great! If you can still find a few gravid females, you could try it, and we can compare notes. But if neither of the ooths hatched, would that be due to photoperiod or the articicially high, indoor temperature (rhetorical question)? Remember, I only want to see what will happen under natural conditions, with one controlled variable.

Also, I should point out that my primary interest in being on this forum is to learn how best to maintain and breed mantises, and any experiment that I may conduct is performed toward that end. I know of no better source of mantis lore than this board, and if I can give back anything that might help people's understanding of their favorite critters, then I am happy.

If I successfully raise a few southwestern species outdoors, I shall have a care free method of maintaining them and will pass on the information. I value a discussion of the significance of photoperiod to mantises only so far as it may affect ooth care. I don't suppose for a moment that it will affect diapause, facultative, obligate, by induction or termination, but it is easily set up (though I had to buy a daylight bulb at Walmart) and easily maintained. Also, contol of the photoperiod may have results that we haven't posited, like increased or decreased hatch, etc. Now, if I can just keep those furkin pigeons aweay from the ooths...

 

[sidewinder]

I don't think it is going to make any differnce. I have kept ooths in a pitch dark room and they still hatched on time.

Rick,

What species oothecae did you keep in the dark?

Scott

 

[MantidLord]

I've had Europeans and Chinese hatch in a pitch black garage with no heating or light (hintitch black). Only a couple survived, because I forgot about them, and they starved and froze, but they still hatched. This was in April, even though it was cold in the garage, they still hatched on time.

 

[Rick]

Rick,What species oothecae did you keep in the dark?

Scott

I don't keep any in the dark intentionally however I used to use a small, pitch black, water heater "closet" as a warm place to keep incubation ooths. Never saw a difference between those and ones I kept out in the light with a normal day/night cycle.

 

[sidewinder]

Rick,

But what species?

Scott

 

[Peter Clausen]

I have two S. limbata oothecae. I collected two females in SE Arizona this summer and bred them with males that I also collected. Each female has now laid her first ootheca.

Female 1, Ootheca 1: was laid on or around October 10th. After a few days indoors at an average of 70 degress, I glue-gunned it to the side of a deli-cup (as I do all my oothecae) and put it outside (Portland, Oregon). It's under an eve of my home so it gets limited exposure to light.

Female 2, Ootheca 1: was laid while I was out of town around on or around October 24th. I glued it to the inside of the same deli-cup container within a week of it being laid.

If anybody has suggestions for anything I might do at this (late?) point to contribute to the experiment here, please feel free to make suggestions. I am expecting additional oothecae out of both of these females, so I can participate from day 1 on them.

My intention was to leave them outdoors for about 6-8 weeks and then bring them in. At the bottom of the 32 ounce deli-cup there is an inch or so of moist coconut fiber substrate. The top of the container is punched out, but has the familiar poly-fiber lining over the holes. Because of our constant rain here, I didn't plan on spraying it again until I brought it indoors to warm them up after what I believed to be a sufficient diapause.

 

[hibiscusmile]

I'm outta this one :mellow:

 

[PhilinYuma]

"I have two S. limbata oothecae. I collected two females in SE Arizona this summer and bred them with males that I also collected. Each female has now laid her first ootheca.

If anybody has suggestions for anything I might do at this (late?) point to contribute to the experiment here, please feel free to make suggestions. I am expecting additional oothecae out of both of these females, so I can participate from day 1 on them."

Now there's a generous offer, particularly since you are a breeder! Here's a suggestion that might prove interesting to members and benefit you as well. If you were to take some freshly laid ooths and immediately expose them to an enviroment with a steady temperature of 80F and, say, 18 hours of artificial light (don't forget those daylight bulbs!) it seems that you would avoid all of Christian's criteria for diapause, and your ooths would hatch early. The hatch/survival rate might be reduced compared with naturally incubated ooths, but the survivors might produce offspring that would be more used to this unnatural state of affairs.

If it worked, it would mean that you would soon have a strain of S. limbata (S. limbata peterii) that would regularly produce nymphs in winter and become adults in the spring, when everyone else is waiting for their ooths to hatch.

It might be that other members have already done this, either accidentally or deliberately, and it would be good to know the outcome.

 

[sidewinder]

If you were to take some freshly laid ooths and immediately expose them to an enviroment with a steady temperature of 80F and, say, 18 hours of artificial light (don't forget those daylight bulbs!) it seems that you would avoid all of Christian's criteria for diapause, and your ooths would hatch early. The hatch/survival rate might be reduced compared with naturally incubated ooths, but the survivors might produce offspring that would be more used to this unnatural state of affairs.If it worked, it would mean that you would soon have a strain of S. limbata (S. limbata peterii) that would regularly produce nymphs in winter and become adults in the spring, when everyone else is waiting for their ooths to hatch.

It might be that other members have already done this, either accidentally or deliberately, and it would be good to know the outcome.

There is a member here, jplelito, that is working on his PhD in entomology. He told me that in his lab, he has two environmental regulated chambers that he keeps Stagmomantis limbata oothecae in and they hatch in approximately 5-7 weeks after being laid. The temperature in both chambers is 80 to 85 degrees F. The light cycle he uses is 16 hours of light, 8 hours of dark in one chamber and 14 hours of light, 10 hours of dark in another. Both seem to work about the same. He has been doing this continuously for over three years.

Scott

 

[sidewinder]

jplelito's data tells us that Stagmomantis limbata does not have an obligatory diapause. So that gives us more data to work from. What it does not tell us is what environmental cues are evaluated by S. limbata embryos to determine if diapause will be entered.

I wish I had a couple of those chambers....

Scott

 

[PhilinYuma]

There is a member here, jplelito, that is working on his PhD in entomology. He told me that in his lab, he has two environmental regulated chambers that he keeps Stagmomantis limbata oothecae in and they hatch in approximately 5-7 weeks after being laid. The temperature in both chambers is 80 to 85 degrees F. The light cycle he uses is 16 hours of light, 8 hours of dark in one chamber and 14 hours of light, 10 hours of dark in another. Both seem to work about the same. He has been doing this continuously for over three years.Scott

Well are we on the bleeding edge or not, Scott?

I don't have a chamber with automated temperature and light control (I wonder if it grows its own food, too?), but I have set up a container that will maintain those parameters pretty consistently. Now all I need is for my female to lay one more ooth!

I'll keep you all posted.