The Influence of Barometric Pressure

[dogpack]

No worries, I'm curious.

 

[Matt Man]

What's the humidity like right now, especially in comparison to the rest of the year?

IMO, it's likely that temperature, pressure, humidity, and even nutrition all might have some influence in triggering a molt, or more precisely, in determining a molting schedule as a tarantula matures.

@AphonopelmaTX , If I remember correctly, you're a bit of a data nerd like me. I'll let you know if I get the system up and running before the end of the year or not.

humidity has been stable mid 60s to low 70s %. Temps fairly stable, Temps 70-78F 21-25C.

my A. bicoloratum molted this weekend. I personally think Ts release a pheromonal trigger, so you can get cascading molts that IMO are more influenced by the pheromonal trigger than by climatic conditions.

people can say my experience doesn't disprove anything, but claiming dropping pressure causes molting and then being presented with data showing the opposite, is typically a theory killer.

 

[Dorifto]

We are not saying it's the only factor that triggers a molt. I basically believe that it's a confluence of factors that triggers them to molt. They could molt outside those parameters? Yes, because it's a physiological need they have, but it's not ideal.

No one ever though why tropical species grow so fast compared to drier species? Maybe the more favorable conditions found after a storm/rain could be a very big reason. Simply the big pressure drop could be an indicative for them for incoming better conditions.

Now being even more hypotheticals, being Ts mostly a presurized body, it's not possible that they could use that external big drop in pressure to move fluids outside more efficiently? It could be a good passive way to lubricate themselves before molting.

 

[l4nsky]

humidity has been stable mid 60s to low 70s %. Temps fairly stable, Temps 70-78F 21-25C.

my A. bicoloratum molted this weekend. I personally think Ts release a pheromonal trigger, so you can get cascading molts that IMO are more influenced by the pheromonal trigger than by climatic conditions.

people can say my experience doesn't disprove anything, but claiming dropping pressure causes molting and then being presented with data showing the opposite, is typically a theory killer.

No, not a theory killer. The data point is just an outlier that needs to be accounted for. Very little is actually known and set in stone in regards to this topic, so there are quite a few theories that could potentially be valid.

Personally though, I think that with what we know about reproduction in the wild, the timing of male maturity in line with certain seasons, and the timing of eggsacks that have been found in situ that weather patterns are the trigger for more mature specimens. It's possible that with species like A. hentzi, where you have mass male maturity and 'migrations', you might also have pheromonal triggers for timing purposes. I think it's quite a stretch though for the answer to be that there is a pheromonal trigger which all species, regardless of the genus/subfamily, will respond to by molting. Just my opinion.

 

[AphonopelmaTX]

No, not a theory killer. The data point is just an outlier that needs to be accounted for. Very little is actually known and set in stone in regards to this topic, so there are quite a few theories that could potentially be valid.

Personally though, I think that with what we know about reproduction in the wild, the timing of male maturity in line with certain seasons, and the timing of eggsacks that have been found in situ that weather patterns are the trigger for more mature specimens. It's possible that with species like A. hentzi, where you have mass male maturity and 'migrations', you might also have pheromonal triggers for timing purposes. I think it's quite a stretch though for the answer to be that there is a pheromonal trigger which all species, regardless of the genus/subfamily, will respond to by molting. Just my opinion.

It is a hormone, not a pheromone, called ecdysone that triggers the process of regeneration leading up to ecdysis (or molting). Backing up a bit, molting is just the point in growth where an arthropod removes its old skin. There are many more processes that occur before and after that event. The hormone ecdysone is present in all invertebrates that molt (crustaceans, insects, arachnids, etc.) and experiments have shown that it is transferable between different types of arthropods. For example, isolating ecdysone from a crab and injecting it into an arachnid will cause the arachnid to undergo ecdysis and vice versa. I can't recall the paper that detailed the experiment proving this, but it can be easily found online.

To be more specific about what this thread is about, we are examining possible environmental triggers for the production of ecdysone, and not ecdysis specifically. As mentioned, it is well known that tarantulas in temperate climates have distinct mating periods that correspond to the seasons. In order for that to be possible, the ultimate molt has to occur prior to the mating season therefore ecdysis corresponds to the seasons as well. What we don't know is if there are environmental triggers that kick off the production of ecdysone, and if so, what they are.

 

[Matt Man]

No, not a theory killer. The data point is just an outlier that needs to be accounted for. Very little is actually known and set in stone in regards to this topic, so there are quite a few theories that could potentially be valid.

Personally though, I think that with what we know about reproduction in the wild, the timing of male maturity in line with certain seasons, and the timing of eggsacks that have been found in situ that weather patterns are the trigger for more mature specimens. It's possible that with species like A. hentzi, where you have mass male maturity and 'migrations', you might also have pheromonal triggers for timing purposes. I think it's quite a stretch though for the answer to be that there is a pheromonal trigger which all species, regardless of the genus/subfamily, will respond to by molting. Just my opinion.

yes, and breeding cycles for certain species come after rainy periods. But male maturity is all over the place in many cases. In So Cal our 2 main specimens A. eutylenum and A. steindachneri have different breeding periods (summer for steindachneri and fall for eutylenum) even though they can both be found in close proximity. So why the different seasons? Probably evolutionary, so they don't conflict. Both seasons also tend to be high pressure, warm, and dry. A hentzi is a fall mate as well, so is A. jonnycashi. This conflicts with say C. cyaneopubescens which mates after monsoon season. So there is no standard across a single genus let alone and entire Phyla.

It isn't a single data point, at this point, it is now half a dozen and counting. So agreed, nothing is in stone, but if dropping pressure was a key trigger, I shouldn't be seeing this number of molts under steady / high pressure. It could be a factor, but these data points indicate there must be something stronger, because you wouldn't have so many outliers if it were the key ingredient. Perhaps you are having similar molt cascades with the first just falling during that period, or are they spread out over multiples?

 

[Dorifto]

So why the different seasons? Probably evolutionary, so they don't conflict. Both seasons also tend to be high pressure, warm, and dry. A hentzi is a fall mate as well, so is A. jonnycashi. This conflicts with say C. cyaneopubescens which mates after monsoon season. So there is no standard across a single genus let alone and entire Phyla

Here I'd take into the account the time they take to lay the eggsac after mating and the hatching time. It could be interesting to see if it matches any specific seasonal conditions

I shouldn't be seeing this number of molts under steady / high pressure

We are talking about a drop in pressure, not specifically low pressure conditions. You can have drops in pressure even in high pressure climatic conditions.

 

[l4nsky]

It is a hormone, not a pheromone, called ecdysone that triggers the process of regeneration leading up to ecdysis (or molting). Backing up a bit, molting is just the point in growth where an arthropod removes its old skin. There are many more processes that occur before and after that event. The hormone ecdysone is present in all invertebrates that molt (crustaceans, insects, arachnids, etc.) and experiments have shown that it is transferable between different types of arthropods. For example, isolating ecdysone from a crab and injecting it into an arachnid will cause the arachnid to undergo ecdysis and vice versa. I can't recall the paper that detailed the experiment proving this, but it can be easily found online.

To be more specific about what this thread is about, we are examining possible environmental triggers for the production of ecdysone, and not ecdysis specifically. As mentioned, it is well known that tarantulas in temperate climates have distinct mating periods that correspond to the seasons. In order for that to be possible, the ultimate molt has to occur prior to the mating season therefore ecdysis corresponds to the seasons as well. What we don't know is if there are environmental triggers that kick off the production of ecdysone, and if so, what they are.

Correct as usual. The entire molting process, like most biological processes, is hormone controlled. Hormones are internal chemical triggers that effect the organism that produced them. Pheromones are externally secreted chemical triggers that effect other specimens, usually of the same species, and can be used to communicate. The question in this case is what triggers the trigger, so to say. The idea of a mass, interspecies pheromonal trigger is what I'm questioning. I can see how multiple species/genus from a common descendent could all retain and use a single hormone for an internal biological process like molting (the "if-it's-broke-don't-fix-it theory"). I can't see how multiple species/genus from all around the world with a common descendent would all retain and use a single pheromone for communication. To me, that's akin to myself and a person only fluent in Mandarin having a complete and productive discussion because we're both descended from the same ancestor, even though I don't speak Mandarin. It's possible, but IMO highly unlikely. Atleast one of us is just going to be confused.

yes, and breeding cycles for certain species come after rainy periods. But male maturity is all over the place in many cases. In So Cal our 2 main specimens A. eutylenum and A. steindachneri have different breeding periods (summer for steindachneri and fall for eutylenum) even though they can both be found in close proximity. So why the different seasons? Probably evolutionary, so they don't conflict. Both seasons also tend to be high pressure, warm, and dry. A hentzi is a fall mate as well, so is A. jonnycashi. This conflicts with say C. cyaneopubescens which mates after monsoon season. So there is no standard across a single genus let alone and entire Phyla.

It isn't a single data point, at this point, it is now half a dozen and counting. So agreed, nothing is in stone, but if dropping pressure was a key trigger, I shouldn't be seeing this number of molts under steady / high pressure. It could be a factor, but these data points indicate there must be something stronger, because you wouldn't have so many outliers if it were the key ingredient. Perhaps you are having similar molt cascades with the first just falling during that period, or are they spread out over multiples?

I think we're both in agreement that barometric pressure isn't the "key ingredient" in triggering a molt . As previously stated, I think it's a highly complex equation with multiple factors. I think as younger animals, it's entirely dependent on the present limiting factor for that specimen in that environment (not enough food, not enough time to complete the internal metamorphosis needed for a molt, not enough moisture, too cold, etc). For older specimens and mature animals, I think it's almost entirely related to the annual weather patterns that they evolved with, which have been transposed and matched up as best as possible to the annual weather patterns of the environment they're raised in.

 

[Matt Man]

We are talking about a drop in pressure, not specifically low pressure conditions. You can have drops in pressure even in high pressure climatic conditions.

but the pressure here has been steady within a single mB the entire time so 29 and change to 30 and change subtly moving about over the last few weeks. No notable drops in pressure. We've had a couple weeks of what most folks would call 'ideal condistions'

It is a hormone, not a pheromone, called ecdysone that triggers the process of regeneration leading up to ecdysis (or molting). Backing up a bit, molting is just the point in growth where an arthropod removes its old skin. There are many more processes that occur before and after that event. The hormone ecdysone is present in all invertebrates that molt (crustaceans, insects, arachnids, etc.) and experiments have shown that it is transferable between different types of arthropods. For example, isolating ecdysone from a crab and injecting it into an arachnid will cause the arachnid to undergo ecdysis and vice versa. I can't recall the paper that detailed the experiment proving this, but it can be easily found online.

To be more specific about what this thread is about, we are examining possible environmental triggers for the production of ecdysone, and not ecdysis specifically. As mentioned, it is well known that tarantulas in temperate climates have distinct mating periods that correspond to the seasons. In order for that to be possible, the ultimate molt has to occur prior to the mating season therefore ecdysis corresponds to the seasons as well. What we don't know is if there are environmental triggers that kick off the production of ecdysone, and if so, what they are.

No, I am talking about a pheromonal release, something on the breeze. Yes, induced by hormones, but an actual pheromone other Ts pick up on. T's can't really pick up on either Ts hormones, all the more so through glass. I am thinking they are picking up something being released, similar to scents being used during mating

 

[Dorifto]

but the pressure here has been steady within a single mB the entire time so 29 and change to 30

A single digit in hg it's a huge drop in mbar. 29hg=982'05 mbar and 30 Hg=1015'92 mBar, so a 33'87 mbar difference.

Usually a good day stays around 1013-1020 mbar.

 

[Matt Man]

A single digit in hg it's a huge drop in mbar. 29hg=982'05 mbar and 30 Hg=1015'92 mBar, so a 33'87 mbar difference.
Usually a good day stays around 1013-1020 mbar.

but we're talking less than a single digit, we're talking fractions tons of a digit. Perhaps I didn't word it correct. High 29s to low 30s meaning 29.88 to 30.02

this will show you how stable we are this week and this is how it has been for the last 3 weeks. Most shifts are less than .06

Atmospheric pressure in San Diego with trend indicator

Know the current atmospheric pressure in San Diego and the pressure variations for the next few days

tides4fishing.com

June Barometer, entire Month 29.8 (low) 30 (high)

San Diego Weather at Mission Trails, CA - Daily / Monthly Weather History From This Station

Personal weather station.

wx4mt.com

Humidity typically 62-68% with a few days when mild Santa Anas blew, and it dropped to about 55%

 

[Dorifto]

but we're talking less than a single digit, we're talking fractions tons of a digit. Perhaps I didn't word it correct. High 29s to low 30s meaning 29.88 to 30.02

this will show you how stable we are this week and this is how it has been for the last 3 weeks. Most shifts are less than .06

Atmospheric pressure in San Diego with trend indicator

Know the current atmospheric pressure in San Diego and the pressure variations for the next few days

tides4fishing.com

That's another thing, now makes more sense.

 

[Matt Man]

That's another thing, now makes more sense.

Sorry I was so vague

 

[Matt Man]

2 more molts (Adult A. geniculata and Juvenile B. hamorri ). At the show in Anaheim, same Barometric Pressure we had a ton of molts in both Tarantulas and Scorpions. Steady 29.98 +/-

 

[Dorifto]

2 more molts (Adult A. geniculata and Juvenile B. hamorri ). At the show in Anaheim, same Barometric Pressure we had a ton of molts in both Tarantulas and Scorpions. Steady 29.98 +/-

Change in humidity? Not only atmospheric but enclosures too (added moisture)

 

[Matt Man]

Change in humidity? Not only atmospheric but enclosures too (added moisture)

not to my knowledge. Humidity has been pretty consistent. A tad more @ my house than @ Anaheim as I live nearer the Ocean. Higher AM and PM due to the Marine Layer. Heats up and dries out during the day, so it goes from say mid 60%s to mid 7o%s
In SoCal this time of year our weather is pretty stable, and nice. Why people come here on vacation

 

[Frogdaddy]

Sorry to burst everyone's bubble, but you can't prove or disprove a correlation between atmospheric pressure and molting without a barometer in the room your tarantulas are in. Molting usually corresponds to changes in seasons which include changes in temperature and/ or rain/ humidity. I'm not saying atmospheric pressure alone isn't a trigger, but you can't assume it is without keeping all other variables at a constant.

Since I don't have a barometer myself to test for changes in atmospheric pressure, I have been able to use my indoor/ outdoor thermometers in my tarantula room to confirm a correlation between changes in temperature as the seasons change here in Texas and when my tarantulas molt. This observation allows me to predict which tarantulas are due for a molt with a reasonable amount of accuracy. Not all of my tarantulas molt on a seasonal schedule, but the majority do. The tarantulas in my collection that have a predictable molting schedule include species of Aphonopelma and Brachypelma both adults and spiderlings. The tarantulas that do not have a predictable molting schedule include species of Grammostola, Euathlus, and Theraphosa. It is interesting to note that the species with predictable molting schedules occur naturally in the northern hemisphere and the ones that do not in the southern hemisphere.

With the tarantulas in my collection with a predictable molting schedule, there are two phases: spring/ early summer and late summer/ fall. When the temperature in my spider room start rising to a temperature of about 80 F in late May to June, the "spring group" stops eating and eventually molts. The "fall group" stops eating and molts when the temperature starts falling from about 85 F to about 70 F. There is no molting activity during the hottest (July-August) and coldest months (January-February) when temperatures in my spider room are steady at around 85 F and 60 F (give or take a few degrees F) respectively.

I also have a thermo-hygrometer which reads temperature and humidity in the same device. I have not seen any correlation between changes in humidity and molting activity, but it is a variable I have not tested for specifically so can't rule it out as a factor. Keeping temperature at a constant to test for only humidity is practically impossible in my situation. Humidity doesn't appear to be a factor in triggering a molting cycle since I never make any attempt to add water to the soil in my tarantula enclosures or let it dry out.

I used to have a weather station from Davis Instruments. It was very accurate, nearly scientific grade equipment. It would log all weather conditions every 4 minutes and keep the log for an entire year.
It would be an interesting experiment to look at the log and match up molting times and see if there is an actual correlation. It might take a few years to get enough data but you could examine all atmospheric conditions at the time of molting.

 

[darkness975]

I can't speak for molting but mine seem to get more agitated before a major storm.

 

[Dorifto]

I can't speak for molting but mine seem to get more agitated before a major storm.

I can corroborate this. They can certainly feel disturbances in climatic conditions. My guess is that they can feel pressure changes, as this comes first, before the storm, along with other parameters.

In my case the pulchra tends to close it's burrow when a severe storm is coming. The geniculata in the other hand climbs the log.

 

[Dorifto]

This week we will have some nice storms, atmospheric pressure range from 1008 to 1020, temps ranging from 31°C max to 18°C low and a RH ranging from 70s to 90s.

The only thing I'll do it's to add more moisture than usual. I've been outside from almost a month and the substrate it's drier than usual. So I'd use the stormy conditions to increase the moisture level. Both Ts acting normally, both took a big hissing roach each yesterday. Pulcha on her burrow like she uses to with big storms and the geniculata outside as always, she didn't climb the log for now.

Let's see something happens!!