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Why do dead House crickets (Acheta domesticus) smell so bad, but dead Banded crickets (Gryllodes sigillatus) barely smell at all?
Hi JButera, - My guess, without real experience with your issue, is that the odors are
essentially derived from dead female crickets. If correct in my assumption what you are smelling is the odors specific mating males have aggregated on the female.
A mated female gets a uniquely chemical profiled scent from each male who has mated. It serves as a signal to other males there is competition from other suitors' sperm.
The next male to mate will then, depending on the number of different predecessors' chemical markers, will then adjust his own allocation of internal resources dedicated to production of seminal fluid. This results in the new male ejaculating less sperm in cases where the female has odor signatures of more prior mating.
Where the difference you describe comes into this paradigm is that Gryllodes sigillatus males "guard" their mated female more so than Acheta domesticus. A visible male hovering near a mated female makes it less neccessary for the herd males to create a strong odor dynamic; whereas if there is less obvious "guarding"
by a male then odor traces becomes more significant.
To be more specific, it is the number of different male signature odors on the female that a prospective male registers for adjusting how many resources he will
dedicate to mating with that female. However, I do not know exactly how many seperate males' odor signatures either of your kinds of make crickets can register - although in some other cricket breeds it is over 10 different males' odor.
So, the male interested in mating is not responding to the total amount of prior mated males' chemical signature odor - but rather how many left those odors. Our nose, on the other hand, is probably registering the amount of odor on the female.
And, then too, the total amount of odor on mated female Gryllodes sigillatus is less than is naturally found on Acheta domesticus.
I also venture that since that male Gryllodes sigillatus "guards" it's female more that those males do not need to expend resources generating an odor that is as strong as an Acheta domesticus male. Part of that could mean the chemical components of one variety of crickets may degrade faster than the other kind of crickets needs to be.
@JButera - are the conditions identical with your G. sigillatus and A. domesticus? you could have an environmental factor that caused one to putrefy and the other to desiccate post mortem?
Thanks gringojay, would you be able to cite any sources so I can look into this a bit further?
Andrew, yes, same conditions.
Correction: For both Acheta domestics & Gryllodes sigillatus crickets will produce more sperm ((not "less" as stated in end sentence of 3rd paragraph 4 comments above)) in relation to there being prior males' having mated with the female.
However, this sperm allocation pattern is not always the case for every kind of cricket or insect. It is for the cited crickets based on Gage & Barnard's (1996) "Male crickets increase sperm number in relation to competition and female size", originally published in the journal Behavioral Ecology & Sociobiology, Vol. 38
The authors reported that for Acheta domesticus the male needs only 20 seconds to mobilize sperm for the newly forming spermato-phore & 6-8 minutes for that new spermato-phore to start to form; which ends up amounting to this cricket taking 45-136 minutes before it can inseminate again. In contrast for Gryllodes sigillatus the male needs about 180 minutes to complete all the steps involved before it can inseminate again.
More of a difference is that G.sigillatus takes the process further than forming a functional spermato-phore & transfers sperm this way during copulation in a spermato-phylax. Furthermore, G. sigillatus is recognized as one cricket that "guards" the female after mating.
In earlier comment I made no mention of the fact the female also gets her signature chemical on the male(s) who she has mated with. These compounds, technically referred to as cuticular hydro-carbons, are also likely to contribute to the dead crickets residual odor.
Hi JButera, - I am assuming you are looking for sources about "guarding" behavior & male/female odor compounds (cuticular hydro-carbons).
Bateman & MacFadyen's (1999) "Mate guarding in the cricket Gryllodes sigillatus: influence of multiple potential partners", originally published in journal Ethology, Vol. 105(11) is an early work which 1st proposed "... mate-guarding period ... influenced by the number of other potential partners ...." Let me know if you were asking for more about "guarding", there are many studies.
F. Ingleby's (2015) "Insect Cuticular Hydrocarbons as dynamic traits in sexual communication", originally published in journal Insects, vol. 6(3) is available on-line as free full text. This can serve as a general introduction which notes that these odor chemicals can exhibit "... changes in ... expression ... within ... short timeframes & in response to ... social environment ... (so that) ... sexual selection & ... mate competition will vary with exposure to different individuals and sex ratios ...." Let me know if you were asking for more about odor chemicals, there are many studies of this as well.
Thanks again, and yes I'm more interested about the odor dead crickets give off.
Hi JButera, - I estimate cricket odor hydro-carbons are predominately anywhere from 28-58% alkanes & 12-23% being methyl-branched alkanes (alkenes seem to be proportionately a lot less) These will have different numbers & orientation of carbon atoms; general categories would have names like tetra-decenol, hexa-decanal, hepta-decane, tri-methyl-penta-decan-2-ol, hepta-decenal, octa-decanal, etc. There are also likely penta-cosane, hexa-cosane, hepta-cosane, otca-cosane, nona-cosane, tria-contane, di-methyl-tria-contane, di-methyl-penta-contane, hexa-tria-contane, etc.
Extrapolating from other insects to crickets would mean that the males synthesize both a greater
number of cuticular hydro-carbons & also generate a greater total amount (mass) of them. Many
of these compounds have low volatility yet rub off more thoroughly than they are readily soluble.
Oxidation (air interaction) does degrade hydro-carbons & liberate odors our nose registers in low ppm concentrations. My surmise is that the other more minor compounds naturally found in cuticular hydro-carbons (alcohols, aldehydes, acids, ketones & un-identified compounds) lose their integrity with the cuticle once the cricket is dead, allowing assorted micro-organisms to deplete (use) these compounds for energy substrates (which a live healthy cricket would otherwise replace as it's life cycle required).
In my scenario, as the cuticle loses these minor compounds that had been alongside the cuticle odor alkane/methly-alkanes oxygen access to them is possile fostering oxidation that
has the side-effect of liberating volatile intermediary molecules our nose registers as un-pleasant. Degradation of hydro-carbons is also going to occur by micro-organisms which can use (re-cycle) the carbon (&/or hydrogen); which also occurs with some insect pathogens that hijack the bug's cuticular hydro-carbons to generate it's (the pathogen) energy &/or intermediate
molecules it can use in some pathway.
Again JButera, - Intact alkanes are not usually very odorous to us because our scent receptors don't bind a lot of the molecules' charged groups; alkanes are stable because they have no partial charges. A dead cricket lets alkanes start to meld with lipids & other components altering what presents itself to our scent receptors.
The alkane of 5 carbon (pentane) & 7 carbon (heptane) smell is likened to starter fluid. A 13 carbon alkane (tridecane) smell is likened to the flower of Kapok bush, a 14 carbon alkane (tetradecane) smell is likened to the sex pheromone of stink bugs & a 15 carbon alkane (petradecane) smell is likened to tamarind.
For another odor compound example a 5 carbon ketone (pent-2-one) smell is likened to the blend of the odors of banana with blue cheese. A ketone reacting with an ether (1 oxygen in middle of carbon chain) molecule can then become an ester (having both 1 oxygen in middle of carbon chain & also 1 oxygen double bonded with a carbon as a carbon-yl). A 2 carbon (ethyl) or 1 carbon (methyl) compounded with a 2 carbon (ethanate) ester smell is likened to glue & an 8 carbon( octyl)-5 carbon (butanoate) ester smell is likened to parsnips.
An alkane is a molecular chain identified by having configurations of 1 carbon bound to 3 hydrogen ("alkyl") via only single bonds ("and"). Microbes that secrete enzymes of alkane oxygen-ase work to get a portion of the alkane carbon/hydrogen into the form of an alcohol that is then oxidized to an aldehyde (an al-de-hyde is alcohol minus a hydrogen), which in turn can be converted into fatty acid(s) whose molecular chain (aliphatic chain) can be used to perform energy production in the microbes' beta-oxidation pathway.
Microbial alkane re-purposing is even better when there is a good supply of nitrogen (& phosphorus), which the dead cricket can provide; if there are nitrogen NH2 containing compounds formed these start to give "stinky" odors. There are also micro-organisms that secrete hydroxyl-ase enzyme(s) which can also attack the cuticular alkane.
Edit: Last word in parenthesis of 1st sentence in 4th paragraph of comment immediately above should read "ane" ((not "and", which was auto-filled by computer)).
I'll have to read that a few times before it sinks in. Thanks again.