Roaches shrinking in size

[Scythemantis]

I keep cockroaches as pets, not feeders, and find a lot of nice big ones locally...but once I get even the largest wild-caught roaches to breed, the captive generation is noticeably smaller. Is this an issue of space, heat, food or all of the above?

I give a high protein diet, but perhaps they could use more fat as well?

 

[ZephAmp]

I have been told by a professor at Purdue university that protein pretty much determines how big of a roach you get. However, I believe this was extrapolated from experiments where two groups of roaches were fed two different diets (one with protein, one with little). In the wild, seasonal conditions dictate roach growth. Most likely, you will find larger wild roaches than captive stock when the wild stock has been exposed to seasonal cooling, then heating, like a spring-summer sort of thing.

 

[Athelas]

I'm curious how you are setting up your mating crosses. Are you capturing and breeding together the largest individuals, or are you releasing large recently captured individuals into your captive population?

In the former case, there could certainly be the environmental affects on body size described by ZephAmp, but potentially there could be some genetic constraints as well (i.e. if the two large individuals are large because of effects of homozygosity at different loci, then mating would produce heterozygosity at those loci and potentially diminish the extreme phenotypes produced by the parental genotypes).

In the latter case, perhaps the extreme phenotype is regressing on the average when the large individual mates with smaller individuals in the captive population? In any population the most extreme individual can only mate with less extremes.

Just a few thoughts at least!

Scott
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[bugmankeith]

I have kept blaberus giganteus, and craniifer and my nymphs I purchased ahve always gotten very large, I always offer them protein in their diet. Cat or dog kibble when young sprayed with water to make it easier to eat, and when my roaches get old (their pets) and cant chew as well I put a small chunk of turkey or beef baby food in a shallow dish and they eat that. I also feed fruit sich as apples and bananas, and vegetables like romaine lettuce and carrots, as well as raw potato and moist white bread.

I have a 3 year old craniifer alive, meaning it;s been an adult for 3 years, so it must be something I did right. I never knew they lived so long! All books I read say 1 year max.

 

[Galapoheros]

I feel like I remember somebody on the AB saying that some species start to release a hormone(something like that) when it gets crowded that makes them reach a smaller size when they are adults, that it's usually not genetic(?), something to double check of course, I don't really know.