Convergent Evolution of Viviparity in Insects & Beyond

    This ScienceDirect article discusses the genome sequencing of D. Punctata, also known as the Pacific Beetle Cockroach. The study which the article discusses focused on several different orders of insects- including Blattodea (Cockroaches), Diptera (Flies), and Hemiptera (True Bugs), and how viviparity evolved independently in each of these orders. In each instance of viviparity, insects have their own specially evolved structures to support this function- such as placenta-like structures, brood sacks which act akin to a uterus... And even the ability to generate something like "milk", in  the instance of the Pacific Beetle Cockroach. These special adaptations to the urogenital system of insects are incredibly important, as otherwise the brood would not be able to receive proper care nor nutrients while within the mother. The development of these special structures rely heavily upon the rate of chitin metabolism- which is a polysaccharide insect exoskeletons are primarily made up of. The article also discusses how the bodies of viviparious insects have certain aspects of their immune system suppressed, so as to decrease the chances of their fetus being rejected. The results of their study suggest that developmental processes strengthen genes when under increasing selection pressure and positive selection.  Their study shows that in general, despite evolving independently several times, the genomic and transcriptional alterations are similar across all instances, be it within mammals, insects, or otherwise. 

    Personally, I find this topic incredibly fascinating. Usually people think of mammals when on the topic of live births, but the fact of the matter is that many other different creatures have the ability to do so. I think that it is interesting that small arthropods such as insects have evolved to be able to give live births, and even further, the adaptations that their bodies have, ie brood sacks and milk production, are even more incredible. Additionally, I find it almost endearing that creatures which may be seen as gross, such as cockroaches, can actually be considered good parents in the animal kingdom. 

Parental Genes? Are We There Yet?

Research conducted at Harvard University has linked genes to parenting behaviors. Relation to the genes is not only on the male and female differences level, but the gene for the hormone vasopressin appears to be linked to the nest-building behavior found in parenting mice.

The long believed idea was that parenting was based on how an individual was parented. Good and attentive parenting skills are produced when an individual is parented in that manner. According to research this is not fully the case, as links between activity in specific genes and parenting differences are apparent across a species. Besides influencing behavior is males and females, certain hormones are being linked to specific genes of specific behaviors in mice. This is one of the first cases in which a link has been identified for parental care in mammals. The important idea to take away from this is the fact that we know environment is influential to parenting behaviors but it is now proven to be a product of gene expression. By a process known as cross fostering, the two focused and closely related mice species were raised by each other. No measurable effect was noticed it is simply based on genetics. To further develop the genetic code and information for these genes, the two species were crossbred then the resulting kin were crossbred. What was discovered was the actual differences between the traits must evolve independently. These sex specific regions of the brain aid in the discovery of this. One area discovered was for affects such as licking, handling and even retrieving while another was just for nest-building tendencies.

A closer look at the region of the brain associated with social behaviors, the hypothalamus, where the area for vasopressin neurons made great demonstrations of activity and peaked the interest of researchers.  With this information, an experiment reared toward the affects of this hormone was conducted where doses were administered to mice and the result was nest-building behavior is both species dropped.  This experiment opens doors for future research among the circuitry and regulation of parental genes among species.

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