Date of Award

2018

Document Type

Honors Thesis (Colby Access Only)

Department

Colby College. Chemistry Dept.

Advisor(s)

David Angelini

Abstract

Polyphenism is a phenomenon in which individuals within a species exhibit two or more distinct phenotypes due to environmental influences. In some species, polyphenism affects both sexes, but may not confer equal advantages, leading to sexual conflict. Dispersal/fecundity polyphenism in the red-shouldered soapberry bug Jadera haematoloma (Hemiptera: Rhopalidae) is dependent on juvenile nutrition, resulting in two discrete wing morphs in adults. Recent evidence has identified a sexual conflict in this polyphenism in which the short-winged morph appears to be maladaptive in males: not only are they unable to fly, but short-winged males have lower fertility than long-winged males. To understand the basis of these fertility differences in the soapberry bug, we must first identify cell populations and genetic markers of the male germline. We use in situ hybridization, histochemistry, and RNA interference (RNAi) to describe spermatogenesis in J. haematoloma and investigate expression patterns of unpaired (upd) and vasa, genes known to be important in spermatogenesis in other organisms. Our results indicate that vasa is not differentially expressed between wing morphs. Expression of vasa in the soapberry bug begins significantly lower and extends farther than in Oncopeltus fasciatus, a bug in the same taxonomic order. upd and vasa expression was not significantly different in the testes of upd RNAi bugs. In bugs in which vasa was knocked-down, there was no effect on upd expression. Nuclear staining of the testes revealed that germline stem cells in the anterior tip of testioles from vasa RNAi bugs were not in the same cell cycle state, a phenotype that was observed in similar experiments in O. fasciatus. Our results provide the first investigation of spermatogenesis in J. haematoloma and indicate that the highly conserved male germline gene vasa is required to maintain synchrony of germ cells early in spermatogenesis.

Keywords

spermatogenesis, soapberry bug, stem cells, sexual conflict

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