Alternative splicing is a key genetic process that allows a single gene to produce multiple final products in the form of different RNA or protein molecules. In multiple systems, this mechanism has been shown to play a part in the regulation of phenotypic plasticity. That is, the organism has the capacity of responding to the environment, mediating this response through the alteration of the abundance and/or proportion of different isoforms of key genes. Gerris buenoi (Hemiptera; Gerridae) is a species of aquatic insect with wing length polyphenism i.e., the length of the wings in this species is determined by the environmental conditions, in particular photoperiod. Under exposure to long light regimes, the adults of the species will present short wings, which inhibit the capacity of flight. When the light regime is short, adults will develop long wings that allow them to fly. Wing length polymorphism is a common feature among water striders, although several species are monomorphic or even wingless. The easy induction of both wing morphs in G. buenoi with alternative photoperiods has facilitated its emergence as a novel model species for studying phenotypic plasticity in insects. In this direction, our lab has identified a wide array of differentially expressed genes between tissues (body and wing buds) and photoperiod treatments. GO-term enrichment analysis of these has allowed to identify key molecular pathways regulating wing formation. The relevance of these genes has been tested and verified using functional studies, including RNAi and qPCR. However, all previous analyses have been restricted to the gene level, with no efforts made to identify wing morph-specific isoforms to date. Yet, “alternative splicing” is one of the relevant categories of the enrichment analyses, indicating that several of the genes regulating wing formation and photoperiod signal transduction may be subject to differences in isoform formation/abundance. Whole-genome alternative splicing studies are still scarce in insects, although previous findings suggest a significant proportion of genes experience differential exon usage (40% of genes in the bumblebee, for instance). Simultaneously, some of the functionally verified genes in G. buenoi are proved to be alternatively spliced in other insects. I would like to explore the extent and consequences of alternative splicing in the water strider G. buenoi. On the one hand, I aim to contextualize the proportion of the genome that is subject to this key regulatory process. On the other, I want to find out whether the genes we already know are differentially expressed between photoperiod present one or multiple isoforms, and what their relative abundances are in each one. To sum up, the goal of the project is to assess and quantify the importance of alternative splicing as a regulatory mechanism for phenotypic plasticity.