Colour vision relies on retinal photoreceptors that express a different predominant visual pigment protein (opsin). In several vertebrates, the primary opsin expressed by a photoreceptor can change throughout ontogeny, although the molecular factors that influence such regulation are poorly understood. One of these factors is thyroid hormone which, together with its receptors, modulates opsin expression in the retinas of multiple vertebrates including rodents and salmonid fishes. In the latter, thyroid hormone induces a switch in opsin expression from SWS1 (ultraviolet light sensitive) to SWS2 (short wavelength or blue light sensitive) in the single cone photoreceptors of the retina. The actions of other hormones on opsin expression have not been investigated. In the present study, we used a transgenic strain of coho salmon (Oncorhynchus kitsutch) with enhanced levels of circulating growth hormone compared to that of wild siblings to assess the effects of this hormone on the SWS1 to SWS2 opsin switch. Transgenic fish showed a developmentally accelerated opsin switch compared to size‐matched controls as assessed by immunohistological and in situ hybridisation labelling of photoreceptors and by quantification of transcripts using quantitative polymerase chain reaction. This accelerated switch led to a different spectral sensitivity maximum, under a middle to long wavelength adapting background, from ultraviolet (λmax ~ 380 nm) in controls to short wavelengths (λmax ~ 430 nm) in transgenics, demonstrating altered colour vision. The effects of growth hormone over‐expression were independent of circulating levels of thyroid hormone (triiodothyronine), the hormone typically associated with opsin switches in vertebrates.

During migratory flight, desert locusts rely on fatty acids as their predominant source of energy. Lipids mobilized in the fat body are transported to the flight muscles and enter the muscle cells as free fatty acids. It has been postulated that muscle fatty acid-binding protein (FABP) is needed for the efficient translocation of fatty acids through the aqueous cytosol towards mitochondrial β-oxidation. To assess whether FABP is required for this process, dsRNA was injected into freshly emerged adult males to knockdown the expression of FABP. Three weeks after injection, FABP and its mRNA were undetectable in flight muscle, indicating efficient silencing of FABP expression. At rest, control and treated animals exhibited no morphological or behavioral differences. In tethered flight experiments, both control and treated insects were able to fly continually in the initial, carbohydrate-fueled phase of flight, and in both groups lipids were mobilized and released into the hemolymph. Flight periods exceeding thirty minutes, however, when fatty acids become the main energy source, were rarely possible for FABP-depleted animals, while control insects continued to fly for more than 2 h. These results demonstrate that FABP is an essential element of skeletal muscle energy metabolism in vivo.

Vitellogenins are the major yolk protein precursors found throughout the animal kingdom. In insects, the primary structures of vitellogenins have been determined in species from most major orders, except for Orthoptera, where only partial sequences have been reported. We amplified and sequenced the complete complementary DNA for two vitellogenins from the desert locust, Schistocerca gregaria (Orthoptera: Acrididae), which code for vitellogenin A and vitellogenin B, two proteins of approximately 200 kDa each. Both proteins are highly expressed at similar rates in adult females only, and their expression can be completely abolished by RNA interference–mediated silencing of the juvenile hormone receptor, methoprene-tolerant (Met). Homologous sequences were inferred from the genome of Locusta migratoria (Orthoptera: Acrididae), yielding complete coding sequences considerably larger than previously published. Vitellogenin A and vitellogenin B from S. gregaria are highly similar to their respective homologues from L. migratoria but show relatively low similarity between each other, suggesting that these genes originated from a common ancestor long before these species diverged.