Repeated Divergence in Opsin Gene Expression Mirrors Photic Habitat Changes in Rapidly Evolving Crater Lake Cichlid Fishes.

AbstractSelection pressures differ along environmental gradients, and traits tightly linked to fitness (e.g., the visual system) are expected to track such variation. Along gradients, adaptation to local conditions might be due to heritable and nonheritable environmentally induced variation. Disentangling these sources of phenotypic variation requires studying closely related populations in nature and in the laboratory. The Nicaraguan lakes represent an environmental gradient in photic conditions from clear crater lakes to very turbid great lakes. From two old, turbid great lakes, Midas cichlid fish (Amphilophus cf. citrinellus) independently colonized seven isolated crater lakes of varying light conditions, resulting in a small adaptive radiation. We estimated variation in visual sensitivities along this photic gradient by measuring cone opsin gene expression among lake populations. Visual sensitivities observed in all seven derived crater lake populations shifted predictably in direction and magnitude, repeatedly mirroring changes in photic conditions. Comparing wild-caught and laboratory-reared fish revealed that 48% of this phenotypic variation is genetically determined and evolved rapidly. Decreasing intrapopulation variation as environments become spectrally narrower suggests that different selective landscapes operate along the gradient. We conclude that the power to predict phenotypic evolution along gradients depends on both the magnitude of environmental change and the selective landscape shape.

Effects of Feeding Adults of Hermetia illucens (Diptera: Stratiomyidae) on Longevity, Oviposition, and Egg Hatchability: Insights Into Optimizing Egg Production.

Larvae of the black soldier fly, Hermetia illucens (L.), have been widely studied for their capacity of generating value-added products through waste bioconversion. Several efforts have been made towards optimization of rearing methods of the larval stages. Despite this, less information regarding the feeding behavior of adults and its effects on life parameters is available. We studied the impacts of subjecting adults to four diets: no diet (control); drinking water (water); a mix of sugar, bacteriological peptone, and milk powder (milk); and agar with sugar (agar). In total five replicates with 50 females and 50 males per treatment were performed. Oviposition and mortality were recorded daily. Additionally, egg hatchability and number of eggs per mass were measured. Results from this study indicate that the amount of eggs was 3 times higher for diets containing a protein source. Furthermore, milk treatment increased the oviposition period by 10 d compared with that of the standard water treatment. No significant difference was found for male longevity; however, females fed with milk diet lived 5 d longer than the control group. Egg hatchability ranged 70-85%, but was not significantly different across treatments. In terms of egg production for both industrial and research purposes, we suggest using a protein-rich diet to maximize oviposition and longevity parameters as adults do benefit from feeding.