Most vertebrates including humans have monochromatic vision at night and color vision during the day. This is explained by the repertoire of retinal photoreceptor cells, that is, a single type of rod cell for scotopic vision and multiple types of cone cells for photopic vision. Rods and cones contain different types of visual pigments, rhodopsin and cone pigments, respectively. Noteworthily, frogs and nocturnal geckos can discriminate colors under scotopic conditions, which is thought to be attributed to multiple types of rods in their retinas. Frogs have two types of rods, one of which contains green-sensitive rhodopsin and the other of which contains blue-sensitive cone pigment. And nocturnal geckos have three type of rods which contain red-, green- and UV-sensitive cone pigments. It is well known that scotopic vision is underlain by a much lower spontaneous activation rate of rhodopsin than of cone pigments. Therefore, it is of interest to investigate whether or not frogs and nocturnal geckos changed the molecular properties of cone pigments to adjust to scotopic vision. Our biochemical analysis showed that frogs and geckos suppressed the spontaneous activation rate of cone pigments to mimic rhodopsin. This shows that frogs and nocturnal geckos uniquely acquired rhodopsin-like cone pigments by convergent evolution for scotopic color vision, which is advantageous for their nocturnality.

It has been independently reported that cardiomyocytes possess a system to synthesize acetylcholine (ACh), which is called non-neuronal ACh, and therefore, this system in the heart is named as the non-neuronal cardiac cholinergic system (NNCCS). This system is involved in many cardiac physiological aspects including cardiac homeostasis, for example, negative regulation of oxygen consumption, enhancement of glucose preference as a cardiac energy substrate, acceleration of angiogenesis, and upregulation of gap junction function etc., in other words, enhancement of resilience against damages by ischemia or hypoxia in the heart. In this review, we provide the history of establishment of the concept of NNCCS, significant findings of NNCCS functions, the pathogenic roles in impairment of NNCCS, the link between NNCCS and extra-cardiac organs through the vagus nerve, and its influences on extra-cardiac organ functions.

Honeybee foragers often return to the nest before filling their crop with nectar. A series of studies conducted in the 1980's considered the mass-dependent metabolic cost of nectar load and suggested that their partial filling is a strategy to optimize the energetic efficiency of foraging. However, some researchers did not agree with this idea and, instead, proposed an alternative hypothesis arguing promotion of communication concerning other potential food sources by frequent returning to the nest. Recent studies revealed that foragers also show a similar adjustment in nectar loading when they leave the nest. The volume and concentration of nectar loaded in the nest as fuel for flight and material for pollen load can be influenced by several factors such as the distance to food source, informational state concerning food source and certainty of foraging. This article reviews studies concerning the two types of nectar adjustment and discusses their underlying mechanisms and function.

Insects have developed their sophisticated olfactory sensory system to utilize the odor information for foraging, mating and communicating between conspecifics. Recently, the analysis of genes related to olfactory reception has been rapidly progressed, and a lot of olfactory receptor genes have been reported in non-model insects. To identify functions of orphan receptor genes, electrophysiological recording method from olfactory sensory neurons expressing the receptor genes is indispensable. Because it requires sophisticated techniques, researchers who can record the olfactory response from the cognate olfactory sensory neurons are very rare around the world. In this paper, we will introduce an electrophysiological recording method called “Single Sensillum Recording (SSR)” that directly record the olfactory responses from olfactory sensory neurons in single olfactory sensilla in insects. Combinations of SSRs with molecular biological experiments and/or neuroanatomical experiments, it will be helpful for the future analysis of odor transduction mechanisms in insects.