Fireflies are the most famous terrestrial luminescent creatures. "Fireflies, flying slowly; summer nights, the wind blows softly...", such a beautiful scene is an ordinary picture in the childhood memories of people born in the 600s and 1970s. Nowadays, people are always lamenting that fireflies are far away, they either exist in memory or only appear on television.
Fireflies have higher requirements for the living environment, and can only survive well in the environment of green water and green mountains, and the use of pesticides, the destruction of natural vegetation and light pollution in the process of urbanization do force fireflies to stay farther and farther away from us.
This does sound sad, but among the more than 2,000 firefly species in about 100 genera of 8 subfamilies around the world, there is another class of fireflies that have not escaped due to urbanization, and can still be seen in the parks, campuses and residential areas of urban centers, and behind the front houses of the countryside. They have been trying to live in harmony with humans. This kind of magical firefly is the flat firefly.
Glowing flat fireflies, male adults above, female adults below (Dong Zhiwei photo)
After years, I was finally able to call out the names of the flat fireflies!
Flat fireflies refer to the collective name for fireflies of the family Lampyridae (Lamprigera). They are found only in the periphery of the Eastern Himalayas in Asia and in Southeast Asian countries, and Yunnan, which is rich in biodiversity, is at the center of this distribution area.
They are hermaphroditic, i.e. male adults and female adults exhibit different shapes. The male has black elytra wings; a large dorsal plate of the forebreast that completely covers the head at rest; a pair of large compound eyes on the head, a pair of very short antennae; and a pair of white luminous organs on the 7th visible abdominal segment (i.e., the 8th abdominal segment) on the ventral surface of the abdomen, which can emit a continuous green light. The female is completely wingless, white, chubby larvae with a pair of luminous organs on the 8th abdominal segment of the abdomen, and may also emit a continuous green light. The larvae have a flattened body, black or brownish-yellow stripes all over the body, and are usually large in size.
On the back of the Yunnan flat firefly, male adults (left), female adults (center) and larvae (right) (Photo by Dong Zhiwei)
Seventeen species of the genus Are reported by 2020. Li Xueyan and his team at the Kunming Institute of Zoology of the Chinese Academy of Sciences have been studying fireflies since 2002, during which they have collected some flat fireflies specimens, including some male adults, female adults and a large number of larvae, however, because the insects have the same insect shape is very similar, and most of the type specimens of the reported species are stored in European museums such as France and have not had the opportunity to examine, so for a long time, researchers have foolishly distinguished who is who and what is the name.
Based on long-term specimen accumulation, with the help of DNA barcoding technology, the research team conducted molecular phylogeny and morphological analysis of specimens from different populations in China, and compared morphologically with the model specimens reviewed by hong Kong peers, and was surprised to find that these seemingly identical flat fluorescent specimens included three new species (Lamprigera alticola Dong & Li, 2021 Alpine Flat Firefly, Lamprigera luquanensis). Dong & Li, 2021 Lu Shu BianFluores, Lamprigera magnapronotum Dong & Li, 2021 Giant-breasted Flat Fireflies), Four New Chinese Record Species (Lamprigera Minor (Olivier, 1885) Small Flat Fluorescent, Lamprigera Morator (Olivier, 1891) Swanfly, Lamprigera nepalensis ( Hope, 1831) Nepalese flat fireflies, Lamprigera nitidicollis (Fairmaire, 1891) bright flat fireflies) and a Chinese reported species (Lamprigera yunnana (Fairmaire, 1897) Yunnan flat fireflies) (Dong etal., Zootaxa, 2021, 4950(3): 441–468).
The results of the study have increased the number of species in the genus to 20 worldwide, and the number of Species in China has increased from 4 to 11. These research results not only provide an important reference for the future study of species identification and other life phenomena of this genus, but also show the rich diversity of fireflies species in Yunnan.
3 new species and 4 new chinese recorded species recently discovered in Yunnan (Dong et al., 2021)
Finally know how to catch the flat firefly!
Like other taxa of fireflies, adult flatflies glow primarily as a mating courtship signal, while larval glow primarily serves as a warning signal. However, unlike the usual imaginary fireflies that flicker on a hot summer night, the insect states of the flat fireflies are green and continuously glowing. It is very interesting that the males do not glow when they fly, they always have a pair of large eyes, quietly flying in the dark, looking for their favorite female partner, and when they find their favorite object and close enough, they open their light bulbs to tell their partners "I have arrived". Compared with males, females are more passive in finding objects, hiding in or near the grass, cocking their tails to reveal bright light bulbs, and signaling "I am here" to males flying in the dark.
In the early days, researchers mainly directly observed or collected fireflies based on their positioning, but such a method encountered flat fireflies with special luminous behavior, which obviously did not work. Therefore, there was little early harvest of flat fireflies, especially male specimens as taxonomic insects, which was reflected in the collections of fireflies from various domestic research institutes and universities that the research team had examined.
In the communication with the Japanese counterpart, the research team learned that the Japanese counterpart usually uses the red band of light to lure the green fluorescent window fireflies, but because there is no distribution of flat fluorescent in Japan, it is not certain whether this method is effective for flat fluorescent. The research team tried to use the red LED light to lure the flat fireflies, when the sky was just dark, the red LED lights were placed near the grass and waited quietly, and they would find that the male flat fireflies that did not know where to hit would suddenly appear around the lamp and carefully turn on its own green light, once it found that the red light that came from it was not a female, it would quickly flee, of course, it was not an easy task to escape the researcher's sight. Since the use of this method, the research team has collected a large number of male insect specimens, and the work of species classification has been advanced.
The larvae prefer to live in well-fed wastelands and forests, and researchers have found that they especially prefer to walk to the side of the road on sunny nights after rain in search of food such as snails and earthworms. After becoming familiar with this habit, the researchers also harvested a lot of larval specimens in such a place on such a night. In Kunming, in the urban park, campus and some residential areas, you will occasionally encounter flat fireflies walking at night. It was once encountered even during the day in a sports training ground in an urban village. Researchers have raised Yunnan flat fireflies and found that these insects have a very mixed diet, in addition to eating snail earthworms and other foods, in the laboratory environment they even eat pork bought from the market.
The picture on the left shows the male fireflies lured by red lights, and the picture on the right shows the Yunnan flat fireflies that are gathered together (Photo by Li Xueyan)
Why do flat fluorescent glow green?
The morphology of fireflies luminescence is the luminous organ (bulb) on the body, and the biochemical basis is that the substrate fluorescein contained in it is catalyzed by luciferase, and the oxidized fluorescein produced is released from an unstable high-energy state to a stable low-energy state, and then emits energy to emit light. The gene encoding the luciferase protein, known as the Luciferase gene, has become an important reporter gene in molecular biology and biomedical research. The color and brightness of the luminescence are related to the characteristics of luciferase.
In order to explore the biochemical basis of flat fluorescent light, the research team cloned and analyzed its luciferase characteristics with Yunnan flat fluorescent as a representative. Its luciferase has 551 amino acids, which is similar to the species sequence of the fluorescence subfamily (72%–77%) higher than that of the fluorescence subfamily (68%–71%). The recombinant luciferase protein in vitro has maximum viability at pH 7.8 with a luminescence wavelength of 566 nm (green light), but has a redshift phenomenon in an acidic environment. It has the highest viability at 37 °C and completely inactivates at 55 °C.
Luminescence spectra of luciferases of Yunnan flat fluorescent fireflies under different pH conditions (Liu et al., 2019)
Whose child is It?
Because of its appearance and luminous habits, it has been considered a member of the subfamily Lampyrinae. Indeed, from its appearance and luminous habits, such attribution is clearly not a problem. However, the results presented by the molecular data completely disrupted the traditional perceptions of researchers. Taking yunnan flat fluorescent as a representative species, the research team found as early as 2006 when constructing a phylogenetic tree based on the mitochondrial 16S marker that the evolutionary status of the flat fluorescent firefly is far from the subfamily fluorescence.
In 2019, when the research team continued to analyze the mitochondrial genome of Yunnan Flat Fluorescent and conducted a comprehensive systematic phylogenetic analysis of the ribosomal genes combined with the nuclear genome, it was found that the flat fluorescent was actually more closely related to the glittering subfamily than the subfamily Fluorescence.
The research team completed the reference genome analysis of Yunnan bianfluorescence in 2020, and phylogenetic studies based on genome-wide data showed that consistent with the research results from the mitochondrial genome, the flat fluorescent does have a closer relationship with the subfamily Fluorite. These data suggest that in the evolutionary history of firefly species, these flat fireflies, which are only distributed around the Eastern Himalayas, are in a special evolutionary position.
Molecular phylogenetic trees show a closer relationship between Lamprigera and the subfamily Pyrifera, with mitochondrial genomes and nuclear rDNA trees on the left (Chen et al., 2019) and genome-wide phylogenetic trees on the right (Zhang et al., 2020).
Why is the flat firefly magical for this?
Why are the flat fireflies scattered around the Eastern Himalayas so magical? The code for the evolution and development of a species is written in the genetic information of its genome. In order to delve into the magic of flat fluorescent, in 2017, the research team used flow cytometry to determine the Yunnan flat firefly and two other species of the same genus (Lamprigera nepalensis (Hope, 1831); Lamprigera nitidicollis (Fairmaire, 1891) and other genera of fireflies, the size of the genomes, found that the miraculous flat fireflies have the larger genomes of fireflies.
Further reference genome analysis and analysis of Yunnan Bian Fluorescent found that the larger genome of Bian Fluorescent originated from a higher proportion of repetitive sequences contained (up to 67% of the whole genome), especially DNA transposons (up to 35% of the whole genome) and long dispersed nuclear elements (LINEs) (up to 15% of the whole genome). Of course, whether and how these special genomic structures contribute to the magical habits and characteristics of flat fireflies still needs to be further explored.
Flat fluorescent fireflies have larger genomes, with the C value determined by flow cytometry (Liu et al., 2017) on the left and the results of genome repeat sequence analysis on the right (Zhang et al., 2020).
The magic of the flat fluorescent firefly will continue to attract researchers
The research team of the Kunming Institute of Zoology of the Chinese Academy of Sciences found 3 new species in Yunnan and 4 new record species in China have brought this kind of magical flat fireflies that have long lived quietly in the Eastern Himalayas and surrounding countries and regions into the vision of peers and the public.
Dr. Branham, a well-known firefly researcher in the United States, wrote in an email to researchers that "flat fireflies are such a cool beetle genus!" I'm really glad you published such a good study! This is a very important contribution!". Professor Lewis, another prominent firefly researcher in the United States and co-chair of the IUCN-SSC firefly expert group, wrote in an email: "Congratulations on this new discovery – lamprigera is now my favorite type of fireflies."
Researchers at the Kunming Institute of Zoology of the Chinese Academy of Sciences will continue on the road of revealing the magic of the flat fireflies. They believe that more new species of flat fireflies will likely be found in China and neighboring countries, and they will continue to explore and reveal the evolution of such fireflies and their biofluorescence from multiple levels such as species diversity and conservation, ecology and genetic resources.
Thanks:
The taxonomy and biofluorescence origin and evolution of glowing beetles such as fireflies have been funded by the National Natural Science Foundation of China (31472035), the Yunnan Provincial Department of Science and Technology (2014FB179), the "Young Scholars in Western China" Project of the Chinese Academy of Sciences (Class A), and the Key Laboratory of Tropical Forest Ecology of the Chinese Academy of Sciences (09KF001B04).
Source: Kunming Institute of Zoology, Chinese Academy of Sciences