The presence of two morphological forms in the Asian dark firefly Lucidina biplagiata (the Japanese name: Oba-botaru) in Japan was suggested by Dr. Sakyo Kanda in 1935, but they have long been considered to be the morphotypes of a single species. In this study, we examined the genetic variations and temporal emergence of Oba-botaru specimens at a single locality in Aichi, Japan. Phylogenetic analyses of mitochondrial and nuclear markers revealed two distinct lineages within L. biplagiata. Adult emergence patterns differed between the two sympatric groups. We found that the mode of the pronotal color patterns could be largely distinguished between the two groups, and also between bimodal emergence. Preliminary mating experiments showed that males and females from the two genetic groups did not mate in captivity. These results strongly support the existence of two sympatric, reproductively isolated species-level lineages within L. biplagiata.
Despite the great diversity of the phylum Chordata, lifelong obligate symbiosis with cyanobacteria is only known in certain species belonging to four genera of didemnid ascidians: Didemnum, Diplosoma, Lissoclinum, and Trididemnum. This photosymbiosis in didemnid ascidians exhibits diversity in photosymbiont taxa, symbiont location in the host ascidian, and modes of vertical transmission of symbionts. While the family Didemnidae comprises over 600 colonial species, approximately 30 symbiotic species are known from tropical waters, alongside many non-symbiotic congeners. This study aimed to elucidate the evolutionary history of this unique photosymbiosis in the family Didemnidae by constructing molecular phylogenetic trees based on the partial sequences of two regions in the mitochondrial cytochrome c oxidase subunit I gene (COI) and mapping the character states of photosymbiosis in each ascidian species harboring obligate photosymbionts onto the trees. The molecular phylogenetic trees generally supported the monophyly of Didemnum, Diplosoma, and Lissoclinum, but not that of Trididemnum. In contrast, the phylogenetic tree did not support the monophyly of the following character states of obligate photosymbiosis in ascidians: photosymbiont taxa (Prochloron, Synechocystis, and filamentous species), photosymbiont location (tunic, tunic cells, and peribranchial/common cloacal cavities), and modes of vertical transmission of photosymbionts in which the symbionts are attached to the larval trunk, collected by the rastrum, or transferred by tunic cells. These results suggest that obligate photosymbiosis with similar character states may have been exclusively established multiple times within the family Didemnidae. Because the modes of vertical transmission are closely associated with symbiont location, similar modes of vertical transmission may have evolved multiple times under similar colony structures and reproductive modes.
Terrestrial organisms employ diverse camouflage strategies, yet the fluctuating humidity and light conditions of arboreal habitats demand dynamic adaptations. This study investigated a novel mechanism of dynamic camouflage in the arboreal snails Hypselostyla camelopardalis (Camaenidae) and Reinia variegata (Clausiliidae). These phylogenetically distant species exhibit a reversible hygrochromic change: their mottled shell patterns disappear upon wetting, turning uniform dark brown, and rapidly reappear as they dry. Using a multimodal approach—including confocal laser microscopy, scanning electron microscopy, and spectrophotometry, this study shows that the colour change is associated with structural modifications within the bilayered organic periostracum. In the white regions, hydration fills microscale voids and smooths surface irregularities, effectively matching the refractive index of the periostracum and increasing light transmittance. While camouflage in terrestrial gastropods was previously considered static, our findings reveal an environmentally responsive system that dynamically adjusts to ambient moisture. This mechanism parallels strategies observed in certain insects, and is consistent with functional convergent evolution. Furthermore, the water-responsive thin-film structure of the snail shell provides a biological blueprint for the development of bioinspired smart materials, such as humidity-sensitive coatings and adaptive optical technologies.
The orangutan (Pongo pygmaeus [Bornean] and Pongo abelii [Sumatran], Linnaeus, 1760) is the most endangered of the great apes, classified as Critically Endangered. Sperm cryopreservation is a valuable tool for banking genetic resources and solving the complexities of relocating animals; however, cryopreservation protocols remain suboptimal for this species. Due to their phylogenetic closeness, this study aimed to explore the applicability of a chimpanzee (Pan troglodytes, Blumenbach, 1775) sperm cryopreservation protocol to orangutans. To guide further modifications to the protocol, we revealed, for the first time, the comprehensive lipidomic and proteomic characterizations of orangutan ejaculates with parallel comparisons to chimpanzee ejaculates. Functional analyses of oxidative and osmotic stress responses were also conducted to provide valuable evidence of the physiological changes and defense mechanisms associated with sperm cryodamage. The cross-species multi-omic analyses revealed that, compared to the chimpanzee, the orangutan sperm lipid profile exhibited significant alterations after the freezing-thawing process, notably characterized by a substantial loss of cholesterol. While interspecies differences in antioxidant enzyme composition and activity were observed, there was insufficient evidence to support a heightened susceptibility of orangutans to oxidative stress. Conversely, orangutan sperm exhibited low tolerance to hypoosmotic conditions. To prevent cryodamage, a modified thawing protocol that implemented a serial dilution approach significantly minimized hypoosmotic shock and improved post-thaw motility to 19%. In conclusion, this study presents the first complete proteome and lipidome analyses of chimpanzee and orangutan ejaculates, providing valuable insights into the physiological changes and defense mechanisms associated with sperm cryopreservation. This knowledge enabled a science-based approach to improving cryopreservation protocols, moving beyond empirical trial-and-error.
Background The transition from fins to limbs in vertebrates required a novel organization of spinal motor neurons to coordinate limb muscle activation. In amniotes, Hoxc9 represses lateral motor column (LMC) identity at thoracic levels, restricting limb-innervating Foxp1(+) motor neurons to brachial and lumbar levels. In elasmobranchs, however, the genomic organization of HoxC genes has undergone extensive modifications, and Foxp1(+) LMC-like neurons have been identified at paired-fin levels in some elasmobranch species lacking Hoxc9. These observations suggest that alternative mechanisms regulate motor neuron fate in chondrichthyans, particularly in sharks, although the responsible factors remain unclear. Results To identify the mechanism underlying this suppression, we examined Foxp1 and Hox gene expression in chicken and cloudy catshark (Scyliorhinus torazame) embryos. In chickens, Foxp1(+) LMC neurons initially appeared at all rostrocaudal levels but became restricted to paired-limb levels through Hoxc9-mediated repression. In contrast, in cloudy catsharks, which lack Hoxc9, Foxp1 was downregulated at inter-fin levels where Hoxa9 is expressed. Sequence analysis revealed that the Foxp1 modulatory domain (MD), associated with LMC repression, is highly conserved in Hoxa9 across all examined chondrichthyan species. Hoxc9 genes are absent in most sharks but retained in rays and holocephalans, and these retained copies preserved the Foxp1 MD. Functional analysis in chicken embryos demonstrated that cloudy catshark Hoxa9 represses LMC identity and promotes preganglionic column (PGC) fate, similar to Hoxc9 in amniotes. Conclusions These findings suggest that conserved Hox9-dependent mechanisms restrict Foxp1(+) motor neurons at thoracic levels in sharks. In the absence of Hoxc9, cloudy catshark Hoxa9 retains the ability to repress Foxp1 and promote PGC fate, thereby contributing to the organization of motor innervation at paired-fin levels.
