BioOne.org will be down briefly for maintenance on 13 August 2025 between 18:00-21:00 Pacific Time US. We apologize for any inconvenience.
Registered users receive a variety of benefits including the ability to customize email alerts, create favorite journals list, and save searches.
Please note that a BioOne web account does not automatically grant access to full-text content. An institutional or society member subscription is required to view non-Open Access content.
Contact helpdesk@bioone.org with any questions.
To elucidate the control mechanism of tail resorption during Xenopus metamorphosis, the expression of mfge8, a macrophage-apoptotic cell bridging molecule that promotes phagocytosis in mammals, was examined. In both Xenopus tropicalis and Xenopus laevis, the mfge8 expression in the tail increased significantly during metamorphosis, reaching its peak at the metamorphic climax, when the tail shortens rapidly. This finding suggests that the up-regulation of mfge8 at metamorphic climax is involved in the clearance of apoptotic tail muscles. To investigate the significance of mfge8 up-regulation, mfge8-deficient X. tropicalis tadpoles were generated using the CRISPR/Cas9 method, and the effects of mfge8-deletion were examined. Delayed tail resorption process was observed in the mfge8-deficient mutants (from 9.8 days [wild type] to 13.2 days [F2 mutant]), suggesting that elevated mfge8 expression during the metamorphic climax contributes to the tail resorption.
Three non-encysted digenean metacercariae were found parasitic in the mesoglea of two of 13 individuals of the staurozoan cnidarian Haliclystus tenuis Kishinouye, 1910 from Yoichi, Hokkaido, Japan. The metacercariae comprised two morphospecies (one oval, the other elongate), for which the gross morphology is described. Partial sequences of the 18S and 28S rRNA genes and the internal transcribed spacer 2 region were determined for both species, and a partial sequence of the cytochrome c oxidase subunit I gene was determined for the oval species. Molecular phylogenetic analyses revealed both digeneans to be in the family Lepocreadiidae, a taxon not previously reported from staurozoans. The oval species was a member of the “Diploproctodaeum Clade.” The elongate species was identified as Prodistomum orientale (Layman, 1930), known to use marine fishes in the genus Scomber Linnaeus, 1758 as definitive hosts. Second intermediate hosts of P. orientale known around Australia include five hydrozoan, one scyphozoan (Cnidaria), and one ctenophoran species. This is the first information on a second intermediate host from Japan; however, we cannot rule out the possibility that staurozoans may also be dead-end hosts. Including an opecoelid species previously reported, three digenean species in two families are now known from a single staurozoan species in the small region comprising the northwestern coast of Hokkaido. Future surveys for parasites in other staurozoan species and regions will likely detect additional digeneans and other parasite groups utilizing staurozoans.
Using mitochondrial DNA and genome-wide SNP, phylogenetic relationships in Chalcorana were investigated. Phylogenetic analyses based on subregions of mtDNA found possible lineages of several cryptic species, but did not support the phylogenetic relationships of some groups. Phylogenetic analyses based on SNP resulted in the same topology as mtDNA, with some exceptions, and clarified the phylogenetic relationships among all lineages. Genome-wide analyses successfully estimated taxonomic positions of several lineages that could not be resolved in mtDNA analyses.
Anemonefish have a characteristic vertical white barred color pattern on an orange background made by a specific distribution of three types of pigment cells: melanophores, xanthophores, and iridophores. This color pattern is an interesting alternative model to zebrafish to understand the cellular and molecular basis of complex color pattern formation. Using transmission electron microscopic observations, we have investigated the pigment cell composition in the skin of the anemonefish Amphiprion ocellaris and found that: 1) white skin comprises iridophores and isolated melanophores; 2) orange skin contains xanthophores and scattered melanophores; and 3) black skin encompasses melanophores only. All three pigment cells can be found in the dermis. Iridophores are also present in the hypodermis, but general cell morphology differs depending on the dermal layer, distinguishing them into S-type and L-type iridophores. While melanophores can mix with xanthophores and iridophores, xanthophores and iridophores are not in direct physical contact, always being separated by melanophores. Anemonefish with differing color patterns than A. ocellaris, either color mutants or other anemonefish species, possess different pigment cell distribution and organization reflecting their respective colors. Our analysis provides key data to inform on the mechanism generating the diversity of color patterns present in anemonefishes.
Snails of the family Eulimidae are parasites of echinoderms in all five extant classes. Despite long years of taxonomic research on Eulimidae in Japan, their local species richness remains to be investigated, and few studies have focused on a eulimid fauna of a certain echinoderm taxon, even if it is a common species. Here, we conducted a comprehensive sampling of Melanella species parasitizing the black sea cucumber Holothuria leucospilota in Shirahama, Wakayama, central Japan. The data used in this study were partly obtained during a summer education program of the Seto Marine Biological Laboratory, Kyoto University. Melanella kuronamako and M. spina parasitized the external surface, and two unidentified species were found inside the host's body cavity. This study represents the first record of M. spina in Japanese waters and eulimids exploiting the internal habitat of H. leucospilota. Morphological and molecular comparisons between the present four species and other Japanese Melanella specimens suggested that they generally exhibit wide geographic distributions and low host specificity. Additionally, the two species from the body cavity were probably seldom observed in central Japan, as inferred from the accumulated results of the dissection of H. leucospilota through a long-running, annual education program at Shirahama.
Copy number variation (CNV) in gene loci in animals can be driven by adaption to the environment. The relationship between CNV in genes for amylase (AMY), which hydrolyzes starch, and dietary adaptation has been well studied. Copy number (CN) of AMY is higher in human populations with high-starch diets, compared with those with low-starch diets. Although CNV in AMY has been reported in humans and some domestic animals, there have been few studies of animals in the wild. The brown bear (Ursus arctos), widespread in the Northern Hemisphere, shows large dietary variation among individuals and groups. Brown bear population genetic structures are associated with the dispersal history due to climate change over the past few tens of thousands of years, and this together with dietary variation should have led to CNV in AMY. In this study, we investigated CNV in AMY in brown bears worldwide by using whole genome sequencing data. We detected AMY CNV among regional groups. AMY CN was similar among brown bears in geographically proximate populations, such as between Hokkaido (Japan) and East Asia, and between the North America mainland and the ABC islands. CNs were smaller in bears from East Asia, including Hokkaido, compared to those from other regions across brown bears' distribution. Our results suggest that CNs of AMY reflect the population demographic history of brown bears after the Last Glacial Maximum.
Symbiosis is a key driver of evolution in life-history traits and reproductive strategies. Some symbiotic microorganisms manipulate host reproduction to enhance their own transmission, a phenomenon well studied in insects but less understood in crustaceans. Among these microorganisms, Cardinium manipulates host reproductive systems, such as parthenogenesis, cytoplasmic incompatibility, and male killing in arthropods. However, its role in ostracods, small bivalve-shelled crustaceans, remains unclear. Some ostracod species reproduce via parthenogenesis, and high Cardinium infection rates in these lineages suggest a potential link between the symbiont and asexual reproduction. To investigate this relationship, we examined Cardinium localization in the parthenogenetic ostracod Heterocypris spadix from Japan. Using tissue clearing and fluorescence in situ hybridization (FISH), we visualized Cardinium within the ovaries. FISH observations revealed a widespread infection across the germarium, nurse cells, and oocytes. In early-stage oocytes, bacteria were evenly dispersed throughout the cytoplasm, whereas in more-developed oocytes, they clustered around the nucleus. Additionally, Cardinium was also detected in the hepatopancreas, indicating infection of both the reproductive and digestive systems. The presence of Cardinium in host reproductive structures, particularly the germarium, nurse cells, and developing oocytes, suggests its role in reproductive manipulation. To our knowledge, this study provides the first detailed localization of Cardinium in ostracods, reinforcing its potential influence on reproduction. Future research using antibiotics and genomic analysis will be crucial to confirm Cardinium's role in parthenogenesis induction.
This article is only available to subscribers. It is not available for individual sale.
Access to the requested content is limited to institutions that have
purchased or subscribe to this BioOne eBook Collection. You are receiving
this notice because your organization may not have this eBook access.*
*Shibboleth/Open Athens users-please
sign in
to access your institution's subscriptions.
Additional information about institution subscriptions can be foundhere