Homeotic transformation in a terrestrial isopod: insights into the appendage identity in crustaceans.

In many crustacean species, an individual possesses both uniramous and biramous appendages that enable us to compare the two types on the same genetic background. Therefore, among the diverse morphologies of arthropod appendages, crustacean biramous appendages provide interesting subjects for studying the developmental mechanisms underlying appendage modifications. In this study, we report a malformed specimen of the terrestrial isopod Porcellio scaber, in which one of the pleopods was transformed into a different structure. Morphological observations of exoskeletons and musculatures by confocal scanning laser microscopy revealed that the transformed appendage was three-segmented, with at least the apical two segments having pereopod-like musculoskeletal structures. The apical segment of the transformed appendage lacked muscles, and the following segment had a pair of muscle bundles. These findings together with those of some previous studies of gene expression patterns in this species suggest that this anomaly could be caused by homeotic transformation of a flap-like pleopod into a three-segmented pereopod tip, which may be a homologous structure of the pleopod.

Pleopodal lung development in a terrestrial isopod, Porcellio scaber (Oniscidea).

During evolution, various lineages of arthropods colonized land and independently acquired air-breathing organs. Some taxa of oniscidean isopods (Crustacea, Isopoda, Oniscidea) are the most successful crustacean lineages on land and possess organs called "lungs" or "pseudotrachea" for air-breathing in their abdominal appendages, i.e., in pleopods. Although these lungs are important for adapting to the terrestrial environment, their developmental process has not yet been elucidated. In the present study, we investigated the process of lung development in Porcellio scaber, the common rough woodlouse with pleopodal lungs in the first two pairs of pleopods. The lungs in the second pleopods developed at the manca 1 stage (immediately after hatching) and became functional at the manca 2 stage. In the first pleopods, which appear at the manca 3 stage, the lungs were gradually developed during the manca 3 stage and became functional in post-manca juveniles. In the second pleopods, epithelial invaginations led to lung development. These results suggest that some novel developmental mechanisms with epithelial invaginations and cuticle formation were acquired during terrestrialization, resulting in the development of functional lungs in the terrestrial isopod lineages.

Parasitism-Induced Intersexuality in a Sexually Dimorphic Varunid Crab, Ptychognathus ishii (Decapoda: Varunidae).

Although many animals that perform sexual reproduction exhibit sexual dimorphism, individuals with intersex traits between the traits of males and females appear in some species, depending on environmental factors. Ptychognathus ishii, a varunid crab, exhibits distinctive sexual dimorphism in the morphology of its abdomen, chelipeds and setal tufts on the chelipeds. In this study, however, we report for the first time that intersex individuals with intermediate characters between those of males and females were occasionally found in wild populations. Morphological features of intersex individuals are described. Their taxonomic positions are identified based on DNA sequences of part of the mitochondrial cytochrome c oxidase I (COI) gene. It was shown that the intersexuality was induced by entoniscid parasites, because all intersex individuals were parasitized by entoniscid isopods, identified as Entionella sp. The apparent correlation between parasitism and morphological anomalies suggests that the parasitic isopods affect physiological conditions, leading to the feminization of male hosts.

First record of Australatyaobscura Han & Klotz, 2015 (Decapoda, Atyidae) from the Ryukyu Islands, Japan.

BACKGROUND: The freshwater shrimp, Australatyaobscura Han & Klotz, has been known only from Taiwan and Panay Island, Philippines. NEW INFORMATION: An adult A.obscura was collected from a river on Ishigaki Island, Ryukyu Islands, Japan. This is the first record of the species in Japan and the northernmost specimen-supported record to date. The species is suggested as having been transported northwards by the Kuroshio Current.

GABA affects novel object recognition memory and working memory in rats.

γ-Aminobutyric acid (GABA) is an amino acid found in unpolished rice, chocolate, tea, and other foods. It is an important inhibitory neurotransmitter. However, the influence of GABA on object recognition and working memory is still unknown. In this study, the effects of GABA on novel object recognition (NOR) memory and working memory were examined. The proper retention interval and delay time were also investigated for the NOR test and T-maze test, respectively. Male 3-wk-old Wistar rats were allowed free access to food and water containing 0.5% GABA or 1% GABA for a month. After that, the rats performed the NOR test at a 48 h retention interval and T-maze test at a 900 s delay time to estimate the effects of GABA on learning behavior. The results showed that the object information in the NOR test was stored as long-term memory and the recognition index (RI) was significantly increased after GABA administration. The accuracy rate also significantly increased after GABA administration. These indicate that GABA may be involved in long-term object recognition memory and working memory.

Facilitated neurogenesis in the developing hippocampus after intake of theanine, an amino acid in tea leaves, and object recognition memory.

Theanine, γ-glutamylethylamide, is one of the major amino acid components in green tea. In this study, cognitive function and the related mechanism were examined in theanine-administered young rats. Newborn rats were fed theanine through dams, which were fed water containing 0.3% theanine, and then fed water containing 0.3% theanine after weaning. Theanine level in the brain was under the detectable limit 6 weeks after the start of theanine administration. Theanine administration did not influence locomotor activity in the open-field test. However, rearing behavior was significantly increased in theanine-administered rats, suggesting that exploratory activity is increased by theanine intake. Furthermore, object recognition memory was enhanced in theanine-administered rats. The increase in exploratory activity in the open-field test seems to be associated with the enhanced object recognition memory after theanine administration. On the other hand, long-term potentiation (LTP) induction at the perforant path-granule cell synapse was not changed by theanine administration. To check hippocampal neurogenesis, BrdU was injected into rats 3 weeks after the start of theanine administration, and brain-derived neurotropic factor (BDNF) level was significantly increased at this time. Theanine intake significantly increased the number of BrdU-, Ki67-, and DCX-labeled cells in the granule cell layer 6 weeks after the start of theanine administration. This study indicates that 0.3% theanine administration facilitates neurogenesis in the developing hippocampus followed by enhanced recognition memory. Theanine intake may be of benefit to the postnatal development of hippocampal function.