We have analysed the effects of the neuromodulator nitric oxide (NO) on proprioceptive information processing by ascending intersegmental interneurons that form part of the local circuits within the terminal abdominal ganglion of the crayfish. NO modulates the synaptic inputs to ascending interneurons, enhancing the amplitude of class I interneurons and reducing the amplitude of class II interneurons. Repetitive proprioceptive stimulation leads to rapid depression in a specific set of identified interneurons but not in others. Bath application of a nitric oxide scavenger, PTIO, causes a significant decrease in the rate of depression of the interneurons showing a rapid depression, independent of interneuron class, but has no effect on the dynamic responses of the interneurons that show little initial depression. These results indicate that NO exerts multiple effects at the very first stage of synaptic integration in local circuits.

One of a pair of cerci was ablated in the first-, fourth- and last-instar nymphs of the cricket, Gryllus bimaculatus. The insects were then reared until the final molt, after which the intensity-response (I-R) relationships for four giant interneurons (GIs) 8-1, 9-1, 9-2 and 9-3 with regard to a controlled air current stimulus were measured. In order to examine the functional changes during postembryonic development and the differences in the physiological plasticity of GIs between nymphs and adults, the obtained I-R curves for each GI were compared with those measured in intact and unilaterally cercus-ablated adult crickets. Each GI showed a distinctive change in response magnitudes after the long-term unilateral cercal ablation. In most cases, the I-R curves for each GI in the crickets ablated from nymphal periods were different from those in the adult crickets mentioned above. Moreover, the pattern of change in response magnitude was different from GI to GI. In contrast to these observations, it was reported that some important characteristics of the wind-evoked escape behavior such as relative occurrence and escape direction in unilaterally cercus-ablated crickets investigated after a long-term rearing were almost identical with those in intact crickets. Therefore, the results obtained in the present study suggest that functional changes occur not only in GIs but also in many other neural elements in the escape-eliciting system in order to maintain the features of wind-evoked escape behavior.

In the adult heart of the isopod crustacean Ligia exotica, the cardiac ganglion acts as the primary pacemaker with the myocardium having a latent pacemaker property. We show several lines of evidence that dopamine modulates the heartbeat of adult L. exotica affecting both pacemaker sites in the heart. Dopamine caused positive chronotropic (frequency increase) and inotropic (amplitude increase) effects on the heartbeat in a concentration dependent manner. The time courses of these effects were considerably different and the inotropic effect appeared later and lasted longer than the chronotropic effect. Dopamine rapidly increased the frequency of the bursting activity in the cardiac ganglion neurons and each impulse burst of the cardiac ganglion was always followed by a heartbeat. Moreover, dopamine slowly increased the amplitude and duration of the action potential plateau (plateau potential) of the myocardium. When the myocardial pacemaker activity was induced by application of tetrodotoxin, which suppresses cardiac ganglion activity, dopamine slowly increased the amplitude and duration of the myocardial plateau potential while decreasing its frequency. These results suggest that dopamine modulates the heartbeat in adult L. exotica producing a dual effect on the two pacemaker sites in the heart, the cardiac ganglion and myocardium.

Honeybee (Apis mellifera) worker bees (workers) are known to perform wide variety of tasks depending on their ages. The worker's brains also show the activity and behavior-dependent chemical and structural plasticity. To test if there are any changes of gene expression associated with different ages in the worker brains, we compared the gene expression patterns between the brains of newly emerged bees and old foraging workers (foragers) by macroarray analysis. The expression of genes encoding signal transduction pathway components, ion channels, and neurotransmitter transporters is elevated in the old forager brains, suggesting that the neuronal activities would be enhanced. The mRNA levels of cell adhesion protein, transcription related factors, and plasma membrane associated proteins are also increased in the old forager brains. Meanwhile, the mRNA level of one putative cell adhesion protein is decreased in the old forager brains. These results thus suggest that the dramatic changes of gene expression occur in honeybee brains associated with ages.

The cumacean Dimorphostylis asiatica (Crustacea) exhibits a circatidal swimming activity rhythm. The animals were exposed to a 12.5 hr sinusoidal change of hydrostatic pressure of 0.3 atm amplitude in the laboratory. Under constant dark conditions, most of the specimens were entrained to a daily bimodal swimming activity rhythm by the hydrostatic pressure cycle. A small number of individuals exhibited a unimodal daily rhythm, with no apparent entraining from the administered cycles. A marked feature was a flexible phase relationship between the entrained daily bimodal rhythm and the hydrostatic pressure cycles: the swimming activity of most of the specimens occurred around the pressure-decreasing phase, but for a small number of individuals it coincided with the pressure-increasing phase. Such flexibility suggests a weak entraining effect of hydrostatic pressure on the circatidal rhythm of this species. When exposed to 24 hr light-dark cycles and a hydrostatic pressure cycle simultaneously, the specimens exhibited a rhythmic activity entrained by the hydrostatic pressure cycle during the dark period, which closely resembles the temporal activity pattern of this species in the field. The light cycles entrained the swimming activity via direct inhibition and induction of activity (i.e., masking). Under light-dark conditions, the specimens exhibited activity on the pressure-increasing phase more frequently compared with specimens kept in constant darkness.

Analyses of complete 1143-base pair sequence of the mitochondrial cytochrome b gene demonstrated a sister relationship between Japanese R. nigromaculata and Korean R. plancyi chosenica, but not with Korean R. nigromaculata, while the allozyme data strongly supported the monophyly of the Korean and Japanese populations of R. nigromaculata. We surmise this discordance to be the result of the inheritance of introduced mtDNA and the dilution of introduced nuclear DNA in mixed lineages after past hybridization and genome introgression between the two species, although the direction of introgression is unknown.

In the present study, inter-male interaction of the domesticated house musk shrew was observed in detail under laboratory conditions. In most cases, during inter-male interaction, male house musk shrews exhibited a sequence of behavior items including tail-wagging, following, mounting and thrusting. In the minority of cases, males did not progress beyond following. Offensive behavior was not sufficiently violent to cause injury. It appeared that role assignment was decided by contact manner and vocalization. One of fundamental characters of this animal made a start of following, in which one shrew followed another, who touched and then separated. Role assignment (i.e., which male led and which followed) was decided in status battle. Roles were often reversed during following. Following behavior was maintained by ‘polite’ mutual contact, and the interaction progressed to thrusting in the majority cases. After role assignment, the variation in contact manner decreased. The ratio of time spent in front-and-behind contact to that spent in multi-lateral contact increased when both males commenced following behavior simultaneously. This ratio was maintained until the following male snapped after he finished thrusting. Even if the following male did not reach thrusting, he mounted the preceding male. The pairs who did not reach thrusting repeated following behavior or mounting. In those cases, while one male concentrated on touching the other to maintain following, the other attempted to divert attention from the following behavior. Male shrews were able to reach thrusting irrespective of sex.

We identified three candidate proteins/genes involved in caste and/or sex-specific olfactory processing in the honeybee Apis mellifera L., that are differentially expressed between the antennae of the worker, queen, and drone honeybees using SDS-polyacrylamide gel electrophoresis or the differential display method. A protein was identified, termed D-AP1, that was expressed preferentially in drone antennae when compared to those of workers. cDNA cloning revealed that D-AP1 is homologous to carboxylesterases. Enzymatic carboxylesterase activity in the drone antennae was higher than in the workers, suggesting its dominant function in the drone antennae. In contrast, two proteins encoded by genes termed W-AP1 and Amwat were expressed preferentially in worker antennae when compared to those of queens. W-AP1 is homologous to insect chemosensory protein, and Amwat encodes a novel secretory protein. W-AP1 is expressed selectively in worker antennae, while Amwat is expressed both in the antennae and legs of the workers. These findings suggest that these proteins are involved in the antennal function characteristic to drone or worker honeybees.

Daphnia is a key crustacean zooplankton of freshwater food chains. One factor that ensures successful propagation is the Daphnia resting eggs, which are able to retain structural integrity under extreme conditions. Until recently little was known about the chemical composition, microanatomy, and physical properties of the egg itself. The current study demonstrates that the resting eggs: (1) have shells that are made up of crystalline calcium phosphate and include a honeycombed structure, and (2) contain magnetic material having properties consistent with magnetite. These properties of the resting eggs may ensure Daphnia survival in harsh environments.

We report scanning and transmission electron microscopic studies of the early development of the Hawaiian acorn worm, Ptychodera flava. In addition, we provide an immunohistochemical identification of the larval nervous system. Development occurs and is constrained within the stout chorion and fertilization envelope that forms upon the release of the cortical granules in the cytoplasm of the egg. The blastula consists of tall columnar blastomeres encircling a small blastocoel. Typical gastrulation occurs and a definitive tornaria is formed compressed within the fertilization envelope. The young tornaria hatches at 44 hr and begins to expand. The major circumoral ciliary band that crosses the dorsal surface and passes preorally and postorally is well developed. In addition, we find a nascent telotroch, as well as a midventral ciliary band that is already clearly developed. The epithelium of tornaria is a mosaic of monociliated and multiciliated cells. Immunohistochemistry with a novel neural marker, monoclonal antibody 1E11, first detects nerve cells at the gastrula stage. In tornaria, 1E11 staining nerve cells occur throughout the length of the ciliary bands, in the apical organ, in a circle around the mouth, in the esophageal epithelium and in circumpylorus regions. Axon(s) and apical processes extend from the nerve cell bodies and run in tracks along the ciliary bands. Axons extending from the preoral and postoral bands extend into the oral field and form a network. The tornaria nervous system with ciliary bands and an apical organ is rather similar to the echinoderm bipinnaria larvae.

We have previously shown that the testicular development of underyearling male masu salmon Oncorhynchus masou reared under a long photoperiod was accelerated by oral melatonin treatment (0.5mg melatonin/kg body weight/day), suggesting that melatonin mediates photoperiodic signaling. In this study, we further examined the effects of a disturbance in the plasma melatonin profile on gonadal development in underyearling male masu salmon by administering a higher dose of melatonin. Fish randomly selected in June were divided into two groups. They were reared under a light:dark (LD) cycle of 16:8 (lights on 04:00–20:00 hr) and fed with pellets sprayed with melatonin or vehicle twice a day at 08:30 and at 15:30 hr (7.5mg melatonin/kg body weight/day) until October. Fish were sampled on Day 0, 25, 60, 90 and 120. The plasma melatonin levels were high in the dark phase and low in the light phase in the control group, while they were constantly high with no significant change in the melatonin-treated group. Melatonin treatment had inhibitory effects on the gonadosomatic index and plasma testosterone levels. Pituitary salmon gonadotropin-releasing hormone content and luteinizing hormone content were significantly lower in the melatonin-treated group on Day 60 and 90, respectively. These results indicate that the plasma melatonin profile is important for mediating photoperiodic signals that regulate brain-pituitarygonadal axis in underyearling precocious male masu salmon.

Previously, we showed that glucose increases the steady-state levels of the mRNAs encoding two distinct preprosomatostatins (each containing [Tyr⁷, Gly¹⁰]-somatostatin-14 at their C-termini; denoted PPSS II’ and PPSS II”) in the endocrine pancreas (Brockmann body) of rainbow trout (Oncorhynchus mykiss). In the present study, isolated islet cells were used to determine whether glucose-stimulated expression resulted from altered rates of transcription and/or from changes in RNA stability. Nuclear runon assays indicated that the number of PPSS II nascent transcripts were significantly higher in nuclei isolated from islet cells cultured in 10 mM glucose compared to those isolated from cells incubated in 4 mM glucose. High glucose (10 mM) did not, however, affect the stability of PPSS II mRNAs. These results indicate that glucose-stimulated somatostatin expression in the Brockmann bodies of rainbow trout results from increased endogenous mRNA transcription and not from altered mRNA stability.

Pylopaguropsis vicina, a new species of the Paguridae, is described and illustrated from southern Japan and Indonesia. This new species is most similar to P. laevispinosa McLaughlin and Haig, but is distinguished by the armature of the chelae and ambulatory dactyli, spination of the telson, and stripe pattern of the pereopods. Reexamination of specimens referred to P. laevispinosa by recent authors has shown these assignments to be incorrect. A brief supplemental description is provided for P. laevispinosa in order to clarify its systematic status. An amended key to species of the genus Pylopaguropsis is presented.

A new species Megabruchidius sophorae (Insecta, Coleoptera) is described from Japan (Honshu). The larval host of this bruchid is the seeds of the tree legume ‘enju’, or chinese scholar tree, Styphnolobium japonicum (a senior synonym of Sophora japonica), which is a new host genus to Bruchidae. Styphnolobium is positioned basally in molecular phylogeny of the leguminous subfamily Papilionoideae. Other members of Megabruchidius are known to feed on Gleditsia, the tree legumes that belong to the most ancestral subfamily Caesalpinioideae. Therefore, Megabruchidius utilizes ancestral groups of legumes as its host plants. Megabruchidius has been inferred to be ancestral, based on its behavior. The character state of the host for this third Megabruchidius species supports that the genus is ancestral, at least in the subfamily Bruchinae. We also reviewed the genera closely related to Megabruchidius, i.e., Bruchidius and Sulcobruchus in Bruchidini, and wrote a key to the species in the genus Megabruchidius.

Phylogenetic relationships among the ferret-badger Melogale moschata, the skunk Mephitis mephitis, and 21 other arctoid carnivorans, representing Mustelidae (Mustelinae: Mustela, Martes, Gulo; Lutrinae: Enhydra; Melinae: Meles), Procyonidae (Procyon), and Ursidae (Ursus, Melursus), were evaluated through maximum-parsimony phylogenetic analysis of concatenated partial nucleotide sequences of the nuclear recombination-activating gene 1 (RAG1) and gene encoding interphotoreceptor retinoid-binding protein (IRBP). The analysis strongly supports Melogale as more closely related to a musteline-lutrine clade (containing Mustela and Enhydra) than to Meles or another musteline clade containing Martes and Gulo (causing Melinae and Mustelinae, as traditionally circumscribed, to be nonmonophyletic). This, together with known morphological and karyological evidence for nonmeline affinities of Melogale, justify the exclusion of the ferret-badgers from the monophyletic Melinae. Therefore, we recommend that Melogale be classified in a distinct mustelid subfamily, the monotypic Helictidinae. Our analysis also strongly supports an outgroup position of the skunks to a clade containing Procyonidae and the nonmephitine Mustelidae (causing Mustelidae, as traditionally circumscribed, to be paraphyletic). This position of the skunks agrees with results of most previous genetic studies. However, it is contradicted by known morphological evidence from both living and fossil taxa, as well as genetic evidence from protein electrophoresis. These consistently support the traditional placement of the skunks within the monophyletic Mustelidae (recently in a close relationship to Lutrinae). Therefore, we consider the recent elevation of the skunks to the level of family as premature, and recommend that this clade be left at the subfamily level (Mephitinae) within the family Mustelidae, pending further evidence.